The onset of tropical deep convection: observational metrics for climate models and the role of entrainment
Abstract
The onset processes for deep convection play a key role in tropical climate and yet there remains great uncertainty in the representation of these in climate models. Recent observational measures for the statistics of the convective onset and related metrics can help constrain and assess the new generation of climate models. While some models do poorly at statistics arising from short time-scale processes, some recent high-resolution models do sufficiently well that the dialogue becomes two-way, with the models helping to interpret the observations. Recent revisions of the Community Atmosphere Model approximately reproduce observational estimates of the critical value for onset of deep convection as a function of column water vapor and temperature. This onset boundary turns out to have a strong dependence on representations of entrainment in the convection scheme, and thus can be used to constrain values of entrainment parameters to a range consistent with observations. The substantial values of entrainment implied in the lower free troposphere yield a self-consistent explanation for the importance of lower free tropospheric water vapor in controlling the onset of convection noted in other observational studies. Implications for lower tropospheric lapse rates are also considered.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.A31H..01N
- Keywords:
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- 1626 GLOBAL CHANGE / Global climate models;
- 3314 ATMOSPHERIC PROCESSES / Convective processes;
- 3365 ATMOSPHERIC PROCESSES / Subgrid-scale parameterization;
- 3371 ATMOSPHERIC PROCESSES / Tropical convection