Using the vegetation temperature condition index for time series drought occurrence monitoring in the Guanzhong Plain, PR China

The aim of this study was to develop and validate a method of determining the warm and cold edges of the Vegetation Temperature Condition Index (VTCI) drought monitoring approach, and to analyse the time series profiles of the VTCI in croplands under both rainfed and irrigated conditions. The linear correlation coefficients between the VTCI and the cumulative precipitation at one or two periods of 10-day intervals are the highest. There are significant linear correlations between the VTCI and soil moisture at the 0-10-cm layer for each 10-day interval during the winter wheat growing seasons. These results indicate that the VTCI is an effective approach for monitoring drought occurrence after the crops turn green. The time series analysis of the VTCI in the 10-day intervals shows that the VTCI profiles are different for irrigated and rainfed conditions. The time series VTCI values under rainfed conditions have a good response to recent precipitation, while those under irrigated conditions have less agreement with recent precipitation due to irrigation practices. The results show that the VTCI is a better indicator of droughts than indices developed from precipitation data.