Study On The Changes In Extreme Precipitation And Its Relationship With Air Temperature On The Qinghai-Tibetan Plateau

The Qinghai-Tibetan Plateau is a sensitive and region of global climate change,and the change of extreme precipitation has a significant impact on the regional water cycle and the design and management of projects.It is of great significance for water resources management in the Qinghai-Tibetan Plateau to study the variation of extreme precipitation over the Qinghai-Tibetan Plateau considering climate change.Based on the daily precipitation data observed at 49 meteorological stations over the QinghaiTibetan Plateau from 1963 to 2019,the percentile method was used to determine the threshold and identify the extreme precipitation events.Linear tendency estimation method and the MannKendall mutation test were used to analyze the change of extreme precipitation index,and the spatio-temporal variations of the trends in extreme precipitation events over the Qinghai-Tibetan Plateau were revealed.The Clausius-Clapeyron relationship was used to explore the relationship between extreme precipitation intensity and the air temperature over the Qinghai-Tibetan Plateau.The response of fast runoff to temperature rise during 1963-2014 in two typical regions,namely the source region of the Yellow River and the source region of the Yangtze River.The results show that the six extreme precipitation indices over the Qinghai-Tibetan Plateau from 1963 to2019 show different spatial trends,and the extreme precipitation amount,frequency and intensity show overall increasing trends,and there was no significant decreasing trend observed at all the stations.The stations that showed significant increase in extreme precipitation index were mainly located in the central,northern and southeastern regions of the Qinghai-Tibetan Plateau.The extreme heavy precipitation amount and the frequency of extreme heavy precipitation over the Qinghai-Tibetan Plateau showed significant increasing trends,and the change of the heavy precipitation corresponding to the 95% percentile was more obvious than that of the extreme heavy precipitation corresponding to the 99% percentile.However,the increasing trend of extreme precipitation intensity was not significant.From 1963 to 2019,the extreme precipitation in the eastern part of the source region of the Yangtze River showed an increasing trend.However,the extreme precipitation in the source region of the Yellow River showed an increasing trend in the northwest and a decreasing trend in the southeast.At the regional scale,the daily extreme precipitation over the Qinghai-Tibetan Plateau from 1963 to 2019 showed a peak structure.It risen first and then declined with the increase of temperature.The rate of the daily extreme precipitation intensity with the temperature change decreased as the increase of the threshold for extreme precipitation,while the peak temperature increased.At the station scale,the rate of change in the90% percentile extreme precipitation intensity with temperature had spatial differences.Most of the extreme precipitation intensity over the central and eastern part of the Qinghai-Tibetan Plateau had a peak structure.Before reaching the peak temperature,the rate of change in extreme precipitation intensity with temperature is less than the theoretical value of Clausius-Clapeyron relationship,which is 7%/?.In the southern part of the Qinghai-Tibetan Plateau,the relationship between 90% percentile extreme daily precipitation intensity and air temperature was commonly negative,and the decreasing rate of extreme precipitation with temperature at most stations were more than 14%/?.The possible reason for the peak structure was that with the temperature reaching a critical point,the humidity in the air decreased,leading to the decrease of the daily extreme precipitation with the increase of the temperature.From 1963 to 2014,the annual total runoff and fast runoff in the source region of the Yellow River both showed a decreasing trend,and the distribution within a year showed a double-peak pattern,while the annual total runoff and fast runoff in the source region of the Yangtze River both showed an increasing trend and the distribution within a year was unimodal.The relationship between the 90 percentile extreme fast runoff and air temperature in the sources of the Yangtze River and the Yellow River also had a peak structure,which was the same as relationship between the 90 percentile daily extreme precipitation and air temperature,but the change rate was different.This difference between the two changes may be caused by human activities and permafrost degradation.The results of this study provide valuable references for the water resources management,engineering design planning on the Qinghai-Tibetan Plateau under the background of climate change.