| Drought is one of most serious nature hazard in China, which has a high frequency, largest affect area, and maximum loss characteristics. China has complicated climate types, and is one of most sensitive regions to climate warming in the worldwide. Drought had been obvious change in China, which caused the drought in the north is more drought, and the extreme drought event in the south increased. Under the background of worldwide climate warming, drought disaster becoming general and coming to all regions in the China, and the drought have obvious regional difference. Agriculture is most sensitive to climate change, and it is an object of drought disaster.In this paper, based on the comprehensive climate drought index(MCI), expressed the drought spatiotemporal distribution and it regional difference, analyzed the drought disaster hazard factors, drought disaster risk characteristics, and the mechanism of drought disaster. Based on the all-county, south, and north drought disaster loss rate and it response to climate warming, we discussed the effect of climate change on the area of main agriculture and production, building a drought risk assessment model combined with drought disaster risk factors and frequency of loss. According to the grade of different agriculture crops against disaster capability, analyzing the effect of regional and different grade drought on agriculture loss, finding the key period of regional drought disaster risk in national, north, and south region. Comparing the regional agriculture drought disaster hazard factors, critical values, dynamic risk characteristics, and its change rules, revealing the key factors on risk attribution and physical mechanism. The results can provide scientific basis to improve the capability of prevention drought disaster risk and risk management levels.(1). Fully recognized drought hazard factor spatial and temporal change and development rules in the national, north and south region of China. Based on the MCI index from 1961 to 2014, systematically analyzed the drought spatial and temporal distribution in the national, north, and south China. The results indicated that the area of drought had been enlarged, the degree and frequency increased in recent 50 years, especially for the serious drought frequency and area, and the east region is higher than west region, north region higher than south region. However, since this century, the drought happened simultaneous in the north and south region, and the area of drought in the south is obvious enlarged, especially for the serious drought. The drought is serious from the middle time of the 1990 s to early 21 th century. According to the drought duration time, there are drought happened in the all seasons, and the duration time can last 11 month. The drought mainly happened in the south of Yellow River and north of Changjiang River. According to the drought frequency, the north is more than south, east is more than west, and the frequency of the Yellow River is larger than 30%.(2). Building the combined risk assessment model based on the agriculture drought disaster risk factor and historical agriculture disaster loss data, and assessed the drought disaster risk in the southwest China. Based on the GIS and RS technology, using analytic hierarchy process and the weighted analysis to analyze the soil humidity data, vegetation index, drought disaster statistical data, and climate data, building the four factors(drought hazard factor, disaster-forming factor, and disaster-bearing objects, and capability of prevention disaster) drought risk assessment index and model. Under the GIS platform, combined the risk assessment index and drought disaster risk characteristics, achieved the drought disaster risk fine and dynamic assessment, systematically analyzed the southwest agriculture drought disaster risk characteristics and mechanism, providing the theory for southwest drought disaster prevention and management for reduction disaster.(3). Systematically analyzed the drought loss rate and it characteristics in north and south. Based on the agriculture drought loss historical data from 1961-2012, the disaster rate, hazard rate, rejection rate, and comprehensive rate increased in recently 50 years, and the China is one of the higher agriculture disaster loss and risk region in the worldwide. With the climate warming, the area and degree of agriculture drought disaster loss increased, and drought risk also increased. The serious drought loss increased obviously. The difference of drought disaster loss is obvious for north and south, the area, degree, and trend of drought disaster in the north are obvious than south. The disaster loss is obvious than south, and the increase speed is faster than south, the drought loss is about 3-4 time than south. The disaster loss in the north related to rainfall, and almost not related to temperature, however, the disaster loss in the south is more depend on temperature than north. The rainfall and temperature in different period had different effect on drought disaster loss.(4). Explaining the characteristics of regional drought disaster loss. The disaster rate, hazard rate, rejection rate, and comprehensive rate increased in recently 50 years. The comprehensive loss rate is largest at the northeast(9.6%), and then north China(9.3%), northwest(8.4%), east China(2.4%), however, the increase degree is most obvious in north China(1.4%/10a). The regional comprehensive loss rate is different in climate space. The temperature has the great effect in the southwest drought. The temperature and rainfall both have effect on south China, east China, middle China drought. The temperature has more contribution than rainfall in the northwest, northeast, and north China. With the temperature increase and rainfall decreased, the comprehensive loss increased, however, the effect of rainfall and temperature are different in different time period.(5). Systematically analyzed the response of main agriculture crops to drought. Based on the main agriculture crop production, cultivated area, and drought loss data, I found that climate warming is hazard for the main agriculture crops production increase, but the response of different agriculture crops different. The climate warming is good for autumn crops, winter wheat, spring wheat, and potato, but not conducive to summer crops, corn, and rice. Temperatures have more effect on crops production than rainfall. With the increase of drought, the crop production trend to decrease, especially for the autumn crops. The winter wheat and rice decreased with drought degree increasing, however, the response of the summer crops, spring wheat, corn and potato are not obvious to climate drought.(6). Cleared the key effecting period of agriculture disaster loss. Based on the drought disaster factor on the drought loss, the drought loss in the north is sensitive to climate drought, and the loss is more than south. The drought loss increased with drought degree, and there are regional difference. Climate drought have the key role on northeast agriculture drought loss, and then north China, northwest, southwest, middle China, south China, and have almost no effect on east China. The drought disaster loss key period in the north is end of spring, summer, and middle of autumn, and come to peak at august. However, the drought disaster loss key period in the south is summer and front of autumn, and also come to peak at august. The key period is began from end of spring to the end of the autumn. The effect of key period in the north is more than south. The time of key period have obvious reginal difference, the key period curve conclude bimodal type and unimodal type, which related to reginal climate, drought change rule, agriculture structure, agriculture types and capability of drought preventions. |
PDF Full Text Request