Study On The Temporal And Spatial Distribution And Correlation Of Precipitation, Temperature And Vegetatio

Precipitation and temperature are climate factors that have an extremely important impact on human production and life and the growth of terrestrial organisms,but are currently facing climate crises such as drought and global warming.As one of the components of terrestrial ecosystem,vegetation plays an active role in improving the climate and ecology in the region.Therefore,studying the spatial and temporal distribution and correlation of precipitation,temperature and vegetation in the Jinsha River basin upstream of the water intake point of the Central Yunnan Diversion Project provides a reference basis for the management and scheduling of water resources in the basin,the dynamic balance of environmental restoration and protection and the rational development of plant resources,which is of great practical significance for protecting the ecological environment and improving the climate.Based on the precipitation,temperature and MODIS-NDVI data from 2000-2019,this paper analyzes the precipitation,temperature,and vegetation NDVI in the Jinsha River basin upstream of the water intake point of the Central Yunnan Diversion Project using a combination of models and methods such as cloud model,kriging interpolation,one-dimensional linear regression trend method,M-K test,wavelet analysis,like element dichotomous model,and correlation analysis.The variation and distribution of precipitation,air temperature and vegetation NDVI in time and space in the Jinsha River basin upstream of the water intake point of the Central Yunnan Diversion Project were analyzed,and the interrelationship between precipitation,air temperature and vegetation NDVI was further studied.The contents of the study and the conclusions obtained are as follows.(1)From the perspective of time,the intra-annual precipitation distribution in the study basin is uneven,with the maximum precipitation in July and the minimum in December,there are three scales of cycle changes in 20 years,and the first main cycle in the study time domain is 15 a.Interannual,spring and autumn precipitation show an upward trend,but only autumn passes the 0.05 significance test;summer The precipitation in summer,winter,and autumn showed a decreasing trend and failed the significance test;according to the magnitude of precipitation,the ranking was "summer,autumn,spring,and winter".Spatially,the interannual precipitation in the study basin shows a trend of "more in the north and less in the east,more in the west",and there is a precipitation extreme low point in Batang County,Sichuan Province.In the four seasons,there are obvious east-west differences only in summer and autumn;the precipitation in most areas of the upper and middle parts of the basin shows an increasing trend,while the precipitation in the lower part of the basin basically shows a decreasing trend;there are obvious latitudinal differences in the trend.(2)From the perspective of time,the average temperature of the study basin has a large monthly difference,with the highest average temperature in July and the lowest in January,and the distribution of precipitation and temperature within the year is similar;over the past 20 years,there are 3 mesoscale cycles of temperature change patterns,6a being the first main cycle of temperature change;interannual and four-season temperatures are on an upward trend,with interannual and spring showing a significant upward trend,in accordance with the high and low temperatures for "The inter-annual and four-season temperature trends are both up,and the interannual and spring show a significant upward trend.From the spatial point of view,the overall trend is "high in the south and low in the north";there are extremely high temperature areas in Batang and Derong counties of Sichuan Province and extremely low temperature areas in Shangri-La City of Yunnan Province;there are obvious differences in temperature between seasons,and there are obvious north-south differences in the basin;the spatial distribution of temperature in each season is similar to the interannual temperature.The spatial distribution of temperature in each season is generally similar to the interannual temperature distribution.The temperature in the vast majority of the basin showed an increasing trend from 2000 to 2019;only a small amount of decreasing trend was observed in the tail of the upper part of the basin and the middle of the lower part of the basin.(3)From a temporal perspective,the NDVI values in the study basin vary widely from month to month during the year,with a maximum value in August and a minimum value in March;over the past 20 years,the interannual and spring and winter NDVI growth trends are significant,while the growth trends in summer and autumn are not significant;the NDVI values of the four seasons are in the order of "summer,autumn,spring and winter".The spatial distribution of interannual and seasonal NDVI values showed a characteristic of "high in the east and low in the west,high in the south and low in the north";the NDVI in most areas of the study watershed tended to be stable and mildly improved over the past 20 years,and the vegetation growth was stable to good.The trend of vegetation cover changes in each level of the study watershed varies,with levels Ⅰand Ⅲ showing a decreasing trend,and levels Ⅱ and Ⅴ showing an increasing trend.(4)The correlation of NDVI with precipitation and air temperature in the study watershed within the year was very high and passed the significance test of 0.01.The response lag of NDVI to precipitation and air temperature was about one month,and the correlation of NDVI with precipitation and air temperature between years was high,and the correlation of NDVI with precipitation was slightly better than that with air temperature,which passed the significance test of 0.05;while the correlation of air temperature with NDVI seasonally was The correlation coefficient between precipitation and NDVI passed the 0.05 significance test only in summer,while the correlation coefficients between air temperature and NDVI in spring,summer and winter passed the 0.05 significance test,and the correlation between NDVI and precipitation and air temperature was better at stations located in the upper part of the watershed and worse in the middle and lower parts of the watershed.Spatially,the area of positive correlations of NDVI with precipitation and air temperature in the interannual,spring,summer and autumn seasons of the basin were larger than the negative correlations,mainly in the upper section of the basin;while the area of positive correlations of NDVI with precipitation and air temperature in winter was smaller than the negative correlations;spatially,the correlations of NDVI with air temperature were better than those with precipitation,which were the same as the results of the temporal correlation study.