Temporal-Spatial Variations Of Extreme Climate Events Of Northeast China In The Last 50 Years

Since human and natural systems may be especially affected by changes of extreme climate event, the main objective of my research is to detect the possible temporal-spatial changes of these extreme events in Northeast China nearly the last fifty years. The extreme climate threshold is defined by the 95th percentile of daily meteorological elements when they are arranged by ascending or descending. Thereby, some major conclusions can be revealed.1. There are obvious differences of extreme high (low) temperature threshold of Northeast between north-south and east-west. The threshold of seasonal extreme high (low) temperature of southwest area is general bigger than that of northeast area. The high threshold of extreme precipitation is mainly distributed in the east of Changbai Mountains and Songnen Plain, whereas the low threshold is in Chifeng City, Tongliao City, Hinggan League and Hulun Buir City of Inner Mongolia (Eastern Inner Mongolia). Seasonal extreme precipitation threshold of Southeastern Northeast China is larger than that of Northwestern region. The minimum threshold of extreme precipitation of each season occurs in Eastern Inner Mongolia.2. Extreme high temperature event occurred in Northeast from 1961 to 2007 rise and extreme low temperature event descend. Extreme high (low) temperature events are up in spring, summer, autumn, and down in winter. Extreme high (low) temperature event occurred in Chifeng and Tongliao of Inner Mongolia, central and western of Liaoning and western of Jilin, but some of contribution differences are in seasonal extreme high (low) temperature event.3. Growing season length of Northeast is in an increasing trend in the last fifty years, and on the contrary, days of frost and ice are on the decline obviously. Chifeng and Tongliao, western of Jilin and most parts of Liaoning are the most obvious reduction areas of ice days. Frost days obviously decreased are mainly distributed in Eastern Inner Mongolia, most of parts of Jilin and Liaoning. Regions of growing season length increased in the past fifty years are concentrated in Northeast Plain.4. Extreme precipitation event in Northeast China were in a weak downward trend, but they changed in a big margin. Extreme precipitation event in spring were a weak inverse parabola shape and the other three seasons are parabolic in different degree. High Frequency of extreme precipitation concentrates in central and eastern parts of Liaoning, southeast Jilin; extreme precipitation rarely occurs in Eastern Inner Mongolia, western Jilin and Liaoning. Four seasons on the spatial distribution of extreme precipitation event are basically as same as extreme precipitation. Large amount of total extreme precipitation concentrated in eastern Liaoning, southeast Jilin , southern and western regions of Heilongjiang. Intensity of extreme precipitation show weak parabolic.5. The average temperature of Northeast China in the past fifty years is consistent with global warming, its annual growth temperature rate increases larger (0.39℃/ 10a). Extreme low temperature event close contact with mean annual temperature, especially extreme low temperature event of winter and extreme low temperature which are negatively correlated significantly with mean annual temperature correlate closely. Cold days, cold nights, warm nights, ice days and growing season length are significantly correlated with mean annual temperature; cold days, cold night and ice days is strongly sensitive of standard deviation of annual mean temperature. Rising of annual mean temperature affect extreme precipitation event unobviously.