The COSMO-LEPS mesoscale ensemble system: validation of the methodology and verification

Abstract

Abstract. 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.

Evaluation of the Plant–Craig stochastic convection scheme (v2.0) in the ensemble forecasting system MOGREPS-R (24 km) based on the Unified Model (v7.3)

“…This quantity can be calculated from model variables and could therefore be used in advance to determine how predictable the convective response will be for a given forecast. This could potentially be useful in an adaptive ensemble sys-tem using two convection parameterizations (see, for example, Marsigli et al, 2005), one of which is stochastic and is better suited to providing an estimate of the uncertainty in weaker forcing cases.…”

A Comparison of ETKF and Downscaling in a Regional Ensemble Prediction System

“…One of the possible choices is dynamical downscaling of a global EPS, which interpolates forecast fields from a set of representative members of the global EPS to obtain different ICs for the regional domain with higher resolution. This method has been successfully applied in some current operational REPS [7][8][9]. Recently, downscaled IC perturbations have also been successfully applied in experimental convection-permitting REPSs with higher resolution [10,11].…”

Flash flood detection through a multi-stage probabilistic warning system for heavy precipitation events

“…Operational meteorological forecast considered is the Limited-Area Ensemble Prediction System (LEPS) of COSMO model (Marsigli et al, 2005). COSMO-LEPS consists of 16 members and are provided on a rotated spherical grid that covers a large portion of Europe with horizontal resolution of about 7 km (∼10 km before December 2009) and temporal resolution of 3 h. COSMO-LEPS is initialized once a day at 12:00 UTC and spans 132 h.…”