What's new in QTCM1 version 2.3

Released August 2002.

• A simple formulation for atmospheric boundary layer winds is used to compute the surface fluxes.
• Vertical momentum advection terms are included in the momentum equations.
• Fourth-order horizontal diffusion is used in the momentum equations in lieu of the second-order diffusion. (See Section 4.6)
• New cloud parameterization is implemented, considering random overlapping of different cloud types. The resulting total cloud fraction is ensured to be less than 1. (See Section 4.3.1).
• The top of the model is raised to 150 HPa and the vertical velocity structure of the 1 baroclinic mode ( ) is held constant above the 280 HPa level for numerical reasons (See Section 4.1).
• The model domain is extended to S - N.
• Corrections to spherical geometry terms are included.
• A moisture depend ence is added to the gross dry stability to simulate the cloud-top effect on . A cap is used so that the gross moist stability would not decrease to a lower value than the minimum value typical of the reference profile region.
• The interception loss Evapi is capped at of precipitation amount (as a numerical safety check)
• The surface pressure gradients can be diagnosed.
• Baroclinic velocity potential can be diagnosed.
• The artificial ocean boundary near the northern and southern boundary used in version 2.2 is removed and the sponge layers are not needed by default. A Fourier filter is used to damp small scale features at high latitudes.
• Available Reynolds SST has been updated from December 1998 to October 2001.
• All boundary data except the cloudiness are updated for the new grid dimensions. There are numerous gaps in the ISCCP cloudiness data at high latitude making an interpolation to the new domain difficult. Currently the cloudiness data are identical to the ones used by QTCM version 2.2. The missing high latitude are set to the zonal means of the closest existing latitude band at 58.75 N and 58.75 S, respectively.
• An option is added to use prescribed observed SST in masked regions and mixed layer ocean in non-masked regions (See Section 4.4).
• Scripts to run ensemble simulations are added (See Section 2.3.2).

Changes in code structure:

• The code is adapted to Fortran-90.
• All common blocks are replaced by modules.
• Example makefiles for different platforms are provided.
• With the simple atmospheric mixed layer the surface stress no longer relates to the resolved winds by a simple linear formula. Therefore the damping parameters (equations (4.33) (4.34) and (5.15) in [2]) have been replaced by the corresponding surface stress terms (equations (4.12) and (4.13) in [2]).
• Stress taux,tauy components are computed on u, v grids, respectively. Previously etc terms related to stress were used in the time marching on u, v grids while the arrays taux, tauy were diagnostic calculated for output on the T grid.
• The order of the indices of the cloud fraction variable cld was changed from ``lon, lat, cld-type'' to ``cld-type, lon, lat''.
• The output routines are rewritten. GrADS control files for the binary output files are automatically generated.
• Adding (removing) an output variable now only requires adding (removing) one subroutine call.
• The scripts to run the model are modified so that multiple runs can be made simultaneously. To this end each run is executed in a separate subdirectory of directory proc.
• The interval to write restart files can now be specified.
• Subroutines to diagnose surface pressure and its derivatives are added.
• When the model blows up, the instantaneous values of standard variables are output for diagnosis and the monthly means for the last month before blowing up are also written.
• The prognostic variable arrays are dimensioned as (nx,0:ny+1) to avoid out-of-bounds access of memory which led to errors on some computers (e.g., IBM-AIX).
• Added ntoutr and nooutr to the input para meters to specify time in days between restart files and days to to specify time in days between restart files and days to skip before starting to write a restart file. Default write interval is one year.
• The restart file output names now include are changed to qtcm_YYYYMMDD.restart.
• The front-end solvers for the FATD package are in qtcm.f90 (used to be in fatdpkg.f). The old front-end solvers for Cartesian Coordinates are deleted. Users can refer to v2.2 or older versions for these or set .
• New preprocessor macros are

  DELTACO2

  Enable radiation code to use a non-s standard CO level.

  TOPO

  Include topography effects due to barotropic divergence.

  MXL_OCEAN

  Use mixed layer ocean.

  BLEND_SST

  Use readsst in mask regions and mixed layer ocean outside.

  NO_WADV

  Switch off vertical advection terms.

  NO_ABL

  Switch off atmospheric boundary layer.

  OBSCLD

  Use ISCCP observed cloud cover climatology.

  SPONGES

  Enable sponge regions.

  CHIWIND

  Diagnose velocity potential using irrotational winds.

  ENSEMB_INI

  Create initial condition files for ensemble runs.