Date of Award
Master of Science
Geological and Atmospheric Sciences
Tsing-Chang (Mike) Chen
General circulation models (GCMs) allow atmospheric scientists to tinker with atmospheric processes and study the resulting climate trends. Atmospheric trends, such as temperature fluctuations, wind shifts, and precipitation patterns are extensively studied in an attempt to realize their impacts on people, places, and other natural processes. Although useful, GCMs have shortcomings with respect to the representation of subgrid-scale meteorological processes, and thus, parameterization is required. One of the toughest components to simulate in climate models is that of clouds, as they are variable over time and spatial scales. Cumulus parameterizations, used to represent convection, have major implications for the precipitation. Cloud-resolving model (CRM) experiments have aided in the improvement of convection parameterizations. Depending on convection closure and trigger mechanisms, precipitation may be suppressed or occur more often. The cumulus scheme also alters the radiation budget as radiation processes are coupled with hydrological ones. The National Center for Atmospheric Research (NCAR) General Circulation Model (CTL) and the Iowa State University General Circulation Model (EXP) are two such models used to study differences in parameterizations, specifically those to convection. Convection scheme modifications in EXP (based on CRM studies) are found to produce closer to observed mean climate simulations in precipitation, convection, and cloud-related variables. A diurnal cycle of precipitation more resembles observations in EXP than CTL. EXP's precipitation occurs less frequently but with more vigor than CTL. Through decomposition of the water vapor flux into rotational and divergent wind components, we find EXP to have a more distinguishable Southeast Asian Monsoon trough and generally stronger convergent centers in monsoon regions. This agrees with precipitation in EXP being less frequent but more vigorous than CTL. Eddy components of the water vapor flux for each model simulation appropriately indicate poleward water vapor transport.
Zachary Alan Mangin
Mangin, Zachary Alan, "Assessment of a General Circulation Model with Modified Convection and Clouds" (2013). Graduate Theses and Dissertations. 13059.