Analysis On The Characteristics And Causes Of Temporal And Spatial Evolution Of Meteorological Drought In Liaoning Province Based On SPI

Drought is one of the most serious natural disasters,which has a huge impact on human security and agricultural production.Liaoning Province has become a major agricultural country.Therefore,the analysis of the characteristics of the temporal and spatial changes of temperature,precipitation and meteorological drought in Liaoning Province is expected to provide guidance and scientific support for climate prediction,agricultural production and drought prediction in Liaoning Province.This article took Liaoning Province as the research object.Based on the analysis of the characteristics of temperature and precipitation in Liaoning Province,the standardized precipitation index(SPI)was used to analyze the characteristics of drought in Liaoning Province from multiple scales.Finally,it discussed the factors and factors affecting drought changes.Main driving force: Analyze the correlation between drought characteristics,atmospheric activity and the relative number of sunspots,and use random forest method to analyze the importance of the drought indicators in Liaoning Province.The main conclusions were as follows:(1)Liaoning Province had different degrees of annual and seasonal increases,with a significant increase in annual average temperature of 0.25?/10a;the increasing rate of temperature in the four seasons was different(winter>spring>autumn>summer),of which the highest increase rate in winter was 0.38 ?/10 a,the lowest in summer,0.14?/10 a.Temperature changes had obvious regional differences in space,and the spatial distribution of temperature was more consistent with altitude and latitude.The main cycle of the annual temperature was 28 years,and the secondary cycle was 8 years.The year and spring,summer,and autumn had four alternating changes of "increasingdecreasing" on the time scale of 26-32 years.The annual and seasonal precipitation trends in Liaoning Province were not significant.The annual and seasonal precipitation(except spring)showed a downward trend.The spring precipitation had an upward trend,and the summer precipitation had the largest decline;the summer average precipitation accounts for the largest proportion of the annual average precipitation,which was64.5%.The change of annual precipitation series was most affected by summer precipitation;precipitation changes had obvious differences in space.(2)The drought index in Liaoning Province from 1960 to 2015 showed a decreasing trend rate of-0.12/10 a.Among the changes in the drought index in the four seasons,the summer drought index had a significant trend,while the other three seasons had no significant changes.The tendency rate of winter was 0.007/10 a,and that of summer was 0.057/10 a,indicating that the drought in winter and spring showed a trend of relief;the decreasing trend of drought index in summer was significant,and the tendency rate was-0.17/10 a respectively;the tendency rate of drought index in autumn was-0.13/ 10 a shows a decreasing trend.From a spatial point of view,the annual scale drought index tendency rate of each station was less than zero,and the drought in Liaoning Province was showing an aggravating trend.The longest drought duration in the eastern and central regions of Liaoning Province was much longer than that in the west,with the longest drought duration being 11 months;the longest drought durations of most stations in Liaoning Province occurred in 2014 and 2015.(3)The annual drought frequency in Liaoning Province was 27.2%,with light droughts being the main ones.From a spatial point of view,the frequency of drought in the west of Liaoning Province was the largest,and the frequency of drought in the east and the middle was smaller;among the frequency of seasonal drought,the frequency of winter and spring in the middle is greater than that in the east and west,the frequency of drought in the middle in summer was less than that in the east and west,and the frequency of drought in autumn was in the east and west.Some areas were small.(4)The annual drought station ratio and annual drought intensity in Liaoning Province showed an increasing trend.In 2014 and 2015,the drought station ratio reached a maximum of 100%.The province was all in drought.During the four seasons,the number of drought stations showed an increasing trend,and the drought range was getting wider and wider.The annual and four-season drought types were mainly without obvious drought,but the annual and four-season global drought frequency was higher,reaching more than 20%(except in summer),and 16.1% in summer.(5)There was a close relationship between meteorological drought and precipitation in Liaoning Province.The increase in the annual drought index in Liaoning Province was the result of the combined effect of the annual average temperature increase and the annual precipitation.The combined effect of seasonal temperature and precipitation had led to the change trend of the drought index in different seasons.The ENSO warm event exacerbated the drought in Liaoning;the annual-scale drought index and the PDO index are positively correlated with the AO index;the annual-scale drought index and the relative number of sunspots are negatively correlated.Combined with the random forest method,it can be seen that the main driving force affecting drought was sunspots;sunspots indirectly affect drought through factors such as temperature and precipitation.