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GEWEX Cloud System Study: Working Group 3

OBJECTIVE AND PHILOSOPHY

This working group is concerned with the parameterization of extra-tropical layer clouds within climate and large scale models.

The approach to be taken is to carry out validated high resolution simulations of these cloud systems and to use this information as synthetic data for developing the parameterizations.

There will be a number of intermediate outcomes of the working group's activities. As is evident from examining other parts of this home page, this working group is assessing the ability of climate models to simulate the essential features of layered cloud systems occurring under the widely varying conditions found in different regions. A critical outcome of the effort will then be a collective assessment of the degree to which climate models can account for the range of cloud conditions that actually occur. This will apply to continental, coastal and oceanic cases.

Updates on such efforts are taking the form of working group scientific review articles, special scientific articles, and in the future the issuing of statements summarizing the working group's assessment of the present capabilities of climate models. Such a statement will be updated as one measure of our progress.

Consideration will also be given to issuing as a legacy of the working group, comprehensive datasets that can be used as benchmarks against which models can be tested.

An important outcome of the working group is also the joint development of the needed tools needed to realize the objectives. This in particular has spawned a great deal of interaction to develop a suitable column model that can be used for model parameterization testing.

An important component of the effort is also concerned with the use of remote sensing tools to actually delineate the structure of layering within large scale organized systems and understanding to what degree this level of detail needs to be accounted for within climate models.

The efforts of this working group are also critical to several other efforts under WCRP and GEWEX in particular. For example, the water budgets of many of the GEWEX Hydrometeorology Panel (GHP) continental-scale experiments is largely dictated by the nature of extra-tropical systems, as studied within this working group. Consequently, strong interactions either have or will be developed with BALTEX, MAGS, GCIP and GAME. In fact, many of the specific cases being examined within the working group were developed by these GHP efforts. In addition, the assessment of our ability to understand layering and its consequences is directly relevant to the GEWEX Radiation Panel and in its developing effort referred to as the GEWEX Water Vapour Project (GVaP). Understanding the processes controlling water vapour must pay a great deal of attention to extra-tropical systems.

In general then, the objectives of this working group are clear, a major effort is ongoing to develop the international linkages to achieve the objectives, and there are many linkages with other efforts and they are relying on us for success.

Suggestions and comments should be sent to Ron Stewart.



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