scholarly journals Model development in practice: A comprehensive update to the boundary layer schemes in HARMONIE-AROME cycle 40

2021 ◽  
Author(s):  
Wim C. de Rooy ◽  
Pier Siebesma ◽  
Peter Baas ◽  
Geert Lenderink ◽  
Stephan de Roode ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Climate Model ◽  
Current Model ◽  
Weather Prediction ◽  
Model Development ◽  
Integral Approach ◽  
General Interest ◽  
Strong Impact ◽  
Low Clouds ◽  
Boundary Layer Processes

Abstract. The parameterised description of subgrid-scale processes in the clear and cloudy boundary layer has a strong impact on the performance skill in any Numerical Weather Prediction (NWP) or climate model and is still a prime source of uncertainty. Yet, improvement of this parameterised description is hard because operational models are highly optimised and contain numerous compensating errors. Therefore, improvement of a single parameterised aspect of the boundary layer often results in an overall deterioration of the model as a whole. In this paper we will describe a comprehensive integral revision of three parameterisation schemes in the HARMONIE-AROME model that together parameterise the boundary layer processes: the cloud scheme, the turbulence scheme, and the shallow cumulus convection scheme. One of the major motivations for this revision is the poor representation of low clouds in the current model cycle. The new revised parametric descriptions provide not only an improved prediction of low clouds but also of precipitation. Both improvements can be related to a stronger accumulation of moisture under the atmospheric inversion. The three improved parameterisation schemes are included in a recent update of the HARMONIE-AROME configuration, but its description and the insights in the underlying physical processes are of more general interest as the schemes are based on commonly applied frameworks. Moreover, this work offers an interesting look behind the scenes of how parameterisation development requires an integral approach and a delicate balance between physical realism and pragmatism.

scholarly journals Comparing Surface Height Used in NCAR Climate Model with That Observed by ICEsat: Effects on Skin Temperature Simulation

2009 ◽  
Vol 2009 ◽  
pp. 1-4
Author(s):  
Menglin Jin
Keyword(s):  
Skin Temperature ◽  
Land Surface ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Current Model ◽  
Model Development ◽  
Climate System Model ◽  
Community Land Model ◽  
Model Community

This paper tries to identify one of the reasons for the poor land skin temperature simulated by a climate model over Greenland. It first compares ICEsat surface height measurements over Greenland with those used by the model and reveals that the surface height of Greenland prescribed in the National Center for Atmospheric Research (NCAR) Community Climate System Model/Community Land Model version 3 (CCSM/CLM3) differs greatly from the satellite measurements from National Aeronautics and Space Administration (NASA) ICEsat at edges and central glacier regions. This deficiency, in part, leads to underestimated skin temperatures at coastal regions—the areas where significant ice sheet melt is observed. Furthermore, sensitivity studies reveal that surface skin temperature simulations of Greenland would be significantly improved if the more accurate surface height is used. The problem of the height used in current global climate model is mainly due to the fact that the model has to use coarse grid size, and within one grid, land surface height has high heterogeneity. How to assign a proper surface height for each model grid and meanwhile adequately present the high heterogeneity of land surface is a great challenge in current model development.

scholarly journals Spatial structures in the heat budget of the Antarctic Atmospheric Boundary Layer

2007 ◽  
Vol 1 (1) ◽  
pp. 271-301
Author(s):  
W. J. van de Berg ◽  
M. R. van den Broeke ◽  
E. van Meijgaard
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Large Scale ◽  
Climate Model ◽  
Heat Budget ◽  
Small Scale ◽  
Strong Impact ◽  
Horizontal Advection ◽  
Vertical Advection ◽  
The Antarctic

Abstract. Output from the regional climate model RACMO2/ANT is used to calculate the heat budget of the Antarctic atmospheric boundary layer (ABL). The main feature of the wintertime Antarctic ABL is a persistent temperature deficit compared to the free atmosphere. The magnitude of this deficit is controlled by the heat budget. During winter, transport of heat towards the surface by turbulence and net longwave emission are the primary ABL cooling terms. These processes show horizontal spatial variability only on continental scales. Vertical and horizontal advection of heat are the main warming terms. Over regions with convex ice sheet topography, i.e. domes and ridges, warming by downward vertical advection is enhanced due to divergence of the ABL wind field. Horizontal advection balances any excess warming caused by vertical advection, hence the ABL over domes and ridges tends to have a relatively weak temperature deficit. Conversely, vertical advection is reduced in regions with concave topography, i.e. valleys, where the ABL temperature deficit is enlarged. Along the coast, horizontal and vertical advection is governed by the inability of the large-scale circulation to adapt to small scale topographic features. Meso-scale (~10 km) topographic structures have thus a strong impact on the ABL winter temperature, besides latitude and surface elevation. During summer, this mechanism is much weaker; and the horizontal variability of ABL temperatures is smaller.

scholarly journals HCLIM38: A flexible regional climate model applicable for different climate zones from coarse to convection permitting scales

2019 ◽  
Author(s):  
Danijel Belušić ◽  
Hylke de Vries ◽  
Andreas Dobler ◽  
Oskar Landgren ◽  
Petter Lind ◽  
...  
Keyword(s):  
Climate Model ◽  
Weather Prediction ◽  
Regional Climate ◽  
Model Development ◽  
Regional Climate Modelling ◽  
Climate Modelling ◽  
Polar Regions ◽  
International Projects ◽  
And Performance ◽  
Nwp Model

Abstract. This paper presents a new version of HCLIM, a regional climate modelling system based on the ALADIN-HIRLAM numerical weather prediction (NWP) system. HCLIM uses atmospheric physics packages from three NWP model configurations, HARMONIE-AROME, ALARO and ALADIN, which are designed for use at different horizontal resolutions. The main focus of HCLIM is convection permitting climate modelling, i.e. developing the climate version of HARMONIE-AROME. In HCLIM, the ALADIN and ALARO physics packages are used for coarser resolutions where convection needs to be parameterized. Here we describe the structure, development and performance of the current recommended HCLIM version, cycle 38. HCLIM38 is a new system for regional climate modelling and it is being used in a number of national and international projects over different domains and climates, ranging from equatorial to polar regions. Our initial evaluation indicates that HCLIM38 is applicable in different conditions and provides satisfactory results without additional region-specific tuning. HCLIM is developed by a consortium of national meteorological institutes in close collaboration with the ALADIN-HIRLAM NWP model development. While the current HCLIM cycle has considerable differences in model setup compared to the NWP version (primarily in the description of the surface), it is planned for the next cycle release that the two versions will use a very similar setup. This will ensure a feasible and timely climate model development and updates in the future and provide evaluation of long-term model biases to both NWP and climate model developers.

scholarly journals HCLIM38: a flexible regional climate model applicable for different climate zones from coarse to convection-permitting scales

2020 ◽  
Vol 13 (3) ◽  
pp. 1311-1333 ◽  
Author(s):  
Danijel Belušić ◽  
Hylke de Vries ◽  
Andreas Dobler ◽  
Oskar Landgren ◽  
Petter Lind ◽  
...  
Keyword(s):  
Climate Model ◽  
Weather Prediction ◽  
Regional Climate ◽  
Model Development ◽  
Model Performance ◽  
Regional Climate Modelling ◽  
Climate Modelling ◽  
Polar Regions ◽  
International Projects ◽  
Nwp Model

Abstract. This paper presents a new version of HCLIM, a regional climate modelling system based on the ALADIN–HIRLAM numerical weather prediction (NWP) system. HCLIM uses atmospheric physics packages from three NWP model configurations, HARMONIE–AROME, ALARO and ALADIN, which are designed for use at different horizontal resolutions. The main focus of HCLIM is convection-permitting climate modelling, i.e. developing the climate version of HARMONIE–AROME. In HCLIM, the ALADIN and ALARO configurations are used for coarser resolutions at which convection needs to be parameterized. Here we describe the structure and development of the current recommended HCLIM version, cycle 38. We also present some aspects of the model performance. HCLIM38 is a new system for regional climate modelling, and it is being used in a number of national and international projects over different domains and climates ranging from equatorial to polar regions. Our initial evaluation indicates that HCLIM38 is applicable in different conditions and provides satisfactory results without additional region-specific tuning. HCLIM is developed by a consortium of national meteorological institutes in close collaboration with the ALADIN–HIRLAM NWP model development. While the current HCLIM cycle has considerable differences in model setup compared to the NWP version (primarily in the description of the surface), it is planned for the next cycle release that the two versions will use a very similar setup. This will ensure a feasible and timely climate model development as well as updates in the future and provide an evaluation of long-term model biases to both NWP and climate model developers.

Representation of Boundary-Layer Processes in Numerical Weather Prediction and Climate Models

2020 ◽  
Vol 177 (2-3) ◽  
pp. 511-539 ◽  
Author(s):  
John M. Edwards ◽  
Anton C. M. Beljaars ◽  
Albert A. M. Holtslag ◽  
Adrian P. Lock
Keyword(s):  
Boundary Layer ◽  
Numerical Weather Prediction ◽  
Climate Models ◽  
Weather Prediction ◽  
Numerical Weather ◽  
Boundary Layer Processes

scholarly journals Spatial structures in the heat budget of the Antarctic atmospheric boundary layer

2008 ◽  
Vol 2 (1) ◽  
pp. 1-12 ◽  
Author(s):  
W. J. van de Berg ◽  
M. R. van den Broeke ◽  
E. van Meijgaard
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Large Scale ◽  
Climate Model ◽  
Heat Budget ◽  
Small Scale ◽  
Katabatic Wind ◽  
Strong Impact ◽  
Vertical Advection ◽  
The Antarctic

Abstract. Output from the regional climate model RACMO2/ANT is used to calculate the heat budget of the Antarctic atmospheric boundary layer (ABL). The main feature of the wintertime Antarctic ABL is a persistent temperature deficit compared to the free atmosphere. The magnitude of this deficit is controlled by the heat budget. During winter, transport of heat towards the surface by turbulence and net longwave emission are the primary ABL cooling terms. These processes show horizontal spatial variability only on continental scales. Vertical and horizontal, i.e. along-slope, advection of heat are the main warming terms. Over regions with convex ice sheet topography, i.e. domes and ridges, warming by downward vertical advection is enhanced due to divergence of the ABL wind field. Horizontal advection balances excess warming caused by vertical advection, hence the temperature deficit in the ABL weakens over domes and ridges along the prevailing katabatic wind. Conversely, vertical advection is reduced in regions with concave topography, i.e. valleys, where the ABL temperature deficit enlarges along the katabatic wind. Along the coast, horizontal and vertical advection is governed by the inability of the large-scale circulation to adapt to small scale topographic features. Meso-scale topographic structures have thus a strong impact on the ABL winter temperature, besides latitude and surface elevation. During summer, this mechanism is much weaker, and the horizontal variability of ABL temperatures is smaller.

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