East Asia and Western Pacific METEOROLOGY AND CLIMATE

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given. This is treated separately for sea and land surface.
For sea, the surface temperature is prescribed by monthly climatological data, and
kept constant during time integration. ,
For land, diffusion equations are used to describe the variation of temperature and
moisture in the soil. Using a three-layer model, the equation for soil temperature may be
written as
dT. IF K(T 4 -T S )
8t pCD { ^Q.SD^Dt
_ K(T d -T s ) K(T d -T d )
dt Q.5Z> 2 U>i -
where ^F represents all surface heat fluxes including solar radiation, long-wave radiation,
sensible and latent heat fulxes, K is the diffusion coefficient, p g and C g the density
and specific heat capacity of soil, and Dl, D2 and D3 are the depths of the layers
respectively.
For soil moisture, there are similar equations.
3.4 Precipitation and Latent Heat Release
To simulate the condensation process in stratiform cloud, the so-called
"saturation-condensation" method is adopted, i.e. wherever q > q SAT (T) occurs at certain
time— step, then an adjustment for T and q is conducted. The adjusted temperature
T * and specific humidity q * should satisfiy
where q SAT is saturated specific humidity and the excess of q becomes precipitation.
For cumulus convection, the modified Kuo (1974) scheme is adopted. The conditions
for convection to take place is a covergence of moisture of background fields (7>0)
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and a conditional unstable laspe rate (-—- >0). Besides, to avoid spurious and random
op
convection due to computational error in moisture convergence and to consider the fact
that systematic convection is often related to synoptic systems, we impose an addional
critirion CAT > 0, f # being vorticity at the lowest model level.
The heating and moistening due to cumulus convection is given by
dP
C p (T e - T)— ,
J p t
where * C" denotes variables in cloud. The moistening parameter b is taken following
Anthes with (RH) C = 0 and n = 3. (Anthes, 1977; Das etal., 1988)
4. RESULTS OF COMPARATIVE FORECAST EXPERIMENTS
Here comparative forecast experiments for a real case is given to illustrate the performance
of the model. The case selected is 12GMT, 14-19 June 1979, the time when the
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