Comparative Study On Drought Monitoring And Drought Space - Time Characteristics Of Guanzhong Area Based On CWSI And

Drought has become one of the high frequent natural disasters over the world, with the variations of global climate and regional eco-environment. Guanzhong area is located in China’s western hinterland, whose special climate, topography, soil, economic and other natural human environment caused frequent drought in this area. Meanwhile, Guanzhong area is an important commodity grain producing region of China, drought poses a great threat to food security and economic stability of this area. Therefore, study on drought monitoring of Guanzhong area, research and development of proper drought monitoringmodel, and timely and accurate analysis of spatial and temporal characteristics of drought are of great significance to the region’s agricultural production and economic development.The drought remote sensing monitoring technology has lots of advantages, such as wide scope of observation, access to large amount of information, a fast accurate drought response and so on, so it has gradually become the main development trend of drought monitoring. Based on analyzing and reviewing current domestic and international research situation of drought monitoring systematically, this paper makes comprehensive analysis and comparison of TVDI’s and CWSI’s drought monitoring results in Guanzhong area, with the combination of remotely sensed data and meteorological observation data. And this paper makes use of appropriate model to explore the spatial and temporal characteristics and influencing factors of drought of Guanzhong area in 2000～2012, main works and conclusions are as follows.(1) The surface observation data and related model validation shows that NASA’s latest MOD 16 surface evapotranspiration data have good precision in Guanzhong area, in which the relative validation error and correlation value of ET products at "points" and "surface" scale are 10.38% and 0.69, the absolute validation error and relative error of PET product are 20.14 mm/month and 20.39%, the spatial validation correlation and time validation correlation of PET are 0.53 and 0.93. MOD16 offers a new idea to realize the construction of CWSI model.(2) The drought monitoring results of Guanzhong area in 2003 show that TVDI and CWSI can describe the spatial and temporal characteristics of Guanzhong area’s drought in different degree. TVDI and CWSI monitoring results show the spatial distribution of drought in Guanzhong area:the drought of Weihe Plain and part of Weibei dryland is more serious, while the drought of Qinling Mountains and North Mountain is slight. On the change of drought during the year, Guanzhong area has notable characteristics:it suffers serious drought in spring and summer and milder drought in autumn and winter.(3) Using SPI and soil moisture (RSM) as evaluation index to make comparisons of the spatial and temporal drought monitoring effects of CWSI and TVDI, results show that CWSI is better than TVDI on describing the soil moisture spatial distribution and change during the year of Guanzhong area. On the spatial distribution, the 20cm depth correlation of CWSI, SPI and RSM is slightly weaker than TVDI, while other indicators correlation are superior to TVDI. The indicators’ correlation of CWSI, SPI, and RSM is higher than that of TVDI on the time change within a year.(4) CWSI’s annual drought monitoring results show that Guanzhong region has suffered different degrees of drought from 2000 to 2012, drought is serious during 2000～2002 and 2008-2011. As the spatial distribution, drought of northeast area is relatively serious, and that of southwest area is lighter. Temperature and precipitation affect crops’ water balance between supply and demand by influencing the vegetation transpiration quantity, and leading to the occurrence of drought’s intensity changes.(5) The utilization types of land are important factors that affecting the surface soil moisture distribution. The risk of drought of all types from high to low are bare land, farmland, garden land, grassland, forest land. The physiological and ecological characteristics and climate conditions of different types determine the frequency and degree of drought.(6) The spatial and temporal analysis on annual drought volatility and trend line of Guanzhong area shows that the annual drought volatility of east and west regions fluctuate remarkably, while that of middle region is relatively stable. The annual drought volatility of Baoji’s north and west area and Xian yang’s southwest mainly presents a trend of improvement, that of Xi’an and Weinan’s southern border and the area around Xi’an city deteriorates significantly.