Projection Of The Future Extreme Precipitation Change With Convection-permitting Simulation Over Eastern China

Due to the influence of Asian monsoon system and multi-scale topography,Eastern China often suffers from extreme precipitation.Under the background of global warming,China,like other parts of the world,has experienced significant temperature changes,which has affected the precipitation pattern.In order to assess climate risk and develop regional strategies to mitigate and adapt to climate change,it is necessary to estimate the characteristics of extreme precipitation over eastern China in more detail.In this paper,the regional climate model WRF is used to project the extreme precipitation in the east of China,especially the dependence of extreme precipitation and temperature,so as to provide a comprehensive understanding of the characteristics of short-term extreme precipitation over eastern China in the future.First,the current climate(1998-2007)simulated by WRF was evaluated and examined using CMORPH,CN05.1 and ERA-interim data.The results show that WRF can capture the characteristics of low-level circulation,including the spatial distribution pattern of wind speed,wind direction and water vapor flux divergence.WRF model can reproduce the main spatial distribution characteristics of summer average precipitation amount,frequency and intensity in most areas of eastern China,but overestimates the summer precipitation in Sichuan Basin and underestimates the wet hour frequency in the upper Yellow River Plain.WRF is not as good as summer in simulating the average precipitation in winter.It often produces too many precipitation events,especially in the area of complex terrain south of the Yangtze River.In addition,the model has a good ability to reproduce the spatial pattern of wet extreme index and hourly precipitation intensity and frequency of different levels.In general,WRF model can simulate the characteristics of precipitation over eastern China,which provides a reference for the projection of future extreme climate by WRF model.Then,the pseudo global warming(PGW)method is used to simulate and project the extreme precipitation over eastern China under RCP2.6,RCP4.5 and RCP8.5scenarios.The projection of extreme precipitation is divided into two parts:daily extreme precipitation projection based on ETCDDI index and hourly extreme precipitation projection based on index and percentile.The projection of daily timescale extreme precipitation shows that climate warming strengthens the circulation of summer monsoon in China and brings strong water vapor supply to the eastern region,and the northeast wind will be more prevalent in the future south of the Yangtze River in winter.Most of the continental regions experienced seasonal precipitation enhancement,with the strongest signal in North China in summer and the Yangtze-Huaihe River Basin in winter.The exception is winter in South China,where severe dryness occurs.The wet index R95p,R99p,R×1day and R×5day increased significantly in the whole eastern region,especially in North China.However,R10 mm and R20 mm decreased or increased little except for North China.The humid trend in North China can be attributed to the significant increase of very heavy precipitation frequency(R20mm).The increase of precipitation in South China and Yangtze-Huaihe River Basin is less than that in North China,which may be due to the decrease of heavy precipitation events(R10 mm)in this region,which partly offset the increase of very heavy precipitation(R20 mm).The projection of hourly extreme precipitation shows that there is almost no change in the diurnal phase of summer precipitation in the future,but the diurnal cycle shows that the precipitation intensity in each phase is increasing.On the hourly scale,the frequent occurrence of heavy precipitation and rainstorm enhanced the seasonal average precipitation intensity in the three eastern sub-regions.In the future,there will be less light precipitation and more extreme precipitation events in eastern China,indicating that the future precipitation events may develop in the direction of short-term and strong.It was also found that the intensity and frequency of hourly precipitation increased,especially in the higher percentile,and RCP8.5 was more clearly enhanced than RCP4.5 and RCP2.6.Finally,the relationship between extreme precipitation and temperature and atmospheric moisture is further studied.The results show that the extreme precipitation temperature(EP-T)relationship of peak structure exists in all regions.The EP-T curve moves along the super Clausius-Clapeyron scaling(>7%k^-1)trajectory to high temperature and high precipitation peaks.When the temperature reaches a certain value,the EP-T curve scaling begins to turn negative in three sub regions of eastern China.Compared with the current simulation,the change of EP-T scaling from positive to negative in the future climate simulation will occur at a higher temperature,about 1-3? to the right,which means that the positive scaling rate can be maintained at a higher temperature,leading to the further enhancement of extreme precipitation intensity.There are two types of EP-T relationship changes in the future climate of the three climatic regions.Compared with the current situation,the EP-T curve in North China extends to the right,while in the Yangtze-Huaihe River Basin and South China,the EP-T curve moves to the right.The change of extreme precipitation intensity is affected by both air temperature and atmospheric moisture.At the beginning of warming,the precipitable water and extreme precipitation intensity increase at the same time,while the limiting of environmental moisture at a certain temperature leads to the decrease of extreme precipitation intensity.