Penetrative turbulence associated with mesoscale surface heat flux variations

TL;DR

This study uses large eddy simulations to analyze penetrative turbulence caused by surface heat flux variations at mesoscale, revealing effects on turbulence cascade and wind oscillations relevant for improving weather models.

Contribution

It introduces a detailed LES-based analysis of mesoscale penetrative turbulence influenced by surface heterogeneity, aiding development of better subgrid parameterizations.

Findings

Surface heterogeneity induces downscale turbulent kinetic energy cascade.

Mesoscale horizontal wind exhibits coherent fluctuations at 100m.

Surface-induced oscillations complicate wind forecast modeling.

Abstract

This article investigates penetrative turbulence in the atmospheric boundary layer. Using a large eddy simulation approach, we study characteristics of the mixed layer with respect to surface heat flux variations in the range from 231.48 W/m$^2$ to 925.92 W/m$^2$, and observe that the surface heterogeneity on a spatial scale of $20$ km leads to downscale turbulent kinetic energy cascade. Coherent fluctuations of mesoscale horizontal wind is observed at 100m above the ground. Such a surface induced temporal oscillations in the horizontal wind suggest a rapid jump in mesocale wind forecasts, which is difficult to parameterize using traditional one-dimensional ensemble-mean models. Although the present work is idealized at a typical scale (20km) of surface heterogeneity, the results help develop effective subgrid scale parameterization schemes for classical weather forecasting mesoscale models.