**2. Physical setting**

The physical features of the earth play a vital role in controlling of temperature, precipitation, natural disasters, evapotranspiration, etc. The temperature decreases from low to high altitude, while it is converse for precipitation. The moisture contents of the soil decrease from high to low altitudes that influence the crop productivity at low lands. Besides, the height of trees and crops and the length of cropping seasons also somehow depended on the topography of the area. In most cases, the crops in arid and semiarid areas are confined to isolated patches, where the soil is fertile and the water is available. There are two arid regions identified in Pakistan, that is, the southern and northern arid region, separated by a wide zone of semiarid, subhumid, and humid region of central and upper Punjab and Khyber Pakhtunkhwa provinces. Therefore, it is necessary to discuss the physiography of the arid regions in Pakistan.

The southern arid region covers Sind, Baluchistan, lower Punjab, and Dera Ismail (DI) Khan as well as Chitral district of the Khyber Pakhtunkhwa province. The landforms of the southern arid region have three main units—the northwestern highland, Baluchistan plateau, and the Indus plain (**Figure 1**). The northwestern highland of Baluchistan consists of two parallel regions of Toba Kakar extending from northeast to southwest in Baluchistan and another parallel range of Sulaiman-Dera Bugti mountains along the Indus plain. The second major physiographic unit is the Baluchistan plateau that lies between the Toba Kakar ranges and the Sulaiman-Kirthar mountains and is also a dry rugged area with harsh environment. Mainly, pastoral agriculture is practiced on the Baluchistan plateau. Crops are grown only in those areas where water is available [3].

**85**

*Environment, Agriculture, and Land Use Pattern DOI: http://dx.doi.org/10.5772/intechopen.83850*

Kech district.

*rainy days etc."*

**3. Weather and climates**

defined inadequately as "*average weather*."

**3.1 Seasonal division**

climate/physical features.

The third major landform unit is the Indus plain, which lies south of the Himalayas and the Salt Range stretching southward to the Arabian Sea. The Sind province and lower Punjab of the Indus plain fall in the arid region. This is the main agricultural area, where the canal irrigation has developed during the nineteenth century. A deltaic plain that has developed at the mouth of the Indus River is also an important agricultural area. The rolling sand plain covers an extensive area to the southeast of the canal-irrigated arid region covering Cholistan and Thar Deserts in Sind and lower Punjab. To the west of Kalat Plateau is the rolling sand plain of Kharan and Chaghi, while in the southwestern Baluchistan, there are dry and arid mountain ranges of the Makran coastal region. They are not very conducive to agriculture because of their dryness and rough topography, but agriculture is practiced to some extent in the Dasht River valley around Turbat in

The northern arid region covers the extreme north of Pakistan, consisting of the Transhimalayas or the Karakoram and Hindu Kush mountains. The slopes are very steep, and natural hazards particularly the landslide are frequent, and the agriculture land is confined to the narrow belts along the rivers and streams in the valley. Therefore, in this rugged mountainous belt, agriculture is practiced mainly in the

The term climatology is a Greek word, which literally means "inclination," i.e., inclination of the sunrays to the ground, to denote the mean weather condition. The word climate refers to the mean or normal condition over a long period, such as 20, 30, and 100 years [4]. According to Petterson [5], *"climatology or statistical meteorology determines the statistical relations, mean values, normal, frequencies, variation distribution, etc., of the meteorological elements, such as temperature, pressure, precipitation, wind speed and direction, humidity, sunshine, cloudiness and number of* 

Blair [6] has defined the climate as "*The summation of weather conditions in historical time*" or "*Climate is the summary of all the manifold weather influences.*" Miller [7] is of the opinion that the science that discusses the weather condition of the earth surface is known as climate. Thus, the wind, temperature, humidity, precipitation, vegetation, sunshine, etc. are subjected to continuous variations, which are more or less invariant at a given place. According to Oliver [8], "*climate is the aggregate of weather at a given area for a given time period*." The term weather refers to the more or less instantaneous conditions of these elements over a relatively short time period. The generalized picture of weather is called climate [9]. Climatology deals with atmospheric conditions over a longer time period and, as a result, is often

This section covers the temporal and areal climate divisions and climate regions.

The distinct period into which the year may be divided, in terms of duration of daylight and climate conditions, as a result of changes in duration and intensity of sunshine and rainfall, is termed as season [10]. According to Moore [11], season is

The temporal division is based on the division of the year into various seasons and the description of each season. The areal division is based on classifying the climate of region only and thus dividing arid region of Pakistan into areas of similar

valleys primarily in the form of terraced cultivation (**Figure 1**).

*Environment, Agriculture, and Land Use Pattern DOI: http://dx.doi.org/10.5772/intechopen.83850*

*Climate Change and Agriculture*

**2. Physical setting**

**Figure 1.**

the arid regions in Pakistan.

those areas where water is available [3].

The physical features of the earth play a vital role in controlling of temperature, precipitation, natural disasters, evapotranspiration, etc. The temperature decreases from low to high altitude, while it is converse for precipitation. The moisture contents of the soil decrease from high to low altitudes that influence the crop productivity at low lands. Besides, the height of trees and crops and the length of cropping seasons also somehow depended on the topography of the area. In most cases, the crops in arid and semiarid areas are confined to isolated patches, where the soil is fertile and the water is available. There are two arid regions identified in Pakistan, that is, the southern and northern arid region, separated by a wide zone of semiarid, subhumid, and humid region of central and upper Punjab and Khyber Pakhtunkhwa provinces. Therefore, it is necessary to discuss the physiography of

*Arid Region Location, GoUSA [2], online, ftp://ftp.glcf.umiacs.umd.edu.*

The southern arid region covers Sind, Baluchistan, lower Punjab, and Dera Ismail (DI) Khan as well as Chitral district of the Khyber Pakhtunkhwa province. The landforms of the southern arid region have three main units—the northwestern highland, Baluchistan plateau, and the Indus plain (**Figure 1**). The northwestern highland of Baluchistan consists of two parallel regions of Toba Kakar extending from northeast to southwest in Baluchistan and another parallel range of Sulaiman-Dera Bugti mountains along the Indus plain. The second major physiographic unit is the Baluchistan plateau that lies between the Toba Kakar ranges and the Sulaiman-Kirthar mountains and is also a dry rugged area with harsh environment. Mainly, pastoral agriculture is practiced on the Baluchistan plateau. Crops are grown only in

**84**

The third major landform unit is the Indus plain, which lies south of the Himalayas and the Salt Range stretching southward to the Arabian Sea. The Sind province and lower Punjab of the Indus plain fall in the arid region. This is the main agricultural area, where the canal irrigation has developed during the nineteenth century. A deltaic plain that has developed at the mouth of the Indus River is also an important agricultural area. The rolling sand plain covers an extensive area to the southeast of the canal-irrigated arid region covering Cholistan and Thar Deserts in Sind and lower Punjab. To the west of Kalat Plateau is the rolling sand plain of Kharan and Chaghi, while in the southwestern Baluchistan, there are dry and arid mountain ranges of the Makran coastal region. They are not very conducive to agriculture because of their dryness and rough topography, but agriculture is practiced to some extent in the Dasht River valley around Turbat in Kech district.

The northern arid region covers the extreme north of Pakistan, consisting of the Transhimalayas or the Karakoram and Hindu Kush mountains. The slopes are very steep, and natural hazards particularly the landslide are frequent, and the agriculture land is confined to the narrow belts along the rivers and streams in the valley. Therefore, in this rugged mountainous belt, agriculture is practiced mainly in the valleys primarily in the form of terraced cultivation (**Figure 1**).

### **3. Weather and climates**

The term climatology is a Greek word, which literally means "inclination," i.e., inclination of the sunrays to the ground, to denote the mean weather condition. The word climate refers to the mean or normal condition over a long period, such as 20, 30, and 100 years [4]. According to Petterson [5], *"climatology or statistical meteorology determines the statistical relations, mean values, normal, frequencies, variation distribution, etc., of the meteorological elements, such as temperature, pressure, precipitation, wind speed and direction, humidity, sunshine, cloudiness and number of rainy days etc."*

Blair [6] has defined the climate as "*The summation of weather conditions in historical time*" or "*Climate is the summary of all the manifold weather influences.*" Miller [7] is of the opinion that the science that discusses the weather condition of the earth surface is known as climate. Thus, the wind, temperature, humidity, precipitation, vegetation, sunshine, etc. are subjected to continuous variations, which are more or less invariant at a given place. According to Oliver [8], "*climate is the aggregate of weather at a given area for a given time period*." The term weather refers to the more or less instantaneous conditions of these elements over a relatively short time period. The generalized picture of weather is called climate [9]. Climatology deals with atmospheric conditions over a longer time period and, as a result, is often defined inadequately as "*average weather*."

#### **3.1 Seasonal division**

This section covers the temporal and areal climate divisions and climate regions. The temporal division is based on the division of the year into various seasons and the description of each season. The areal division is based on classifying the climate of region only and thus dividing arid region of Pakistan into areas of similar climate/physical features.

The distinct period into which the year may be divided, in terms of duration of daylight and climate conditions, as a result of changes in duration and intensity of sunshine and rainfall, is termed as season [10]. According to Moore [11], season is

defined as, "Those periods of the year, which are characterized by special climate conditions, mainly caused by the inclination of the earth's Axis to the plane of the Ecliptic and the revolution of the earth about the sun." In order to study the seasonal variation of weather elements, the year has been divided into two main seasons, that is, summer and winter. The interrelation of factors affecting climate of the arid region in Pakistan shows that the summer month in coastal areas may not be the summer month inland and a summer month in plain may not be that of the mountains. Therefore, months of the year having mean temperature of above 22°C, maximum temperature of above 34°C, and minimum temperature of above 10°C are suggested as summer months, otherwise winter (**Figure 2**). In spite of this, months having positive deviation from the mean temperature are considered as summer months, whereas months having negative deviation from the mean temperature have been placed in winter season. Generally, in plain the summer lasts from April to October and winter from November to March. In highland, the summer has a span from May to September and winter from October to April. These two main seasons are further condensed into four sub-seasons that are cold, hot, warm, and monsoon seasons. The cold season of the country is from mid-November to mid-April with all months' mean monthly temperature below 20°C, rainfall below 6 cm (2.4 inches), moderate humidity, high pressure, minimum sunshine period, and low evapotranspiration. The hot season varies from mid-April to June with each month's mean monthly temperature of above 30°C; low rainfall, humidity, and pressure; maximum sunshine period; and high evapotranspiration. The monsoon season ranges from July to mid-September with all months' mean monthly temperature below 30°C, rainfall above 6 cm (2.4 inches), moderate humidity, low pressure, and high sunshine period and evapotranspiration. Nonetheless, the warm season remains from mid-September to mid-November, with mean monthly temperature below 25°C, low rainfall and humidity, moderate pressure and sunshine period, and high evapotranspiration. However, November is completely the winter month in hilly areas, while April is the summer month in plain. These months are thus divided into two parts, and the average of 15 days has been added to each season.

**87**

areas [12].

*Environment, Agriculture, and Land Use Pattern DOI: http://dx.doi.org/10.5772/intechopen.83850*

warm fronts either at the surface or aloft.

follows [12].

*3.1.1 Cold season*

The average rainfall indicates that it increases with a decrease in temperature from December to March, while at the rise of temperature, a decrease occurs from March to June. In July it exceeds 9 cm (3.6 inches) and then decreases till September and onward up to November (below 3 cm or 1.2 inches). The annual variation of rainfall and humidity also shows two-time positive and negative deviation from the mean condition (**Figure 2**). From September to November, the arid region of Pakistan is covered by anticyclone and reversible monsoon lows. These months, with moderate temperature and low rainfall, constitute as warm season. Generally, the local thunderstorms give high rainfall in the Northern Areas and constitute as a rainy season of the northern arid region in Pakistan. The month of the year having a mean monthly rainfall below 3 cm and temperature above 17°C has been suggested as a dry month, otherwise moist. The characteristics of each season are as

The cold season lasts from mid-November to mid-April, which is completely winter months in the hilly areas. It is the season when, because of the prevalence of anticyclone, air subsides over Pakistan and the weather is feeblest. A cross section of the atmosphere about 78° east meridian shows the southern branch of the jet stream over northern Pakistan and India just south of the Himalayas, with the middle latitude westerly reaching down to the surface or, nearly so, north of about 25° [13]. The modest winter rainfall over northern Indo-Pakistan is associated with disturbances, which enter the area in the extreme northwest, after passing through Iraq, Iran, and Afghanistan. These disturbances reach their maximum development in winter when the jet stream lies south of the highlands, but they also occur though less frequently, in fall and spring. On the surface synoptic charts, the western disturbances usually first appear in the northwest in the vicinity of the surface polar front [7]. A cold continental air from eastern Europe and Western Asia break through the lower highland and spills out on the Indus lowlands. The front form between the continental polar air and the dry but warmer air of the Pakistani lowlands may not in the beginning be very active weather-wise. If the resulting depression acts to pull in a vigorous inflow of humid tropical maritime air mass from the Arabian Sea, the convergence is likely to produce extensive light rains. These are mid-latitude disturbances, a good proportion of that are not well-developed cold or

The rainfall generated by these western disturbances of the cooler season is usually fairly widespread and light to moderate. It is locally heavy where thunderstorms are associated with the disturbances particularly in hot dry season. This fall in the cool season, when losses from evaporation are low, is highly effective for the growth of winter crops. On the plain, the total fall for the three winter months is only 1–3 inches, and yet this is of vital importance. Such storms also provide a much larger amount of winter precipitation in the form of snow and ice in the highland, whose water melts in hot season (summer) and furnishes the indispensable irrigation water for the Indo-Gengetic plain. These disturbances give high rains over the northwestern parts of Pakistan, which progressively decrease toward southeast and west. This variation, in general, leads to its long trajectory over land

The season is usually characterized by cold weather with low mean monthly temperature, moderate rains, high humidity and pressure, low sunshine period, and gentle breeze. In cold season, most of the rains are caused by low-pressure depressions called western disturbances. These waves travel from the Mediterranean Sea and enter to Pakistan at the western margin after passing through Iraq, Afghanistan,

**Figure 2.** *Pakistan arid region temperature (°C), rainfall (cm) and relative humidity (%) 1931–2017.*

*Environment, Agriculture, and Land Use Pattern DOI: http://dx.doi.org/10.5772/intechopen.83850*

The average rainfall indicates that it increases with a decrease in temperature from December to March, while at the rise of temperature, a decrease occurs from March to June. In July it exceeds 9 cm (3.6 inches) and then decreases till September and onward up to November (below 3 cm or 1.2 inches). The annual variation of rainfall and humidity also shows two-time positive and negative deviation from the mean condition (**Figure 2**). From September to November, the arid region of Pakistan is covered by anticyclone and reversible monsoon lows. These months, with moderate temperature and low rainfall, constitute as warm season. Generally, the local thunderstorms give high rainfall in the Northern Areas and constitute as a rainy season of the northern arid region in Pakistan. The month of the year having a mean monthly rainfall below 3 cm and temperature above 17°C has been suggested as a dry month, otherwise moist. The characteristics of each season are as follows [12].

#### *3.1.1 Cold season*

*Climate Change and Agriculture*

defined as, "Those periods of the year, which are characterized by special climate conditions, mainly caused by the inclination of the earth's Axis to the plane of the Ecliptic and the revolution of the earth about the sun." In order to study the seasonal variation of weather elements, the year has been divided into two main seasons, that is, summer and winter. The interrelation of factors affecting climate of the arid region in Pakistan shows that the summer month in coastal areas may not be the summer month inland and a summer month in plain may not be that of the mountains. Therefore, months of the year having mean temperature of above 22°C, maximum temperature of above 34°C, and minimum temperature of above 10°C are suggested as summer months, otherwise winter (**Figure 2**). In spite of this, months having positive deviation from the mean temperature are considered as summer months, whereas months having negative deviation from the mean temperature have been placed in winter season. Generally, in plain the summer lasts from April to October and winter from November to March. In highland, the summer has a span from May to September and winter from October to April. These two main seasons are further condensed into four sub-seasons that are cold, hot, warm, and monsoon seasons. The cold season of the country is from mid-November to mid-April with all months' mean monthly temperature below 20°C, rainfall below 6 cm (2.4 inches), moderate humidity, high pressure, minimum sunshine period, and low evapotranspiration. The hot season varies from mid-April to June with each month's mean monthly temperature of above 30°C; low rainfall, humidity, and pressure; maximum sunshine period; and high evapotranspiration. The monsoon season ranges from July to mid-September with all months' mean monthly temperature below 30°C, rainfall above 6 cm (2.4 inches), moderate humidity, low pressure, and high sunshine period and evapotranspiration. Nonetheless, the warm season remains from mid-September to mid-November, with mean monthly temperature below 25°C, low rainfall and humidity, moderate pressure and sunshine period, and high evapotranspiration. However, November is completely the winter month in hilly areas, while April is the summer month in plain. These months are thus divided into two parts, and the average of 15 days has been added to each season.

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**Figure 2.**

*Pakistan arid region temperature (°C), rainfall (cm) and relative humidity (%) 1931–2017.*

The cold season lasts from mid-November to mid-April, which is completely winter months in the hilly areas. It is the season when, because of the prevalence of anticyclone, air subsides over Pakistan and the weather is feeblest. A cross section of the atmosphere about 78° east meridian shows the southern branch of the jet stream over northern Pakistan and India just south of the Himalayas, with the middle latitude westerly reaching down to the surface or, nearly so, north of about 25° [13]. The modest winter rainfall over northern Indo-Pakistan is associated with disturbances, which enter the area in the extreme northwest, after passing through Iraq, Iran, and Afghanistan. These disturbances reach their maximum development in winter when the jet stream lies south of the highlands, but they also occur though less frequently, in fall and spring. On the surface synoptic charts, the western disturbances usually first appear in the northwest in the vicinity of the surface polar front [7]. A cold continental air from eastern Europe and Western Asia break through the lower highland and spills out on the Indus lowlands. The front form between the continental polar air and the dry but warmer air of the Pakistani lowlands may not in the beginning be very active weather-wise. If the resulting depression acts to pull in a vigorous inflow of humid tropical maritime air mass from the Arabian Sea, the convergence is likely to produce extensive light rains. These are mid-latitude disturbances, a good proportion of that are not well-developed cold or warm fronts either at the surface or aloft.

The rainfall generated by these western disturbances of the cooler season is usually fairly widespread and light to moderate. It is locally heavy where thunderstorms are associated with the disturbances particularly in hot dry season. This fall in the cool season, when losses from evaporation are low, is highly effective for the growth of winter crops. On the plain, the total fall for the three winter months is only 1–3 inches, and yet this is of vital importance. Such storms also provide a much larger amount of winter precipitation in the form of snow and ice in the highland, whose water melts in hot season (summer) and furnishes the indispensable irrigation water for the Indo-Gengetic plain. These disturbances give high rains over the northwestern parts of Pakistan, which progressively decrease toward southeast and west. This variation, in general, leads to its long trajectory over land areas [12].

The season is usually characterized by cold weather with low mean monthly temperature, moderate rains, high humidity and pressure, low sunshine period, and gentle breeze. In cold season, most of the rains are caused by low-pressure depressions called western disturbances. These waves travel from the Mediterranean Sea and enter to Pakistan at the western margin after passing through Iraq, Afghanistan, and Iran. These low-pressure waves give 3.83 cm (1.5 inches) average rainfall in the arid region of Pakistan. Areas located at the western border of the country record high rains in cold season as compared to other seasons. The highest rainfall from these winds is recorded at Dir (24.22 cm or 9.7 inches) in March, which is the moistest month of the season. The highest mean monthly total precipitation of the season is 83.5 cm or 33.4 inches at Dir, and lowest is 0.8 cm or 0.32 inches at Mohenjo Daro with highest relative humidity recorded at Ormara and lowest at Khuzdar. The lower Indus plain has almost recorded high temperature, while it decreases up to −7.8°C at Astore. Most of the Northern Areas receive rain from these winds as compared to other sources. The rainfall from western depression progressively decreases from the northern mountainous region, toward northwest and southeast due to long trajectory of these lows over continental areas. Most of the highland receives rain in the form of snow, which is a guarantee for the agriculture activities in the hot season. The temperature of the country decreases from southwest toward northeast, but sometime cold waves are caused by heavy snowfall in mountains and decrease temperature after sunset below freezing point in Baluchistan plateau and the lowlands, influencing plant growth and human activities.

#### *3.1.2 Hot season*

The season ranges from mid-April to June and is characterized by high temperature and aridity. It is sometime called as the hot dry period to distinguish it from the cool dry season of winter and the hot wet season of summer and early fall. From April to June, the anticyclone subsidence and clear skies, characteristic of the winter months, still prevail, and this in combination with a much stronger solar radiation sets the weather pattern for the season. Temperatures are high, and a heavy, dry haze envelops in the interior, but drought still grips most of the country particularly upper and lower Indus plain.

The areal rainfall distribution in hot season is not fundamentally different from that of winter. The upper and lower Indus plain as well as Baluchistan, where maximum subsidence prevails, is still the driest parts of the country, and the Northern Areas with mountainous north are the wettest. The most perceptible areas of rainfall increase are the northern mountains and Azad Jammu and Kashmir, while most of the plains have less than 2 cm rains in these particular months.

According to Trewartha [13], in the far south, the added rainfall reflects the creeping northward with the sun of the ITC and the equatorial westerly. The increased rainfall in the north is furnished by the western disturbances. These perturbations are able to produce much precipitation in the more humid air of the north, they yield much more abundant rainfall, and some of it is associated with strong convective systems.

The hot season, in general, is characterized by violent weather, in the form of thunder squalls in the northern part of the country. In the drier land of Pakistan, the rainfall accompanying this vigorous convective system is low, but occasionally well-developed cumulonimbus clouds are generated with strong squall wind and violent dust storms.

In hot season, the mean monthly temperature exceeds 30°C with rare rains, low humidity and pressure, and high sunshine duration, evapotranspiration, and wind speed. These are the specific determinants, which cause parching of leaves in plants and evaporation of sweats from human bodies. In hot season, the western depression continues to travel along the northern latitude of Pakistan, which caused thunderstorms (with some rains) over the mountains and dust storms or dust-raising winds over the plain and Baluchistan plateau. The cold waves are rare in April, but hailstorms are frequent in April and rare in May, which caused widespread

**89**

*Environment, Agriculture, and Land Use Pattern DOI: http://dx.doi.org/10.5772/intechopen.83850*

*3.1.3 Monsoon season*

damages to fruit trees in the western and Northern Areas of Pakistan. June is the driest month of the season with mean monthly rainfall of 2.42 cm or 0.96 inches and also the hottest with mean monthly temperature of above 30°C. The highest mean monthly total precipitation of the season is 35.1 cm or 14.04 inches at Garhi Dupatta, and the lowest is 0.1 cm (0.04 inches) at Mohenjo Daro (arid region). The highest mean monthly humidity is recorded at Ormara, and the lowest is at Chilas and Dalbandin (arid region). The highest mean monthly temperature of the season is recorded at Sibi, and the lowest is at Astore. In hot season, the Northern Areas of the country receive rainfall above 10 cm or 4 inches, which decreases toward south. This high temperature in the southern part of Pakistan produces a trough of low pressure, which attracts monsoon depression in the hot moist season. The variation in temperature, generally, shows the same pattern as in cold season. As the hot season progresses, the belt of highest day temperature takes over Pakistan from south to north. Moreover, in this season the average rainfall of Pakistan is 2.9 cm or 0.99 inches, which is insufficient for vegetation growth and human activities [12].

According to Moore [11], the term monsoon is derived from the Arabic word "mausim" which literally means "season." Originally, it was applied to the regular winds of the Arabian Sea, blowing for 6 months from the northeast and for the remaining 6 months from the southwest. Now generally, the term is applied to those and some other winds that blow with considerable regularity in different seasons of the year, due to the seasonal reversal of pressure over land masses and their neighboring oceans. In the typical area of the Indian subcontinent and southeast Asia, it is the seasonal inflowing moist winds that bring rains; hence, the monsoon season is considered as synonymous with the rainy season, and the term monsoon is applied to the rain without reference to the winds. The monsoon season of Pakistan ranges from July to mid-September, while in some areas it continues up to October. The deflected monsoon currents, generally, travel westward along the foothills of the Himalayas and reach Pakistan in July and are well established by the middle of that month [10]. The Arabian Sea branch of monsoon reaches to Sind-Makran coast by the end of June. However, it is of low vertical extant and, generally, produces stratus clouds in the coastal areas. The monsoon currents remain steady till it begins retreating toward the beginning of September. The second monsoon current enters Pakistan at upper Indus plain and gives more rains in Punjab, upper Sind, and northeastern Baluchistan. The third branch of the monsoon lows arrives at Kashmir Vale and the northern mountainous region of the country. Due to mountain trigger and high moisture index, these areas record high rains from these lows as compared to other regions of Pakistan. The rainfall from these winds generally decreases from northeast to southwest. This variation in rainfall intensity from monsoon is due to its long trajectory decreasing the moisture index of these depressions as they travel over continental areas. These winds are the only source, saving the lower Indus plain of Pakistan from aridity. In monsoon season, the mean monthly temperature of Pakistan drops below 30°C with high rainfall of 3–9 cm (1.2–3.6 inches) and humidity, low pressure, maximum sunshine period, and high evapotranspiration and wind speed. These winds give torrential rains with showers and caused damages to residential areas, crops, and vegetables. It gives above 7 cm or 2.8 inches of rainfall in Pakistan, which is higher than the other seasons. The maximum rainfall from these winds has been recorded at Balakot in July being the moistest month of the season with mean monthly rainfall of above 9 cm or 3.6 inches. However, in some areas especially in the mountainous north, August is the moistest month of the season. The highest mean monthly total precipitation of the season is recorded

*Environment, Agriculture, and Land Use Pattern DOI: http://dx.doi.org/10.5772/intechopen.83850*

damages to fruit trees in the western and Northern Areas of Pakistan. June is the driest month of the season with mean monthly rainfall of 2.42 cm or 0.96 inches and also the hottest with mean monthly temperature of above 30°C. The highest mean monthly total precipitation of the season is 35.1 cm or 14.04 inches at Garhi Dupatta, and the lowest is 0.1 cm (0.04 inches) at Mohenjo Daro (arid region). The highest mean monthly humidity is recorded at Ormara, and the lowest is at Chilas and Dalbandin (arid region). The highest mean monthly temperature of the season is recorded at Sibi, and the lowest is at Astore. In hot season, the Northern Areas of the country receive rainfall above 10 cm or 4 inches, which decreases toward south. This high temperature in the southern part of Pakistan produces a trough of low pressure, which attracts monsoon depression in the hot moist season. The variation in temperature, generally, shows the same pattern as in cold season. As the hot season progresses, the belt of highest day temperature takes over Pakistan from south to north. Moreover, in this season the average rainfall of Pakistan is 2.9 cm or 0.99 inches, which is insufficient for vegetation growth and human activities [12].

#### *3.1.3 Monsoon season*

*Climate Change and Agriculture*

influencing plant growth and human activities.

particularly upper and lower Indus plain.

strong convective systems.

violent dust storms.

*3.1.2 Hot season*

and Iran. These low-pressure waves give 3.83 cm (1.5 inches) average rainfall in the arid region of Pakistan. Areas located at the western border of the country record high rains in cold season as compared to other seasons. The highest rainfall from these winds is recorded at Dir (24.22 cm or 9.7 inches) in March, which is the moistest month of the season. The highest mean monthly total precipitation of the season is 83.5 cm or 33.4 inches at Dir, and lowest is 0.8 cm or 0.32 inches at Mohenjo Daro with highest relative humidity recorded at Ormara and lowest at Khuzdar. The lower Indus plain has almost recorded high temperature, while it decreases up to −7.8°C at Astore. Most of the Northern Areas receive rain from these winds as compared to other sources. The rainfall from western depression progressively decreases from the northern mountainous region, toward northwest and southeast due to long trajectory of these lows over continental areas. Most of the highland receives rain in the form of snow, which is a guarantee for the agriculture activities in the hot season. The temperature of the country decreases from southwest toward northeast, but sometime cold waves are caused by heavy snowfall in mountains and decrease temperature after sunset below freezing point in Baluchistan plateau and the lowlands,

The season ranges from mid-April to June and is characterized by high temperature and aridity. It is sometime called as the hot dry period to distinguish it from the cool dry season of winter and the hot wet season of summer and early fall. From April to June, the anticyclone subsidence and clear skies, characteristic of the winter months, still prevail, and this in combination with a much stronger solar radiation sets the weather pattern for the season. Temperatures are high, and a heavy, dry haze envelops in the interior, but drought still grips most of the country

The areal rainfall distribution in hot season is not fundamentally different from that of winter. The upper and lower Indus plain as well as Baluchistan, where maximum subsidence prevails, is still the driest parts of the country, and the Northern Areas with mountainous north are the wettest. The most perceptible areas of rainfall increase are the northern mountains and Azad Jammu and Kashmir, while

According to Trewartha [13], in the far south, the added rainfall reflects the creeping northward with the sun of the ITC and the equatorial westerly. The increased rainfall in the north is furnished by the western disturbances. These perturbations are able to produce much precipitation in the more humid air of the north, they yield much more abundant rainfall, and some of it is associated with

The hot season, in general, is characterized by violent weather, in the form of thunder squalls in the northern part of the country. In the drier land of Pakistan, the rainfall accompanying this vigorous convective system is low, but occasionally well-developed cumulonimbus clouds are generated with strong squall wind and

In hot season, the mean monthly temperature exceeds 30°C with rare rains, low humidity and pressure, and high sunshine duration, evapotranspiration, and wind speed. These are the specific determinants, which cause parching of leaves in plants and evaporation of sweats from human bodies. In hot season, the western depression continues to travel along the northern latitude of Pakistan, which caused thunderstorms (with some rains) over the mountains and dust storms or dust-raising winds over the plain and Baluchistan plateau. The cold waves are rare in April, but hailstorms are frequent in April and rare in May, which caused widespread

most of the plains have less than 2 cm rains in these particular months.

**88**

According to Moore [11], the term monsoon is derived from the Arabic word "mausim" which literally means "season." Originally, it was applied to the regular winds of the Arabian Sea, blowing for 6 months from the northeast and for the remaining 6 months from the southwest. Now generally, the term is applied to those and some other winds that blow with considerable regularity in different seasons of the year, due to the seasonal reversal of pressure over land masses and their neighboring oceans. In the typical area of the Indian subcontinent and southeast Asia, it is the seasonal inflowing moist winds that bring rains; hence, the monsoon season is considered as synonymous with the rainy season, and the term monsoon is applied to the rain without reference to the winds. The monsoon season of Pakistan ranges from July to mid-September, while in some areas it continues up to October. The deflected monsoon currents, generally, travel westward along the foothills of the Himalayas and reach Pakistan in July and are well established by the middle of that month [10]. The Arabian Sea branch of monsoon reaches to Sind-Makran coast by the end of June. However, it is of low vertical extant and, generally, produces stratus clouds in the coastal areas. The monsoon currents remain steady till it begins retreating toward the beginning of September. The second monsoon current enters Pakistan at upper Indus plain and gives more rains in Punjab, upper Sind, and northeastern Baluchistan. The third branch of the monsoon lows arrives at Kashmir Vale and the northern mountainous region of the country. Due to mountain trigger and high moisture index, these areas record high rains from these lows as compared to other regions of Pakistan. The rainfall from these winds generally decreases from northeast to southwest. This variation in rainfall intensity from monsoon is due to its long trajectory decreasing the moisture index of these depressions as they travel over continental areas. These winds are the only source, saving the lower Indus plain of Pakistan from aridity. In monsoon season, the mean monthly temperature of Pakistan drops below 30°C with high rainfall of 3–9 cm (1.2–3.6 inches) and humidity, low pressure, maximum sunshine period, and high evapotranspiration and wind speed. These winds give torrential rains with showers and caused damages to residential areas, crops, and vegetables. It gives above 7 cm or 2.8 inches of rainfall in Pakistan, which is higher than the other seasons. The maximum rainfall from these winds has been recorded at Balakot in July being the moistest month of the season with mean monthly rainfall of above 9 cm or 3.6 inches. However, in some areas especially in the mountainous north, August is the moistest month of the season. The highest mean monthly total precipitation of the season is recorded

#### *Climate Change and Agriculture*

at Murree and lowest at Nok Kundi (arid region), with highest mean monthly humidity at Jiwani and lowest at Chilas. The lower Indus plain as well as Baluchistan (arid region) has recorded high temperatures, while the lowest is at Murree and the adjoining areas of Malakand and Mansehra divisions (humid region). The rainfall of Pakistan, in monsoon season, generally, decreases from northeast to southwest [12].

In Pakistan, the transition from the relatively dry and weather less spring to the cloudy, rainy season of summer, with its numerous perturbations, is abrupt and is usually associated with strongly disturbed weather. The so-called monsoon rains begin over Burma in May or even late April [13], but in Pakistan, they arrive from 15th of June in coastal areas, and the first week of July in mountainous north, and are well-established up to the mid-July in the whole country. Usually, the advance of the monsoon currents toward north over India and Pakistan is accompanied by turbulent weather in the form of thunderstorms, but its frequency decreases after the summer circulation is established. The monsoon begins to retreat from northern Pakistan in late August, and the withdrawal continues southward through September and October [12].

The later arrival of monsoon currents in Pakistan may result from the fact that during the winter and spring, there is an orographically determined upper trough, oriented Northsouth at about 85°E, over the western Bay of Bengal. It acts to accelerate the southwesterly monsoon flow over Burma located east of this trough while at the same time retarding it over Indo-Pakistan to the west [14]. As the subcontinent is heated intensively in April and May, the zonal westerly's over northern India and Pakistan begin to move northward, and it changes its direction under the influence of the mountain ranges, toward southwest. As a result, the jet stream, which had been south of the highland at about 30°N during winter and spring, tends to disappear and then reappear alternately south of the mountains. Disappearance becomes more frequent as the season advances, and each disappearance is associated with a northward surge of the summer monsoon. Finally, in late May or early June, the jet disappears completely over northern Pakistan and takes up a position at about 40°N of the Himalayas and Tibet. Simultaneously, there occurs a shift of the low-latitude trough and ridge positions, and the upper trough which previously was located at about 85°E quickly moves westward some 10° and takes up a position over western Indo-Pakistan subcontinent at approximately 75°E. With the disappearance of the jet over northern India and a westward shift of the upper trough, the equatorial westerly, or summer monsoon, surges northward over India accompanied by unsettled weather. The heating of the subcontinent and the development of a surface pressure trough are unable to produce a northward advance of the ITC until large-scale dynamic features of the circulation aloft become favorable [13]. When the jet stream reappears south of the Himalayas, again in fall, the summer monsoon again retreats southward and is called reversible monsoon.

#### *3.1.4 Warm season*

The season varies from mid-September to mid-November and is characterized by pleasant weather with moderate temperature and low rainfall. As the thermal trough over northern Pakistan weakens, paralleling a decline in insulation, the flow of southwesterly equatorial air across Indo-Pakistan subcontinent and up to the Bay of Bengal likewise weakens; the ITC, as well as the paths of the monsoon depressions, retreats slowly southward; and rainfall declines in the north [7]. With this retreat of the equatorial westerly, a greater intrusion of the north Pacific trades into the Bay of Bengal and over Indo-Pakistan. By the late fall, the trough of low pressure, separating the easterly and westerly air currents, becomes established over the

**91**

*Environment, Agriculture, and Land Use Pattern DOI: http://dx.doi.org/10.5772/intechopen.83850*

the southwestern part of the Bay of Bengal.

**3.2 Climates of the arid region**

following micro-regions.

Pakistan is classified into the following subregions.

*3.2.1 Hot long summer and mild short winters (HsMw')*

Sea regenerating over coastal areas of Indo-Pakistan.

control of weather in northernmost India and Pakistan [13].

southern part of the Bay of Bengal and adjacent to southern Indo-Pakistan subcontinent. Along the discontinuity between the equatorial westerly and the zonal easterly, various kinds of perturbations develop ranging all the way from weak monsoon depressions to hurricanes. The depressions follow less well definite tracks than in summer, but in general, their progress is westward so that their rainfall effects are concentrated in coastal region of Pakistan, which lies in close juxtaposition to the earth's most active region of cool season tropical cyclogenesis, located in

Within Pakistan and India, severe hurricane storms are more numerous in this season particularly in the coastal region of Pakistan and Bay of Bengal. Some of these storms, in weakened form, appear to have the western north of the Arabian

During the fall months, the dynamic features of the circulation aloft, including jet stream and the orographically imposed troughs and ridges, begin to approach their cool season positions, with the reappearance, south of the mountainous north of Indo-Pakistan subcontinent in October or November of the middle latitude westerly and the jet stream, and the re-establishment of the polar front in the extreme northwest of Pakistan. The western disturbances once more become an important

In warm season, the temperature of the country falls below 30°C with low rainfall and humidity, moderate pressure and sunshine, high evapotranspiration, and gentle breeze. In these months the monsoon lows give way to those of winter currents (western depression), and most of the rains are caused by thunderstorms, which develop due to local low pressure, especially in mountainous areas. The retreat of monsoon from the north Arabian Sea is marked by disappearance of the stratus clouds with a gradual increase in daytime temperature over Sind-Makran coast [10]. The highest mean monthly total precipitation of the season is recorded at Sialkot, while the lowest is at Nok Kundi with highest relative humidity at Ormara and lowest at Chilas (Arid region). The highest temperature of the season marked at Las Bela with lowest at Astore. In warm season, the rainfall of Pakistan decreases from northeast to south, while the temperature decreases from south toward north.

The arid climate is characterized by low rainfall and covers a vast region in the southern as well as northern parts of Pakistan, where the annual total rainfall is between 0–10 inches. According to Hasan and Khan [12], the arid region of

The region is designated by hot and arid climates with mean temperature of the hottest month, June, above 32°C and warmest month, November, 10–21°C with average summer temperature more than 25°C. This climate type is divided into the

*3.2.1.1 Winter dry and summer rainfall with average day humidity of 55–60% (wx')*

The region consists of Hyderabad, Mirpur Khas, and parts of Dadu District. The annual total rainfall of the area is 5–10 inches with summer concentration and annual day relative humidity of 55–60%. The mean monthly evapotranspiration is 7.1 mm or 0.28 inches at Hyderabad with annual sunshine of 8.2 h/day. The subregion has long, hot, and moist summers and short, mild, and dry winters. The mean

#### *Environment, Agriculture, and Land Use Pattern DOI: http://dx.doi.org/10.5772/intechopen.83850*

*Climate Change and Agriculture*

September and October [12].

southward and is called reversible monsoon.

*3.1.4 Warm season*

southwest [12].

at Murree and lowest at Nok Kundi (arid region), with highest mean monthly humidity at Jiwani and lowest at Chilas. The lower Indus plain as well as Baluchistan (arid region) has recorded high temperatures, while the lowest is at Murree and the adjoining areas of Malakand and Mansehra divisions (humid region). The rainfall of Pakistan, in monsoon season, generally, decreases from northeast to

In Pakistan, the transition from the relatively dry and weather less spring to the cloudy, rainy season of summer, with its numerous perturbations, is abrupt and is usually associated with strongly disturbed weather. The so-called monsoon rains begin over Burma in May or even late April [13], but in Pakistan, they arrive from 15th of June in coastal areas, and the first week of July in mountainous north, and are well-established up to the mid-July in the whole country. Usually, the advance of the monsoon currents toward north over India and Pakistan is accompanied by turbulent weather in the form of thunderstorms, but its frequency decreases after the summer circulation is established. The monsoon begins to retreat from northern Pakistan in late August, and the withdrawal continues southward through

The later arrival of monsoon currents in Pakistan may result from the fact that during the winter and spring, there is an orographically determined upper trough, oriented Northsouth at about 85°E, over the western Bay of Bengal. It acts to accelerate the southwesterly monsoon flow over Burma located east of this trough while at the same time retarding it over Indo-Pakistan to the west [14]. As the subcontinent is heated intensively in April and May, the zonal westerly's over northern India and Pakistan begin to move northward, and it changes its direction under the influence of the mountain ranges, toward southwest. As a result, the jet stream, which had been south of the highland at about 30°N during winter and spring, tends to disappear and then reappear alternately south of the mountains. Disappearance becomes more frequent as the season advances, and each disappearance is associated with a northward surge of the summer monsoon. Finally, in late May or early June, the jet disappears completely over northern Pakistan and takes up a position at about 40°N of the Himalayas and Tibet. Simultaneously, there occurs a shift of the low-latitude trough and ridge positions, and the upper trough which previously was located at about 85°E quickly moves westward some 10° and takes up a position over western Indo-Pakistan subcontinent at approximately 75°E. With the disappearance of the jet over northern India and a westward shift of the upper trough, the equatorial westerly, or summer monsoon, surges northward over India accompanied by unsettled weather. The heating of the subcontinent and the development of a surface pressure trough are unable to produce a northward advance of the ITC until large-scale dynamic features of the circulation aloft become favorable [13]. When the jet stream reappears south of the Himalayas, again in fall, the summer monsoon again retreats

The season varies from mid-September to mid-November and is characterized by pleasant weather with moderate temperature and low rainfall. As the thermal trough over northern Pakistan weakens, paralleling a decline in insulation, the flow of southwesterly equatorial air across Indo-Pakistan subcontinent and up to the Bay of Bengal likewise weakens; the ITC, as well as the paths of the monsoon depressions, retreats slowly southward; and rainfall declines in the north [7]. With this retreat of the equatorial westerly, a greater intrusion of the north Pacific trades into the Bay of Bengal and over Indo-Pakistan. By the late fall, the trough of low pressure, separating the easterly and westerly air currents, becomes established over the

**90**

southern part of the Bay of Bengal and adjacent to southern Indo-Pakistan subcontinent. Along the discontinuity between the equatorial westerly and the zonal easterly, various kinds of perturbations develop ranging all the way from weak monsoon depressions to hurricanes. The depressions follow less well definite tracks than in summer, but in general, their progress is westward so that their rainfall effects are concentrated in coastal region of Pakistan, which lies in close juxtaposition to the earth's most active region of cool season tropical cyclogenesis, located in the southwestern part of the Bay of Bengal.

Within Pakistan and India, severe hurricane storms are more numerous in this season particularly in the coastal region of Pakistan and Bay of Bengal. Some of these storms, in weakened form, appear to have the western north of the Arabian Sea regenerating over coastal areas of Indo-Pakistan.

During the fall months, the dynamic features of the circulation aloft, including jet stream and the orographically imposed troughs and ridges, begin to approach their cool season positions, with the reappearance, south of the mountainous north of Indo-Pakistan subcontinent in October or November of the middle latitude westerly and the jet stream, and the re-establishment of the polar front in the extreme northwest of Pakistan. The western disturbances once more become an important control of weather in northernmost India and Pakistan [13].

In warm season, the temperature of the country falls below 30°C with low rainfall and humidity, moderate pressure and sunshine, high evapotranspiration, and gentle breeze. In these months the monsoon lows give way to those of winter currents (western depression), and most of the rains are caused by thunderstorms, which develop due to local low pressure, especially in mountainous areas. The retreat of monsoon from the north Arabian Sea is marked by disappearance of the stratus clouds with a gradual increase in daytime temperature over Sind-Makran coast [10]. The highest mean monthly total precipitation of the season is recorded at Sialkot, while the lowest is at Nok Kundi with highest relative humidity at Ormara and lowest at Chilas (Arid region). The highest temperature of the season marked at Las Bela with lowest at Astore. In warm season, the rainfall of Pakistan decreases from northeast to south, while the temperature decreases from south toward north.

#### **3.2 Climates of the arid region**

The arid climate is characterized by low rainfall and covers a vast region in the southern as well as northern parts of Pakistan, where the annual total rainfall is between 0–10 inches. According to Hasan and Khan [12], the arid region of Pakistan is classified into the following subregions.

#### *3.2.1 Hot long summer and mild short winters (HsMw')*

The region is designated by hot and arid climates with mean temperature of the hottest month, June, above 32°C and warmest month, November, 10–21°C with average summer temperature more than 25°C. This climate type is divided into the following micro-regions.

#### *3.2.1.1 Winter dry and summer rainfall with average day humidity of 55–60% (wx')*

The region consists of Hyderabad, Mirpur Khas, and parts of Dadu District. The annual total rainfall of the area is 5–10 inches with summer concentration and annual day relative humidity of 55–60%. The mean monthly evapotranspiration is 7.1 mm or 0.28 inches at Hyderabad with annual sunshine of 8.2 h/day. The subregion has long, hot, and moist summers and short, mild, and dry winters. The mean

#### *Climate Change and Agriculture*

monthly summer temperature exceeds 25°C, and the winter temperature is less than 15°C. June with mean temperature of above 32°C is the hottest month of the region, and January with mean temperature of less than 20°C is the coldest month. The mean monthly temperature of the area varies between 25°C and 30°C, with 35°C–40°C maxima and 10°C–15°C minima. The mean daily range is above 10°C, with 30–35°C daily maximum and 20°C–25°C daily minimum temperature.

The region is characterized by severe summers and moderate winters having 50°C ever recorded maximum temperature at Hyderabad in June, while the lowest minimum temperature of 1°C recorded in January. This subregion has 8.9 numbers of rainy days, while the average wind speed is 5.1 knots.

High-loam and clayey soil characterizes the zone with some pediment plain near the foothill of Kirthar mountains. High water table has caused waterlogging and salinization problems, depressing crop growth or making land unproductive for agriculture. However, areas having well-developed canal system and less salinization are characterized by intensive agriculture. Agriculture is the main activity in this zone, but there are also areas of rough grazing, riverine forests, and tracts of flooded backswamps. Wood resources come from riverine and thorn forests and trees of farmlands, much of which are used for firewood.

#### *3.2.1.2 Winter dry and summer rainfall with relative humidity of 60–65% (wv)*

The subregion includes Badin and northeastern part of Thatta. June is the hottest month with mean monthly temperature above 32°C, while January is the coldest month with mean temperature less than 20°C. The summers are hot, long, and moist, while the winters are short, mild, and dry. The area receives much of rainfall from monsoon lows particularly from the Arabian Sea branch. The annual total rainfall of the area is 5–10 inches with summer concentration, and average day relative humidity is 55–60%. The mean temperature of the region is 25°C–30°C, with 35°C–40°C maxima and 15°C–20°C minima. The mean daily range of temperature varies between 10°C and 15°C, with 30°C–35°C daily maximum and 15°C–20°C daily minimum temperature. The extreme maximum temperature of the subregion is 49.4°C recorded in June, and the lowest minimum is −2°C recorded in January. The annual evapotranspiration is 7 mm or 0.28 inches with annual sunshine of 8.2 h/day. The number of rainy days is 9.2 with average wind speed of 6.7 knots.

The region is characterized by sandy clayey soil, which is not suitable for agriculture, and therefore, the area has very little agriculture activities excluding those parts where water is easily available for irrigation. The water logging and salinization are the dominant factors of low agriculture production of the region. Vegetation resembles that of arid desert, with the addition of thorn scrub and light scrub forests. The land is mostly used for grazing of cattle, sheep, and goats. Moreover, the groundwater is acidic and is not suitable for drinking as well as vegetation growth.

#### *3.2.1.3 Uniform rains with summer concentration and relative humidity of 55–60% (Usx')*

Thal Desert and Dera Ismail Khan districts belong to this subregion, where the mean temperature of the coldest month that is January is above 10°C and hottest month that is June exceeds 32°C. The area receives both summer and winter rains, but the contribution of summer rains particularly from monsoon lows is high as compared to winter rainfall. The annual total rainfall of the region is 5–10 inches with average day relative humidity of 55–60%. The evapotranspiration of the region is 4.3 mm or 0.17 inches with annual sunshine of 8.4 h/day, which makes the summer of the region hottest as compared to the adjoining regions. The mean temperature

**93**

*Environment, Agriculture, and Land Use Pattern DOI: http://dx.doi.org/10.5772/intechopen.83850*

grazing land for livestock.

humidity of 45–50%.

of the subregion particularly at Dera Ismail Khan is 20°C–25°C, with 36.7°C maxima and 13°C minima. The area has high range of temperature both in summer and in winter seasons. The annual range of temperature is 10°C–15°C, with 30°C–35°C as the mean daily maximum and 15°C–20°C as the daily minimum temperature. The extreme maximum temperature of the region is 50°C, recorded in May, the hottest month of the region, while the lowest minimum temperature is −3°C, recorded in January. The number of rainy days is 18.2 with average wind speed of 2 knots.

The area is characterized by low agriculture practices due to nonavailability of water and poor soil. In some areas of Dera Ismail Khan, soil is fertile and having good agriculture, while most of the Thal Desert has sandy soil with some loams. The summer's "loo*"* (hot wind) is the important characteristic of the region, which not only increases the temperature of the region but also affects plant growth and its production, due to high evapotranspiration. The area has subtropical thorn forests with some irrigated plantation near canal banks and is used, in general, as a

*3.2.1.4 Summer dry and winter rainfall with average relative humidity of 45–50% (sy')*

Panjgur and Turbat (Baluchistan) are included in this subregion, where the summers are long and dry, while the winters are short and moist. The annual total rainfall is less than 5 inches with winter concentration particularly from western disturbances. The area has severe summers and mild winters. The mean temperature varies between 20°C and 25°C, with 30°C–35°C maxima and 5°C–10°C minima. The mean daily range exceeds 15°C, with 25°C–30°C daily maximum and 10°C–15°C daily minimum temperature. The ever-recorded maximum temperature of the region is 45°C, recorded in June, the hottest month, while the lowest minimum temperature is −7.8°C, recorded in December, the coldest month of the year. The number of rainy days of the area is 10.2, while the wind speed is 4.5 knots with average day relative

Hot arid desert covers the area in the border with Iran and areas near the Makran coast. The soil of the area is sandy with sand dunes, badly eroded by running water. Vegetation is closely related to soil moisture, with grass along "nullah" (seasonal rivers) and on piedmont plain, associated with small trees and shrubs. The main species are *Pistacia* spp. and *Quercus ilex* with evergreen oaks occurring above 1200 m. Woodlands here provide fuel wood, nuts, fruits, and brows for camels.

The land is used mainly for grazing. Pockets of cultivation are fed by water from karez system or spate irrigation along rivers. Vegetation is extremely variable, from completely barren ground to medium-density shrub and tree cover. Any wellwatered land is cultivated, and all the vegetation are grazed, browsed, or cut for

It is generally characterized by warm desert, where the June temperature exceeds 32°C, while the mean January temperature is between 0°C and 10°C with mean summer temperature of above 25°C. It is further divided into the following subregions [12].

Parts of Chaghi and Kharan districts (Nok Kundi) belong to this region, where the annual total rainfall is less than 5 inches. The lowest rainfall of

*3.2.2.1 Summer dry and winter rainfall with average day relative humidity* 

Wetter areas have relatively good grazing for livestock.

domestic requirements, particularly near urban centers.

*3.2.2 Hot long summer and cool short winters (HsCw')*

*of 30–35% (sz)*

#### *Environment, Agriculture, and Land Use Pattern DOI: http://dx.doi.org/10.5772/intechopen.83850*

*Climate Change and Agriculture*

monthly summer temperature exceeds 25°C, and the winter temperature is less than 15°C. June with mean temperature of above 32°C is the hottest month of the region, and January with mean temperature of less than 20°C is the coldest month. The mean monthly temperature of the area varies between 25°C and 30°C, with 35°C–40°C maxima and 10°C–15°C minima. The mean daily range is above 10°C, with 30–35°C daily maximum and 20°C–25°C daily minimum temperature.

The region is characterized by severe summers and moderate winters having 50°C ever recorded maximum temperature at Hyderabad in June, while the lowest minimum temperature of 1°C recorded in January. This subregion has 8.9 numbers

High-loam and clayey soil characterizes the zone with some pediment plain near the foothill of Kirthar mountains. High water table has caused waterlogging and salinization problems, depressing crop growth or making land unproductive for agriculture. However, areas having well-developed canal system and less salinization are characterized by intensive agriculture. Agriculture is the main activity in this zone, but there are also areas of rough grazing, riverine forests, and tracts of flooded backswamps. Wood resources come from riverine and thorn forests and

The subregion includes Badin and northeastern part of Thatta. June is the hottest month with mean monthly temperature above 32°C, while January is the coldest month with mean temperature less than 20°C. The summers are hot, long, and moist, while the winters are short, mild, and dry. The area receives much of rainfall from monsoon lows particularly from the Arabian Sea branch. The annual total rainfall of the area is 5–10 inches with summer concentration, and average day relative humidity is 55–60%. The mean temperature of the region is 25°C–30°C, with 35°C–40°C maxima and 15°C–20°C minima. The mean daily range of temperature varies between 10°C and 15°C, with 30°C–35°C daily maximum and 15°C–20°C daily minimum temperature. The extreme maximum temperature of the subregion is 49.4°C recorded in June, and the lowest minimum is −2°C recorded in January. The annual evapotranspiration is 7 mm or 0.28 inches with annual sunshine of 8.2 h/day. The number of rainy days is 9.2 with average wind speed of 6.7 knots. The region is characterized by sandy clayey soil, which is not suitable for agriculture, and therefore, the area has very little agriculture activities excluding those parts where water is easily available for irrigation. The water logging and salinization are the dominant factors of low agriculture production of the region. Vegetation resembles that of arid desert, with the addition of thorn scrub and light scrub forests. The land is mostly used for grazing of cattle, sheep, and goats. Moreover, the groundwa-

*3.2.1.2 Winter dry and summer rainfall with relative humidity of 60–65% (wv)*

ter is acidic and is not suitable for drinking as well as vegetation growth.

*3.2.1.3 Uniform rains with summer concentration and relative humidity of* 

Thal Desert and Dera Ismail Khan districts belong to this subregion, where the mean temperature of the coldest month that is January is above 10°C and hottest month that is June exceeds 32°C. The area receives both summer and winter rains, but the contribution of summer rains particularly from monsoon lows is high as compared to winter rainfall. The annual total rainfall of the region is 5–10 inches with average day relative humidity of 55–60%. The evapotranspiration of the region is 4.3 mm or 0.17 inches with annual sunshine of 8.4 h/day, which makes the summer of the region hottest as compared to the adjoining regions. The mean temperature

of rainy days, while the average wind speed is 5.1 knots.

trees of farmlands, much of which are used for firewood.

**92**

*55–60% (Usx')*

of the subregion particularly at Dera Ismail Khan is 20°C–25°C, with 36.7°C maxima and 13°C minima. The area has high range of temperature both in summer and in winter seasons. The annual range of temperature is 10°C–15°C, with 30°C–35°C as the mean daily maximum and 15°C–20°C as the daily minimum temperature. The extreme maximum temperature of the region is 50°C, recorded in May, the hottest month of the region, while the lowest minimum temperature is −3°C, recorded in January. The number of rainy days is 18.2 with average wind speed of 2 knots.

The area is characterized by low agriculture practices due to nonavailability of water and poor soil. In some areas of Dera Ismail Khan, soil is fertile and having good agriculture, while most of the Thal Desert has sandy soil with some loams. The summer's "loo*"* (hot wind) is the important characteristic of the region, which not only increases the temperature of the region but also affects plant growth and its production, due to high evapotranspiration. The area has subtropical thorn forests with some irrigated plantation near canal banks and is used, in general, as a grazing land for livestock.

### *3.2.1.4 Summer dry and winter rainfall with average relative humidity of 45–50% (sy')*

Panjgur and Turbat (Baluchistan) are included in this subregion, where the summers are long and dry, while the winters are short and moist. The annual total rainfall is less than 5 inches with winter concentration particularly from western disturbances. The area has severe summers and mild winters. The mean temperature varies between 20°C and 25°C, with 30°C–35°C maxima and 5°C–10°C minima. The mean daily range exceeds 15°C, with 25°C–30°C daily maximum and 10°C–15°C daily minimum temperature. The ever-recorded maximum temperature of the region is 45°C, recorded in June, the hottest month, while the lowest minimum temperature is −7.8°C, recorded in December, the coldest month of the year. The number of rainy days of the area is 10.2, while the wind speed is 4.5 knots with average day relative humidity of 45–50%.

Hot arid desert covers the area in the border with Iran and areas near the Makran coast. The soil of the area is sandy with sand dunes, badly eroded by running water. Vegetation is closely related to soil moisture, with grass along "nullah" (seasonal rivers) and on piedmont plain, associated with small trees and shrubs. The main species are *Pistacia* spp. and *Quercus ilex* with evergreen oaks occurring above 1200 m. Woodlands here provide fuel wood, nuts, fruits, and brows for camels. Wetter areas have relatively good grazing for livestock.

The land is used mainly for grazing. Pockets of cultivation are fed by water from karez system or spate irrigation along rivers. Vegetation is extremely variable, from completely barren ground to medium-density shrub and tree cover. Any wellwatered land is cultivated, and all the vegetation are grazed, browsed, or cut for domestic requirements, particularly near urban centers.

#### *3.2.2 Hot long summer and cool short winters (HsCw')*

It is generally characterized by warm desert, where the June temperature exceeds 32°C, while the mean January temperature is between 0°C and 10°C with mean summer temperature of above 25°C. It is further divided into the following subregions [12].

#### *3.2.2.1 Summer dry and winter rainfall with average day relative humidity of 30–35% (sz)*

Parts of Chaghi and Kharan districts (Nok Kundi) belong to this region, where the annual total rainfall is less than 5 inches. The lowest rainfall of

Pakistan that is 1.4 inches has been recorded in this region, and the average day relative humidity varies between 30 and 35%. The area receives more rains in winter season, while the summer season is dry, with two dry spells in a year: the first is from mid-April to June, while the second is from mid-September to mid-December. The summers are long and hot, while the winters are moist and cool. The annual evapotranspiration is 5.4 mm or 0.22 inches with mean sunshine duration of 8.5 h/day. The mean temperature of the region is 20°C–25°C, with 35°C–40°C maxima and 10°C–15°C minima. The mean daily range is above 15°C with mean daily maximum temperature of 30°C–35°C and with a daily minimum above 15°C. The number of rainy days of the subregion is 4 with annual wind speed of 7.6 knots. The ever-recorded maximum temperature exceeds 45°C in June, while the lowest minimum temperature is less than −10°C in December, due to cold Siberian currents.

The soil of the region is sandy with arid piedmont plain and barren Chaghi hills. It constitutes as the western Baluchistan rangelands. The land is used, in general, for grazing, but some patches of cultivated land are also located in the karez-fed areas. The land is badly eroded by geomorphic agents due to sparse vegetation. Vegetation varies from barren ground and mountains to medium-density scrubs and trees, with acacia and jajoba as the main species. The forests are mostly used for domestic purposes and browsed for camels.

### *3.2.2.2 Summer dry and winter rainfall with average day relative humidity of 35–40% (sz')*

Parts of Kharan and Chaghi districts (Dalbandin) are the specific areas of the region. The summers are long and dry, while the winters are short and moist. The area receives most of the rains in winter from western disturbances with annual total rainfall below 5 inches. The evapotranspiration of the area is 5.1 mm or 0.2 inches with annual sunshine duration of 8.6 h/day and the average day relative humidity of 35–40%. The mean monthly temperature of the area is 20°C–25°C, with mean maximum temperature of 35°C–40°C and minimum temperature of 5°C–10°C. The annual daily range varies between 15 and 20°C with mean daily maxima of 30°C–35°C and mean daily minima of 10°C–20°C. The highest maximum temperature of the area is above 50°C, recorded in June, and the lowest is below 10°C, recorded in December, due to Siberian cold winds. The number of rainy days of the area is 8.7, and the average wind speed is 3.2 knots.

The physiography and soil of the land are the same pattern as given in 2.1. subregion. However, the area is badly eroded and having barren mountains, particularly the Chaghi hills. Most of the areas near Dalbandin are piedmont plain, while toward south, the area is sandy, and sandy dunes cover a vast area with scrubs and bushes. The land is mostly used for grazing and browsed for camels. Due to sandy soil, agriculture practices are confined to isolated patches in the area. The barren Chaghi hills increase the daytime temperature while decrease the nighttime temperature of the region due to high absorption, deflection, reflection, and releasing of solar energy.

#### *3.2.3 Hot long summer and short warm winters (HsWw')*

The region is a hot desert, where mean temperature of the hottest month June is above 35°C and that of coldest month January is between 21°C and 32°C. The mean summer temperature of the area exceeds 25°C. It is further divided into the following sub-climatic regions [12].

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patches of land.

*Environment, Agriculture, and Land Use Pattern DOI: http://dx.doi.org/10.5772/intechopen.83850*

whereas January is the coldest month of the region.

and the area continuously going toward severe aridity.

January, the coldest month of the region.

(India), sand ridges, inter-dune valleys, and saline lakes and flats.

*3.2.3.2 Winter dry and summer rainfall with relative humidity 40–45% (wy)*

Kach-Sibi areas fall in this region. It has hot long moist summers and warm short dry winters. The mean annual total rainfall of the area varies between 5 and 10 inches, with average day relative humidity of 40–45%. The mean annual evapotranspiration of the region is 4 mm or 0.16 inches, with mean sunshine duration of 8.2 h/day, number of rainy days 12.1, and wind speed of 2.9 knots. The mean temperature of the area is 25°C–30°C, with 30°C–35°C maxima and 10°C–15°C minima. The mean daily range of temperature varies between 15 and 20°C, with 35–40°C daily maximum and 15°C–20°C daily minimum. In Sibi, more than 50°C maximum temperature has been recorded for three times in June, making it the hottest region of the country. The lowest minimum temperature of the area is −3.3°C, recorded in

Aridity prevail the whole region, with less fertile sandy soil. Kachhi plain is a desert, with no vegetation. However, in the irrigated areas, the natural vegetation in general is xerophytes with shrubs and grasslands, with medium size trees. The area is mostly used for grazing, where there are karezes and there are some agriculture

The region consists of Khanpur and the upper irrigated Sind. The annual total rainfall of the region is less than 5 inches with annual day relative humidity of 55–60%. The summers are long hot and moist, while the winters are warm short and dry. The annual evapotranspiration is 6.7 mm or 0.27 inches (Jacobabad),

*3.2.3.3 Winter dry and summer rainfall with relative humidity of 50–55% (wx)*

*55–60% (wx')*

*3.2.3.1 Winter dry and summer rainfall, with average day relative humidity of* 

Bahawalpur, Bahawalnagar, Mianwali, and Multan districts are included in this region. The area is characterized by hot long moist summers and short warm dry winters. The annual total rainfall varies between 5 and 10 inches with average day relative humidity of 55–60%. The mean evapotranspiration of the region is 5.5 mm or 0.22 inches, with annual sunshine of 8–10 h/day. The number of rainy days is 10–15, while the wind speed is 2–4 knots. The mean monthly temperature ranges between 25°C and 30°C, with 35°C–40°C maxima and 10°C–20°C minima. The mean daily range of temperature is 10°C–15°C, with 30–35°C daily maximum and 15–20°C daily minimum. The extreme maximum temperature of the region varies between 45°C and 51°C, recorded in May and June, while the lowest minimum temperature is 0°C to −5°C, recorded in January. May and June are the hottest months,

It is the extension of the Rajasthan Desert, but due to well-developed canal system, intensive agriculture is practiced in parts of the region. The area has sandy soil, but alluvial soil has also developed near the banks of Indus and its tributaries. The eastern part of the region has sandy loams with terraces of the "Hakra River"

Natural vegetation comprises xerophytic trees, shrubs, and grasses, but some irrigated plantations have also been grown along the river−/canal banks. The pressure on these limited tracts of shrubs vegetation from fuel woodcutters is intense. Land, otherwise, is used only for livestock production, hunting, and agriculture. Due to rapid deforestation, temperature of the region increases with passage of time *Climate Change and Agriculture*

to cold Siberian currents.

purposes and browsed for camels.

*of 35–40% (sz')*

and releasing of solar energy.

ing sub-climatic regions [12].

Pakistan that is 1.4 inches has been recorded in this region, and the average day relative humidity varies between 30 and 35%. The area receives more rains in winter season, while the summer season is dry, with two dry spells in a year: the first is from mid-April to June, while the second is from mid-September to mid-December. The summers are long and hot, while the winters are moist and cool. The annual evapotranspiration is 5.4 mm or 0.22 inches with mean sunshine duration of 8.5 h/day. The mean temperature of the region is 20°C–25°C, with 35°C–40°C maxima and 10°C–15°C minima. The mean daily range is above 15°C with mean daily maximum temperature of 30°C–35°C and with a daily minimum above 15°C. The number of rainy days of the subregion is 4 with annual wind speed of 7.6 knots. The ever-recorded maximum temperature exceeds 45°C in June, while the lowest minimum temperature is less than −10°C in December, due

The soil of the region is sandy with arid piedmont plain and barren Chaghi hills. It constitutes as the western Baluchistan rangelands. The land is used, in general, for grazing, but some patches of cultivated land are also located in the karez-fed areas. The land is badly eroded by geomorphic agents due to sparse vegetation. Vegetation varies from barren ground and mountains to medium-density scrubs and trees, with acacia and jajoba as the main species. The forests are mostly used for domestic

Parts of Kharan and Chaghi districts (Dalbandin) are the specific areas of the region. The summers are long and dry, while the winters are short and moist. The area receives most of the rains in winter from western disturbances with annual total rainfall below 5 inches. The evapotranspiration of the area is 5.1 mm or 0.2 inches with annual sunshine duration of 8.6 h/day and the average day relative humidity of 35–40%. The mean monthly temperature of the area is 20°C–25°C, with mean maximum temperature of 35°C–40°C and minimum temperature of 5°C–10°C. The annual daily range varies between 15 and 20°C with mean daily maxima of 30°C–35°C and mean daily minima of 10°C–20°C. The highest maximum temperature of the area is above 50°C, recorded in June, and the lowest is below 10°C, recorded in December, due to Siberian cold winds. The number of rainy days

The physiography and soil of the land are the same pattern as given in 2.1. subregion. However, the area is badly eroded and having barren mountains, particularly the Chaghi hills. Most of the areas near Dalbandin are piedmont plain, while toward south, the area is sandy, and sandy dunes cover a vast area with scrubs and bushes. The land is mostly used for grazing and browsed for camels. Due to sandy soil, agriculture practices are confined to isolated patches in the area. The barren Chaghi hills increase the daytime temperature while decrease the nighttime temperature of the region due to high absorption, deflection, reflection,

The region is a hot desert, where mean temperature of the hottest month June is above 35°C and that of coldest month January is between 21°C and 32°C. The mean summer temperature of the area exceeds 25°C. It is further divided into the follow-

*3.2.2.2 Summer dry and winter rainfall with average day relative humidity* 

of the area is 8.7, and the average wind speed is 3.2 knots.

*3.2.3 Hot long summer and short warm winters (HsWw')*

**94**
