Risk assessment of main meteorological disasters of winter wheat in North China

Abstract: North China Plane is one of the most important area for winter wheat planting, but meanwhile it is severely influenced by meteorological disasters, which may lead to serious reduction in yield. This research is carried out to evaluate the integrated risk for winter wheat in North China Plane through establishing the comprehensive risk model, which is made up of the integration of hazard, exposure and vulnerability models. The meteorological data in 1961－2010 and the winter wheat developmental stages data and yield data in 1981－2010 from 48 agro-meteorological observatories and MODIS data are employed to establish the risk model. According to the growth and development characteristics of winter wheat, the whole growing period is divided into three stages, which are early stage (from sowing to standing stage), middle stage(from jointing to flowering stage) and late stage (from filling to mature stage),respectively. In addition to the climatic conditions in the three stages, the precipitation in the period before sowing is also taken into account in the impact analysis for periodical disasters toyield reduction of winter wheat in North China. Disaster hazards in different growing stages are analyzed based on the drought index and dry hot wind index. According to the embryology mechanism of meteorological disasters and the regional environmental characteristics, the hazard, exposure and vulnerability models are established and thus the integrated risk model come into being, with which the integrated risk of meteorological disasters for winter wheat in North China Plain is evaluated, and then the risk distribution is demonstrated based on GIS technology. Results showed that, 1) According to the hazard model, in the stage before sowing, the hazard weights were generally low. Weights of drought hazard in early stage and middle stage were generally high, and middle stage had the highest weights in most area. The highest weight of dry hot wind hazard located in middle and south of Hebei Province. In late stage, the weights ratio of drought to dry hot wind could explain the main meteorological disaster locally, it showed that drought dominated in middle and western part of Henan Province, and its impact decreased from south to north, thus the impact of dry hot wind increased. According to the vulnerability model, the highest value area sat in Huanghua and Botou of Hebei Province, Juxian in south of Shandong, Lushi and Sanmenxia in Henan Province. According to the exposure model, the highest exposed area lie in southwest of Shandong and northeast of Henan. The weights of hazard, exposure and vulnerability were 0.3272, 0.3116 and 0.3612, respectively. 2) There were two high risk value centers in North China Plain, one of them lay in the junction of Hebei, Shandong and Henan province. The other one lay in Huanghua and Botou, Hebei province. Risk values decreased from center to surroundings. 3) North China Plain was divided into 5 parts according to the integrated risk value. In conclusion, in the whole growing period, the highest hazard value appears in the middle stage, for the late stage, differences in dominant meteorological disasters exist over the research domain, which could be coped by local measures according to their risk features. Vulnerability occupies the biggest component in the risk index. In the study, county is the smallest unit in carrying out the risk assessment, which means the result is more targeted and typical, so that it can provide reference in the management of agro-meteorological disasters for winter wheat in North China Plane.