Study On The Distribution Of High Temperature Damage Torice In The Middle And Lower Reaches Of The Yangtze

With global warming, hot weather occurred frequently, of which high temperature damage(HTD) impacted on rice increasingly. The middle and lower reaches of the Yangtze river region is one of the main production areas of rice in China, studies on the occurrence rules of HTD of which is of great significance to reduce high temperature threat and the economic loss. In this paper, based on the records from 1951 to 2010 of a total of 104 weather stations in the middle and lower reaches of the Yangtze river region, mathematical statistics and GIS technology was used to analyze the time-space distribution features of HTD, and build the high temperature event probability model to simulate the probability of high temperatures in the region. The main research contents and conclusions are as follows:1. Space calculation model was used to analyze the spatial distribution of all parts in the region with the factors HTD occurrence frequency and high temperature strength separately. The results showed that the extent of the damage in the areas with high altitude or offshore was generally weak, relatively weaker at high altitudes, most serious in Jiangxi and Zhejiang Midwest, and of the 6 provinces the extent of HTD in Jiangsu was the weakest.2. HTD in the middle and lower reaches of the Yangtze river region slightly increased, which was found by statistical analysis of the high temperature damage for almost 50 years. Frequency and intensity of HTD were with the decadal variation characteristics of decreasing firstly and then increasing after. Among the 10 years in the early 21 st century the average frequency of HTD reached to the most 3.21 times per year, and the average intensity reached at maximum 31℃ per year.3. Mann- Kendall was used to test mutation of the historical average high temperature strength in all the provinces. The results showed that four provinces Anhui, Jiangsu, Zhejiang and Hubei existed mutation phenomenon in 2002. Before 2002, high temperature strength in the middle and lower reaches of the Yangtze river region was 20.56℃/a, and after 2002 was 33.72℃/ a, which rose more than 50%.4. Two-dimensional joint distribution function was constructed by day sequence and its high temperature strength as random variables to simulate the occurrence probability of high temperature events in day sequence and its high temperature strength. The model passed through the reliability testing at the significant level 0.001, the simulation effect was acceptable.5. The model constructed before was applied to determine the date on which high temperature event occurred the most probably, and the probability of the most concentrated 10 days on which the high temperature incident occurred, and its start date and end date in each area. The results indicated that the damage occurred most frequently in late July, and during the period the probability of the high temperature incident occurred around 10 days was between 14.33% ~ 26.55%, and the average probability was 19.68%.6. High temperature value-at-risk as an indicator was put forward to measure the HTD threat degree in different period of time received in each area. With the day sequence of one-day on which high temperature occurred most probably as the center, high risk degree was inspected at three date intervals ranging around 10, 20 and 30 days respectively. The results suggested that HTD threat degree was the largest in Lishui and Jinhua in Zhejiang, Ji’an and Guixi in Jiangxi, Hengyang in Hunan, and Badong in Hubei. Furthermore, according to the probability at different date interval, measures against to HTD for the areas with different risk levels were put forward.