Overview of all working group cases

The workshop will consist of investigation into three topics of cloud modeling: mixed-phase clouds, deep convection, and cloud chemistry. Within each topic area is two specific cases developed to test certain components within models. Each case is briefly described below along with links to more complete descriptions and specific instructions to run the experiments. Researchers are encouraged to simulate one or more cases and send a courtesy email to the case leader. Even if the simulations do not meet or exceed your own expectations, participation in the workshop is encouraged.

Orographic mixed-phase stratiform cloud (case #1)
This case is composed of two parts. Part 1 is an orographic cloud and precipitation system simulated using stable upslope flow impinging on an idealized bell-shaped mountain. Sensitivity is easily tested by varying the initial thermodynamic conditions and mountain height to produce either blocked flow or a hydrostatic wave. Microphysical sensitivities are tested by varying CCN and aerosol constituents. Part 2 of this case is simulation in 2D of an observed event in the Swiss Alps on 08 March 2004. Initial aerosol values are provided based on actual field campaign observations. Other observations include precipitation, radar reflectivity, cloud droplet concentration and liquid water content for evaluation of simulation results. A primary focus of model intercomparison will be the partitioning of condensate between liquid and ice phase and the resulting accumulated precipitation. Furthermore, estimates of the indirect aerosol effect on mixed-phase clouds and precipitation will be compared.
Case leaders: Andreas Muhlbauer and Ulrike Lohmann

Files to download for Case 1:

Arctic mixed-phase stratiform clouds (case #2)
This case is constructed from an observed mixed-phase Arctic stratus cloud on 07 May 1998, that persisted for nearly three weeks during the SHEBA field project. The event was characterized by a single layer mixed-phase cloud at the top of a well-mixed boundary layer and minimum temperature of −20°C above a sea ice-covered surface with weak turbulent surface fluxes. There were extensive cloud and thermodynamic measurements from ground-based and aircraft instrumentation. Simulations are ideally suited for single-column, cloud-resolving, and LES models. This case is being conducted jointly with the GCSS Working Group on Polar Clouds. The primary focus of this workshop case is the ability of models to maintain a long-lived mixed-phase cloud layer despite the weak forcing and relatively low temperatures.
Case leader: Hugh Morrison

Files to download for Case 2:

Mid-latitude squall line (case #3)
This case is composed of two parts. The first is an idealized two-dimensional squall line created with an initial, prescribed warm bubble. The second part is to simulate a real mid-latitude squall line that developed in western Oklahoma (USA) during the IHOP field campaign on 12–13 June 2002. Thunderstorms initiated near the Oklahoma panhandle late on the 12th and matured into a squall line that passed through Oklahoma City approximately 10–12 hours later. The development stage was captured by the NCAR S–POL polarimetric radar whereas the mature squall line was observed with the NEXRAD radar at KTLX. In addition to radar data, surface mesonet observations detail the development and propagation of the cold pool and precipitation amounts. The primary focus of this workshop case is storm and cold pool initiation and morphology, and the models ability to develop the trailing stratiform rain region.
Case leaders: Greg Thompson

More details …

Deep convection, supercell (case #4)
This case is intended to simulate a tornadic supercell observed on 29 June 2000 northwest of the town of Goodland, Kansas. The event was documented in Kuhlman et al. (2006) and the purpose of this workshop case is investigation of sensitivities of microphysics to observed storm features and evolution. Kuhlman et al. (2006) produced a reasonable simulation of the event using an idealized sounding and warm bubble perturbation, and we will replicate many of their steps to model the observed storms. Comparisons among model simulations and to detailed observations will be the primary focus of the workshop.
Case leaders: Matthew Gilmore

More details …

Cloud chemistry, urban region (case #5)
During the ICARTT field campaign in Summer 2004, the Canadian Convair 580 sampled a number of trace gases, aerosols, and cloud parameters. Measurements of aerosol particle chemistry were made using an AMS and PILS. Cloud droplet residuals were determined using an AMS downstream of a CVI. On 10 August, the aircraft sampled in and below a cumulus cloud downwind of Chicago along the 84°W and 86°W meridians between 40.5 and 42.6°N. A large plume impacting the clouds was encountered along both meridians. This workshop case is well suited for comparison of cloud chemistry in regional-scale models with concentrated focus on how the models simulate the processing of nitrogen and sulpher through cloud, how carbonyl compounds are scavenged by cloud, and the effects of cloud microphysics on chemistry.
Case leaders: Richard Leaitch, Wanmin Gong, Anne Marie MacDonald, Junhua Zhang

Files to download for Case 5:

Cloud chemistry, towering cumulus (case #6)
A second cloud chemistry case relating to chemical processing by towering cumulus is being developed. The case includes measurements taken below cloud and at multple levels within cloud and is suitable for cloud-scale and parcel models. More details to follow later.
Case leaders: Richard Leaitch, Wanmin Gong, Anne Marie MacDonald, Junhua Zhang

Files to download for Case 6: