**1. Introduction**

166 Solar Radiation

Kato, O. and Seguchi, M. (2001). The flow features and forming process of tidal flat in Ariake

Moqsud, M.A., Hayashi, S., Du, Y.J. and Suetsugu D. (2007). Impacts of acid treatment

Moqsud M.A., Hayashi S., Du Y.J., Suetsugu D., Ushihara Y., Tanaka S. and Okuzono K.

Japan." The 21st ICSW, March 26-29.,Philadelphia, USA. 2006, pp.436-445. Moqsud M. A., Hayashi S., Du Y. J., Suetsugu D."Evaluation of thermal properties of the

Nassar IN, Horton R,Flerchinger GN (2000) Simultaneous heat and mass transfer in soil columns exposed to freezing/thawing conditions. Soil Sci. 165 (3): 208-216. Naidu A. and Singh D.. "A generalized procedure for determining thermal resistivity of soils." International Journal of thermal Sciences. Vol.43, 2004, pp. 43-51. Ochsner T E., Horton R.,Ren T. "A new perspective on soil thermal properties." Soil science

Rickard, D. and Morse, J.W. (2005). Acid volatile sulfide (AVS). Marine chemistry, 97:141-

Sorensen, J. and Jorgenson, B.B. (1987). Early diagnosis in sediments from Danish coastal

Wierenga P J., Nielsen D.R and Hagan R M. "Thermal properties of soil based upon field

Wu, S.S., Tsutsumi, H., Kita-Tsukamoto, K., Kogure, K., Ohwada, K. and Wada, M. (2003).

Yadav M R and Saxena G S.. "Effect of compaction and moisture content on specific heat

Yadav M R and Saxena G S.. "Effect of compaction and moisture content on specific heat

Yang-Ki C., Kim T., You,K.,Park,L., Moon, H., Lee,S.,Youn, Y., (2005). "Temporal and spatial

water: microbial activity and Mn-Fe-S geochemistry. Geochimica et Cosmochimica

and laboratory measurements". Soil science society of America Journal, Vol.33,

Visualization of the respiring bacteria in sediments inhabited by *Capitella* sp.1.

and thermal capacity of soils". Journal of Indian society of soil science, Vol.21,

and thermal capacity of soils". Journal of Indian society of soil science, Vol.21,

variability in the sediment temperature on the Baeksu tidal flat,Korea." *Estuarine* 

management of enclosed coastal seas. EMECS 2001, 6-368.

Southeast Asian geotechnical society, 38 (2): 79-86.

September 14-16. (2006 a )Saga, Japan, pp. 263-268.

society of America Journal, Vol. 65, 2001, pp.1641-1647.

197.

Acta, 51: 1883-1890.

1969, pp. 354-360.

1973,pp. 129

1973,pp. 129

Fisheries Research, 69:170-175.

*coastal and shelf science*, Vol. 65, pp. 302-308.

Sea. A report on the fifth international conference on the environmental

practice on geo-environmental conditions in the Ariake Sea, Japan. Journal of

"Effects of acid treatment on geo-environmental conditions in the Ariake Sea,

mud of the Ariake Sea." International symposium on lowland technology,

Solar radiation is the set of electromagnetic radiation emitted by the Sun. The Sun behaves almost like a black body which emits energy according to Planck's law at a temperature of 6000 K. The solar radiation ranges goes from infrared to ultraviolet. Not all the radiation reaches Earth's surface, because the ultraviolet wavelengths, that are the shorter wavelengths, are absorbed by gases in the atmosphere, primarily by ozone.

The atmosphere acts as a filter to the bands of solar spectrum, and at its different layers as solar radiation passes through it to the Earth's surface, so that only a fraction of it reaches the surface. The atmosphere absorbs part of the radiation reflects and scatters the rest some directly back to space, and some to the Earth, and then it is irradiated. All of this produce a thermal balance, resulting in radiant equilibrium cycle (figure 1).

Fig. 1. Effects of clouds on the Earth's Energy Budget. This image is from a NASA site

Depending on the type of radiation, it is known that the 324 Wm-2 reaching the Earth in the upper atmosphere (1400 Wm-2 is the solar constant), 236 Wm-2 are reissued into space infrared radiation, 86 Wm-2 are reflected by the clouds and 20 Wm-2 are reflected by the ground as short-wave radiation. But part of the re-emitted energy is absorbed by the atmosphere and returned to the earth surface, causing the "greenhouse effect".

The average energy that reaches the outside edge of the atmosphere from the sun is a fixed amount, called solar constant. The energy contains between the 200 and 4000 nm wavelengths and it is divided into ultraviolet radiation, visible light and infrared radiation.

Ultraviolet radiation: Consists of the shorter wavelengths band (360 nm), it has a lot of energy and interacts with the molecular bonds. These waves are absorbed by the upper atmosphere, especially by the ozone layer.

Visible Light: This radiation band corresponds to the visible area with wavelengths between 360 nm (violet) and 760 nm (red), it has a great influence on living beings.

Infrared radiation: Consists of wavelengths between 760 and 4000 nm, it corresponds to the longer wavelengths and it has little energy associated with it. Its absorption increases molecular agitation, causing the increase of temperature.

Fig. 2. Spectrum of solar radiation above the atmosphere and sea level. prepared by Robert A. Rohde as part of the Global Warming Art project

Solar radiation on the earth can be classified as:

Direct radiation: This radiation comes directly from the sun without any change in its direction. This type of radiation is characterized by projecting defined shadow onto the objects that intersect.

Depending on the type of radiation, it is known that the 324 Wm-2 reaching the Earth in the upper atmosphere (1400 Wm-2 is the solar constant), 236 Wm-2 are reissued into space infrared radiation, 86 Wm-2 are reflected by the clouds and 20 Wm-2 are reflected by the ground as short-wave radiation. But part of the re-emitted energy is absorbed by the

The average energy that reaches the outside edge of the atmosphere from the sun is a fixed amount, called solar constant. The energy contains between the 200 and 4000 nm wavelengths and it is divided into ultraviolet radiation, visible light and infrared radiation. Ultraviolet radiation: Consists of the shorter wavelengths band (360 nm), it has a lot of energy and interacts with the molecular bonds. These waves are absorbed by the upper

Visible Light: This radiation band corresponds to the visible area with wavelengths between

Infrared radiation: Consists of wavelengths between 760 and 4000 nm, it corresponds to the longer wavelengths and it has little energy associated with it. Its absorption increases

Fig. 2. Spectrum of solar radiation above the atmosphere and sea level. prepared by Robert

Direct radiation: This radiation comes directly from the sun without any change in its direction. This type of radiation is characterized by projecting defined shadow onto the

atmosphere and returned to the earth surface, causing the "greenhouse effect".

360 nm (violet) and 760 nm (red), it has a great influence on living beings.

molecular agitation, causing the increase of temperature.

A. Rohde as part of the Global Warming Art project

Solar radiation on the earth can be classified as:

objects that intersect.

atmosphere, especially by the ozone layer.

Diffuse radiation: This radiation comes from all over the atmosphere as a result of reflection and scattering by clouds, particles in the atmosphere, dust, mountains, trees, buildings, the ground itself, and so on. Global radiation: Is the total radiation. It is the sum of the two radiations above. On a clear day with a clear sky, the direct radiation is predominant above the diffuse radiation.

Animals with thermoregulatory abilities and mobility can seek or avoid certain features of current weather. In contrast, terrestrial plants are rooted in place and must accept that the rates of their metabolic processes are determined by the ambient conditions.

Crop communities exert a strong influence over their local microenvironment. Nearly all cropping practices are geared toward, or have the effect of, modifying chemical and physical aspects of that environment (aerial and soils properties).

One of the most important factors that influences plants development is the solar radiation intercepted by the crop. The solar radiation brings energy to the metabolic process of the plants. The principal process is the photosynthetic assimilation that makes synthesize vegetal components from water, CO2 and the light energy possible. A part of this, energy is used in the evaporation process inside the different organs of the plants, and also in the transpiration through the stomas.

Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Depending on how carbon dioxide is fixed the plants can be grouped into three types: C3, C4, and CAM. The C3 plants are the more usual superior plants, which are the temperate weather crops (wheat, barley and sunflower, etc); the C4 category are species from arid weathers or hotter or tropical weathers (corn, sugar or sorghum). The C3 type are generally considered less productive than C4 (figure 3).

Fig. 3. Typical theorized relationships between cumulated aboveground biomass and cumulated intercepted solar radiation for C4 and C3 species. From Gosse et al. 1986.

One difference lies in the fact that photorespiration is very active in C3 plants. The photorespiration makes plants increase the oxygen consumption when they are illuminated by the sun, and this is very important for agriculture in temperate zones. In a hot day with no wind, the CO2 concentration in the plant decreases considerably for photosynthesis consumption, therefore, the relationship between carbon and oxygen decreases, and the CO2 fixation increases the photorespiration.
