Regional Drought Long-Term Forecasting And Agricultural Drought Risk Comprehensive Assessment

China is a water shortage country. With the social and economic development and environmental changing, the extreme weather phenomenon in China is more and more frequent. Drought is the main restraining factors which affects the economic development and agriculture production. Consequently, regional drought forecasting and risk assessment have been the key to the researches. Knowning the regional drought developing rules and drought risk is the main contents of drought-resisting. This article studies on the drought long-term forecasting and risks assessment. The research results are listed as follows:(1) The regional drought development law analysisThis paper summarizes the drought definition, classification and the representative indices. According to the reflection different spaces or times distribution merits of SPI (Standardization Precipitation Index), it is used for drought development law analysis of Chaoyang City. Based on the power methods, it concludes that a five to ten years fluctuation drought cycle has been presented.(2) Drought grade combining precipitation model based on wavelet decomposition methodPrecipitation is showing a trendy, periodicity and volatility characteristics. Based on a strong decompose ability of wavelet theory, precipitation trendy, periodicity and volatility components are separated. Then use different prediction models to forecast the different components of precipitation, respectively, and take the predicted results of reconstruction of the three parts as the final predictions. For the difficult volatility characteristics of precipitation, the paper screened the circumfluence factors, and used these factors sets for precipitation model building. Comparison of results with the other models shows that the combination of wavelet decomposition precipitation precipitation model reduces the precipitation forecasted error and improved the forecast passing rate. Then, the precipitation is converted to drought grade according to national standard. And the study result shows that this method is feasible.(3) Soil moisture simulation based on soil-water balance modelThe annual and seasonal changing rules of soil moisture are aummarized. We found that the soil moisture is not only relates to the precipitation quantity, but also relates to the precipitation seasonal distributing characters. According to the complex calculations of crop water requirement in the soil water balance model, BP network is used for crop water requirement simulation. It shows that the BP simulation gets a similar result to the Penman-Monteith. The usage of ET based BP network for the soil moisture simulations will be feasible when the information is incomplete.(4) Soil moisture prediction based on precipitation prediction system of GFSSoil moisture is an important index for agricultural assessment. It will provide more dependable information if known soil moisture the before drought occurs. Based on the characteristics of higher prediction precision of no rain and light rain of global forecasting system, the precipitation forecasting information of GFS is used for soil moisture quantity forecasting. During making a detailed plan to fight the drought, policy-makers concern more about the drought degree and when the drought degree will be reduced. According to the national drought standard, the quantity forecasting result is translated into drought grade. It shows that the prediction passing percent is high. The study results are used for August drought prediction and the satisfying outcomes.(5) Agricultural comprehensive drought risk assessment based on variable fuzzy setsBased on the fuzzy characteristics of comprehensive drought risk in agriculture, variable fuzzy sets theory was used for agriculture comprehensive drought risk assessment of the fourteen cities in Liaoning province of China. Multi-layers and multi-indices variable were established using fuzzy evaluation model and estimated the agriculture drought risk in terms of dangerousness, vulnerability, exposure and drought-resistibility of the fourteen cities respectively. According to the combination weights of the four drought risks factors, agriculture comprehensive drought risk grade of each city was obtained. According to the assessment results, agriculture drought risk zoning map was drawn by the software of MapInfo. The assessment result shows that agriculture comprehensive drought risk of Liaoning province has strong regional features. The western region of Liaoning is a high-risk area for agricultural drought, the central region of Liaoning is moderately risky area, and the eastern region of Liaoning is a low risk area.Finally, the conclusions are drawn and the problems to be further studies are discussed.