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Lanzhou University (2017)

Trends in Summer Daily Precipitation in the Northwest China during 1957-2014


Titre : Trends in Summer Daily Precipitation in the Northwest China during 1957-2014

Auteur : 朱煜思;

Grade : Master’s Theses 2017

Université : Lanzhou University

Climate warming will change the global precipitation patterns,precipitation pattern change and regional differentiation will have greater uncertainty,so the research trend of precipitation in different regions is one of the research hotspots in the current global climate change.In recent decades,precipitation in Northwest China,especially in Xinjiang,has increased significantly,which may have an important impact on the ecosystem.The results show that there is a spatial difference between the total precipitation and daily precipitation in Northwest China,which can be used as a basis for analyzing the spatial variability of vegetation spatial heterogeneity in the future.Based on 1957-2014 summer season(June-August)meteorological data collected from 187 weather stations across the northwest China(33°-48°N,73°-116°E),this study uses the Mann-kendall Test and ordinary Kriging interpolation method.The study(1)assessed the similarity and difference among 11 widely used daily precipitation indices using cluster analysis,(2)compared the spatial and temporal trends in these indices before and after the 1987.The daily precipitation indice can be used to describe the characteristics of precipitation in different aspects,the indices are divided into two categories : the first cluster analysis cluster characterization of precipitation(precipitation days and precipitation intensity)events,the first clustering can be divided into three groups,second clustering description precipitation distribution.The results show that:1)The northwest China 1957-2014 summer annual precipitation average value is 183 mm,the northwest China 1957-2014 summer precipitation increased from the west to the east gradually increasing trend in recent 58 years,annual precipitation decreased(-0.78mm/10a),but the number of days of precipitation,drought duration,precipitation intensity increased,precipitation is more and more uneven,which Eastern and southern precipitation in Xinjiang was the lowest,only 0-50 mm.2)The average annual precipitation in Xinjiang in recent 58 years is 61 mm,precipitation,precipitation days and precipitation intensity increase,the number of days of drought has decreased,precipitation is more and more uniform,especially in Western Xinjiang.And 1957-1986 years and two years with 1987-2014 regression line displacement is very obvious,they intercept vary greatly,that around 1987 precipitation intensity does produce a sudden change,there was a sudden change of climate,climate change from warm dry to warm wet.3)The average annual precipitation of Gansu-Qinghai area in the past 58 years is 151 mm,which is mainly in 0-300 mm,the overall trend is increasing from northwest to Southeast,and the precipitation in the southern part of Qinghai is the highest.In the past 58 years,precipitation,precipitation days and precipitation intensity showed an increasing trend,and the growth rate slowed down after 1987,and the precipitation in the future Gansu-Qinghai area may increase.4)The overall trend in the Loess Plateau in summer precipitation is increasing from northwest to Southeast,during the past 58 years the average annual precipitation is 271 mm,differences in the spatial distribution of precipitation trend in Loess Plateau is great,mainly in 100-400 mm.Over the past 58 years precipitation decreased,reduce the number of days of precipitation,but the drought duration,increasing precipitation intensity,precipitation is more and more uneven,after 1987,the entire study area especially Loess Plateau,the spatial distribution of precipitation is the most uneven.5)The spatial redistribution of precipitation resulted in a trend of “dry regions get wetter,wet regions get dryer” in our study area,which is different from the global trend of “dry regions dry out further,whereas wet regions become wetter as the climate warms”

Mots clés : the northwest China; climate change; trend; daily precipitation; precipitation indice; spatial and temporal distribution; Mann-kendall test;

Présentation (CNKI)

Page publiée le 25 janvier 2018