New PP: Consolidation of COSMO ensemble (CONSENS) Chiara Marsigli ARPA-SIM, Bologna, Italy

Aim of the Project Consolidating the ensemble forecasting systems for the mesoscale built within COSMO in the past years COSMO-LEPS and COSMO-SREPS have been designed for different forecast ranges (day 3-5 and 1-3, respectively) and with different perturbation strategies The aim of the project is to build a unique “multi-perturbation- strategy” COSMO ensemble system, benefiting of perturbations able to produce appropriate spread for the entire forecast range (i.e., day 1-5)‏ The ensemble should have a wide set of model perturbations to guarantee a good description of the COSMO model error A calibration strategy should also be developed, to be applied to the ensemble output

Actions (I)‏ 1. COSMO-SREPS suite availability: COSMO-SREPS will be maintained as a system running regularly, also providing initial and boundary conditions to the COSMO-DE-EPS system 2. Model perturbations: Testing of perturbations of parameters of the COSMO model physics will be carried on, analysing also the impact of combining perturbations (positive impact?). It will be studied a methodology to perturb also the model lower boundary. This could be done by switching among fields obtained with different methodologies or by applying perturbations directly to the fields (define how!)‏ 3. Ensemble merging: Define the “multi-perturbation-strategy” to be used in the COSMO ensemble system, which perturbations appropriate for both the short and medium range (from day 1 to 5) -> comparison of the multi-model approach with the single-model ensemble or even multi-model ensemble ones for the different forecast ranges

Actions (II)‏ 4. Calibration: Development and testing of a calibration strategy for the high-resolution precipitation output. The reforecasts run by MeteoSwiss for the COSMO-LEPS system will be used for this action. Different methodologies should be compared: CDF calibration using model climatology (following Fundel et al., 2008), which is the technique already applied by MeteoSwiss to COSMO-LEPS precipitation forecasts standard bias correction as described in Hamill and Whitaker (2006)‏ logistic regression analog technique (Hamill and Whitaker, 2006)‏ collection of precipitation data on the whole domain is essential to perform a complete ensemble calibration

Links Link with TIGGE-LAM and with the SRNWP Programme Interoperability as regards the possibility of nesting the COSMO model on other global models Link with model development for getting new tunable parameters or meaningful combinations of the existing ones in the parametrisation schemes, or even for obtaining new alternative schemes PP COLOBOC for obtaining reasonably perturbed lower boundary fields or techniques for perturbing them COSMO-DE-EPS PP KENDA

Main risks Lack of Billing Units for running at ECMWF. Since a robust statistical analysis of the alternative options is needed in order to decide about the future ensemble set-up, it is necessary to run COSMO-SREPS for the whole period and parallel runs on some periods (already accounted for in the BU request)‏ Difficulty of calibrating high-resolution precipitation forecasts. Most of the works found in literature deal with lower resolution systems. Furthermore, a dense and homogeneous precipitation network providing data over a very long period is needed for calibration and it seems difficult to obtain this over the whole COSMO ensemble area

People and FTEs 2-year Project Estimated resources needed in total: 5.0 FTEs Estimated resources needed for 2009: 2.45 FTEs Estimated resources needed for 2010: 2.55 FTEs Institution/People involved: ARPA-SIM (Cesari, Diomede, Marsigli, Montani: 3.4 FTE)‏ HNMS (Gofa, Louka: 1.4 FTE)‏ MeteoSwiss (Fundel: 0.2 FTE)‏