Simulation Of Summer Precipitation In The Middle Of Qinling Mountains Based On WRF Model

The Qinling Mountains,as an important water supply area for the north-south geographic boundary of China and the middle route of the South-to-North Water Transfer Project,is also an important eco-environmental transition zone and climate change sensitive area.It has an unusually significant response to global climate change.However,the lack of precipitation observation data in high mountain areas has restricted people's research on the Qinling alpine climate and water resources for a long time.Therefore,a new generation of mesoscale numerical simulation system WRF was used in this paper to study the spatial distribution of precipitation in the qinling Mountains and its relationship with altitude,so as to further reveal the source of water vapor in the Qinling Mountains in summer.By designing comparative tests of different cumulus convection parameterization schemes and horizontal resolutions,the effects of cumulus convection parameterization schemes and horizontal resolutions on precipitation simulation capability are quantitatively analyzed,and the necessity of using cumulus convection parameterization scheme in the innermost layer under high resolution is discussed,as well as whether the process of cumulus convection can be explicitly analyzed.The mechanism of the influence of WRF on precipitation was studied from the two aspects of water condition and atmospheric instability,providing an important reference for the simulation of alpine precipitation and optimization of WRF simulation effect.The main conclusions are as follows:(1)Comparing with the STATION and precipitation product CGPA,it is found that WRF model can provide highly reliable precipitation simulation results.Compared with CGPA,high-resolution precipitation simulation results can better depict the changes of precipitation with the topographic relief of Dabashan Mountain,Qinba Valley and Qinling Mountain.Among them,BMJ scheme has the best applicability in Qinling Region,especially the simulation of precipitation intensity shows obvious advantages.Compared with the observation data,the deviation of precipitation simulation results is mostly within 1 mm/d.(2)Based on the simulation results of BMJ,an optimal parameterization scheme,the spatial distribution of precipitation in Qinling Mountains and its water vapor sources were studied.The results show that the summer precipitation in Qinling Mountains varies with the latitude from south to north,and there is a large precipitation zone within the range of 33.5°N-34°N in the main area of Qinling Mountains,and the average daily precipitation in summer exceeds 10 mm/d.At the same altitude,the precipitation on the south slope is much higher than that on the north slope due to the warm and humid airflow moving northward in summer and the hindrance of the tall Qinling Mountains to the airflow.In the meridional section of Qinling Mountains,the precipitation varies with the relief of the terrain,and the rain peaks and valleys basically correspond to the peaks and valleys.Water vapor in the Qinling Mountains mainly comes from the Bay of Bengal and the Western Pacific Ocean in summer.The southwest monsoon mainly affects the water vapor transport intensity of the Bay of Bengal through the northeast side of the Qinghai-Tibet Plateau and the Sichuan basin.The southeast monsoons often affect the transport of moisture from the western Pacific through the middle and lower reaches of the Yangtze River.(3)The improvement of horizontal resolution can significantly improve the simulation of precipitation intensity,which can reduce the phenomenon of high precipitation in GF scheme and KF scheme by nearly 80%and nearly 60%respectively.The average deviation of precipitation in BMJ scheme is less than 0.2mm/d.Under the condition of 2 km high resolution,the simulation effect of the innermost layer,even if no cumulus parameterization scheme is adopted,is better than that of all the schemes under 6 km.However,extreme precipitation points are likely to occur at higher altitudes,so the synergistic effect of cumulus convection parameterization is needed.(4)The influence mechanism of different cumulus convection parameterization schemes and horizontal resolution on precipitation simulation was discussed from two aspects,namely water condition and atmospheric instability.The results show that under the condition of 6 km resolution,the main reason for the excessive simulated precipitation in KF scheme is that the simulated convective instability is significantly stronger than the other two schemes,which stimulates the simulation of excessively high convective precipitation,resulting in the overall higher precipitation results.In GF scheme,because the simulated atmosphere in the middle and lower troposphere,which is most prone to precipitation,is relatively wet,the instability of atmospheric environment is easy to stimulate the water vapor at the grid scale to reach saturation,leading to the overestimation of the precipitation at the grid scale.The water vapor and atmospheric instability simulated by BMJ scheme are the minimum,so the simulated precipitation is the closest to the observed precipitation.The improvement of the horizontal resolution will weaken the convective effective potential energy and the moisture condition of each layer of the atmosphere,inhibit the occurrence of extreme precipitation values in high mountain areas,and thus improve the precipitation simulation.However,the influence of the change of the horizontal resolution on the change trend of the vertical velocity is uncertain,which may aggravate the phenomenon that the precipitation value is larger in some areas.