| Description |
Weather prediction models have benefited from the advances in computational power, enabling finer grid resolutions. Land-surface heterogeneity exists at all spatial scales and is not rapidly blended by the flow, impacting the near-surface region of the atmosphere. Traditionally, momentum and energy fluxes linking the land-surface to the flow have been parameterized using atmospheric surface layer similarity theory. However, heterogeneity leads to large deviations in the traditional theory, especially in the transport of scalar quantities, such as moisture and temperature. In this work, we propose to use high-resolution numerical simulations to further investigate the effect of surface thermal heterogeneities on the atmospheric flow, an area that is still far from being fully understood. The goal is to create new knowledge that can be used for new parametrizations of thermal surface heterogeneities. We describe the comparison of the performance and cost of three dealiasing techniques (3/2-rule, Fourier truncation, and Fourier smoothing) to evaluate their advantages and limitations. Two studies of the influence of surface thermal heterogeneities on the atmospheric boundary layer flow are then presented in this work, using the geostrophic forcing and thermal patch size as parameters. While comparing the different dealiasing techniques, the computational cost is considered, as well as its variation with the numerical resolution. The accuracy of the methods is also studied, as they can lead to over-dissipate the turbulent motions in the near-wall region. The first study of the surface thermal heterogeneities focuses on dispersive fluxes as a measure of the effect of the surface conditions on the flow and distinguishes between different regimes depending on the geostrophic forcing. The second study introduces the heterogeneity parameter, used to describe the dynamics of the thermal heterogeneities. The influence of the surface conditions on the turbulent and dispersive fluxes is studied under different geostrophic forcings using spectral analysis to emphasize which scales are affected by the heterogeneities. |
