Slovenian mesoscale project as a part of MAP-activities

The analysis, modeling and prediction in mesoscale enables more exact regionalisation of general weather forecast, more precise timing of forecasted events and a quantitative assessments of predicted values (cumulatives and intensities). The possibility of semi-operational modeling in mesoscale on the platform of workstation (with data flow from a host computer) can enable a faster response of operational weather forecasts to significant changes in the predicted model output values. Such fast response is important specially for the end users of weather forecasts such as agriculture, hydrology, traffic, military and general public. The incorporation of mesoscale modeling technique into Slovenian meteorological service would constitute an improvement and enable it to follow world trends.

As a collaboration between our University and the Meteo-France has been established few years ago in a field of limited area numerical modeling and extended also to the Slovenian Meteorological Institute, we plan to contribute to MAP in this field. Also as a workstation version of the French model ALADIN is expected to be ready for experimental work already in 1995 (as the German DM of the DWD already is now available as a workstation version), it is planned to perform the following:

• the model and code implementation on workstation, testing of software in this environment, some test runs, diagnostic studies of the phenomena that are specially relevant to Slovenia and its weather
• numerical study of intense precipitation events, analysis of atmospheric conditions leading to it, and improvement of precipitation parameterisation within the model
• study of dynamical adaptation to even finer grid
• study and improvement of snow-rain transition in precipitation parameterisation
• study of parameterisation of stratus clouds.

The topics above are co-ordinated with the ALADIN collaboration and suit well also the MAP concept. With the first point we want to achieve full implementation of ALADIN and of the DM of the DWD on the workstation environment. This would enable us to have direct access to mesometeorological model output, mostly for diagnostic and study purposes. Partly also the prognostic use can profit as the interpretation of new model output would improve the forecast skill also in operational praxis. With the second point we want to study those meteorological events (synoptic and mesoscale) that led to strong precipitation over complex topography of Slovenia. We want specially to concentrate on enhanced precipitation at onset of Mediterranean cyclones when orographically enhanced fronts are stationary over Southeast Alps. Within this topic we plan to perform some case studies and some numerical investigations to determine the parts of model that have special influence on the subject studied.

Three next points are incorporated within various ALADIN activities. The results of research will be incorporated into the model and results should be useful for the whole research team. To achieve the proposed aims we plan to use the following methods:

• Numerical modeling of physical processes in the atmosphere. We will use partly the existing software tools such as a semi-operational version of mesometeorological model ALADIN that was developed by the ALADIN collaboration in intense co-operation with the ARPEGE and ECMWF teams. (As also the German DM is available as a workstation version, we could perhaps also compare both models).
• Diagnostic studies of interesting weather situations. Diagnostic modeling enables non-operative study of events with as complete input datasets as possible, and with a model space resolutions that exceed operational and are designed to resolve the scale of special processes studied without limitations of the real time modeling.
• Changes of model space resolution to study the dynamical adjustment of the model, its parametrisations and algorithms and with a possibility to assimilate non-standard input data.
• Mesometeorological analysis the available data (all standard and non-standard data) obtained by MAP special observing periods to get as complete input datasets as possible to be used as an initial state for model simulations.
• Study, generation and testing of algorithms, computer programs and procedures for calculation of separate parts of numerical simulation of atmospheric processes. With the study of theoretical background and the analysis of observed data it is possible to generate the algorithms that transferred into computer code enable different and/or better, more exact calculation of separate parts of the mesometeorological model.
• Verification studies. For each change that is introduced into a numerical model of the atmosphere it is necessary to verify, how a separate change is affecting the performance of the model as whole. To verify the performance it is possible to rerun the model with same input data and later statistically analyse the output data, to determine whether the changed model simulated the events studied better or not. To perform statistical verification it is necessary to have also good diagnostic data in same resolution as model output data are.

The project is a part of the international collaboration ALADIN (LACE) with 8 countries and about 15 research institutions participating. It is is partly financed by French-Slovenian joint fund PROTEUS. It is important to mention also that within a Central European Initiative (CEI) an international collaboration was started some years ago to develop a Limited Area model for Central Europe (LACE) with a mesoscale resolution, and that later, due to collaboration of many of the countries of the area with Meteo France, the model ALADIN, nested within French ARPEGE was envisaged as a possible core for LACE. So our project is also a part of pre-LACE activities and can be regarded as a preparatory stage for further Slovenian participation in LACE.

MAP Data Centre - April '05 - MAP WebMaster