Spatiotemporal Variability Of The Relationship Between Precipitation And Temperature And The Response Of Vegetation In Northern China

The evolution of the relationship between precipitation and temperature has a significant impact on water resources and ecological environment.However,the spatiotemporal variability of the relationship between precipitation and temperature has not been fully and systematically revealed,and the response of vegetation to the relationship between precipitation and temperature is not clear.In north China,the region is wide,climate types,more representative in response to global climate change,revealing the relationship between precipitation and temperature in northern China the space-time variability and the response of vegetation to thorough solution to climate change,on northern china,even though a global scale to address water issues and improve the ecological environment and so on all has certain practical reference value.Based on the north China region as the study area,the use of the study area and its surrounding areas,357 weather stations from January 1951 to February 2019,the average minimum temperature,average temperature,average highest temperature and precipitation data,in March 2000 ? 2019 February the normalized difference vegetation index(NDVI)data,using climate trend rate method,correlation coefficient method and so on,analyzed the relationship between precipitation and temperature of space and time variability,and the relationship between the vegetation of precipitation and temperature response of qualitative and quantitative research.The main conclusions are as follows:1.The relationship between precipitation and temperature of warm dry,warm wet,cold dry and cold wet four categories,warm dry and warm wet type relationship and most of the time late to qinghai area in western Inner Mongolia,east and west are a trend of getting early,The occurrence time of cold-dry and cold-wet relationship becomes later from west to east on the whole,and the duration of cold-dry relationship interannual,spring,summer,the duration of the growing season dry,warm wet type relationship longer from west to east,autumn,winter two season decreased with latitude,shorten;in interannual,spring and growing season becomes longer from east to west.In other seasons,the duration of cold-wet relationship decreases with the decrease of latitude.Except winter,the duration of cold-wet relationship becomes longer from north to south.2.In the 1950 s,on the whole,precipitation and temperature is given priority to with cold dry,the relationship between the cold wet,mostly in the 1960 s,the relationship between cold dry,cold wet coverage gradually narrow west,warm dry,warm wet began to become the main relationship type of the northeast,north China and other regions,since the 1970 s,the overall precipitation and temperature in the majority with warm dry,warm wet type relationship,and continued into the 1990 s,after entering the 21 st century,interannual,growth season,the spring precipitation and temperature still is given priority to with warm dry and warm wet,and summer,autumn,winter season three will appear again in the northeast,north China,such as small area,cold dry,cold wet relations.3.The spatial distribution of vegetation index decreased from southeast to northwest in the study area,which was consistent with the climate pattern of warm and humid in the southeast and cold and dry in the northwest.Vegetation index(NDVI)decreased in spring and growing season,and increased in interannual,summer,autumn and winter seasons,especially in central Xinjiang,with the fastest increasing rate in Shanxi and northern Shaanxi,and a gradual slowing trend in northeast and northwest directions.4.Changes in vegetation about the relationship between precipitation and temperature response time and space differences obviously,at the beginning of the 21 st century,the vegetation in the study area is mostly dependent on the relationship between warm dry and warm wet type,and in recent research time 5 ? 6 years,warm dry type relationship and the vegetation growth in the northeast in the studied area more favorable than warm wet type,warm wet,cold,wet relations to rising western vegetation in the study area have a bigger role in promoting,type person relationship can be in a certain extent,optimize in the southeastern part of the study area of vegetation cover condition.5.Vegetation index in different time scales,the relationship between precipitation and temperature response is different,and the growing season in interannual,summer time scales,warm wet type relationship most good for the growth of vegetation in the study area,among them,under the interannual scale wet type relationship,when precipitation in 50 ? 750 mm,the temperature-5 ? 25 ?,vegetation index mostly response between 0.25 ? 0.3.In summer and growing season(all of which are warmwet type),precipitation usually varies from 50 to 600 mm,from 50 to 400 mm,temperature varies from 6 to 30 ?,and from 5 to 21?,respectively.Vegetation index responds to the variation of 0.6-0.7 and 0.3-0.4,respectively,In spring and autumn,the promoting effect of cold-wet and warm-wet relationship on vegetation was greater than that of warm-dry and cold-dry.On the time scale of spring and autumn,the precipitation and temperature under the cold-wet relationship varied between 0?200mm and 2?20?,and the vegetation index responded to it between 0?0.2.The response degree of vegetation in winter to all kinds of relationships is opposite to that in spring and autumn,that is,the warm-dry relationship in winter is the most favorable to the growth of vegetation.However,under the warm-dry relationship in winter,the precipitation is mostly less than 100 mm and the temperature is lower than 0 ?.In this case,the vegetation index mainly responds between 0 and 0.16.In addition,the responses of vegetation to precipitation and air temperature have the same or overlapping regions.For example,when precipitation and temperature change between 100?150mm and10?15?,respectively,the responses of vegetation are both in the range of 0.1?0.2 and0.25?0.3.