| The Tibetan Plateau(TP)is sensitive to global warming and is a sensitive region for global climate change,while the TP can also have significant effects on the TP and its surrounding areas,as well as global weather and climate,through thermal and dynamical effects.In recent years,extreme weather events have occurred frequently,therefore,it is important to study the spatial and temporal distribution characteristics of extreme precipitation in the surrounding areas of the TP and the occurrence mechanism for the prevention of catastrophic weather.This paper analyzes the spatial and temporal distribution characteristics of precipitation and extreme precipitation around the TP using ERA5 reanalysis data;evaluates the simulation capability of CMIP6 highresolution model data on precipitation around the plateau and predicts the risk of occurrence of extreme precipitation around the plateau in the future;explores the possible causes of extreme precipitation around the plateau by combining the reanalysis data,and the main findings are as follows.(1)The spatial and temporal distribution characteristics of precipitation around the TP are revealed.The spatial and temporal distribution of precipitation in the area around the TP is uneven.On the south side,precipitation shows a distribution form of increasing first and then decreasing from west to east,while precipitation on the east side gradually increases from north to south,and precipitation on the north side gradually increases from west to east,and there is a high value area of precipitation on the north slope of the plateau.The trend of precipitation around the plateau shows that the precipitation in the precipitation high value area of 95°E on the south side shows a decreasing trend.The annual precipitation on the south side of the plateau has no obvious trend and is in a fluctuating state overall.The annual precipitation on the east side of the plateau shows an obvious decreasing trend from 1979 to 2010.In the period of 2010-2020,the precipitation shows an increasing trend.In the area on the north side of the plateau,the annual precipitation spacing level is the most complicated,and there is no obvious trend.The daily variation of precipitation around the plateau is characterized by two peaks and two valleys,with the peak of precipitation occurring between 14-20 and 02-08 Beijing time and the valley occurring between 08-14 and 20-02 Beijing time.Among them,the maximum value of precipitation occurs between 14-20 hours and the minimum value occurs between 20-02 hours.(2)The spatial and temporal distribution of extreme precipitation around the TP is given.In the southern region of the TP,the extreme precipitation threshold in the middle region is the largest,the precipitation threshold in the region closest to the plateau is the second largest,and the extreme precipitation threshold in the region far from the plateau is the smallest.In the eastern side of the plateau,the greater the distance from the main body of the plateau,the greater the extreme precipitation threshold.In the northern region,the extreme precipitation threshold is greatest in the middle region,followed by the region far from the plateau and least in the region closest to the plateau.Compared to the southern and eastern regions,the extreme precipitation threshold is smallest in the north-side study area.95 th percentile compared to 99 th percentile thresholds,the larger the quantile,the greater the threshold for extreme precipitation follows.Regardless of the quantile,the distribution of the thresholds coincides with the topographic trend of the plateau.The region of large values of extreme precipitation contribution to total precipitation is more consistent with the region of large values of annual average precipitation.The extreme precipitation thresholds in the areas around the plateau each have a certain degree of distance dependence.(3)Evaluation of the MIROC6 model in the area around the TP and prediction of the future.Based on the simulation results of the historical MIROC6 model scenarios,the model simulates better in the northern part of the plateau as well as the southern region.It is found that the trend of extreme precipitation frequency changes within the three regions in the northern part of the plateau is more consistent,from 2015-2100,the maximum number of extreme precipitation in the eastern part of the plateau occurs in the SSP5-8.5 scenario in 2016 with 981 events,and the minimum number of extreme precipitation occurs in the SSP5-8.5 scenario in 2022 with 108 events.Compared to the southern and eastern sides of the plateau,the slope of its linear regression fit is lower,but it also shows a slight increasing trend.The number of extreme precipitation occurrences in the high forcing scenario is higher than that in the low forcing scenario.(4)The mechanism of extreme precipitation around the TP was explored.When the temperature of the plateau decreases and the temperature of the northern side of the plateau increases,the temperature difference between the two areas leads to the weakening of the latitudinal vertical circulation,while the temperature increase on the northern side of the plateau also weakens the anticyclonic circulation at 700 h Pa and suppresses the downdraft.At the same time,the water vapor over the northern side of the plateau is more abundant,which is conducive to the formation of more precipitation,as well as the generation of extreme precipitation.When the paratroop is unusually easterly,it is favorable to the strengthening of the trans-equatorial flow near 80°E and120°E.On the contrary,when the vice high is easterly,the anomalous westerly airflow on the north side of the vice high flows from south China to the west,and is influenced by the uplifting effect of the plateau topography in the southwest,the airflow at the low level in the southwest appears to be uplifted along the plateau topography,and the precipitation in the southwest is high due to the airflow uplifting and convergence effect;on the contrary,when the vice high is westerly,the anomalous westerly airflow on the north side of the vice high flows from the plateau to the east,and sinks along the plateau in the southwest.The dispersion of airflow caused by the sinking of airflow leads to the low precipitation in the southwest.At the same time,the extreme precipitation also becomes more or less. |
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