**3. Results and discussion**

#### **3.1. Precipitation and evapotranspiration in São Paulo State between 2000 and 2010**

**Figure 2** shows the spatial distribution of monthly average precipitation (January to De‐ cember) in SP between 2000 and 2010 obtained from TRMM satellite data.

**Figure 2.** Spatial distribution of monthly average precipitation (mm month−1) in SP for the period between 2000 and 2010.

Generally, it is noted that images from January to March and from October to December show higher precipitation as compared to April to September. This reflects the well‐defined rainfall regime in SP: the rainy season (October to March) and the dry season (April to Sep‐ tember) [30]. It is possible to note that in most of the year highest values of precipitation are located in the Coastal Plain and Serra do Mar regions. This dynamic is associated to frontal systems (cold fronts) and the South Atlantic Convergence Zone (SACZ), which oc‐ cur during the year in SP and act mainly in the areas near the coast, as well as the fact that the Serra do Mar conditions the formation of orographic rainfall through the condensation of humid winds from the ocean [31]. In contrast, lower values of precipitation are observed over the year in the Western Plateau region, where organized local convection is the main source of rainfall [32].

( ) <sup>2</sup> <sup>0</sup><sup>η</sup> <sup>2</sup> <sup>1</sup> <sup>η</sup> <sup>4</sup> <sup>η</sup> *<sup>i</sup> e e* w p

98 Tropical Forests - The Challenges of Maintaining Ecosystem Services while Managing the Landscape

**3.1. Precipitation and evapotranspiration in São Paulo State between 2000 and 2010**

cember) in SP between 2000 and 2010 obtained from TRMM satellite data.

**Figure 2** shows the spatial distribution of monthly average precipitation (January to De‐

**Figure 2.** Spatial distribution of monthly average precipitation (mm month−1) in SP for the period between 2000 and

Generally, it is noted that images from January to March and from October to December show higher precipitation as compared to April to September. This reflects the well‐defined rainfall regime in SP: the rainy season (October to March) and the dry season (April to Sep‐ tember) [30]. It is possible to note that in most of the year highest values of precipitation are located in the Coastal Plain and Serra do Mar regions. This dynamic is associated to frontal systems (cold fronts) and the South Atlantic Convergence Zone (SACZ), which oc‐ cur during the year in SP and act mainly in the areas near the coast, as well as the fact that the Serra do Mar conditions the formation of orographic rainfall through the condensation of humid winds from the ocean [31]. In contrast, lower values of precipitation are observed

remnants.

2010.

**3. Results and discussion**


where *η* is the dimensionless time parameter, and *ω*0 represents the dimensionless frequency. Here, it is important to point out that Torrence and Compo algorithm was compiled in MATLAB version 7.9.0 and that the analysis was performed exclusively for forest remnants of Atlantic Rainforest. Therefore, values used to generate wavelets referred to the monthly average precipitation (TRMM) and evapotranspiration (MOD16) in the analyzed forest

Y = (2)

**Figure 3** shows the monthly precipitation in SP between 2000 and 2010. Monthly precipitation ranged between 4.3 (August 2004) and 386.9 mm month−1 (January 2003), which indicates an absolute variation of 382.6 mm month−1. On average, monthly precipitation between 2000 and 2010 was 128.9 mm month−1.

**Figure 3.** Monthly precipitation (mm month−1) in SP between January of 2000 and December 2010. The red line repre‐ sents the moving average of the time series (period = 2).

Average monthly precipitation ranged from 35.8 to 298.5 mm month−1, where June is the driest month and January is the wettest. This result is observed in the January and June images shown in **Figure 2**. These two images differ significantly when compared to the other images, especially the image of January, since the image of June has some resemblance to the image of August. In June, it is possible to note that most of precipitation is lower than 48 mm month−1, except in the Southern region, where values close to 76 mm month−1 were found. Regarding to the image of January, most of precipitation is higher than 300 mm month−1, except in the western edge of the state, where values of ~216 mm month−1 were found.

Analysis of the dry season (April to September) and the rainy season (October to March) has revealed that the average monthly precipitation was, respectively, 64.5 and 193.2 mm month−1. Therefore, average month precipitation in the rainy season was ~200% higher than the observed average in the dry season. Annual precipitation in São Paulo State ranged between 1403.5 and 2029.5 mm year−1. In this sense, 2002 was the least rainy year, while 2009 was the most rainy year. Average annual precipitation was 1546.5 mm year−1, with ~25% of that occurring in the months corresponding to the dry season and ~75% of the average annual precipitation in the months corresponding to the rainy season. Monthly precipitation in 2002 ranged between 10.4 (June) and 267.8 mm month−1 (January), while in 2009 monthly precipi‐ tation ranged from 62.4 (June) to 314.7 mm month−1 (January).

It is important to note that TRMM satellite estimates were not validated in this study. In this context, researches present in literature suggest relative errors ranging from ~5 [33] to ~25% [34]. Still, it is noted that the results regarding the precipitation regime in SP are consistent with several observation meteorological studies conducted in the state, such as [35, 36].

**Figure 4** shows the spatial distribution of monthly average actual evapotranspiration (Janu‐ ary to December) in São Paulo State between 2000 and 2010, derived from MOD16 algo‐ rithm.

**Figure 4.** Spatial distribution of monthly average actual evapotranspiration (mm month−1) in SP corresponding to the period between 2000 and 2010.

Visual inspection of **Figure 4** reveals a spatial and temporal pattern for evapotranspiration similar to the one found in precipitation (**Figure 2**). However, evapotranspiration images provide a better perception of subtle changes along the state. Generally, images corresponding to the rainy season have higher values for evapotranspiration when compared to images of the dry season. Evaporation depends on variation in solar radiation, local atmospheric circulation process, which regulates the precipitation system and air and soil moisture conditions, and vegetation conditions, which show considerable changes following the rainy or dry season [37]. Among these conditions, solar radiation stands out, whose incident amount depends, among other factors, on the season [38]. Therefore, this pattern is expected because highest incidence of solar radiation occurs during the rainy season [39]. It is also worth mentioning that throughout the year highest values of evapotranspiration are located in the southern and eastern SP, while lowest values are situated in the northern and western regions of the state.

**Figure 5** shows monthly average actual evapotranspiration in SP between 2000 and 2010. Monthly evapotranspiration varied between 26.1 and 116.8 mm month−1, representing an absolute variation of 90.7 mm month−1. Accordingly, lowest monthly value was found in July 2000 and the highest in January 2003. Considering the period between 2000 and 2010, monthly evapotranspiration corresponded, on average, to 68.2 mm month−1.

Analysis of Precipitation and Evapotranspiration in Atlantic Rainforest Remnants in Southeastern Brazil from... http://dx.doi.org/10.5772/64533 101

**Figure 4** shows the spatial distribution of monthly average actual evapotranspiration (Janu‐ ary to December) in São Paulo State between 2000 and 2010, derived from MOD16 algo‐

100 Tropical Forests - The Challenges of Maintaining Ecosystem Services while Managing the Landscape

**Figure 4.** Spatial distribution of monthly average actual evapotranspiration (mm month−1) in SP corresponding to the

Visual inspection of **Figure 4** reveals a spatial and temporal pattern for evapotranspiration similar to the one found in precipitation (**Figure 2**). However, evapotranspiration images provide a better perception of subtle changes along the state. Generally, images corresponding to the rainy season have higher values for evapotranspiration when compared to images of the dry season. Evaporation depends on variation in solar radiation, local atmospheric circulation process, which regulates the precipitation system and air and soil moisture conditions, and vegetation conditions, which show considerable changes following the rainy or dry season [37]. Among these conditions, solar radiation stands out, whose incident amount depends, among other factors, on the season [38]. Therefore, this pattern is expected because highest incidence of solar radiation occurs during the rainy season [39]. It is also worth mentioning that throughout the year highest values of evapotranspiration are located in the southern and eastern SP, while lowest values are situated in the northern and western regions

**Figure 5** shows monthly average actual evapotranspiration in SP between 2000 and 2010. Monthly evapotranspiration varied between 26.1 and 116.8 mm month−1, representing an absolute variation of 90.7 mm month−1. Accordingly, lowest monthly value was found in July 2000 and the highest in January 2003. Considering the period between 2000 and 2010, monthly

evapotranspiration corresponded, on average, to 68.2 mm month−1.

rithm.

period between 2000 and 2010.

of the state.

**Figure 5.** Monthly actual evapotranspiration (mm month−1) in SP between January of 2000 and December 2010. The red line represents the moving average of the time series (period = 2).

The months of August and January presented, respectively, lowest and highest monthly average evapotranspiration (values of 36.6 and 107.1 mm month−1). Relating precipitation and evapotranspiration, it denotes that August had the second lowest monthly average precipita‐ tion, while January had the highest monthly average precipitation.

Monthly average evapotranspiration in the dry season was 48.0 mm month−1, while in the rainy season it corresponded to 88.3 mm month−1, which shows an increase of ~84% in evapotranspiration during the wetter period of the year in São Paulo State. Annual evapo‐ traspiration values ranged between 765.7 and 942.0 mm year−1, with 2003 and 2009 present‐ ing, respectively, lowest and highest estimates. In 2003, monthly evapotranspiration ranged from 32.7 (August) to 116.8 mm month−1 (January), while in 2009 monthly evapotranspira‐ tion ranged between 44.6 (June) and 110.4 mm month−1 (December). Regarding yearly aver‐ age evapotranspiration, the estimate found for the period between 2000 and 2010 was 817.9 mm year−1. On average, for the period between 2000 and 2010, evapotranspiration ac‐ counted for ~53% of precipitation in São Paulo State.

It should be noted that MOD16 algorithm estimates were not validated for this study. Ideally, validation process should be performed using surface measurements throughout SP in order to identify biases in the estimates found according to the conditions studied. However, there is a lack of such information for the study area, both the spatial and temporal perspective, which prevents this type of analysis. For comparison, [22], in a validation study for the MOD16 algorithm, found relative errors of 18–22% in tropical forest areas, 20% in seasonal flooding areas and 33% in agricultural areas. Finally, it should be noted that results found about the evapotranspiration regime in SP agree with the results from a modeling study using the Simple Biosphere Model (SiB2) performed by [40].
