Towards regional drought monitoring with Sentinel-3 vegetation temperature condition index in the Sichuan Basin, PR China

As one of the most destructive natural disasters, drought has a large negative impact on economic development. Reliable indexes for drought monitoring contribute to the adjustment of water resources and food security. Vegetation temperature condition index (VTCI) derived from multiyear moderate resolution imaging spectroradiometer (MODIS) data has proven to have superior capacity for monitoring drought. Sentinel-3 was launched by the European Space Agency (ESA) within the last 10 years, providing high-quality and high-resolution remotely sensed data for drought monitoring at the regional scale. To explore whether the novel Sentinel-3 satellite has the potential for monitoring drought based on VTCI, this study determined cold and warm edges and calculated multiyear VTCI using Sentinel-3 reflectance product and land surface temperature product. To verify whether the multiyear Sentinel-3 VTCI meets the needs for monitoring drought, drought condition reflected by Sentinel-3 VTCI values in the Sichuan Basin, PR China was quantitatively and qualitatively. The drought monitoring potential of Sentinel-3 VTCI was validated through the correlation analysis with meteorological data and the consistency analysis with multiyear MODIS VTCI. The results showed that two severe droughts occurred in early July and mid-August in 2022 in the Sichuan Basin, which is consistent with the actual drought conditions. In addition, the RMSE of MODIS VTCI and Sentinel-3 VTCI remained in the range of 0.08-0.18, which indicated that there was a reasonable consistency between multiyear MODIS VTCI and multiyear Sentinel-3 VTCI, but also difference. The past 10-day cumulative precipitation demonstrated the strongest correlation with multiyear Sentinel-3 VTCI compared to that of other time scales. In addition, Sentinel-3 VTCI showed a strong negative correlation with the maximum temperature and minimum temperature, and a strong positive correlation with the relative humidity. These results indicated that multiyear VTCI derived from Sentinel-3 data enabled monitoring the spatiotemporal variation of drought conditions in the Sichuan Basin, PR China and highlighted the potential of Sentinel-3 VTCI in large-region drought monitoring tasks. • The multiyear Sentinel-3 VTCI identified two severe droughts in Sichuan Basin, PR China in 2022. • The multiyear Sentinel-3 VTCI has strong consistency with the multiyear MODIS VTCI. • The Sentinel-3 VTCI showed a strong correlation with meteorological data.