Simulation And Projection Of The Regional Meteorological Drought Event Over China

An improved drought index based on the effective precipitation index, called IWAP, has been developed in this article. Then, using the output of CanESM2from CMIP5(Coupled Model Intercomparison Project),simulation of daily precipitation and IWAP drought index of the570stations in China was carried out. Besides, with applying GLM downscaling technique and the objective identification technique of regional extreme events (OITREE), China’s regional meteorological drought events were identified. And the simulation capability of CanESM2is assessed by means of comparison between observation and simulation, In the end, the feature is been analyzed, which is the projection of regional meteorological events in next nearly100years. The main conclusions are as follows:(1)Based on the effective precipitation drought index of the Weighted Average Precipitation (WAP),an improvement study which includes two aspects was carried out. After determining the two parameters of the WAP index and removing regional and seasonal differences, an improved WAP drought index named IWAP index has been developed. Then, a comparison analysis between IWAP index and Ci index was carried out, and the results shows that IWAP index has a good correlation with Ci index in most of China especially in mid-eastern China. In identifying Regional meteorological drought events, IWAP index also shows good consistency with Ci index on beginning time, ending time, impacted area and drought center. In addition, IWAP index shows a stable ability during a drought process, while Ci index and Pa index tend to show unreasonable instability mainly because of the algorithms of themselves. However, IWAP index also has some limitations, such as that the index is unsuitable to be applied in most of the Tibet Plateau and the regions with annual average precipitation less than300mm.(2)Using the new drought index IWAP, it was found that CanESM2has a good ability in simulation of IWAP, with correlation coefficients between the simulation and the observation exceeding0.5nationwidely, only relatively small in the Sichuan region and the root mean square error decreasing from inland of the northwest to the southeast coast, with the minimum in regions from the Central China to the East. The frequency of China’s regional meteorological event in the simulation shows a weak decreasing trend (-0.2/10years), while that in the observation has a weak upward trend (0.2/10years). The seasons when the regional meteorological drought events start and end show agreement in the simulation and observation. The extreme intensity, the cumulative impact area, the greatest impact area and the integrated intensity in both simulation and observation show no significant increase and decrease trends, while the cumulative intensity and the duration show obvious upward trends, which means the cumulative intensity has a decreasing trend and the days of drought events has got longer. The spatial distribution patterns of frequency and cumulative strength in simulation and observation show good consistency, with only the area of high frequency in simulation being much bigger than in observation.(3)The feature of regional meteorological event in the next nearly100years has been analyzed, and it was found that the average IWAP index has a downward trend, which means an aggravation in drought. During the projection period, drought days show low values in the eastern Inner Mongolia to the Central China, the North China and the Yangtze River region, the days of drought events has got longer and high values in the eastern part of the Northeast China, the southeastern coast of China and the western Southwest China. From winter to summer, drought days gradually increase, and then gradually decrease in autumn. The greatest impact area, the extreme intensity and the duration has a weak downward trend, which means in the future the greatest impact area will be smaller, the days of drought events will get shorter and the extreme intensity at a single station will be severer. Meanwhile the cumulative intensity, the cumulative impact area and the integrated intensity has a upward trend, which means the cumulative intensity will be weaker, the cumulative impact area will be bigger and there will be a severer drought period in the future. The frequency of drought event has high values in the east of the Northeast China, the Bohai Sea region, the Southeast China and the east of the Tibetan Plateau to the Yunnan region, and weak high values in the West China. But there has low values in the North China、the Central China to the Guizhou region. There is a good relationship between the spatial distribution of the frequency and the cumulative strength. There are both same point and different point between the spatial distribution of the cumulative strength of projection and simulation.