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Northwest Normal University (2022)

Response of NDVI to Extreme Climate in Semi-arid Sandy Land in China


Titre : Response of NDVI to Extreme Climate in Semi-arid Sandy Land in China

Auteur : 张海妮

Grade : Master 2022

Université : Northwest Normal University

Résumé partiel
Climate is one of the main factors affecting vegetation dynamics.Long-term climate change leads to slow changes in vegetation distribution and dynamics,and vegetation responds acutely to short-term climate extremes.At present,there are no studies on how extreme climate affects vegetation coverage in four sandy lands in semi-arid China.Based on the MODIS NDVI data from 2001 to 2019 and the temperature and precipitation data from 1958 to 2019 of 26 stations in the semi-arid sandy land,the extreme climate indices of each station were calculated by using RClim Dex model.The spatial-temporal variation characteristics of extreme climate events,the spatial-temporal variation characteristics of vegetation index(NDVI)and its response to extreme climate were analyzed by using trend analysis and correlation analysis.The main conclusions are :(1)The interannual variation trend of 16 extreme temperature indices from 1958 to2019 showed that the overall warming trend was significant in the four sandy lands in the semi-arid region.The extreme temperature indices such as TN90 p,TX90p,SU25,TR20,WSDI and the four extreme indices all showed a significant upward trend(P<0.05).Frost days(FD0),freezing days(ID0),cold duration index(CSDI)and other extreme temperature indexes that represent low temperature showed a very significant downward trend(P <0.01).The change trend of extreme temperature index at each station is consistent with the general trend,showing that the warm index increases,while the cold index decreases.The slope difference of extreme temperature extreme index among different stations is not big.(2)From 1958 to 2019,the interannual variation trend of extreme precipitation index in the study area showed that the total precipitation in the study area increased slightly(P>0.05).The five short-term extreme precipitation indexes,one-day maximum precipitation(RX1day),five-day continuous maximum precipitation(RX5day),heavy precipitation(R95p),extremely extreme precipitation(R99p),and annual mean rainy day precipitation intensity(SDII),showed an increasing trend.The precipitation day indices such as moderate rain days(R10)and heavy rain days(R20)showed an increasing trend,and the variation trend of extreme precipitation indices at different stations was significantly different.

Mots clés : NDVI ;Extreme climate ;Change trend ;Correlation analysis

Présentation (CNKI)

Page publiée le 6 mai 2023