Spatio-temporal Evolution Trend And Influencing Factors Of Precipitation In Belt And Roud Based On TRMM Data

In the context of global warming,the frequency and intensity of extreme weather events continue to rise.Precipitation is one of the most basic climatic factors,and its temporal and spatial changes have an important impact on human life.It is of great significance to study the distribution characteristics,change rules and influencing factors of regional precipitation to analyze the water cycle and forecast under the background of climate warming.In the context of global warming,the advancement of the “Belt and Road” strategy is inseparable from the consideration of climate change.Therefore,a correct understanding of the characteristics and influencing factors of precipitation changes in the “Belt and Road” regions will be the prediction of future climate change in the “Belt and Road” region,Provide reference for forecasting disaster reduction.Based on Tropical rainfall measurement satellite data(TRMM),from 1998 to 2018,the Spatio-temporal evolution trend of precipitation in the "Belt and Road" region and its relationship with ENSO were analyzed by using the method of trend analysis,correlation analysis and Annual Precipitation Concentration Index(PCI).The results show that:(1)The spatial precipitation distribution in the Belt and Road area has obvious in sea-land distribution and significantly different in seasonal distribution.East Asia,Southeast Asia and South Asia have the most precipitation in summer,the least in winter,and the seasonal differences are obvious.More,less in summer.The annual precipitation presents a spatial distribution that gradually increases from low-value centers in the arid region of northwest China—central Central Asia—Iranian plateau—Arab Peninsula—Egypt to the southeast and northwest.(2)Except for the precipitation in the Belt and Road is decreasing in autumn,the spring,summer and winter seasons and annual precipitation are increasing.In the climatic zones,tropical zones precipitation is decreasing in spring,autumn and winter,increasing in summer and annual precipitation;warm temperate zones spring,summer and annual precipitation are decreasing,autumn and winter precipitation is increasing;arid zone except winter precipitation is decreasing,spring,summer and autumn season and annual precipitation are increasing.The four seasons and annual precipitation in the snow zone and the polar zone are increasing.The spatial distribution of the change trend revealsthat the autumn and annual precipitation in 60% of the study area indicates an increasing trend,and the area of the increase and decrease trend in spring,summer,winter are basically half of the study area.Seasonal differences in change trends in most regions are obvious.The coefficients of variation for each season and annual precipitation range from 0-4,and the areas with spring,summer,autumn,winter and annual precipitation coefficients greater than 1 account for 5%,14%,12%,9%,and 0.7% of the Belt and Road region,respectively.The spatial distribution of variation coefficient is similar to annual precipitation.(3)The analysis of the spatial and temporal distribution of precipitation concentration index and the change trend show that the PCI in Southeast Asia is the smallest,and the precipitation is evenly distributed throughout the year.The precipitation PCI in southwestern Egypt and northern Saudi Arabia is the largest,and the precipitation is concentrated throughout the year.The remaining 65% of the regions have seasonal changes in precipitation.Judging from the annual distribution of precipitation,the largest precipitation month in 51% of the regions is in summer.Among the five climatic zones,the PCI in the tropical zone is the smallest,followed by the warm temperate zone,the snow zone zone,and the polar zone,and the PCI in the arid zone is the largest.The largest precipitation month in 51% of the study area is distributed in summer,and the climatic zone in the middle tropics,snow zone zone and polar zone shows insignificant increasing trends,the speeds are 0.21% / a,0.01% / a,0.01% / a;warm temperate zone;The concentration of precipitation in the arid zone and the arid belt represents the trend of decreasing fluctuations,the speeds are-0.02% / a and-0.05% / a,respectively.For the entire region,the concentration of 55% in the southeastern Egypt,Saudi Arabia,Iran and other regions indicates a decreasing trend.(4)The vertical distribution of precipitation is generally characterized by a gradual decrease in precipitation with increasing altitude.The change trend of precipitation is an increasing trend at the altitudes of 600m-1600 m and 4200m-5400 m,and the trend of precipitation increase and decrease alternately at 1800m-4000 m.The vertical distribution of the PCI multi-year average shows an M-shaped change trend.The elevations of 800-1000 m and 5000-5200 m above sea level are PCI high-value stages.PCI changes in trend except for areas where the elevation is less than zero,and PCI in areas with an elevation of less than 3400 m.In areas where the elevation is greater than 3800 m,PCI is increasing.(5)Correlation between precipitation and atmospheric circulation indicates that AO is significantly negatively correlated with precipitation in Europe and negatively correlated in Central Asia;NAO is significantly positively correlated with precipitation in Southwest Asia and Central Asia,and the rest Signifi cantly negative correlation.The correlation coefficients between PNA and AAO and precipitation did not pass the significance test in most areas.(6)The correlation between monthly precipitation and sea surface temperature in the Nino3.4 area during the same period indicates that the proportion of areas with positive and negative correlations is 76.6% and 23.4%,of which the areas that pass the 0.05 level significance test The area is 39% and 8%,respectively.The difference in average precipitation between ElNino and LaNino indicates a positive value in 47% of regions in East Asia,Central Asia,and the southern Arabian Peninsula.The difference in most regions is 500–1000 mm,and the remaining regions represent negative values.The relationship between precipitation and NINO 3.4 indicates that the monthly precipitation in 55% of the study area is most related to the SST with a delay of 0–3 months.Except for Western Europe and southern Egypt,93% of the time-delay correlation coefficients in the study area passed the 0.05 level significance test(indicating that positive and negative correlations accounted for 78% and 15%,respectively),indicating that the time-delay correlation is Closer than that of the same period.