| Under the background of global climate change,extreme temperature events occur In the context of global climate change,extreme temperature events occur frequently.Compared with changes in the average climate,extreme climate changes have a more significant and stronger impact on socio-economic development and ecological environment evolution.Yunnan and Guizhou provinces are areas with high ecological fragility and are extremely sensitive to temperature changes.At the same time,vegetation coverage plays an extremely important role in the ecological service functions of Yunnan and Guizhou provinces.In recent years,the frequent occurrence of extreme temperature events has caused adverse effects on the atmospheric regulation function,water and soil conservation capacity,and the sustainable and stable development of the ecosystem in Yunnan and Guizhou provinces.In view of this,studying the historical change characteristics,spatial differences and future change trends of extreme temperature events in Yunnan and Guizhou provinces,analyzing the causes of extreme temperature events,and further exploring the effects of extreme temperature events on vegetation coverage are not only beneficial to promoting regional ecology The maintenance of environmental protection and ecological construction results can also provide strong support for the sustainable economic development decision-making of Yunnan and Guizhou provinces.Based on the daily average temperature and daily maximum(low)temperature data from the surface weather stations in Yunnan and Guizhou provinces and regions in China from 2000 to 2019,this paper calculates 16 extreme temperature indexes,and analyzes the trend,continuity and cycle of extreme temperature events in Yunnan and Guizhou provinces.Comprehensive and in-depth analysis of characteristics,mutation characteristics,spatial patterns,etc.;at the same time,based on NDVI data to analyze the temporal change trend,mutation characteristics and spatial distribution characteristics of NDVI in Yunnan and Guizhou provinces and regions in China from2000 to 2019;finally,use correlation Analyze and explore the characteristics of the impact of extreme temperature events on NDVI in the region.The main conclusions of this article are as follows:(1)Within 20 years,NDVI has shown an overall increasing trend,and the vegetation coverage level of related areas has shown an upward trend in different seasons.The overall pattern of each season is roughly the same as the annual average pattern,and both show an increasing trend.(2)The results of research on NDVI show that in terms of spatial distribution,NDVI shows very significant differences in distribution characteristics.The data from low to high are northwest,central,southwest and southeast.(3)The extreme temperature in Yunnan and Guizhou provinces is showing a warming trend.In general,the growth rate of the extreme warmth index is higher than the decrease rate of the extreme temperature cold index;the extreme temperature index has different spatial trends;the extreme temperature index has abrupt changes;In the future,the maximum monthly maximum temperature,heat persistence index,cold night days,and cold persistence index will increase in the future,while the number of summer days,hot night days,minimum monthly minimum temperature,maximum monthly minimum temperature,warm The number of night days and warm days will also show a downward trend in the future.(4)The El Ni(?)o-Southern Oscillation Index has the greatest impact on extreme temperature events,and it has a significant impact on extreme low temperature events.Other atmospheric circulations have little effect on extreme temperature events,and all have an impact on extreme temperature intensity events.(5)The warming of extreme temperatures in the past 20 years has played a role in promoting the average annual NDVI.The extreme warmth index and the average annual NDVI are positively correlated,while the extreme cold index and NDVI show a negative correlation.(6)Among the correlations between annual NDVI and annual extreme temperature index,the number of warm night days shows the most significant level of correlation.The correlation between the frequency index of extreme high temperature and NDVI is positive,and except for SU25,the other frequency indexes of extreme high temperature also have a significant effect on NDVI.The influence of low temperature index is higher than that of high temperature index.(7)In the correlation between monthly NDVI and monthly extreme temperature index,the number of warm night days is also the most influential factor.Extreme high temperature index Extreme temperature events have a positive impact on the NDVI in most areas,and the extreme low temperature index shows a significant negative effect on the NDVI results in the study area.If the hysteresis feature is introduced into the research system,it can be confirmed that the impact of the extreme high temperature index of the current month and the previous month on NDVI is generally lower than that of the current month's temperature index,and shows certain spatial differences throughout the study area. |
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