Performance of COSMO-LEPS over the Alpine region

2012

This paper analyzes the capabilities of Limited Area Model COSMO-CLM to simulate the main features of the observed climate over an area characterized by complex terrain. A simulation driven by ERA40 Reanalysis of the XX century climate (1971-2000) has been performed at a spatial resolution of 8 km, in order to provide an assessment of regional model performance on local scale for impact studies. 2-meters temperature (minimum, maximum and average values) and total precipitation have been analyzed, comparing their values with two observational datasets: ETH for precipitation and EOBS for temperature.

2008

Nonlinear Processes in Geophysics, 2005

The limited-area ensemble prediction system COSMO-LEPS has been running every day at ECMWF since November 2002. A number of runs of the non-hydrostatic limited-area model Lokal Modell (LM) are available every day, nested on members of the ECMWF global ensemble. The limited-area ensemble forecasts range up to 120 h and LM-based probabilistic products are disseminated to several national and regional weather services. Some changes of the operational suite have recently been made, on the basis of the results of a statistical analysis of the methodology. The analysis is presented in this paper, showing the benefit of increasing the number of ensemble members. The system has been designed to have a probabilistic support at the mesoscale, focusing the attention on extreme precipitation events. In this paper, the performance of COSMO-LEPS in forecasting precipitation is presented. An objective verification in terms of probabilistic indices is made, using a dense network of observations covering a part of the COSMO domain. The system is compared with ECMWF EPS, showing an improvement of the limited-area high-resolution system with respect to the global ensemble system in the forecast of high precipitation values. The impact of the use of different schemes for the parametrisation of the convection in the limited-area model is also assessed, showing that this have a minor impact with respect to run the model with different initial and boundary condition.

The project focused on building an ensemble system for the short-range using the COSMO model, called COSMO-SREPS. During the first phases of the project, the ensemble was designed and implemented, then it was tested over long periods, in order to derive a robust statistical assessment of its features. In particular the system was running during the whole DOP of the MAP D-PHASE project (June to November 2007). The analysis of its performances was carried out over two COSMO regions: an alpine area and Greece.

2008

A snapshot of the ongoing development of short range probabilistic NWP in the European HIRLAM, ALADIN, and Lace consortia is given. The initial system will be based on global ensembles constructed by combining the ECMWF operational northern hemispheric singular vectors (SVs) with SVs targeted at final time to three sub-domains in Europe. This “TEPS for Europe” provides initial and lateral boundary data to limited area models (HIRLAM and ALADIN) integrated in a common domain. LAM EPS forecasts are made up to 60 hours with ~20km horizontal resolution and 40 layers in the vertical. New developments will gradually refine this system. Experimental developments include LAMspecific initial perturbations (SVs, ETKF, SLAF), stochastic physics, and variation of physical parameters. In practice, the idea is to utilize computer power distributed amongst national weather services, and synthesize the entire ensemble at ECMWF. Statistical methods will be used for bias corrections and calibration, ...

Monthly Weather Review, 2021

This paper presents the semi-implicit compressible EULAG as a new dynamical core for convective-scale numerical weather prediction. The core is implemented within the infrastructure of the operational model of the Consortium for Small Scale Modeling (COSMO), forming the NWP COSMO-EULAG model (CE). This regional high-resolution implementation of the dynamical core complements its global implementation in the Finite-Volume Module of ECMWF’s Integrated Forecasting System. The paper documents the first operational-like application of the dynamical core for realistic weather forecasts. After discussing the formulation of the core and its coupling with the host model, the paper considers several high-resolution prognostic experiments over complex Alpine orography. Standard verification experiments examine the sensitivity of the CE forecast to the choice of the advection routine and assess the forecast skills against those of the default COSMO Runge-Kutta dynamical core at 2.2 km grid size...

Atmosphere

There is an ongoing debate in the climate community about the benefits of convection-permitting models that explicitly resolve convection and other thermodynamical processes. An increasing number of studies show improvements in Regional Climate Model (RCM) performances when the grid spacing is increased to 1-km scale. Up until now, such studies have revealed that convection-permitting models confer significant advantages in representing orographic regions, producing high-order statistics, predicting events with small temporal and spatial scales, and representing convective organization. The focus of this work is on the analysis of summer precipitation over the Alpine space. More specifically, the driving data are downscaled using the RCM COSMO-CLM first at an intermediate resolution (12 km) over the European Domain of Coordinated Downscaling Experiment (EURO-CORDEX domain). Then, a further downscaling at 3 km, nested into the previous one, is performed over the Alpine domain to expl...

2011

One of the main challenges for numerical weather prediction (NWP) is still recognised as quantitative precipitation forecasting. The use of the probabilistic approach via the ensemble forecasting has now become commonplace to tackle the chaotic behaviour of the atmosphere and to support forecasters in the management of alert procedures for events with little deterministic predictability. In the framework of limited–area ensemble forecasting, the COSMO–LEPS system (Montani et al., 2003 ) was the first mesoscale ensemble application running on a daily basis in Europe since November 2002. A number of system upgrades had a positive impact on COSMO–LEPS forecast skill of precipitation in the short and early medium–range, documented by Montani et al. (2010). As computer power resources increase, it was investigated the extent to which an increase in horizontal resolution of COSMO–LEPS runs could have a benefit on the probabilistic prediction of those surface fields, like precipitation and...

Tellus A, 2011