The landscape of Texas is subject to frequent episodes of below-average precipitation and recurrent intervals of prolonged, severe drought. Since 1996, much of the west-central portion of Texas has experienced severe drought conditions with annual precipitation falling to less than 60 percent of normal. Drought has affected regional ranching operations and the harvests of important cash crops. In addition, statewide reservoir storage levels have fallen to a 16-year low in a state experiencing a booming economy and rapid population growth.

Data collected by the Advanced Very High Resolution Radiometer (AVHRR) sensor onboard the NOAA Polar Orbiter satellites can be used to examine the response of vegetation to changing climatic conditions throughout the year. The primary means to monitor drought landscapes involves the calculation of a vegetation index using a ratio of the red visible and near infrared bands of the AVHRR sensor. The resulting images represent normalized difference vegetation indices (NDVI) for the region.

UT-CSR operates a satellite receiving station that collects the data stream from AVHRR sensors during every orbit over Texas. The individual satellite images are georectified to a common coordinate system and composited to mitigate the effect of cloud cover. Images of this kind can provide objective information about the impact of drought conditions in different regions of the state.

AVHRR (http://www.csr.utexas.edu/rs/avhrr.html)

NDVI (http://earthobservatory.nasa.gov/Library/MeasuringVegetation/)

Satellite receiving station (http://www.csr.utexas.edu/rs/station.html)