Sensitivity Study of the South China Sea Summer Monsoon in 1998 to Different Cumulus Parameterization Schemes

In this study, the improved high-resolution regional climate model of the China National Climate Center （RegCM_NCC） is used to examine the sensitivity of the simulated circulation and rainfall during the South China Sea summer monsoon （SCSSM） period during 1998 in an effort to compare to other cumulus param- eterization schemes. The investigation has indicated that the model is capable of simulating the seasonal march of the SCSSM and that the results were very sensitive to the choice of cumulus parameterization schemes. It seems that the Kuo cumulus parameterization scheme simulates the process of the SCSSM onset reasonably well, which can reproduce the onset timing and dramatic changes before and after the onset, especially the upper- and lower-level wind-fields. However, there are still some discrepancies between the simulations and observations. For example, the model can not completely simulate the intensity of the rainfall or the location of the western Pacific subtropical high as well as the feature of the rapid northward propagation of seasonal rain belt.

Impact of Horizontal Resolution and Cumulus Parameterization Scheme on the Simulation of Heavy Rainfall Events over the Korean Peninsula

In this paper, we present the results from high-resolution numerical simulations of three heavy rainfall events over the Korean Peninsula. The numerical results show that the prediction accuracy for heavy rainfall events improved as horizontal resolution increased. The fine-grid precipitation fields were much closer to the real precipitation fields in the case of large synoptic forcing over the Korean Peninsula. In the case of large convective available potential energy and weak synoptic forcing, it seems that even when using a high resolution, the models still showed poor performance in reproducing the observed high precipitation amounts. However, activation of the cumulus parameterization scheme in the intermediate resolution of 9 km, even at a grid spacing of 3 km, had a positive impact on the simulation of the heavy rainfall event.

Sensitivity of Numerical Simulations of the East Asian Summer Monsoon Rainfall and Circulation to Different Cumulus Parameterization Schemes

A 5-level spectral AGCM (ImPKU-SLAGCM) is used to examine the sensitivity of the simulated results of the summer monsoon rainfall and circulation in East Asia to different cumulus parameterization schemes in the climatological-mean case and in the cases of weak and strong Asian summer monsoons, respectively. The results simulated with the Arakawa-Schubert's(hereafter A-S's), Kuo's and Manabe's cumulus parameterization schemes show that these simulated distributions of the summer monsoon rainfall and circulation in East Asia depend strongly on the cumulus parameterization schemes either in the climatological-mean case or in the cases of weak and strong Asian summer monsoons. From the simulated results, it might be shown that the Kuo scheme appears to be more suitable for the simulation of the summer monsoon rainfall and circulation in East Asia than the A-S scheme or the Manabe scheme, although the A-S scheme is somewhat better in the simulations of the tropical rainfall. This might be due to that the Kuo's cumulus parameterization scheme is able to reflect well the characteristics of rainfall cloud system in the East Asian summer monsoon region, where the rainfall system used to be a mixing of cumulus and stratus.

Sensitivity of Precipitation over China to Different Cumulus Parameterization Schemes in RegCM4

The effect of different cumulus parameterization schemes（CPSs） on precipitation over China is investigated by using the International Centre for Theoretical Physics（ICTP） Regional Climate Model version 4.3（Reg CM-4.3） coupled with the land surface model BATS1e（Biosphere-Atmosphere Transfer Scheme version1e）. The ERA-interim data are utilized to drive a group of simulations over a 31-yr period from September1982 to December 2012. Two typically sensitive regions, i.e., the eastern Tibetan Plateau（TP; 29°–38°N,90°–100°E） and eastern China（EC; 26°–32°N, 110°–120°E）, are focused on. The results show that all the CPSs have well reproduced the spatial distribution of annual precipitation in China. The simulation with the Emanuel scheme shows an overall overestimation of precipitation in China, different from the other three CPSs which only overestimate over northern and northwestern China but underestimate over southern China. Seasonally, the Tiedtke scheme shows the smallest overestimation in winter and summer, and the best simulation of the annual variance of precipitation. Interannual variations of precipitation among the four CPSs are generally simulated better in summer than in winter, and better for entire China than in the subregions of TP and EC. The precipitation trend is simulated better over EC than over TP, and better in summer than in winter. An overestimate（underestimate） of the East Asian summer monsoon index（EASMI） exists in the simulations with the Grell and the Emanuel（the Kuo and the Tiedtke） schemes.The smallest EASMI bias in the Tiedtke simulation could explain its small precipitation bias. A negative correlation between the EASMI and summer precipitation over the middle and lower reaches of Yangtze River is found in the Grell and the Emanuel simulations, but was missed by the simulations using the Kuo and the Tiedtke schemes.

The Structure and Rainfall Features of Tropical Cyclone Rammasun (2002)

Tropical Rainfall Measuring Mission (TRMM) data [TRMM Microwave Imager/Precipitation Radar/Visible and Infrared Scanner (TMI/PR/VIRS)] and a numerical model are used to investigate the structure and rainfall features of Tropical Cyclone (TC) Rammasun (2002). Based on the analysis of TRMM data, which are diagnosed together with NCEP/AVN [Aviation (global model)] analysis data, some typical features of TC structure and rainfall are preliminary discovered. Since the limitations of TRMM data are considered for their time resolution and coverage, the world observed by TRMM at sev- eral moments cannot be taken as the representation of the whole period of the TC lifecycle, therefore the picture should be reproduced by a numerical model of high quality. To better understand the structure and rainfall features of TC Rammasun, a numerical simulation is carried out with mesoscale model MM5 in which the validations have been made with the data of TRMM and NCEP/AVN analysis.

Sensitivity of simulated tropical intraseasonal oscillations to cumulus schemes

The sensitivity of simulated tropical intraseasonal oscillations (ISO) to different cumulus parameterization schemes was analyzed using an atmospheric general circulation model (latest version-SAMIL2.2.3) developed at the Laboratory for Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG) at the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences.Results show that the basic features of tropical climatological intraseasonal oscillations (CISO) can be captured using all three cumulus schemes.The CISO simulated by the Tiedtke scheme was found to be more realistic than that of the Manabe and Zhang-McFarlane schemes.The results of simulated transient intraseasonal oscillations (TISO) indicate that although the Tiedtke and the Zhang-McFarlane schemes in the new version SAMIL2.2.3 have been adjusted according to different problems,only the latter can simulate the eastward propagation of the 27-50-day TISO mode.It may be associated with the more realistic diabatic heating profile simulated by the Zhang-McFarlane scheme.In addition,the Manabe scheme in SAMIL2.2.3 is the same as that in the prior version SAMIL2.08.However,some aspects of the physical process,such as the radiation scheme and aerosol condition,have been changed.Conversely the eastward propagation from 100°E to the west of the tropical 27-50-day TISO mode only can be simulated using the Manabe scheme of SAMIL 2.08.Consequently,not all the improvements of physical parameterization schemes work well in every respect.The coordinated developments between dynamic frame and physical processes,and among different physical processes,are important methods that may be used to improve the model.

Application of TRMM/PR Data for Numerical Simulations with Mesoscale Model MM5

Numerical simulations of two heavy rainfall cases in the Changjiang-Huaihe River basin are performed with TRMM/PR (precipitation radar) data incorporated into the PSU/NCAR meso scale model MM5. The mixing ratio of rainwater q r is obtained from the R −q r relation (R is the rainfall rate), and the mixing ratio of water vapor q v in the model is replaced by q 1′v = q v+q r. Then, TRMM/PR data are used to modify humidity analysis obtained from conventional radiosonde data, and sensitivity experiments (STE) are performed and compared to control experiments (CTL). Results show that both the heavy rainfall distribution and its maximum amounts from STE are improved compared with those from CTL.