Cumulus Convection and Large-Scale Tropical Flows

New Mexico Institute Of Mining And Technology, Socorro NM

Investigators

Abstract

Research under this grant will refine and extend our understanding of the thermodynamic control of tropical convective clouds and precipitation over a broader range of tropical weather systems including tropical cyclones (hurricanes), convectively coupled Kelvin waves, tropical easterly waves (which can develop into hurricanes), and the Madden-Julian oscillation. The research uses a combination of simple models, observations from field campaigns, and a cloud resolving model (CRM) to identify the most important physical processes which govern tropical convection and its relationship to the large-scale atmospheric circulation. Specific tasks of the project would include 1) Extension of the theory of covective quasi-equilibrium. The quasi-equilibrium state for tropical convection which is assumed in much of the theoretical literature on tropical circulation dynamics does not develop fully in CRM simulations. This research will use simple models to understand the implied limitations of quasi-equilibrium theory; 2) Extension of the Raymond-Fuchs model of convectively coupled tropical waves. The Raymond-Fuchs model has been successful in reproducing convectively coupled waves, and the proposed extensions would be used to study the effects of top-heavy, botttom-heavy, and tilted heating profiles associated with observed tropical convection; 3) Examination of the role of convection in the development of tropical cyclones. The research would address the nature of the vertical convective mass flux in tropical cyclone development, paticularly the extent to which the mass flux happens in a few intense "vortical hot towers" rather than a large number of unexceptional clouds; 4) Examination of the structure and dynamics of easterly waves, particularly the extent to which their development is controlled by surface wind speed, temperature, humidity, wind shear, and surface fluxes of heat and moisture. The project will support and train two graduate students and one undergraduate, thereby training the next generation of scientists in the field of tropical convection. The graduate students will gain experience with large field campaigns through participation in the NSF PREDICT project. The work will support international collaboration in science through the collaboration of a scientist in Croatia, and international scientific outreach will be promoted through a workshop held in Split. The work has broader scientific impact due to its relevance to the task of developing cumulus parameterization schemes for use in weather and climate models.