基于点扩散函数的条件植被温度指数降尺度转换方法

Downscaling Transformation Method for Vegetation Temperature Condition Index Based on Point Spread Function

以陕西省关中平原为研究区域,基于MODIS数据反演的条件植被温度指数(VTCI)的定量化干旱监测结果(MODIS-VTCI)和基于Landsat数据反演的VTCI相对干湿监测结果(Landsat-VTCI),应用点扩散函数(PSF)将930 m空间分辨率的MODIS-VTCI降尺度转换至30 m,并对降尺度转换的VTCI进行定量化验证。结果表明,降尺度转换的VTCI与Landsat-VTCI间的相关系数和结构相似度均较大,降尺度转换的VTCI与累计降水量间的相关性和MODISVTCI与累计降水间的相关性相近,且均高于Landsat-VTCI与累计降水量间的相关性,说明降尺度转换的VTCI既考虑了Landsat-VTCI的空间变异,又保持了MODIS-VTCI较为准确的定量化干旱监测特性。

The vegetation temperature condition index（ VTCI） has been widely used in drought monitoring,which is in the assumption that their shape of the scatter plots of normalized difference vegetation index（ NDVI） and land surface temperature（ LST） was a triangular at a regional level. Bsaed on the vegetation temperature condition index（ VTCI） drought monitoring results retrieved from the moderate-resolution imaging spectroradiometer（ MODIS） data products（ MODIS-VTCI） and the relative VTCI derived from the Landsat OLI/TIRS products（ Landsat-VTCI） in the Guanzhong Plain,China,the MODIS-VTCI was transformed from a coaser resolution of 930 m to a finer resolution of 30 m by using the point spread function,called PSF-VTCI,and the PSF-VTCIs were validated for their quantification. The results showed that there was good agreement between the PSF-VTCIs and the Landsat-VTCIs terms of their correlation coefficient and structural similarity index. The correlation coefficients between the PSFVTCIs and the cumulative precipitation were similar to those between the MODIS-VTCIs and the cumulative precipitation, which were both larger than those between the Landsat-VTCIs and the cumulative precipitation,indicating the PSF-VTCIs were not only related to the space heterogeneity of the Landsat-VTCIs but also the accurate quantitative drought monitoring results of the MODIS-VTCIs.