Transition of the Future Precipitation Types in the Tianshan Mountains Region, China

Abstract The general circulation models (GCMs) from the coupled model intercomparison project phase 5 (CMIP5) were used to evaluate the simulation capabilities of rainfall-to-precipitation ratio (RPR) from 1961 to 2018 at 28 meteorological stations in the Tianshan Mountains region (TMR). Moreover, it was estimated the change of RPR in the months experiencing freezing-thawing transitions from 2011 to 2100 under three representative concentration pathways (RCPs), RCP2.6, RCP4.5, and RCP8.5. The results indicated that the simulated air temperature from CMIP5 was highly correlated with the observed values, while the performance for precipitation was poor. Therefore, it is feasible to forecast the future RPR employing the temperature provided by CMIP5 and the observed meteorological factors by the BP neural network (BNN). Under three emission scenarios, the RPR in the months experiencing freezing-thawing transitions during 2011-2100 will increase compared to that during the baseline period (1981-2010). Under the same emission scenario, values of RPR will increase as the time goes on. Besides, in terms of spatial variation, values of RPR in the south slope will be larger than that in the north slope under three emission scenarios. Furthermore, values of RPR exhibit different variation characteristics under different emission scenarios. Under the RCP2.6 emission scenario, as the time goes on, values of RPR at more stations will change slightly. Under the RCP4.5 emission scenario, the increase of RPR will occur in the whole TMR and stabilize in the north slope by the end of this century. However, values of RPR will increase significantly through 21st century in the whole TMR under the RCP8.5 emission scenario.