RegCM/NCC high resolution regional climate model and its
application to prediction of monsoonal rainfalls in East Asia
Ding Yihui
National Climate Center, Beijing 100081
Fax: 86-10-62180679, E-mail: dinghy@cma.gov.cn
Extended Abstract
Based on the regional climate model NCAR/RegCM2, a high resolution regional climate
model has been developed by modifying the physical processes such as land-surface process,radiation transfer process, cumulus convectire process, topography and boundary layer
parameterization scheme, and the expansion of west boundary to have the Tibetan Plateau
included. The model, having 16 levels in vertical direction and 60km horizontal resolution, can benested with the coupled atmosphere-ocean model. It is capable of simulating and predicting thecharacteristics of regional climate in East Asia, especially the activities and evolutions of monsoon
and rainfall belt.
1) Modification of radiation scheme
The modifications have been made by incorporating the radiation schemes of CCM3 andECWMF T213 model into the regional climate model. The results show that the new radiation
scheme improves the modeling performance obviously.
2) Improvement of cumulus parameterization scheme
A mass flux scheme (MFS) for cumulus convective parameterization has been developed andintroduced into the regional climate model. The simulation results show that he model with themass flux scheme has the capability of simulating the regional climate characteristics andvariations. Compared with other cumulus parameterization schemes, the mass flux scheme
improved the simulations of ground temperature, rainfall area, and heavy rainfall events. Also,
Betts-Miller (BM) convective parameterization scheme has been used to simulate the cases ofheavy rainfalls in China and obtain better simulation results compared with Kuo scheme.
3) Modification of boundary layer scheme
The TKE scheme has been proposed and tested by using the observation data. Now thescheme has been incorporated into the regional climate model. The simulation results show thatthe scheme improves the modeling performance, especially the height of planetary boundarylayer(PBL) and location of rain belts.
4) The BATS land process model has been modified based on analysis of soil temperature andmoisture in China.
A LMP-ZD scheme has been included in this model which considerably improved theprediction of land surface temperature with suppression of unrealistic high land surface
temperature.
5) 3-dimensional nesting scheme and data initialization and post-processing
The accumulation of lateral boundary error and linear and non-linear error in regional climate
simulation has been investigated when the nesting method was used to perform the regional
climate model. The results of experiments with 3D nesting method used show that the simulations

of short-term regional climate have been improved. In addition, the pre- and post-processing
programs for the regional climate model have been completed, with the focus on the diagnostic
and analyzing methods in the post-processing. The advanced teachnique of POP has been
introduced to evaluate the performance fo the regional climate model.
6) The prolonged rainfalls and rainstorms in China during three sever folding years 1991,1994
and 1998 have been simulated and tested by use of this model.
Out of these simulations, it was very successful for RegCM/NCC to reproduce the position
and movement of the seasonal rainbelt, and moisture transport in 1998 summer in East Asia. A
deficiency of this model is the overestimate of precipitation amount and moisture transport.
RegCM/NCC has a potential to be used in the LAPS study, especially for the role of theplanetary boundary layer in triggering and maintaining the precipitation in the Huaihe RiverBasion. The TKE PBL scheme is capable to capture the major features and evolution of the PBL
during prolonged heavy rainfall event or episode. The prediction of the height of PBL is quite
encouraging.