Evaluation Of Simulation Performance Of WRF Model In Tropical Zone

The assessments of the present climate and climate change are the important means to validate the simulation performance of the model,and to understand the sources of model errors.The model is strongly influenced by lateral boundary conditions forcing.And the simulated performances of precipitation in tropical are highly sensitive to the different combinations of physical parameterization schemes,especially the appropriate cumulus convection parameterization schemes,and the suitable radiation parameterization schemes.In order to evaluate the performance of simulation,the WRF model has been set to periodic boundary from east to west.In addition,for the purpose of choosing better combinations of physical parameterization schemes in the terms of better simulation of tropical climate,there are eight sensitivity experiments have been run in this paper,specifically the freedom combinations of four cumulus convection parameterization schemes(new Tiedtke,KF,new SAS,Tiedtke),and two radiation parameterization schemes(RRTMG and CAM).By analyzing the basic features of 2m temperature,precipitation,wind field at 10 m and the diurnal cycle of precipitation in boreal summer,the following main conclusions are drawn:(1)The model can better reproduce the large-scale features of temperature at 2m,but there are still systematic deviations in some complex terrain areas.Compared with different parameterization schemes,RRTMG radiation parameterization scheme shows better simulation performance on 2m temperature,while CAM radiation parameterization scheme displays significantly colder bias of temperature,especially these biases over land are more clearly than in other areas.Over land,by comparing and analyzing the latitudinal variations of 2m temperature,maximum temperature and minimum temperature,it can be discovered that both the maximum temperature and the minimum temperature have contributions to the cold errors with CAM radiation parameterization scheme,but the cold errors of 2m temperature mainly comes from the simulating daily minimum temperature which is much lower than the observed temperature.(2)Based on the spatial distribution of precipitation in the tropical belt during the boreal summer,the simulation results of 8 groups experiments with different parameterization schemes are evaluated.The research shows that the precipitation of simulating in the northern part of the Bay of Bengal is less than observed,and that in most parts of the equatorial western Pacific is higher than observed.These simulated precipitation biases are also general problems,in regards to the simulation of precipitation by current regional climate model.However,it is deserved to point out that each group of simulation experiments reproduce the narrow-band distribution of precipitation in the double equatorial convergence zone.Among them,the experiment using both RRTMG radiation parameterization scheme and the new Tiedtke cumulus convection parameterization scheme,is the best one to simulate precipitation.The value of spatial correlation coefficient between the simulated and observed is 0.80,with an mean relative error of 19.52%.(3)By comparing the changes of the zonal wind field at 10 m between the simulation and observation in the boreal summer,it is revealed that the model clearly reproduces the basic structure of the surface easterly wind.Moreover,the model also displays the westerly wind in the Indian monsoon region,and the regional wind fields distribution of some terrain-related regions.Compared with the results of the reanalysis,the easterly wind simulation in the northwest equatorial Pacific is stronger.Furthermore,the westerly wind simulation in the Arabian Sea,the Bay of Bengal and the South China Sea are also stronger than observed,and they are extends eastward.For the simulation of the zonal wind field,the results of the experiments using CAM radiation parameterization scheme are more obviously terrible than those of using RRTMG radiation parameterization scheme.(4)During the boreal summer,the diurnal cycle of precipitation shows clearly land-sea distribution and detailed regional patterns associated with the topographic.Under the influence of sea-land breeze,the maximum of daily precipitation on land mostly occurs in the afternoon or evening of local time,between 1300-2200 LST;and the maximum of daily precipitation on ocean mostly occurs in the midnight or early morning of local time,between 0000-0700 LST.Under the action of mountain-valley wind,the maximum of daily precipitation occurs obviously at night in the basins.Comparing the simulation results of eight groups of experiments,it is found that,the experiment,using RRTMG radiation parameterization scheme and new Tiedtke cumulus convection parameterization scheme,shows better performance in terms of the diurnal cycle of precipitation.For this experiment,the simulated characteristics of the diurnal cycle of precipitation are closest to the observed,it not only depicts more accurately for the regional distribution of the diurnal cycle of precipitation,but also reproduces the semi-diurnal pattern of diurnal cycle of precipitation more truthfully.