The Influence Of Different Parameterization Schemes On The Numerical Simulation Of The Plateau Shear Line Heavy Rain Process

Firstly,using 16 kinds of cloud microphysical parameterization schemes in the mesoscale numerical model WRF V3.8.1 to compare the rainstorm process dominated by a plateau shear line in Sichuan-Chongqing region from August 26 to 27,2014,and the simulation results are quantitatively tested.Then six schemes with obvious characteristics are selected to analyze the reasons for the difference of precipitation through the distribution characteristics of hydrous substances in clouds.At the same time,the better simulation results of the aggregates and the accuracy of ensemble prediction were proved.Finally,in the case of determining the best cloud microphysical scheme,four kinds of cumulus convection schemes were compared using the outer grid data.The same method was used to test the simulation results,and the differences of the main physical quantity fields were discussed.The simulation results are tested by the same method,and the differences of main physical quantities are discussed.The precipitation process was analyzed by calculating Q₁ and Q₂.The main conclusions are as follows:?1?The characteristics of the precipitation results of 16 kinds of cloud microphysical schemes are similar,which correspond with the actual situation,but the storm belts and central precipitation simulated by each scheme have great differences.The three statistics of the NSSL 2-moment scheme have certain advantages,and the simulation results are the best,while the Ferrier scheme has the worst effect.The TS score results show that the model has the strongest simulation ability for light rain,and most of the schemes score above 0.4,while the simulation for heavy rain is the most unstable,and the differences between the schemes are large.In the main precipitation area,the hourly precipitation peaks simulated by the six cloud microphysical schemes are generally 4⁵ h behind the actual precipitation,and the suddenness of precipitation is stronger.The accumulative precipitation of NSSL 2-moment and SUB_YLIN schemes in this area is higher than the actual situation.The NSSL 2-moment with CCN scheme basically coincides with the actual situation.The simulated precipitation rainfall in this scheme has certain advantages,while the other three schemes are lower than the real one,and the precipitation intensity is insufficient.?2?The scheme with more precipitation is mainly due to the contribution of cold cloud precipitation,in which the content of snow particles is much larger than other ice particles,and the latent heat release caused by its formation in the condensation process is not only conducive to the development of convective activities,but also can promote precipitation through the melting process.The content of snow particles corresponds to the size of precipitation.?3?The method of ensemble averaging can significantly improve the simulation effect of precipitation.The ensemble prediction can also accurately predict the precipitation probability,which corresponds to the actual precipitation,indicating that the precipitation process is more predictable.?4?The influence of cumulus convection scheme on precipitation is less than that of cloud microphysical scheme,and GD scheme has the best overall performance.The precipitation of BMJ and SAS schemes is concentrated in time and space.The central rainfall is far more than the actual situation.The precipitation of KF and GD schemes is relatively scattered,especially the GD scheme.The cumulative precipitation of the main rainstorm areas basically coincides with the real precipitation.Generally speaking,GD has the best overall performance and SAS has the worst overall performance.?5?The bottom precipitation centers simulated by the four schemes are all in the relatively warm and humid zone,and the convergence zone overlaps the positive vorticity zone.Convergence at the bottom and divergence at the upper and lower levels and upward transport of unstable energy in the atmosphere are very conducive to the development of convection.In addition,a large amount of water vapor is transported by low-level jet,which results in strong precipitation.The large difference of physical quantity field between different cumulus convection schemes directly leads to the difference of precipitation.?6?The large value areas of and coincide with the heavy rain area.The cumulus convection parameterization scheme directly affects the precipitation by changing the release of condensation latent heat.There is a positive feedback mechanism between Q₁,Q₂ and vertical velocity,which promotes each other.The vertical transport is the main contribution of Q₁,while the main contribution of the bottom layer of Q₂ is the horizontal advection term,and the upper layer also relies on vertical transport.