East Asia and Western Pacific METEOROLOGY AND CLIMATE

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Comparison of the surface temperature fields (results not
shown here) at 5-km and 2-km shows that the overall patterns are
similar. Both simulations predict that the Pearl Estuary will hold
back the advancement of the cold air and temperatures at Macau will be
four degrees lower than that at RO. There are some evidences of warm
air being held back behind the hills over the Hong Kong territory for
the 2-km run but not for the 5-km run. However, with only limited
test results, this difference may not be statistically significant. A
smaller grid size test was not made by reason of the much longer
computer time required.
4. Conclusion
This experiment
shows that dynamic numerical models at
fine enough grid resolution (in this case, 5-km) under near steady
meteorological conditions are able to augment synoptic scale models in
providing more detailed temperature field forecast for local regions.
As the current model uses only one sky condition for the
whole domain and forecast period, local variation in cloud cover will
cause disparity between forecast value and observation.
Experiment with 2-km nested grid yields no marked differences
against the 5-km grid results and more test runs are needed to
elicit the influence of terrain.
The experiment also shows that forecasts longer than
twelve hours are affected by inadequate boundary treatments. Therefore,
unless accurate boundary conditions are available, say from
larger area models, increasing the domain size to about 1000 km may be
needed to achieve a better 24-hour forecast.
5. Acknowledgement
The authors would like to thank the Director of the Meteorological
Research Institute
of Japan for making the model available
for the present study. The authors also wish to thank Mr. K.Y. Tarn and
Mr. K.L. Tang for the preparation of the graphs and the Data Processing
Division of the Royal Observatory
and support.
for their computational services