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A new regional climate model operating at the meso-gamma scale: performance over Europe
Stockholm University, Faculty of Science, Department of Meteorology . Swedish Meteorological and Hydrological Institute, Sweden.
Stockholm University, Faculty of Science, Department of Meteorology . Swedish Meteorological and Hydrological Institute, Sweden.
Stockholm University, Faculty of Science, Department of Meteorology . Swedish Meteorological and Hydrological Institute, Sweden.
2015 (English)In: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 67, 24138Article in journal (Refereed) Published
Abstract [en]

There are well-known difficulties to run numerical weather prediction (NWP) and climate models at resolutions traditionally referred to as 'grey-zone' (similar to 3-8 km) where deep convection is neither completely resolved by the model dynamics nor completely subgrid. In this study, we describe the performance of an operational NWP model, HARMONIE, in a climate setting (HCLIM), run at two different resolutions (6 and 15 km) for a 10-yr period (1998-2007). This model has a convection scheme particularly designed to operate in the 'grey-zone' regime, which increases the realism and accuracy of the time and spatial evolution of convective processes compared to more traditional parametrisations. HCLIM is evaluated against standard observational data sets over Europe as well as high-resolution, regional, observations. Not only is the regional climate very well represented but also higher order climate statistics and smaller scale spatial characteristics of precipitation are in good agreement with observations. The added value when making climate simulations at similar to 5 km resolution compared to more typical regional climate model resolutions is mainly seen for the very rare, high-intensity precipitation events. HCLIM at 6 km resolution reproduces the frequency and intensity of these events better than at 15 km resolution and is in closer agreement with the high-resolution observations.

Place, publisher, year, edition, pages
2015. Vol. 67, 24138
Keyword [en]
grey-zone, HARMONIE, high resolution, dynamical downscaling, regional climate model, precipitation extremes
National Category
Meteorology and Atmospheric Sciences
Identifiers
URN: urn:nbn:se:su:diva-114758DOI: 10.3402/tellusa.v67.24138ISI: 000348723200001OAI: oai:DiVA.org:su-114758DiVA: diva2:794645
Note

AuthorCount:4;

Available from: 2015-03-12 Created: 2015-03-09 Last updated: 2017-12-04Bibliographically approved
In thesis
1. On the representation of precipitation in high-resolution regional climate models
Open this publication in new window or tab >>On the representation of precipitation in high-resolution regional climate models
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Weather and climate models applied with sufficiently fine mesh grids to enable a large part of atmospheric deep convection to be explicitly resolved have shown a significantly improved representation of local, short-duration and intense precipitation events compared to coarser scale models. In this thesis, two studies are presented aimed at exploring the dependence of horizontal resolution and of parameterization of convection on the simulation of precipitation. The first examined the ability of HARMONIE Climate (HCLIM) regional climate model to reproduce the recent climate in Europe with two different horizontal resolutions, 15 and 6.25 km. The latter is part of the ”grey-zone” resolution interval corresponding to approximately 3-10 km. Particular focus has been given to rainfall and its spatial and temporal variability and other characteristics, for example intensity distributions. The model configuration with the higher resolution is much better at simulating days of large accumulated precipitation amounts, most evident when the comparison is made against high-resolution observations. Otherwise, the two simulations show similar skill, including the representation of the spatial structure of individual rainfall areas of primarily convective origin. The results suggest a ”scale-awareness” in HCLIM, which supports a central feature of the model’s description of deep convection as it is designed to operate independently of the horizontal resolution. In the second study, summer season precipitation over the Alps region, as simulated by HCLIM at different resolutions, is investigated. Similar model configurations as in the previous study were used, but in addition a simulation at the ”convection-permitting” 2 km resolution has been made over Central Europe. The latter considerably increases the realism compared to the former regarding the distribution and intensities of precipitation, as well as other important characteristics including the duration of rain spells, particularly on sub-daily time scales and for extreme events. The simulations with cumulus parameterization active underestimate short-duration heavy rainfall, and rainspells with low peak intensities are too persistent. Furthermore, even though the 6.25 km simulation generally reduces the biases seen in the 15 km run, definitive conclusions of the benefit of ”grey-zone” resolution is difficult to establish in context of the increased requirement of computer resources for the higher-resolution simulation.

Place, publisher, year, edition, pages
Stockholm: Department of Meteorology, 2016. 30 p.
Keyword
Regional climate modeling, high-resolution, convection parameterization, precipitation, extremes, statistical analysis
National Category
Meteorology and Atmospheric Sciences
Research subject
Atmospheric Sciences and Oceanography; Meteorology
Identifiers
urn:nbn:se:su:diva-128382 (URN)
Presentation
2016-04-11, C609, Arrhenius Laboratory, 6th Floor, Svante Arrhenius Väg 16C, Stockholm, 11:15 (English)
Opponent
Supervisors
Available from: 2016-04-19 Created: 2016-03-24 Last updated: 2016-04-19Bibliographically approved

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