Abstract:
Abstract: It is significant to research the drought occurring and extent regularities to provide technical supports for disasters prevention. The new meteorological drought evaluation index was suggested, which fully considered the matching degree between precipitation process and crop water requirement. Based on daily mean temperature and precipitation data from 1951 to 2010, the meteorological drought occurring features for corn in Xi'an City, Shaanxi Province were analyzed by the fractal analysis method. Meanwhile, the crop production loss caused by drought was calculated based on information diffusion technology, according to the unit yield data of corn in Xi'an from 1949 to 2015. Firstly, the values of meteorological drought extent for corn in historical year were calculated by the new meteorological drought index. According to the rescaled range analysis method, the trend values of meteorological drought extent for corn were calculated and the time characteristics were analyzed. The occurrence time of meteorological drought had fractal characteristics. The rescaled range method could achieve good results when the number of samples was about 14 according to a large number of tests. In the past 60 years, the meteorological droughts occurred for 30 times in Xi'an, once every 2 years on average. From 2001 to 2010, the frequency increased to once every 1.25 years on average. The extent of meteorological drought for corn mainly showed a very slow upward trend, and the Hurst index for meteorological drought extent sequence was 0.930 7. Secondly, according to the moving average method improved by information diffusion technology, the values of trend production of corn were calculated. The tendency of trend production of corn was described by information diffusion regression method. On basis of trend production calculation, the values of yield reduction rate of corn that were considered to reflect the extent of crop drought were analyzed by information diffusion fitting technology. The trend yield of corn increased in fluctuation, and the average trend yield of corn from 2011 to 2015 was 5 468 kg/hm2. The crop drought degree showed a slow downward trend. Comparing the extent of meteorological drought and the features of crop drought for corn in Xi'an, it was found that the correlation between the meteorological drought degree of corn and the drought degree of crops was not obvious, but their cycles of change were basically the same, and after treatment by using information diffusion technology, the trend presented a feature of alternation of obvious peaks and troughs. Finally, the meteorological drought degree in Xi'an in 2023, which is about the fortieth drought year, is estimated to be about 1.2. The yield loss is estimated at about 1.35%, according to the current drought resistance ability and technical level, and the estimated corn yield per unit area is about 5 394 kg/hm2. This research is of guiding implications to the prevention of disaster and yield reduction of corn in Xi'an City.