Risk Analysis, Forecast And Early Warning Research Of Low Temperature Disaster To Double Cropping Rice In Southern China

Based on the daily meteorological data from 708 weather stations located in the planting region of double cropping rice in the south during 1961 to 2010, together with meteorological industry standards, the distribution characteristics of the trend to low temperature disaster in the nearly 50 years was revealed according to the trend rate of each station. By using information diffusion method and taking the probability and intensity of each level of low-temperature disaster into consideration, the comprehensive risk index of each weather station was constructed and the distribution characteristics of risk of low temperature disaster to double cropping rice was revealed. Based on 74 kinds of atmospheric circulation characteristics during 1960 to 2010, using factor puffing and correlation analysis, stepwise regression prediction model of the level to annual first low temperature disaster was established in high risk area, increasing trend area and low risk and decreasing trend area. Based on the data of 8 meteorological factors, using Fisher’s discriminant analysis method, the early-warning model of rolling on a daily basis to level was established during the next 10 days of early rice and the next 5 days of late rice in high risk areas. The main results are listed as follows:(1) The low temperature disaster of double cropping rice is given priority to decreasing trend, while the increasing trend is relatively not obvious. The increasing trend areas of spring low temperature disaster of early rice are mainly located in Shaanxi planting area, the north of Sichuan planting area, central of Yunnan planting area, north of Guangxi and central and north of Guangdong, etc, in which the increase rate is 0-0.05 times per 10 years. The increasing trend areas of cold dew wind of Japonica rice are mainly located in the east of Hubei, central and east of Hunan, west of Jiangxi, main of Guangxi and border between Guangdong and Fujian, etc, in which the increase rate is 0-0.04 times per 10 years. The increasing trend areas of cold dew wind of Indica rice are mainly located in the west and east of Yunnan planting area, in which the increase rate is more than 0.1 times per 10 years.(2) The high risk areas of spring low temperature disaster of early rice in the nearly 50 years are mainly located in the south of Hunan, south of Jiangxi Nanchang, west of Zhejiang, main of Fujian and north of Guangxi and Guangdong, etc, in which the risk index is more than 0.15. The high risk areas of cold dew wind of Japonica rice and Indica rice are mainly located in the Shaanxi planting area, north of Sichuan planting area and main of Yunnan planting area, in which the risk index is respectively more than 0.2 and 0.5.(3) Based on 74 kinds of atmospheric circulation characteristics, stepwise regression prediction model of the level to annual first low temperature disaster was established inⅠarea(high risk area), Ⅱarea(increasing trend area) and Ⅲ area(low risk and decreasing trend area). The average basically consistent accuracy of prediction of stepwise regression prediction model inⅠarea of early rice is 100%, while it is 100% in Ⅱarea and 83.3% in Ⅲ area. As to Japonica rice, the average basically consistent accuracy of prediction is 83.3% inⅠarea, 83.3% in Ⅱarea and 100% in Ⅲ area. When it comes to Indica rice, the average basically consistent accuracy of prediction of all the three areas is 83.3%.(4) Based on the Fisher’s discriminant analysis method, the early-warning model of rolling on a daily basis to level was established during the next 10 days of early rice and the next 5 days of late rice in high risk areas. In the high risk area of spring low temperature disaster of early rice, the average basically consistent accuracies of back substitution and prediction are respectively 95.5% and 90.5%. In the high risk area of cold dew wind of Japonica rice, the average basically consistent accuracies of back substitution and prediction are respectively 83.1% and 74.2%. In the high risk area of cold dew wind of Indica rice, the average basically consistent accuracies of back substitution and prediction are respectively 79.5% and 80.3%.