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利用MODIS植被指数和陆地表面温度产品建立全国3个农业气候区NDVI Ts、NDVI ΔT和NDVI ATI空间,并由NDVI Ts、NDVI ΔT和NDVI ATI空间分别建立温度植被干旱指数(TVDI)、温差植被干旱指数(DTVDI)和表观热惯量植被干旱指数(AVDI)3个干旱评价指标研究全国干旱分布,利用实测土壤含水量对3个干旱指标进行检验评价。NDVI ΔT空间中的湿边基本与横坐标平行,表明当土壤水分处于饱和状态或植被完全无水分胁迫条件下,植被和土壤对缓冲环境温度变化的能力大体相当;由NDVI ATI空间看出,随着植被覆盖增加,表观热惯量有增加的趋势。对比3个干旱评价指标表明:当监测范围较大,区域内地形复杂时,由NDVI Ts空间计算的TVDI评价干旱最合理,由NDVI ΔT空间计算的DTVDI在干旱监测中也具有一定的价值,而由NDVI ATI空间计算的AVDI已经不能合理评价干旱。
NDVI Ts, NDVI ΔT and NDVI ATI space of three agro-climatic zones in China were established using MODIS vegetation indices and land surface temperature products. The TVDI, NDVI and NDVI ATI space were set up for NDVI Ts, NDVI ΔT and NDVI ATI space respectively, Index (DTVDI) and apparent thermal inertia vegetation drought index (AVDI) were used to study the drought distribution in China. The three drought indices were tested and evaluated using the measured soil moisture content. The wet edge in NDVI ΔT space is basically parallel to the horizontal axis, indicating that the capacity of vegetation and soil to change the buffer ambient temperature is roughly the same when the soil moisture is saturated or the vegetation is completely free from water stress. From the NDVI ATI space, Vegetation cover increases, apparent thermal inertia tends to increase. Compared with the three drought evaluation indexes, it is shown that the TVDI evaluated by NDVI Ts space is most reasonable when the monitoring range is large and the terrain is complex in the region. DTVDI calculated by NDVI ΔT space also has certain value in drought monitoring AVDI calculated from the NDVI ATI space can no longer properly estimate the drought.