Impact of high resolution elevation and land use data on simulated convective activity over Central Greece

The aim of this research is to investigate the impact of very high spatial resolution topography and land use data in the characteristics of convective activity simulated by the non-hydrostatic Weather Research and Forecasting model with the Advanced Research dynamic solver (WRF-ARW, version 3.5.1) in the framework of project DAPHNE. The main objective of the project is the assessment of the agricultural drought in the region of Thessaly in central Greece by means of Weather Modification. During the last years the need of high resolution data into numerical weather prediction (NWP) models are emphasized, in order to represent the physical processes in most accurate way.

The three model domains, covering Europe, the Mediterranean Sea and northern Africa (d01), the wider area of Greece (d02) and central Greece – Thessaly region (d03) are used at horizontal grid-spacings of 15km, 5km and 1km respectively. ECMWF operational analyses at 6-hourly intervals (0.25 deg x 0.25 deg lat.-long.) are imported as initial and boundary conditions of the coarse domain, while in the vertical, all nests employ 39 sigma levels (up to 50 hPa) with increased resolution in the boundary layer. Microphysical processes are represented by WSM6 scheme, sub-grid scale convection by Kain-Fritsch scheme, longwave and shortwave radiation by RRTMG scheme, surface layer by Monin-Obukhov (MM5), boundary layer by Yonsei University and soil physics by NOAH Unified model.

Previous studies have examined a series of model configurations through sensitivity runs and compared the characteristics of the WRF simulated convective activity over Thessaly against radar data. For the first time during project DAPNHE, high resolution (3 arc sec – 90 m) elevation data from Shuttle Radar Topography Mission (SRTM – version 4) are inserted in the WRF's innermost domain (d03) along with Corine Land Cover 2000 raster data (100x100 m, v.17). Corine land cover data are reclassified into USGS land use categories. The better spatial representation of the special topography characteristics in the vicinity of Thessaly region in conjunction with the updated land use data increase the ability of the WRF model to simulate the spatial and temporal evolution of the convective activity in the area of interest.

The day with the best scores (ME, MAE) from each one of the six (6) upper-air synoptic circulation types associated with convective activity from April to September in this region, is selected in order to ingest the high resolution elevation and land use data into WRF model. The period of interest is from 2006 to 2010. The resulting aforementioned case studies are compared with the same case studies which used the USGS elevation and land use dataset, and are evaluated against observation data from stations along with a C-Band (5cm) radar interfaced to TITAN (Thunderstorm Identification, Tracking, Analysis, and Nowcasting) system, located at Liopraso (within domain d03 (39.674 N, 21.837 E)).

Acknowledgements: This research is co-financed by the European Union (European Regional Development Fund) and Greek national funds, through the action "COOPERATION 2011: Partnerships of Production and Research Institutions in Focused Research and Technology Sectors" (contract number 11SYN_8_1088 - DAPHNE) in the framework of the operational programme "Competitiveness and Entrepreneurship" and Regions in Transition (OPC II, NSRF 2007-2013).