| This paper selects the monthly data of average temperature,precipitation,maximum temperature and minimum temperature of 7 stations in Mianyang City from 1968 to 2018,using linear tendency estimation method,Mann-Kendall mutation test method and wavelet analysis method to analyze Mianyang Analyze the temporal characteristics of the city's climate,and use the IDW inverse distance weighting method to analyze the spatial characteristics of Mianyang's climate.The main results are as follows:(1)The annual and four-season average temperature of Mianyang City has warmed significantly in the past 51 years.The annual temperature growth rate in the northern plateau and mountain area is 0.232?/10 a,and the central and southern plains and hilly areas have a significant warming trend,reaching 0.492?/10 a.The temperature rises quickly in spring and autumn,and slower in summer and winter.During the study period,there were mutation points,all of which were mutation years from 2000 to 2018,and the temperature increased significantly.The mutation years in the plateau and mountain regions are earlier than those in other regions.The mutation occurs earliest in autumn,and the mutation trend is more pronounced than in other seasons.The annual average temperature has the characteristics of multi-time-scale variation.Plain and hilly areas have a change period of 8a,>51a,and high mountain areas have a change period of 4a,7a,and 41 a.The average temperature of the four seasons also has the characteristics of multi-time scale changes.The spatial distribution of annual average temperature in Mianyang City is decreasing from the southeast to the northwest,and the regional spatial differences are large.The annual average temperature tendency rate gradually decreases toward the north,east,and south with Fucheng District as the center.The main reason is that the urban scale of Fucheng District continues to expand and the urban heat island effect is becoming more and more obvious.Pingwu County has the lowest average temperature tendency rate.This is because Pingwu is a mountainous area with high altitude and relatively lagging social and economic development.(2)In the past 51 years,the average annual maximum temperature increase rate in Mianyang City is higher than that of the plain and hilly area(0.335?/10a)than the mountain area(0.205?/10a);the average annual minimum temperature increase rate is the plain and hilly area(0.529?/10a)Larger than high mountain areas(0.126?/10a).The annual average maximum temperature rises quickly in spring and summer,and slower in autumn and winter;the annual average minimum temperature is the fastest in spring and decreases in winter.The mutation points of the annual average maximum and minimum temperature all appeared in the 1990 s,and it was a significant mutation year after entering the 21 st century.The annual average maximum temperature increased significantly;the mutation time of the high mountain area was earlier than that of the plain and hilly area.The annual average maximum temperature has periodic changes on multiple time scales,with larger amplitudes in plain and hilly areas;the annual average minimum temperature also has periodic changes on multiple time scales,with larger amplitudes in high mountain areas.The spatial distribution of the annual average maximum and minimum temperatures in Mianyang City decreases from southeast to northwest.The temperature tendency rate of the annual average maximum temperature gradually decreases from southeast to north and from west to east;the temperature tendency rate of the annual average minimum temperature is respectively Santai County and Fucheng District are high centers and decrease outwards.The temperature tendency rate of the four seasons is the smallest in the northeast and the largest in the south.(3)In the past 51 years,there are obvious regional and seasonal differences in the temporal changes of precipitation in Mianyang City.The annual average precipitation has an increasing trend in the southern hilly area,and the variation is large;in the northern high mountain area,it has a decreasing trend,with a small variation;in the central plain area,it decreases significantly with a large variation.Seasonal average precipitation showed a decreasing trend in alpine regions except for autumn,with a small change;plain areas increased in spring and autumn,and decreased in summer and winter;hilly areas increased except in autumn.The average annual precipitation fluctuates frequently during the study period,but there is no sudden change.Summer precipitation in high mountain areas decreased significantly from 1988 to 2003,and winter precipitation increased significantly from 1994 to 1996;seasonal precipitation in plain areas fluctuates frequently;autumn precipitation in hilly areas was significant in the 1990 s and 2000 s Decrease,winter precipitation increased significantly in the late 1990 s.The annual average precipitation has the characteristics of multi-time-scale variation.There are 3a,9a,20 a,37a change cycles in plain areas,11 a,17a,37 a change cycles in high mountain areas,and 2a,9a,21 a change cycles in hilly areas.The periodic oscillation of the seasonal average precipitation is stronger than the annual average precipitation,and the four seasons have obvious multi-time-scale periodic changes.The average annual precipitation is unevenly distributed,with more in the northwest and less in the south,showing a trend of decreasing precipitation with Beichuan as the center.From the perspective of growth rate,Jiangyou City is the area with the largest growth rate in the study area(prone to flood disasters),with Jiangyou City as the center,decreasing to the surrounding area,and the negative growth rate in Fucheng District is the most obvious.The reason is that the urban scale of Fucheng District continues to expand,and the urban heat island effect and dry island effect are becoming more and more obvious.In spring and autumn,there is more precipitation in the south and less in the north;summer precipitation is the most in the northwest;autumn precipitation is the most in the northwest and southeast.In terms of growth rate,the growth rate of precipitation in spring is the largest in the south;negative growth in the west in summer,the growth rate of Jiangyou City is high,and summer waterlogging is prone to;the overall negative growth in autumn,the negative growth in southeast is slightly slow;the growth rate in northwest and southwest is large in winter. |
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