| CASE STUDY | SIMULATION SET UP | RESULTS TO SUBMIT | TIMETABLE |
As a first step, a case study, based on the GCSS WG4 Case 3 intercomparison project (Xu et al. 2000) will be investigated. This case is well documented by a large data set collected by the ARM (Atmospheric Radiation Experiment) project. It corresponds to summer convection over the Southern Great Plains (SGP) of Oklahoma, an area characterized by an early evening maximum of cumulonimbus clouds in summer (Lazarus et al. 2000). We will focus on the subcase A corresponding to a 4-day period beginning the 26th of June 1997 2330 UTC. Of particular interest for this case is the triggering of convection and its coupling with boundary layer processes. Sensitivity tests and the elaboration of a more idealized simulation from this observed case will be defined latter, once the models have been validated on this case.
The simulations, for both SCMs and CRMs will be run with the large scale forcings and prescribed surface fluxes used for GCSS WG4 Case 3, the horizontal winds being nudged towards observed. In this initial model set up, the atmospheric radiative heating rate is also prescribed.CRMs will use cyclic lateral boundary conditions over a horizontal domain a few hundred km width, with a horizontal grid size of the order of 1 km.
A full description of the model set-up can be found in Krueger et al. (1999) (note that we focus on the subcase A only).The corresponding data files as well as useful fortran programs reading these data can be found on the ARM SCM web page (look for "multi-layer data", "single-level data" and "ECWMF radiative heating rates"/"SubcaseA" on this page). The multi-layer and single-level data files cover the whole CSM/IOP period.
Alternatively, you may want to use data files covering the 4-day period of subcaseA only. Files layer_ca3a.dat and surface_ca3a.dat are available, together with fortran programs reading them (read_layer.f and read_surface.f respectively), simply adapted from the one provided by ARM/GCCS Case3.The corresponding figures are available for viewing as gif files:
for time-height plots of layer_ca3a.dat fields: tz0.gif, tz1.gif, tz2.gif, tz3.gif, tz4.gif, tz5.gif, tz6.gif, tz7.gif and tz8.gif for time series of surface_ca3a.dat fields: t0.gif , t1.gif., t2.gif, and t3.gif.
The corresponding gzipped poscript files are tz.ps.gz and t.ps.gz.Participants should run their model once with the prescribed radiation and once using their own scheme.
Once ready, participants can send their datafiles via email to F. Guichard.
The list of model output will probably increase with time, but as a first step, we retain the list proposed for GCSS WG4 Case3 , including time height series of temperature, humidity, cloud hydrometeors contents and cloud fraction, as well as updraught and downdraught cloud mass fluxes. The full list of model output files, including file names and data format, can be found Krueger et al. (1999).
In addition, we would like to get the time height series of the apparent heat source Q1 and apparent moisture sink Q2 (unit: K/day, format (F7.4), file items 12 and 13 respectively), as well as the large scale forcings for temperature and moisture in the same unit and format as Q1 and Q2, file items 31 and 32 respectively, in order to check the consistency among simulations.
Nota 1: another document describing the procedure to run SCMs for this case exists (Cederwall et al., 1999), with different names/numbering for the model output. Please follows the ones provided in Krueger et al. (1999). They correspond to a subset of the full list of model output proposed in Krueger et al. (1996) for the previous GCSS WG4 Case 2 model intercomparison, except for the addition of items 0 and 30.
Nota 2: for the time series, the following fields are not absolutely needed at the present stage of the project: radiative fluxes - as the radiative heating rate is fixed in the initial simulation - (Group 1, field 2), convective and stratiform precipitation (Group 1, fields 9 and 10).
Radiative fields will be investigated in a latter stage, and will not only include the OLR but both LW and SW fluxes at the surface and TOA (Top of Atmosphere).
| Case release | deadline for sending results | meeting |
| October 2000 | January 2001 | beginning of 2001 |
REFERENCES
Cederwall, RL. T., S. K. Krueger, S. C. Xie and J. J. Yio 1999: ARM/GCSS single column model (SCM) intercomparison: Procedures for Case3: Summer 1997 SCM IOP.
Krueger S. K., R. T. Cederwall, S. C. Xie and J. J. Yio 1999: GCSS Working Group 4 model intercomparison, procedures for Case3: summer 1997 ARM SCM IOP. Technical report.
S. K. Krueger, D. Gregory, M. W. Moncrieff, J.-L. Redelsperger, and W.-K. Tao, 1996: GEWEX Cloud System Study Working Group 4: First Cloud-Resolving Model Intercomparison Project. Case 2. Technical report.
Lazarus, S. M., S. K. Krueger and G. G. Mace, 2000: A cloud climatology of the Southern Great Pains ARM CART. J. Climate, 13, 1762-1775.
Xu, K.-M., S. K. Krueger, L. J. Donner,
F. Guichard, W. Grabowski, D. E. Johnson, M. Khairoutdinov, J. C. Petch,
D. A. Randall, C. J. Seman, W.-K. Tao, R. T. Cederwall, S. C. Xie,
J. J. Yio and M.-H. Zhang, 2000: Cloud-resolving model intecomparison with
the ARM summer 1997 IOP data, proceedings of the 10th ARM science
team meeting,March 13-17, 2000, San Antonio, Texas (proceeding).
