A5024924770- Meteorological Phenomena and Simulations
- Climate variability and models
- Wind and Air Flow Studies
- Atmospheric aerosols and clouds
- Fluid Dynamics and Turbulent Flows
- Plant Water Relations and Carbon Dynamics
- Atmospheric and Environmental Gas Dynamics
- Aeolian processes and effects
- Tropical and Extratropical Cyclones Research
- Optical Network Technologies
- Atmospheric Ozone and Climate
- Radiative Heat Transfer Studies
- Landslides and related hazards
- Spacecraft Design and Technology
- Solar Radiation and Photovoltaics
European Centre for Medium-Range Weather Forecasts
2022-2024
Goethe University Frankfurt
2018-2023
Senckenberg Biodiversity and Climate Research Centre
2023
German Meteorological Service
2022
Abstract Numerical weather prediction models operate on grid spacings of a few kilometers, where deep convection begins to become resolvable. Around this scale, the emergence coherent structures in planetary boundary layer, often hypothesized be caused by cold pools, forces transition from shallow convection. Yet, kilometer-scale range is typically not resolved standard surface operational measurement networks. The campaign Field Experiment Submesoscale Spatio-Temporal Variability Lindenberg...
© 2023 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses). This article is licensed under a Creative Commons Attribution 4.0 license (http://creativecommons.org/licenses/by/4.0/). Corresponding author: Arianna Valmassoi, avalmass@uni-bonn.de
Abstract Recently, observational and numerical evidence has accumulated against the concept of a critical Richardson number Ricr beyond which too-stable stratification would extinguish turbulence. It also appeared that characteristics “weak turbulent regime” where Prandtl σt increases proportionally to Ri can be explained via conservation total energy in strongly anisotropic flow. Having “No Ri(cr)” situation together with due consideration anisotropy thus leads correct asymptotic behavior...
Abstract Coherent plume structures in the convective boundary layer over non‐flat terrain are investigated using large‐eddy simulation. A conditional sampling method based on concentration of a decaying passive tracer is implemented order to identify boundary‐layer plumes objectively. Conditional allows quantification contribution vertical transport heat and moisture. first set simulations analyzes flow an idealized valley, where elevation only varies along one horizontal coordinate axis. In...
A new turbulence scheme with two prognostic energies is presented. The an extension of a kinetic energy (TKE) following the ideas Zilitinkevich et al. but valid for whole stability range and including influence moisture. second used only modification parameter. Thus, downgradient, turbulent fluxes are proportional to local gradients diffused variables. However, parameter consequently exchange coefficients not strictly anymore have character. authors believe that these characteristics enable...
The most frequently used boundary-layer turbulence parameterization in numerical weather prediction (NWP) models are kinetic energy (TKE) based-based schemes. However, these parameterizations suffer from a potential weakness, namely the strong dependence on an ad-hoc quantity, so-called length scale. physical interpretation of scale is difficult and hence it cannot be directly related to measurements or large eddy simulation (LES) data. Consequently, formulations for basically all TKE...
Abstract The vertical heat and moisture exchange in the convective boundary layer over mountainous terrain is investigated using large-eddy simulation. Both turbulent advective transport mechanisms are evaluated simple orography of a quasi-two-dimensional, periodic valley with prescribed surface fluxes. For analysis, flow decomposed into local part, mean circulation, large-scale part. It found that thermal upslope winds important for export from to mountain tops. Even relatively shallow...
Abstract The impact of precipitation in shallow cumulus convection on the moisture variance and third‐order moments is investigated with help large‐eddy simulations. Three idealized simulations based Rain Cumulus over Ocean field experiment are analyzed: one nonprecipitating, a smaller domain, two precipitating cases, larger domain different initial profiles moisture. Results show that associated cloud organization lead to increased generation higher‐order (HOM) compared nonprecipitating...
The single-column mode (SCM) of the ICON (ICOsahedral Nonhydrostatic) modeling framework is presented. primary purpose SCM to use it as a tool for research, model evaluation and development. Thanks simplified geometry SCM, various aspects model, in particular physics, can be studied well-controlled environment. Additionally, has reduced computational cost low data storage demand. utilized idealized cases—several well-established cases are already included—or semi-realistic based on analyses...
Abstract The formation of low stratus cloud over idealized hills is investigated using numerical model simulations. main driver for the radiative cooling due to outgoing longwave radiation. Despite a purely horizontal flow, advection terms in prognostic equations heat and moisture produce vertical mixing across upper edge, leading loss water content. This behavior depicted via budget analysis. More precisely, this spurious caused by diffusive error scheme regions where sloping surfaces...
Numerical weather prediction (NWP) of radiation fog, particularly over complex terrain, remains a formidable challenge. Many operational NWP models often struggle with slow or no fog formation after sunset and too rapid dissipation in the morning. This study investigates role physical processes atmospheric boundary layer (ABL) shaping limitations low stratus (FLS) representation within ICON model. Specifically, it evaluates effects turbulence parameterizations vertical resolution on...
Abstract In this paper, we present a new and more stable numerical implementation of the two-energy configuration Third Order Moments Unified Condensation N-dependent Solver (TOUCANS) turbulence scheme. The original time-stepping scheme in TOUCANS tends to suffer from spurious oscillations stably stratified turbulent flows. Because their high frequency, resemble so-called fibrillations that are caused by coupling between exchange coefficients stability parameter. However, our analysis...
<p>The most frequently used turbulence parameterizations in numerical weather prediction (NWP) and general circulation (GC) models are kinetic energy (TKE) schemes. These schemes strongly dependent on a key component, the length scale. The scale is to parameterize molecular dissipation of TKE also required for calculating coefficients. Traditionally, formulations do not take into account transfer across scales, as they designed scales above production range spectra. However,...
<p>The most frequently used boundary-layer turbulence parameterization in numerical weather prediction (NWP) models are kinetic energy (TKE) based schemes. However, these parameterizations suffer from a potential weakness, namely the strong dependence on an ad-hoc quantity, so-called length scale. The physical interpretation of scale is difficult and hence it cannot be directly related to measurements or large eddy simulation (LES) data. Consequently, formulations for basically...
Abstract The influence of the initial vertical moisture profile on precipitating shallow cumulus cloud organization in terms column‐averaged variance is investigated using large‐eddy simulations. Five idealized simulations based Rain Cumulus over Ocean field experiment with different profiles are investigated. All cases simulate convection a marine sub‐tropical region under large‐scale subsidence. results show that mainly generated through interaction flux and gradient production term at top...
The unified parameterization of turbulence and clouds in the atmospheric boundary layer is one challenges current weather climate models. updated two-energy scheme able to successfully model both stratocumulus cases shallow convection without need an additional for non-local fluxes. update includes introduction entropy potential temperature distinguish between a regime. In addition, coupled simplified assumed PDF method order achieve more universal representation cloudy regimes. has been...