Operational high‐resolution numerical weather prediction models are now able to partially resolve turbulent motions due increased computing power. The partitioning of resolved and parametrized fluxes becomes important in the representation transfer that determines state atmospheric boundary layer. In this study, successive simulations a convective layer using Met Office Large Eddy Model from large‐eddy simulation mesoscale limit compared with corresponding coarse‐grained fields examine model...

Abstract Numerical simulations of two cases morning boundary layer development are conducted to investigate the impact grid resolution on mean profiles and turbulent kinetic energy (TKE) partitioning from large eddy simulation (LES) mesoscale limit. Idealized LES, using 3‐D Smagorinsky scheme, is shown be capable reproducing evolution when compared against measurements. However, increasing spacing results in damping resolved TKE production superadiabatic temperature layer. Turbulence...

Numerical weather prediction (NWP) models are now capable of operating at horizontal resolutions in the 100-m to 1-km range, a grid spacing similar scale that turbulent eddies present atmospheric convective boundary layer (CBL). Known as 'grey zone' turbulence, this regime is characterized by significant contributions from both resolved and subgrid components represent dominant motions system. This study examines how initiation turbulence – concept commonly referred 'spin-up'– can be delayed...

Abstract. In this study, we discuss the differences in total precipitable water (TPW), retrieved from a Cimel sun photometer operating at continental site southeast Europe, between version 3 (V3) and 2 (V2) of AErosol RObotic NETwork (AERONET) algorithms. addition, evaluate performance two algorithms comparing their product with TPW obtained collocated microwave radiometer nearby radiosondes during period 2007–2017. The all three instruments was highly correlated, showing same annual cycle,...

Abstract A scale-dependent Lagrangian-averaged dynamic Smagorinsky subgrid scheme with stratification effects is used to simulate the evolving convective boundary layer of Wangara (Australia) case study in gray-zone regime (specifically, for grid lengths from 25 400 m). The and standard approaches are assessed first- second-order quantities comparison results derived coarse-grained large-eddy simulation (LES) fields. In LES regime, schemes produce very similar results, albeit some modest...

Abstract A scale-dependent dynamic Smagorinsky model is implemented in the Met Office/NERC Cloud (MONC) using two averaging flavors, along Lagrangian pathlines and local moving averages. The approaches were compared against conventional Smagorinsky–Lilly scheme simulating diurnal cycle of shallow cumulus convection. simulations spanned from LES to near-gray-zone gray-zone resolutions revealed adaptability across scales different stability regimes. can produce a scale- stability-dependent...

A single‐column model of the dry, shear‐free, convective boundary layer is presented in which non‐local transports by coherent structures such as thermals are represented partitioning fluid into two components, updraught and environment, each with a full set prognostic dynamical equations. Local eddy diffusive transport entrainment detrainment parametrizations similar to those used diffusivity mass flux schemes. The inclusion vertical diffusion velocity shown be important for suppressing an...

Abstract Two‐fluid modelling has recently emerged as a promising approach to representing cumulus convection in weather and climate models. This study applies the two‐fluid model described Part II shallow case over land (ARM). Large‐eddy simulation data are used tune majority of closures that determine properties entrained detrained air. The is generally able reproduce profiles mean turbulent quantities all stages diurnal cycle. As such, initiation evolution cloud layer well captured....

Abstract A new method is introduced to identify coherent structures in the convective boundary layer, based on optimizing vertical scalar flux a two-fluid representation of turbulent motions as simulated by large-eddy simulation. The approach partitions joint frequency distribution (JFD) velocity and transported into (fluid 2) their environment 1) maximizing that part resolved mean properties fluid 2 1. proposed does not rely any priori criteria for partitioning flow nor pre-assumptions...

A recent pragmatic blending approach treats sub‐grid turbulent mixing using a weighted average of 1D mesoscale model and 3D Smagorinsky formulation. Here the is modified extended to incorporate scale‐dependent dynamic scheme instead static scheme. Results from simulating an evolving convective boundary layer show that new able improve representation turbulence statistics potential temperature profiles at grey‐zone resolutions during transition shallow morning deep afternoon layer. This...

Abstract We hypothesize that the convective atmospheric boundary layer is marginally stable when damping effects of turbulence are taken into account. If modeled as an eddy viscosity and diffusivity, then idealized analysis based on hypothesis predicts a well-known scaling for magnitude diffusivity. It also modes should have vertical horizontal scales comparable to depth. A more quantitative numerical linear stability presented realistic potential temperature profile found support hypothesis.

Abstract A simple thermodynamic parameterization based on a modified version of the Whiteman and McKee inversion destruction model is presented to simulate evolution vertical temperature structure during breakup period in idealized valleys under clear, undisturbed weather conditions. The proposed method adopts simplified semiempirical parameterizations radiation surface energy budgets at valley floor sidewalls an empirical scheme for partitioning atmosphere, eliminating need selecting...

Abstract The multifluid equations are derived from the compressible Euler (or any of usual approximate equation sets used in meteorology) by conditional filtering. They have potential to provide basis for an improved representation cumulus convection and its coupling boundary layer larger scale flow numerical models. present article derives prognostic subfilter‐scale turbulent second moments framework, along with certain systematic simplifications them, thus providing a analogue well‐known...

Abstract The factors that affect the atmospheric energy budget approach used in thermodynamic valley inversion destruction model of Whiteman and McKee are investigated theoretically. height at which sinking top meets rising convective boundary layer to destroy inversions can be uniquely determined by topographic characteristics an adjustable parameter, relating fraction sensible heat flux going growth, through a simple parabolic relationship. time required break temperature expressed with...

Abstract. In this study, we discuss the differences in total precipitable water (TPW), retrieved from a Cimel sunphotometer operating at continental site South-East Europe, between Version 3 (V3) and 2 (V2) of Aerosol Robotic Network (AERONET) algorithms. addition, evaluate performance two algorithms comparing their product with TPW obtained collocated microwave radiometer nearby radiosondes during period 2007–2017. The all three instruments was highly correlated, showing same annual cycle,...

Abstract We examine the ability of two dynamic turbulence closure models to simulate diurnal development convection and transition from dry shallow cumuli then deep convection. The are compared with conventional Smagorinsky scheme at a range cloud‐resolving grey‐zone resolutions. schemes include Lagrangian‐averaged, scale‐dependent model mixed model. fails reproduce stage beyond large‐eddy simulation regime, continuously building up convective available potential energy that eventually leads...

Abstract Dynamic subgrid models are increasingly being used in simulations of the atmospheric boundary layer. We have implemented several variant forms dynamic UK Met Office Large Eddy Model (MetLEM), including a state‐of‐the‐art Lagrangian‐Averaged‐Scale‐Dependent (LASD) model. The implementation includes optional use stability functions specification eddy viscosity and diffusivity, as well within calculation Smagorinsky parameter. This paper reports on behaviour LASD model with different...