Effects of Wind Shear on Turbulence Kinetic Energy Distributions around Shallow Cumulus Clouds

Clouds and their feedback into large circulation models are one of the greatest sources of uncertainty in climate science today. In this study, we use the MicroHH LES code to explore the relationship between windshear and the distribution of Turbulence Kinetic Energy (TKE) around a cloud. Performing data analysis in Python, we examine datasets from the Barbados Oceanographic and Meteorological Experiment (BOMEX) case, The Rain in Cumulus Clouds over the Ocean (RICO) case, and the Southern Great Plains (SGP) case. Using a decay function, we model the distance from a cloud boundary (where clouds are defined as a cell with nonzero liquid water content) to the environmental value of TKE. The distance from the cloud boundary to this norm is called the length scale. We use this model for every elevation and time step, and, using image processing techniques, rotate the cloud field so that we can see the length scale at every angle around the cloud. We then compare the angle of wind shear, defined as the difference in wind magnitude at an elevation within the cloud from that at cloud base, to direction of the maximum length scale. What we find is that in the steady state cases (sea-air interaction) BOMEX and RICO there is a strong correlation between the direction of windshear and the maximum length scale; however, in the case of the SGP case (land-air) interaction, while the relationship still exists, it is not always guaranteed.