多时相中分辨率卫星影像在2006年川东和重庆旱情监测中的应用研究

Drought monitoring using MODIS data

本文采用多时相的中分辨率成像光潜仪（MODIS）地表温度与地表反射率数据和温度植被旱情指数（TVDI）对2006年6～9月川东和重庆地区的旱情进行了评估，同时分析了TVDI对降水和气温的响应，并利用土壤湿度数据对干旱监测结果进行评估。从代表性站点的8d合成的TVDI与同期降水量随时间变化的曲线可以看出TVDI能较好的反映降水的时空变化，6～9月各月平均TVDI与当前两月降水总量均明显负相关，说明TVDI一定程度上能反映由于前期降水不足造成的干旱。7～8月月平均TVDI与当月降水总量显著相关，其中8月相关系数最高，该月降水最少，早情最为严重：8～9月月平均TVDI与当月平均气温均显著相关，其中8月份相关系数略高于9月份。后两月TVDI与平均气温的相关关系明显高于前两月，说明在干旱后期高温天气也是导致干旱的一个重要原因。最后，采用同期重庆地区的土壤湿度数据对8d合成的TVDI进行验证，发现站点和面平均TVDI与土壤饱和度在时间上具有较好的相关性，说明TVDI作为旱情监测指标的有效性。

The Terra/MODIS products of surface reflectance and vegetation index were applied to construct NDVI/Ts space, and the temperature-vegetation dryness index （TVDI） was used to study the drought status from June to September of 2006 in the eastern Sichuan and Chongqing. The meteorological data and soil moisture data were collected to compare with TVDI. Comparing the 8-day TVDI curve with rainfall, it was found that TVDI was sensitive to the uneven distribution of the rainfall both in space and time. There was obvious negative correlation between TVDI and the two-month cumulative rainfall from June to September, which showed that TVDI could be used for monitoring the drought condition caused by less antecedent rainfall. A significant correlation was found between monthly rainfall and TVDI in August and September. It had the least rainfall and caused a serve drought in August. This was consistant with the fact that the correlation coefficient between rainfall and TVDI in August was the highest. It was also found that correlation between monthly average air temperature and TVDI in August and September was significantly higher than those in June and July, which demonstrated that the high air temperature had important impact on the drought development at the later period. Finally, the soil moisture data in Chongqing was used to evaluate the drought degree detected by TVDI, It was found that the TVDI and soil saturation had an obvious negative correlation, which illustrated the validity of TVDI for drought evaluation.