Transitional Atmospheric Boundary Layer in the GABLS4 Experiment Modelled Using the Explicit Algebraic Reynolds-stress Model

TL;DR

This paper applies a novel explicit algebraic Reynolds-stress (EARS) model to simulate a transitioning atmospheric boundary layer over multiple diurnal cycles, accurately capturing turbulence and fluxes during stable and convective conditions.

Contribution

The study demonstrates that the EARS model can effectively simulate a transitioning ABL with a unified approach for stable and convective states, including transitional effects.

Findings

First-order statistics are well predicted by the model.

The model captures residual turbulence during transitions.

Horizontal turbulent fluxes are accurately modeled.

Abstract

A recently developed so-called explicit algebraic Reynolds-stress (EARS) model is applied to a transitioning atmospheric boundary layer (ABL). The simulation describes a diurnal cycle with a deep convective ABL during daytime and an extremely thin and stably stratified ABL during nighttime. The predictions of the EARS model are compared to large-eddy simulations (LES) of Couvreux \emph{et al.}~ (Bound Layer Meteorol 176:369-400, 2020). The model simulation is extended in time in order to study several consecutive diurnal cycles. The EARS model uses the same parametrization and model coefficients for stable and convective ABL and is applicable over a wide range of thermal stratifications. First-order statistics are shown to be well predicted by the model. We also show that the model can predict transitional effects such as residual turbulence as well as horizontal turbulent fluxes, which are an inherent part of the EARS model solution.