Determining NDVI Response to Nexrad Rainfall

The Normalized Difference Vegetation Index (NDVI) is derived from AVHRR sensors aboard NOAA series satellites, which represents the amount and type of ground cover present on the land surface. The primary objective of this study is to analyze the relationship between NDVI and rainfall estimates derived from NEXRAD (NEXt generation weather RADars). NEXRAD is ground based radar installed across the entire United States (US) to produce rainfall estimates at 1 Km2 and/or 4 Km2. Numbers of studies have been done on finding out relationship between NDVI and rainfall. But, the rainfall data used are point measurements obtained from raingages located across the study area. NDVI pixel value which is closer to the raingage stations were selected for those studies. There is a possibility that these point and single-pixel comparisons could exhibit lots of uncertainties in determining the relationship between land use and rainfall. Hence, this study analyzed the effect of spatially distributed NEXRAD rainfall on NDVI for Texas, US. Correlation coefficient (r) was used as the statistical parameter for comparison. The results showed that there is a good correlation of 0.934 between NDVI and the NEXRAD rainfall obtained three weeks before, and during the spring season. Spatial correlation based on soils showed correlation of 0.498 with four weeks time lag. The results will be used to develop a methodology for locating potential recharge zones in Texas.