Occurrence Pattern On Spring Frost Injury Of Winter Wheat In Jiangsu Province And Its Forecasting And Alarming

The quality and yield of winter wheat are influenced severely by an high frequency of spring frost damages in Jiangsu province. Under the background of global warming, the extreme weather and climare events occurred frequently, which lead to the distinct change of the last spring frost date and the first fall frost date. Therefore, it is very valuable and meaningful to study the occursace pattern, forecasting and early warning of the spring frost damage of winter wheat.Based on the observed data of conventional meteorological stations and the investigated data of the winier wheat during the different growth periods in Jiangsu Province from1980to2009, in this paper, some plaguing indices for the spring frost injury were designed, an empirical orthogonal function (EOF) and a method of wavelet analysis were used to investigate the spatial-temporal distribution of the spring frost injuries in the province and an risk index was suggested to evaluate the climatic risks of the injuries and decide their divisions in the province. The results showed:(1) The annual occurrence frequency of winter wheat in Jiangsu Province had been increasing from1980to1987and it has been decreasing since1987. In this30years, the temporal evolving tendencies of the spring frost injuries in different grades were consistent with the change of the annual occurrence frequency.(2) Frost occurred from early January and to late Aprirl, and the most in late February.(3)There were different occurrence cycles of the spring frost injuries such as a obvious cycle of22years,11years definitely,4years and2years.(4) The maximum occurrence area of the heavy spring frost injuries was Shuyang County where situated in the north side of Huaihe Rever Valley, but the largest occurrence area of the middle and light injuries appeared in Dafeng City along the Yellow Sea coast of Jiangsu Province.(5) The area of low-frenquency was Xinghua,while high-frenquency is Dafeng.The frenquency of light and middle injures is higher in the south side of Huaihe Rever Valley than in the north side of Huaihe Rever Valley, but the frenquency of heavy injure is higher in the north side of Huaihe Rever Valley than the south side of Huaihe Rever Valley.(6) The high risk areas distributed in Xinyi City, Shuyang County, Dafeng City, Rugao City and Rudong County in the northern part of Jiangsu Province. The moderate risk regions were Xuzhou Region (Xinyi City was excluded), Lianyungang Region, Shuqian Region (Shuyang County was excluded), Huaian Region, Yancheng Region (Dafeng City was excluded),Yangzhou Region (Gaoyou City was excluded), Taizhou Region (Xinhua City was excluded) and Nantong (Rugao City and Rudong County were excluded). The low risk areas were the south part of the province and Xinhua City, Gaoyou City of the Lixiahe River Region.In this study, a typical spring frost injury weather event of winter wheat occurred during March3rd to5th in2005was analyzed in Jiangsu Province, China. The atmospheric circulation, influence system and engendering mechanisms of the frost injury was analyzed using6-hourly NECP1°×1°analysis data. The spatial patterns of meteorological elements on the surface which was collected from54conventional meteorological stations across the province were investigated during the frost injury occurred. Based on some plaguing indices for the spring frost injury, the spatial distribution of the typical spring frost injury weather event in the province was investigated. The results were showed as follows:(1) The synoptic background of the typical spring frost injury weather was listed:There was a horizontal trough on500hPa at the north of Xinjiang Manucipalty Region, and the cold air from the high latitudes continuously pervaded into the south with the horizontal trough turning to a vertical trough.The cold high, cold temperature center and cold temperature advection appeared in the surface layer.(2) The cold advection and clear sky radiance cooling at night controlled was the main synoptic causes for the severe frost injury.(3) The main variations of meteorological factors in surface layar for this typical spring frost injury event include lower air temperature, weaker wind speeds and smaller air humidity.The cold air spread over Jiangsu province from the north to the south,so that the disaster is more serious in the north of Jiangsu.(4) The higher pressure, weaker wind speeds and smaller air humidity were favorable conditions for engendering frost injury and these conditions were important in the forecast of frost injury.(5)The winter wheat suffered from light spring frost injury in Xuzhou Region, middle spring frost injury in Huaian Region, Rugao City and Kunshan City,and heavy spring frost injury in Shuyang County,Binhai County and Dafeng City. While the winter wheat did not suffered from any spring frost injury in Ganyu County, Xuyi County and Xinhua City.Firstly, the forecast factors which are better forecasted are selected using the spring frost days data and hourly surface meteorological observational data of3stations (Xuzhou, Ganyu, Kunshan) in Jiangsu province for30years from1980to2009. Then, based on the investigated data of the winter wheat during the different periods of these stations, the frost forecasting model of winter wheat in Jiangsu province is established in the method of multivariate regression. Finally, combined with the plaguing indices for the spring frost injury, the early warning of the different growth periods of winter wheat is made using the forecasting model.The results were showed as follows:(1)The surface meteorological factors in the day before the frost day possessed the characteristic:high pressure, low humidity at night, little cloud or fine day at night and weak wind.(2) There were some factors that the good correlations existed between them and the minimum temperature of the frost day:pressure at8:00am and20:00pm in the day before the frost day, the temperature at8:00am and20:00pm in the day before the frost day, the relative humidity at8:00am and20:00pm in the day before the frost day, the water vapor pressure at8:00am and20:00pm in the day before the frost day.The second were the total clood amount at8:00am and20:00pm in the day before the frost day, the wind speed at8:00am sod20:00pm in the day before the frost day.(3) The established multivariate regression equations were tested and the effect was very remarkable. The forecasting identical rate of different grades frost for3stations was50%to90%and the identical rates in the north side of the Huaihe River were higher than in the south side of the Huaihe River. The trial forecasting effect in2007and2008was good The accuracy attained100%for the forecasting of the light frost injures during the returning green to the jointing in Xuzhou Region, the light and middle frost injuries during the returning green to the jointing in Ganyu County and the heavy frost injures during the jointing to the heading in Kunshan City.