MODIS数据在陕西省干旱监测中的应用

Drought monitoring based on MODIS in Shaanxi

以MODIS归一化差异植被指数(normalized difference vegetation index,NDVI)和陆地表面温度(land surface temperature,Ts )数据为基础,构建双抛物线型NDVI-Ts 特征空间,利用实测土壤湿度对其进行验证,并基于该特征空间的温度植被干旱指数(temperature vegetation dryness index,TVDI)监测和分析了2000-2016年间陕西省旱情时空分布特征和规律。结果表明,NDVI-Ts 特征空间呈双抛物线型,基于该特征空间的TVDI与10 cm深土壤湿度呈显著负相关关系( P <0.05)。空间上,2000-2016年间陕西省旱情主要分布在陕北西北部、北部以及关中北部、东部地区;时间上,2000年陕西省受旱面积占比为31.95%,2016年为27.65%。榆林市北部大部分地区、延安市中部部分地区、关中地区中部以及陕南零散地区旱情得到显著缓解,约占14.45%,而全省84.48%地区旱情虽发生了变化,但变化不显著;全省97.62%地区变异系数较小,位于0~0.8之间,主要分布在陕北北部和关中南部,表明全省旱情较稳定。全省23.74%地区旱情与降雨量呈显著负相关关系( P <0.1),随着降雨量的增加TVDI减少,旱情越轻,主要分布在陕西省榆林市大部分地区,延安市中部部分地区,汉中市北部、西北部,安康市、渭南市北部、商洛市东部部分地区及宝鸡市西部、北部部分地区;其余地区旱情变化并未受到降雨量显著影响。进一步分析表明,平均气温也不是影响陕西省旱情变化的主导因素。

Based on MODIS normalized difference vegetation index (NDVI) and land surface temperature (Ts ) data,the authors constructed a bi-parabolic NDVI-Ts space which was verified by the filed measured soil moisture,and monitored the spatial and temporal distribution characteristics of drought conditions in Shaanxi Province from 2000 to 2016 based on the TVDI obtained from bi-parabolic NDVI-T s space.The results show that the NDVI-Ts space was bi-parabolic and there was a significant negative correlation (P<0.05) between TVDI and 10 cm depth filed measured soil moisture.Spatially,the drought in Shaanxi Province during 2000-2016 were mainly distributed in the northwest,north of Shaanxi and the northeastern regions of Guanzhong plain;the drought area of Shaanxi Province accounted for 31.95% in 2000 and 27.65% in 2016,respectively.It is found that drought was significantly relieved in most northern part of Yulin City,the middle part of Yan'an City and the central part of Guanzhong Plain and some parts of southern Shaanxi,which accounted for 14.45 %.The drought conditions in 84.48 % of the province were changed,but the change failed to pass the significant test.97.62% of the province had a small variation coefficient,which was between 0 and 0.8.It was mainly distributed in northern Shaanxi,south of Guanzhong Plain,and it showed that the drought conditions were stable in Shaanxi Province.There was a significant negative correlation between drought and annual precipitation,accounting for 23.74 %(P<0.1).With the increase of rainfall,TVDI decreased,and the drought was relieved.It was mainly distributed in most areas of Yulin City,central parts of Yan'an City,north and northwest of Hanzhong City,Ankang City,northern parts of Weinan City,eastern parts of Shangluo City and western and northern parts of Baoji City.It is found that the changes of drought in other areas were not significantly affected by precipitation.The annual temperature was not dominant factors that resulted in the change of drought in Shaanxi Province.