Spatio-Temporal Variation of Water Deficit (WD) over Songnen Plain in the Growing Season from 2000 to 2009

摘要

Water deficit (WD) defined as the difference between evapotranspiration (ET) and precipitation (PE) is usually used as sensitive index to measure the wetness and drought degree of climate and the water supplying condition of agriculture. In this paper, spatial pattern of actual ET in Songnen Plain of 2000-2009 growmg season (denoted as gs) (from May to Sep.) was mapped using the MODerate resolution Imaging Spectra radiometer (MODIS) timeseries products and meteorological data. Estimated ET was validated using eddy covariance system. It was found that the trend of the calculated and observed ET was highly consistent with the determination coefficient (R2) of up to 0.82. Then, WD was calculated based on estimated ET and observed PE, spatio temporal patterns of WD were analyzed by using the GIS spatial methods. The results showed that multi-year average WD over the Songnen Plain differentiated from place to place with the value ranging from 26.91 to 692.5lmm/gs and an average value of 228.74mm/gs. Regional average WD over the Songnen Plain varied significantly with the maximum value of 358.3lmm/gs appearing in 2001 and the minimum value of 89.23mm/gs appearing in 2003. The sequence data of regional average WD displayed obvious decreasing trend with the negative slope of about -16.62mm/gs. At the monthly step, regional average WD varied a lot with the highest value appearing in May or Jun. and lowest monthly WD value appearing in Jul. or Aug. in most cases. Average WD values for different land covers in the total growing season were positive and exhibited decreasing trend in the order of waterbody, wetland, woodland, cropland, built-up and grassland.