To explore the applicability of the FY-3 Series in the Sichuan Basin, this study used FY-3D/MERSI-Ⅱ NDVI and LST products to calculate the Temperature-Vegetation Dryness Index (TVDI) as a drought monitoring indicator. MODIS data of the same type were used for validation. The spatiotemporal distribution characteristics of drought in the Sichuan Basin from June to October 2022 were then analyzed. Correlation validation was conducted using 10-40 cm soil moisture data from 53 representative soil moisture stations in the Sichuan Basin to evaluate the accuracy of the FY-3D/MERSI-Ⅱ TVDI for drought monitoring.The results showed that: (1)Under clear sky conditions, the correlation coefficients (R) between the FY-3D/MERSI-Ⅱ LST products and MODIS LST products, derived using the split-window algorithm, ranged from 0.72 to 0.84. The R values for NDVI products ranged from 0.55 to 0.67. Both sets of R values passed the 0.05 significance test, demonstrating that both products can be used for regional drought monitoring. (2)From June to October 2022, most areas in the Sichuan Basin experienced varying degrees of drought. The largest drought area occurred in July, covering 85.95% of the region, with 47.07% classified as moderate drought. The drought situation worsened in August, with severe drought areas increasing to 13.27%. (3)The correlation coefficient between the FY-3D/MERSI-Ⅱ TVDI and 10 cm soil relative humidity from June to October ranged from -0.65 to -0.32, passing the 0.05 significance test and showing a significant negative correlation. This indicates that the FY-3D/MERSI-Ⅱ TVDI has good potential as a reference for drought monitoring in the Sichuan Basin.
大量田间试验证明,LST与NDVI之间存在显著的负相关,利用LST/NDVI直线的斜率可以表示研究区土壤水分状况,LST/NDVI直线斜率越接近水平线,表示该区域土壤含水量越高,反之,直线斜率越大,则表明该区域土壤中水分含量越低。因此,结合NDVI和LST可以很好地反映土壤湿度状况[24]。Moran M S等在此理论基础上提出NDVI-LST的散点图呈梯形的特点[11],本文利用Sandholt等通过NDVI和LST构建的TVDI为监测指标[12],公式如下:
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