Observational studies and numerical simulations of marine convective boundary layers
Abstract
Observational study of a convective boundary layer over Lake Michigan in the winter season has shown that the condensational heating in the cloud layer strongly influences the turbulence budgets involving virtual potential temperature. The buoyancy profile in the TKE budget is found to be large near the surface, as well as in the cloudy layer. The buoyancy-turbulence interaction is deduced to be responsible for the production of heat flux and heat variance in the cloud layer or even near the surface. Type I CTBLs are also strongly affected by the entraining air extending downward from the overlying inversion layer. Statistics obtained from model simulations are generally taken over both time and horizontal planes. In order to investigate the reliability of the statistics, we divided the horizontal plane into different parts, over which averages were taken. The one-time area average is found to be adequate for the first moments. The longer period of time is required for the second and third moment averages. The liquid phase Large-Eddy Simulation (LES) of the CTBLs showed that the Type I CTBL is more dynamically active, and is characterized by strong positive skewness. The ice phase large eddy simulation model has been developed to more adequately simulate the marine convective boundary layer with snow. Major improvements over the previous MP1 model include the diagnosis of cloud ice mixing ratio, the precipitation of snow and the parameterization of detailed microphysical processes. The comparison of statistical profiles among liquid phase LES (MP1), ice phase LES (MP2) and the LESS observations showed that the MP2 model simulation agreed better with LESS. Results also suggest that the presence of precipitation and the associated microphysical processes have a significant effect on the structures within the convective boundary layer.
Degree
Ph.D.
Advisors
Agee, Purdue University.
Subject Area
Atmosphere|Mechanical engineering
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