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Northern China is a main winter wheat production area and plays an important role in ensuring food security. Wheat aphids, as one kind of main agricultural pest, threaten wheat production. Based on wheat aphids disaster and prevention data, planting area and yield loss of wheat, growth period of winter wheat, and daily meteorological data at 561 observation stations from 1958 to 2018 in 8 main wheat production provinces of northern China, relationships between surface meteorological factors and the occurrence area of wheat aphids for every province in North China and Huanghuai area are fully analyzed using methods of correlation analysis, principal component analysis and stepwise regression analysis in various time-periods from last December to 10 June. Eight key meteorological factors which affect the occurrence area of wheat aphids in North China and 6 key meteorological factors for Huanghuai area are determined. The climate disaster indices of wheat aphids are established based on the normalized key meteorological factors and validated in 8 provinces. Furthermore, climatic risk aspects are assessed to explore the occurrence tendency of winter wheat aphids in northern China. The frequencies of different-level decadal climate disasters are taken as hazard index, the ratio of occurrence area of wheat aphids to the wheat-sown area is defined as vulnerability index, and the ratio of controlled area to occurrence area is calculated to measure the disaster prevention and mitigation capability.Comprehensive risk index is built by integrating hazard, vulnerability, disaster prevention and mitigation capability indexes to assess risk development trend in decades. The results show that the climatic hazard for wheat aphids tends to increase gradually and there are significant differences in different decades. The vulnerability for wheat aphids tends to be severe over time.The disaster prevention and mitigation capability for wheat aphids tends to improve gradually especially in the 1990s, and the trend slows down since 2001. The comprehensive climatic risk has been more severe and their scopes of the highest risk have been larger since the 1990s. The climatic risk is highest in Beijing, Tianjin, central-south Hebei, part of north Shandong. And it's the second highest in most of Shandong, north Henan, eastern and southern Shanxi, and north Jiangsu area, where effective measures should be taken to reduce the detriment of wheat aphids.

Based on the principle of energy balance, the method for calculating latent evaporation was simplified, and hence, the construction of the drought remote sensing monitoring model of crop water shortage index was also simplified. Since the modified model involved fewer parameters and reduced computing times, it was more suitable for the operation running in the routine services. After collecting the concerned meteorological elements and the NOAA/AVHRR image data, the new model was applied to monitor the spring drought in Guanzhong, Shanxi Province. The results showed that the monitoring results from the new model, which also took more considerations of the effects of the ground coverage conditions and meteorological elements such as wind speed and the water pressure, were much better than the results from the model of vegetation water supply index. From the view of the computing times, service effects and monitoring results, the simplified crop water shortage index model was more suitable for practical use. In addition, the reasons of the abnormal results of CWSI > 1 in some regions in the case studies were also discussed in this paper.