East Asia and Western Pacific METEOROLOGY AND CLIMATE

439
BMC LIMITED AREA MODEL: OPERATIONAL APPLICATION AND RESEACH
Guo Xiaorong, Yan Zhihui & Zheng Guoan
National Meteorological Center, State Meteorological Administration,
Beijing •
ABSTRACT
The limited area 5-layer primitive equation model, as the first
operational precipitation forecast model in China, has been run at Beijing
Meteorological Center (BMC) for more than five years. The operational
results show that this model gives continuous services without
interruptions, and the forecast skill is satisfactory for the forecast of
weather systems such as extratropical cyclone, cold front, meiyu front
and the precipitation associated with them. Forecast guidance based on
the model is widely used at local weather services nowadays.
Some experiments on the sensitivity of sub-grid scale convective
effects to horizontal resolution were carried out with a nested version of
this model. The results show that the contribution of the sub-grid scale
convective condensation, computed by the Kuo's scheme, to the total
precipitation decreases remarkably with the increase of horizontal
resolution. It is 62% of total precipitation in the 381km grid, but only
10% in the 47.625km grid. It seems that the precipitation produced by
grid scale condensation will take a dominate proportion in total
precipitation when the resolution is high enough (less than 50km).
I. INTRODUCTION
Since August 1983, a limited area 5-level primitive equation model
has been running once a day at BMC for the routine regional forecast.
The purpose of this model is to make short-range forecasts of synoptic
circulation systems as well as 24h total amount of precipitation over
China. Forecast guidance is sent to local weather services by facsimile
transmission and the grid variables in code. This model has proved to
be effective in forecasting the development of some synoptic systems,
such as cyclone, landing typhoon, front and the precipitation brought
about by them.
The original form of this model was designed by a NWP research
group in Peking University (NWP Group, Peking University, 1980), Some
improvements including the treatment of lateral boundary condition, a
modified Kuo's convective parameterization scheme and the initialization
were.made for the operational application ( Guo, et al., 1982 and Zhang.et