Characteristics And Trend Judgment Of Drought And Flood In North - Qinling Mountains

Under the background of global warming, China’s climate and environment is also changed significantly. The global warming gives rise to the dramatic changes of all factors of the regional climate system, resulting in a series of natural disasters including the extremely high temperature, low temperature, drought, flood, hail and typhoon etc. and the frequent secondary disasters which dramatically devastate our ecological environment and thwart the stable development of economy and society. As the representative border between north and south, Northern and Southern Regions of Qinling Mountain is the vulnerable and leading district of the climatic change. And the abnormal changes are bound to have great adverse influences on the overall climate. Therefore, it is of great significance to make a deep research on the climatic change and the spatial and temporal changing features of drought and flood and its tendency judgment aiming to apply some theoretical basis and foundation for the plan of water resources, the improvement of ecological environment and the prevention and reduction of the disasters.This paper takes the Northern and Southern Regions of Qinling Mountain as the region for study, which can be divided into three regions:Northern and Southern Regions of Qinling Mountain, Qinling Moutain and Sourthen Regions of Qinling Mountain. With the monthly meteorological data such as average temperature, precipitation, relative humidity and wind speed observed by meteorological stations, the study analyzes the spatial and temporal variations in the Northern and Southern Regions by using the method of logarithm trend line fitting, spline interpolation and tendency judgment. Besides, based on the statistics of the grade and frequency of regional droughts in each station, the paper studies the evolutional law of regional droughts and makes a tendency judgment according to the years that droughts happened. Then, the factors that influence drought are explored.The main results are as follows:(1) During 1960 to 2013, the average annual temperature of the Northern and Southern Regions of Qinling Mountain arises obviously, which is mainly occurred after 1990. The arising trend is also significant in the three divisions, where the temperature rises rapidly after 1990. In the spatial distribution, the annual average temperature roughly shows a distribution feature that decreases from southeast to northwest. The high temperature is mainly distributed in the Qinling Mountains, east and other places south to the Qinling Mountains, while the low temperature center is mainly distributed in the east of Guanzhong Plain, Longdong area as well as other places in Hanzhong--southern Shaanxi. According to the temperature trend rate, the temperature in three regions is ranked as the north of the Qinling, followed by the Qinling Mountains and south of the Qinling.(2) The precipitation of the Northern and Southern Regions of Qinling Mountain from 1960 to 2013 presents an undramatic variation trend. From the division, Qinling Mountain has a tendency of increasing, and the precipitation of the other two regions decreases. The spatial division of the precipitation represents as:less precipitation to the North region of it, especially the Sichuan Basin. The precipitation of both regions is inversely proportional to the rate on the basis of the spatial division. That is, the tendency rate in the high value is a little lower while the precipitation in the low value is increasing.(3) The wind speed of northern and southern region of Qinling Mountain has been slower since 1960 to 2013, especially from 1980s. the fastest wind in this region is concentrated on the east of Guanzhong Plain, southern part of Shaanxi province, the southwest of Henan province, northwest of Sichuan Basin and Hanzhong etc. The lowest wind is concentrated on the middle of Qinling Mountain, northwestern Hubei, the west of Henan province and eastern and southern part of Longnan. From the tendency judgment, the wind speed is becoming slower in this region.(4) The moisture of northern region of Qinling is lower since 1960 to 2013, while the moisture of Qinling Mountain and southern region of Qinling is relatively higher than before. In general, the moisture of Qinling Mountaion and the southern part of Qinling Mountain is relatively high while the Guanzhong Basin and southern part of Shaanxi province is relatively low. That is to say, there are two lowest moisture areas of northern and southern regions of Qinling Mountain, which are Longdong and the northeast region of Guanzhong Basin.(5)During 1960 to 2013, the phenomenon of drought and flood of northern and southern regions of Qinling Mountain is totally converse. That is to say, northern region has more droughts while southern region has more floods. Qinling Mountain is becoming a little drier but not too obvious. Generally speaking, both northern and southern regions of Qinling Mountain are becoming drier.(6) The drought and flood trend of Northern and Southern Regions of Qinling Mountain is concentrated on the year of 2015 to 2018, which will happen in recent 4 years. Northern region of Qinling Mountain will have more droughts in 2017 while southern region of Qinling Mountain will have more floods in 2016. Moreover, we have to pay more attention that both northern and southern region of Qinling Mountain will have more droughts in winter and summer in the year of 2016 which is in accordance with the single people predict.(7) According to the statistic of the activity of sunspots and the frequency of droughts in this region since 1960, it is found that the less active the sunspots are, the more rains fall in this region. While the more active the sunspots are, the more droughts will occur in this region.