**Current
Model :( Jan 2004)
**

** ****
***
**** Data assimilation
**

**
****Scheme: 3-dimensional variational
method (derived from NCEP Spectral
Statistical ****
****Interpolation scheme)
**

**
****Update cycle: 6-hourly
**

*** Dynamics**

**
Horizontal
resolution: Triangle truncation 179 waves
**

**
Vertical resolution: 30 sigma levels
**

**
Time step: 480 sec
**

**
Diffussion: 4 ^{th }order horizontal diffusion
**

**
Prognostic variables: vertical vorticity, horizontal divergence,****
****surface pressure, specific
humidity****,****
virtual potential temperature
**

***
Physics
**

**Radiation:
Harshvardhan et al.(1987)
**

**Cumulus:
relax Arakawa-Schubert scheme(Moothi and Suarez 1992)
**

**Large
scale precipitation
**

**Shallow
convection: Li(1994)
**

**Vertical turbulence mixing:**
**TKE-e
scheme(Detering and Etling 1985)
**

**Surface flux: similarity theory(Businger 1971)
**

**Soil model: one layer model with restoring force nudging to climate
**

**Gravity wave drag: Palmer et al.(1986)
**

**
**

**Operational
Procedure:
**

**Now
the global model is running four times a day.
**

**For
the 00Z run, model performs a 120 hours forecast.
**

**For
the 12Z run, model performs a 192 hours forecast.
**

**For
the 06Z and 18Z, model performs a 6 hours forecast.
**

**Future
task:
**

**Enhance
the use of new radiance data of new satellites.
**

**Upgrade
soil model from one layer to multi-layer.
**

**Improve
moist physical process by TRMM information.
**

**Increase
the resolution from T179L30 to T239L40.
**

**Develop
cloud scheme to resolve grid-scale precipitation.
**

**
**

**Reference:
**

Businger,
J. A., J. C. Wyngaard, Y. Izumi, and E. F. Bradley, 1971: Flux-profile
relationships in the atmospheric surface layer, ** J. Atmos. Sci**,

Detering,
H. W., and D. Etling, 1985: Application of the E-
turbulence model to the atmostheric boundary layer. ** Bound
–Layer Meteor**., 33, 113-133.

Harshvardhon,
R. Davies, D. A. Randall, and T. G.. Corsetti, 1987: A fast radiation
parameterization for atmospheric circulation models,**
J. Geophys. Res.**

Li,
J.-L., 1994: On shallow cumulus parameterization scheme for large-scale
planetary boundary layers, Ph.D. thesis, University of Wisconsin-Madison, pp203.

Liou,
Chi-Sann, Jen-Her Chen, Chuen-Teyr Terng, Feng-Ju Wang, Chin-Tzu Fong, Thomas E.
Rosmond, Hong-Chi Kuo, Chih-Hui Shiao, and Ming-Dean Cheng, 1997: The
second-generation global forecast system at the central weather bureau in
Taiwan. ** Weather and Forecasting**,

Moothi,
S., and M. J. Suarez, 1992: Relaxed Arakawa-Schubert: A parameterization of
moist convection for general circulation models. ** Mon. Wea. Rev**.,

Palmer,
T. N., G. Shutts, and R. Swinbank, 1986: Alleviation of a systematic westerly
bias in general circulation and numerical weather prediction models through an
orographic gravity wave drag parameterization. ** Quart. J. Roy. Meteor. Soc.**,

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