Evaluation Of Multi-source Precipitation Products In Central Asia And Research On Diurnal Variation Characteristics Of Extreme Precipitation

Extreme precipitation events occur frequently,and extreme precipitation events with short duration have increased more significantly under global warming.Central Asia is more sensitive to climate change due to its complex geographical conditions and ecological environment.Therefore,it is of great significance to reveal the temporal and spatial characteristics of the diurnal variations of extreme precipitation and its possible driving factors in Central Asia,which will improve the forecasting and warning capabilities of meteorological disasters in this region.Considering the lack of hourly station observation data in central Asia,it is necessary to systematically evaluate the applicability of multi-source precipitation products in Central Asia before conducting relevant research.Therefore,this study selects 5 sets of satellite precipitation products(TRMM 3B42 RT,TRMM 3B42,PERSIANN,PERSIANN-CCS and IMERG),4 sets of reanalysis precipitation products(ERA-Interim,ERA-5,JRA55,MERRA-2),and 1 set of multi-source fusion precipitation product(MSWEP).This is a new evaluation method called double instrumental variable(IVd)that does not require gauge data as a comparison,evaluates each set of precipitation products in detail with indicators such as correlation coefficient and root mean square error.After selecting a better product,based on the“optimal” product,namely MSWEP,analying the diurnal variability of extreme precipitation in Central Asia from 1979-2016.Finally,starting from the atmospheric water balance equation,the driving factors for the diurnal variation are discussed.The main conclusions are as follows:(1)From the perspective of correlation coefficient(CC),root mean square error(RMSE)and the number of evaluable grid points,IMERG performs best,and MSWEP performs best among reanalysis and multi-sources precipitation products.From the evaluation results at different times,except for MERRA-2,the RMSE of 3h precipitation during the day is less than that at night.The CC and RMSE distribution of all other products for 3h precipitation at all times are similar.All products have similar capacity in the extreme precipitation amount and frequency at all times.(2)According to the assessment results of annual and seasonal 3h precipitation and extreme precipitation,the overall performance of satellite precipitation products is better than reanalysis and multi-sources precipitation products,especially for winter night precipitation,most times are TRMM3B42.Judging from the evaluation results of the national border and geographic elevation regions,the most optimal product based on CC is MSWEP,and the optimal product based on RMSE is IMERG.(3)15% of precipitation events in central Asia contribute nearly 50% of the precipitation.In Tajikistan and Kyrgyzstan,the light rain is decreasing,the heavy rain is increasing,and the decrease amount of light rain is more than the increase of heavy rain.(4)The characteristics of the diurnal variation of extreme precipitation in Central Asia are divided into three types.The first is a single-peak type,the representive areas are the northern area of Kazakhstan,the western Tianshan area and the eastern Tianshan area,with a peak in the afternoon.The second is a bimodal type,the representive area is the western area of Kazakhstan with the main peak period in the afternoon and the second peak period in the night.The third is a peakless type,the representative area is the Central Asian plain area with no obvious diurnal changes.(5)There is no obvious diurnal characteristics in the Central Asia plain,where precipitation is little.