Soil Moisture Retrieval Using Remote Sensing Spectral Indexes And Tempo-spatial Drought Analysis In East China Winter Wheat-planting Area

Soil moisture is an important variable in climate system and in drought observation byquantitative remote sensing method. Plant evapotranspiration connects precipitation andtemperature with soil moisture. In the water interaction between atmosphere, plant and soil,soil moisture is relative to the air humidity and the response of plant to water. East China isan important crop-planting area in China, and winter wheat is the main crop in East China, soit is promising to study the drought problem in East China winter wheat-planting area usingsoil moisture. The objective of the research is to retrieve soil moisture from hyper spectralremote sensing data and to analyze the drought trend from the year2001to2010in EastChina wheat-planting area. In the research, data derived from MODIS is used to constructspectral index, and observation data in situ at meteorological stations is used for validation.First, Normalized Vegetation Difference Index (NDVI), Normalized Difference Water Index(NDWI) and Normalized Multi-band Drought Index (NMDI) are discussed by comparing tosoil moisture, precipitation and temperature to analyze their performance to meteorologicaldrought and agricultural drought. Second, since spectrums in red and infrared are sensitive towater, Perpendicular Drought Index (PDI) is calculated in red-infrared feature space.Validation of PDI was processed in Hebei Province. Third, Modified Perpendicular DroughtIndex is calculated to improve the precision in high vegetation fraction. Validation of MPDIwas processed in Henan Province. Finally, MPDI is selected from all five spectral indexes toconduct tempo-spatial analysis the drought trend from2001to2010in East China winterwheat-planting area. Results show that:(1) among NDVI, NDWI, NMDI, PDI and MPDI,MPDI has the highest correlation coefficient with soil moisture, which reaches-0.8873.(2)Performances of PDI and MPDI are improved when soil texture is taken into consideration.(3) During the year2001to2010, before regreening stage of winter wheat, drought becamenotable severer in border area of Beijing, Tianjin and Heibei Province and the border area ofHebei, Shandong and Henan Province. After regreening stage of winter wheat, droughtbecame notable severer in the middle of Shandong Province.