Risk Assessment Of Main Meterological Disasters Of Winter Wheat In North China

The meteorological data in1961-2010and the winter wheat developmental stages datain1981-2010from48agro-meteorological observatories are employed to construct the riskindex of winter wheat in North China. According to the growth and developmentcharacteristics of winter wheat, the whole growing period is divided into three stages, whichare early stage(from sowing to standing stage),medium stage(from jointing to flowering stage)and late stage(from filling to mature stage),respectively. In addition to the weather conditionsin the three stages, the precipitation in the period before sowing is also taken into account inthe impact analysis of periodical disaster to the yield of winter wheat in North China.Thespatial and temporal distributions of meteorological disasters of winter wheat in differentgrowing stages are analysed based on the drought index and dry hot wind index.According tothe embryology mechanism of meteorological disasters and the regional environmentalcharacteristics,the risk,exposure and vulnerability models and thus the integrated risk modelare established,which can evaluate the integrated risk of meterological disasters of winterwheat in North China.The risk distribution map of the meteorological disasters in North Chinais presented by GIS.Main results of the paper are showed below:(1) According to the standardized precipitation evapotranspiration index, the drought appearedto aggravate in past50years, and the northern part was heavier than that of the southernpart. There is a fallen tendency of precipitation in the pre-sowing period. Based on the cropwater deficiency index in each growing stage,it is found that the value of drought index ofeach development stage of winter wheat is relatively high, and the water deficiency is acommon phenomenon in every stage, which is most serious in medium stage. The droughtindices of early and late stages increase from southeast to northwest part of China.(2) There is a number of stations that dry hot wind disaster occur. The middle and south part ofHebei Province is the most seriously affected region by dry hot wind, while northwest partof Shandong Province and north part of Henan Province are also easily affected.The dryhot wind disaster alleviated from1960s to1990s,but it aggravated in21st century. (3) According to the hazard assessment model, there are high hazard weights of winter wheatin early and medium stages, and the weight of medium stage is always larger than that ofthe early stage in most regions of North China. The hazard weights are low in pre-sowingstage in research region. In early growing stage, the hazard increase from south to northpart of the research region. In medium growing stage, hazard are generally high. Two mainmeteorological disasters occur in the late growing stage. High drought hazard regionsdistribute in the middle part of North China, while high dry hot wind hazard regions lie inmiddle and south part of Hebei Province. As for the integrated hazard value, it increasefrom south to north part of the research area. The regions that are mostly exposed tometeorological disasters lie in southwest of Shandong Province and northeast of HenanProvince. The vulnerability of winter wheat in North China shows good connectivity.Thehighly vulnerable areas lie in Beijing,Tianjin,most part of Hebei Province, middle and westpart of Shandong Province, northeast part of Henan Province, and there is an obviousregional variation in vulnerability as well. The integrated risk index decreased from centralto surroundings of North China. Some regions like Xingtai,Shijiazhuang in HebeiProvince,Liaocheng,Dezhou in Shandong Province and Xinxiang in Henan Province aremost possibly affected by meteorological disasters,with the highest risk index value inthese areas.