In the context of non-hydrostatic MM5 version we have explored the impact ofconvective parameterization schemes on uncertainty in mesoscale numerical prediction of South Chinaheavy rain and mesoscale heavy rainfall sh...In the context of non-hydrostatic MM5 version we have explored the impact ofconvective parameterization schemes on uncertainty in mesoscale numerical prediction of South Chinaheavy rain and mesoscale heavy rainfall short-range ensemble simulation by using two kinds ofphysics perturbation methods through a heavy rain case occurring on June 8, 1998 in Guangdong andFujian Provinces. The results show the physical process of impacts of convective schemes on heavyrainfall is that different latent heat of convective condensation produced by different convectiveschemes can make local temperature perturbation, leading to the difference of local vertical speedby the intrinsic dynamic and thermodynamic processes of atmosphere, and therefore, making differenceof the timing, locations and strength of mesh scale and subgrid scale precipitation later. Newprecipitations become the new source of latent heat and temperature perturbation, which finally makethe dynamic and thermodynamic structures different in the simulations. Two kinds of methods areused to construct different model version stochastically. The first one is using differentconvective parameterization and planetary boundary layer schemes, the second is adjusting differentparameters of convective trigger functions in Grell scheme. The results indicate that the firstensemble simulations can provide more uncertainty information of location and strength of heavyrainfall than the second. The single determinate predictions of heavy rain are unstable; physicsensemble predictions can reflect the uncertainty of heavy rain, provide more useful guidance andhave higher application value. Physics ensembles suggest that model errors should be taken intoconsideration in the heavy rainfall ensembles. Although the method of using different parameters inGrell scheme could not produce good results, how to construct the perturbation model or adjust theparameter in one scheme according to the physical meaning of the parameter still needs furtherinvestigation. The limitation of the current展开更多
The mei-yu front heavy rainstorms occurred over Nanjing on 3 5 and 8 9 July 2003 and were simulated in this paper using the Weather Research and Forecasting Model (WRFv3.1) with various mesoscale convection parameteri...The mei-yu front heavy rainstorms occurred over Nanjing on 3 5 and 8 9 July 2003 and were simulated in this paper using the Weather Research and Forecasting Model (WRFv3.1) with various mesoscale convection parameterization schemes (MCPSs). The simulations show that the temporal and spatial evolution and distribution of rainstorms can be modeled; however, there was incongruity between the comparative simulations of four different MCPSs and the observed data. These disparities were exhibited in the simulations of both the 24-hour surface rainfall total and the hourly precipitation rate. Further analysis revealed that the discrepancies of vertical velocity and the convective vorticity vector (CVV) between the four simulations were attributed to the deviation of rainfall values. In addition, the simulations show that the mid-scale convection, particularly the mesoscale convection system (MCS) formation, can be well simulated with the proper mesoscale convection parameterization schemes and may be a crucial factor of the mei-yu front heavy rainstorm. These results suggest that, in an effort to enhance simulation and prediction of heavy rainfall and rainstorms, subsequent studies should focus on the development and improvement of MCPS.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos. 40175028 and 40475045.
文摘In the context of non-hydrostatic MM5 version we have explored the impact ofconvective parameterization schemes on uncertainty in mesoscale numerical prediction of South Chinaheavy rain and mesoscale heavy rainfall short-range ensemble simulation by using two kinds ofphysics perturbation methods through a heavy rain case occurring on June 8, 1998 in Guangdong andFujian Provinces. The results show the physical process of impacts of convective schemes on heavyrainfall is that different latent heat of convective condensation produced by different convectiveschemes can make local temperature perturbation, leading to the difference of local vertical speedby the intrinsic dynamic and thermodynamic processes of atmosphere, and therefore, making differenceof the timing, locations and strength of mesh scale and subgrid scale precipitation later. Newprecipitations become the new source of latent heat and temperature perturbation, which finally makethe dynamic and thermodynamic structures different in the simulations. Two kinds of methods areused to construct different model version stochastically. The first one is using differentconvective parameterization and planetary boundary layer schemes, the second is adjusting differentparameters of convective trigger functions in Grell scheme. The results indicate that the firstensemble simulations can provide more uncertainty information of location and strength of heavyrainfall than the second. The single determinate predictions of heavy rain are unstable; physicsensemble predictions can reflect the uncertainty of heavy rain, provide more useful guidance andhave higher application value. Physics ensembles suggest that model errors should be taken intoconsideration in the heavy rainfall ensembles. Although the method of using different parameters inGrell scheme could not produce good results, how to construct the perturbation model or adjust theparameter in one scheme according to the physical meaning of the parameter still needs furtherinvestigation. The limitation of the current
基金supported jointly by the Projects of Jiangsu Key Lab of Meteorological Disaster (Grant No. Klme060207)the National Natural Science Foundation of China (Grant No. 40875031)
文摘The mei-yu front heavy rainstorms occurred over Nanjing on 3 5 and 8 9 July 2003 and were simulated in this paper using the Weather Research and Forecasting Model (WRFv3.1) with various mesoscale convection parameterization schemes (MCPSs). The simulations show that the temporal and spatial evolution and distribution of rainstorms can be modeled; however, there was incongruity between the comparative simulations of four different MCPSs and the observed data. These disparities were exhibited in the simulations of both the 24-hour surface rainfall total and the hourly precipitation rate. Further analysis revealed that the discrepancies of vertical velocity and the convective vorticity vector (CVV) between the four simulations were attributed to the deviation of rainfall values. In addition, the simulations show that the mid-scale convection, particularly the mesoscale convection system (MCS) formation, can be well simulated with the proper mesoscale convection parameterization schemes and may be a crucial factor of the mei-yu front heavy rainstorm. These results suggest that, in an effort to enhance simulation and prediction of heavy rainfall and rainstorms, subsequent studies should focus on the development and improvement of MCPS.
