A drought index based on slopes in NDVI-Ts spaces used in monitoring drought in China

In the study, the NDVI and land surface temperature (Ts) were calculated using NOAA-AVHRR image to construct the NDV/-Ts space from which a dryness index-temperature/vegetation dryness index (TVDI) which was based on the slopes was suggested according the interpretation of NDVI-Ts SPACE. With the dryness index, the drought spatial patterns in China for every ten days in May 2000 were studied. The dryness index that combines the land surface temperature with vegetation spectral index is computationally straightforward because it was based on the information derived from satellite data only. Using the TVDI, the surface moisture status in May in 2000 was studied. The TVDI spatial pattern was compared with the measured topsoil moisture from the weather stations around China with the linear regression strategy. A negative linear correlation between TVDI and the measures soil moisture was found, thus TVDI’s validity in monitoring drought was verified. TVDI and CWSI that was based on Ts only were compared. Results showed that TVDI had a more remarkable relation than CWSI to soil moisture. So we can reach the point safely that TVDI based on the combinational information of Ts and NDVI was superior to CWSI solely based on Ts in monitoring regional drought.

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