In: Wagner W., Székely, B. (eds.): ISPRS TC VII Symposium - 100 Years ISPRS, Vienna, Austria, July 5-7, 2010, IAPRS, Vol. XXXVIII, Part 7B 
223 
i) Rainfall and NDVI (Telemaco Borba - location 5) 
Figure 2. Interannual variation (2000-2007) for NDVI and 
Rainfall: a), c), e), g), i) and for NDVI and Actual 
Evapotranspiration: b), d),J), h) and j). 
Candido de Abreu a) b) 
NDVI x rainfall (2000-2007) 
Candido de Abreu 
NDVI »Actual Evapotranspiration (2000-2007) 
♦ 
. 
R* = 0.07 * ~ 
R —0.53 ë 
* :> yt 
_ _ 
. 
Jaguariaiva e) f) 
Figure 3. Linear regressions for all time series (2000-2007) 
between NDVI and rainfall: a), c), e), g), i) and for NDVI 
and Actual Evapotranspiration: b), d),f), h),and j). 
j) Actual Evapotranspiration and NDVI (Telemaco Borba - 
location 5) 
fact that when the rainfall reaches the land surface, part of the 
water is diverted as runoff, and part infiltrates and is retained 
in the upper layers of the soil which is thereafter used for 
vegetation growth. The vegetation then absorbs the soil water 
and uses it through the process of évapotranspiration (Sarma 
and Lakshmi, 2006). Cihlar et al (1991) found similar results 
for the relation between NDVI values from NOAA/AVHRR 
and Evapotranspiration for different ecosystems. They 
reported that there was a highly significant association 
between NDVI and Actual Evapotranspiration values (r= 
0.77) or between NDVI and potential évapotranspiration (r = 
0.86). High correlation was also found between cumulative 
NDVI and cumulative Actual Evapotranspiration over the 
entire growing season (r = 0.96). 
5 CONCLUSIONS 
Results from the analysis showed that the seasonal and 
interannual variability of the vegetation index (NDVI) serves 
as a good indicator for identifying variations, mainly impacts 
of climate anomalies on vegetation and, consequently, on 
crops production (in this case, soybean crop). NDVI curves 
were able to differentiate vegetation responses associated 
with above and below precipitation during soybean growing 
season. Actual Evapotranspiration (AE) showed best 
agreement with soybean NDVI in relation to rainfall, 
probably due to the fact that this variable integrates 
information of rainfall, temperature and soil water holding 
capacity. 
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