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Calculation of the Parameters in qtcmpar.f90

 

A summary of the variables in this file is given in Section 2.4.1. The parameters in qtcmpar.in are generated by a Fortran 90 program, par.f90. To recalculate qtcmpar.f90 (and qtcmpar.gs) uncomment the build lines in the makefile and execute make qtcmpar.f90 It produces the file, qtcmpar.f90. The input reference profile for par.f is Tqo3.ref which includes SST (K), air temperature (K), water vapor mixing ratio (kg/kg), and ozone mixing ratio (kg/kg) in 1 hPa interval from 1000 hPa to 1 hPa.

For calculating a1, 900 hPa cloud base and 150 hPa cloud top are used. Below the cloud base, the atmosphere is dry adiabatic; above the cloud base, the atmosphere is moist adiabatic. Relative humidity profile is a linear fit to the observed reference relative humidity, which is 85% near surface and 60% at 150 hpa. Tqo3.ref is used to calculate reference values of the gross moist stability and the gross moisture stratification. However, for some sensitive quantities, the values from the single profile in qtcmpar.f90 are used as a guideline balanced with other considerations. In particular, reference values of the gross dry stability and gross moisture stratification, GMsr and GMqr, are assigned in qtcmpar.in based after sensitivity testing. Relevant factors include: (i) the choice of dry stability affects numerical stability. Sometimes a larger value of this parameter is useful to avoid sporadic blow-up after decades of run. (ii) the moisture tends to adjust nonlinearly in the model so the climatological value in the warm pool region may be somewhat off the values in the reference profile. (iii) Estimates of the gross moist stability M in @CROSSREF[11] differed in absolute value among different data sets, but the relative value of M/Ms was more consistent and is more dynamically important. There is thus some freedom to choose GMsr and GMqr within known constraints to attempt to obtain better numerical stability and reasonable output values of M and GMq. In version 2.3 GMsr=3.5 and GMqr=3.0.

Model top in the calculation of all basis functions was set at 200mb in v2.2 and earlier. This was partly motivated by the values of tex2html_wrap_inline2276 that result above 200 mb from the contribution of tex2html_wrap_inline2888 in the vertical integration of the hydrostatic equation and the impact of these in tex2html_wrap_inline2890 and tex2html_wrap_inline2892 coefficients. In v2.3, the velocity basis function tex2html_wrap_inline2276 is held constant above 280 mb and the model top can thus be extended to 150mb, more typical of the tropical troposphere. Since temperature at the uppermost levels is not strongly held to quasi-equilibrium, it is reasonable to cap tex2html_wrap_inline2276 values there to prevent impact in the higher order terms. This impacts momentum transport terms, including effects of the vertical advection of momentum.


next up previous contents
Next: Land-Surface Parameterization Scheme Up: Model Physics Previous: Model Physics

Climate Systems Interaction Group
Sun Aug 25 00:58:46 PDT 2002