East Asia and Western Pacific METEOROLOGY AND CLIMATE

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observed precipitation rates focuses the development of precipitation
results in a superior short-range forecast.
early in the model and
Y.-H. Kuo and his colleagues have used MM4 to investigate ways of using wind and
temperature soundings derived from a network of profilers. Kuo eiaJU (1987a) conducted a series
of OSSEs which tested the sensitivity of MM4 forecasts to characteristic measurement errors
associated with a number of hypothetical profiler networks. These results, which used a static
initialization technique, indicated that profiler wind observations would have a positive impact on
short-range numerical weather prediction. They also showed that the use of temperatures derived
from the profiler winds (Kuo filal., 1987b) gave superior results to those derived from the
profiler radiometric measurements; however the derived temperatures were less accurate than
radiosonde temperature measurements.
In an extension of earlier work, Kuo and Guo (1989) tested a dynamic initialization
procedure for continuous assimilation of observations from a network of profilers. The results of
this study indicate:
(i) Dynamic initialization by nudging can successfully assimilate wind profiler
observations to improve the initial analysis compared to a static initialization scheme.
(ii)
(iii)
The improved initial analysis results in a superior forecast.
Assimilation of the wind field is superior to assimilation of the temperature field;
however best results are obtained when both wind and temperature observations are
assimilated.
4.0 REAL-TIME FORECASTS USING MM4
A stringent test of any modeling system is its use in real time. Recently, Warner and
Seaman (1989) have adapted a version of MM4 for running in real time at the Pennsylvania State
University for use in research, instructional, and public service applications. A two-way
interacting nested grid system is used with a fine mesh of 30 km and a coarse mesh of 90 km.
The quasi-operational version of MM4 has been tested on a number of cases since it's
inception in April 1989. The results indicate that MM4 has the potential to contribute to the
improvement of real-time forecasts of rnesoscale phenomena. Work is now underway at Penn State
to make the operational version of the model relocatable and to run the model in real time on a
large number of cases.
5.0 REGIONAL CLIMATE SIMULATION
Realistic simulation of regional climates probably requires a horizontal resolution of
approximately 50 km x 50 km, which represents an increase of a factor of 10 x 10 over that of
present climate models. Such an increase would require an increase in computational power of
approximately ten thousand over present capability. Until such computational power becomes
available, one approach to modeling regional climates over certain areas of interest is to embed a
high-resolution limited-area model in a GCM over the specific region of interest. The GCM is run
first and the output used to provide LBC to the regional model. In this way the large-scale global
climate forcing can be supplied to the regional model, which can in principle add regional details
such as those associated with high-resolution variations in terrain or land-surface
characteristics.
The nesting of a limited-area model (MM4) into a GCM (the NCAR Community Climate
Model-CCM) for the study of the regional climate of the western United States has been
undertaken by Dickinson ejtaL. (19.89). " In initial tests of the coupled CCM-MM4 system,
Dickinson gtal.. (1989) performed 20 days of January simulations to examine five precipitation
events selected from three Januaries of the CCM simulation. Dickinson et al (1989) show that the