Review on Disaster of Hot Dry Wind for Wheat in China

Hot dry wind (HDW) is one of the major agro-meteorological disasters which impact wheat production in North China. From the aspect of its definition, classification and research methods, recent progress are reviewed on its influencing mechanism, meteorological environmental causes, disaster index, spatial-temporal distribution, monitoring and forecasting measures, defensive and mitigation ways, and the future research direction is discussed. In China, HDW can be classified as three major kinds, including high temperature with low humidity, green-dry after rain, and dry wind. HDW can intensify transpiration, damage flag leaf, weaken root activity, shorten growth duration, and decrease accumulated dry matter, chlorophyll content and photosynthetic rate. Meteorological environment of HDW is mainly determined by dry hot-air weather system, influenced by climate warming and soil moisture. Disaster index of HDW can be divided into three kinds:Morphological, synoptic, and comprehensive index. The damage of HDW to wheat is heavy in both east and west parts while light in the central part of China. HDW mainly occurs in three areas, including the Huang-Huai-Hai Plain, Hexi Corridor and Xinjiang. The damage decreases with elevation of altitude, and generally it has no impact in areas higher than 1700-1800 meters. One month before harvest is the main occurrence period of HDW. It starts from early May in China, and postpones to mid-late July from south to north and from southeast to northwest. For winter wheat, the disaster date is earlier than spring wheat. Presently, major monitoring and forecasting methods include ground meteorological monitoring, remote sensing monitoring, classification and forecast based on weather prediction, statistic forecast, and numerical prediction products. Temporal and spatial pattern of HDW in China is obviously affected by the change of wheat plantation layout, climate, irrigation and field management. Under historical climate warming condition, HDW days in most regions have a sudden change in the 1980s and 1990s. During the recent 30 years, HDW days and the degree of influence have increased obviously. Improvement of irrigation conditions obviously relieves its occurrence and influence. Future research directions include incorporating soil moisture into the existing HDW hazard grade index, researching and developing process-based disaster monitor and assessments, prediction and early warning methods, model simulations and business application technologies, investigating the change of spatial and temporal distribution of HDW and the formation of its meteorological environment under future climate change and wheat planting layout change.