Evaluation of the GFS and MM5 meteorological models for the Paranal, Mac ón and Pachón zones

1. Evaluation of the GFS and MM5 meteorological models for the Paranal, Macón and Pachón zones Arlette Chacón, Omar Cuevas & Michel Curé - AstroMeteorology group. Universidad de Valparaíso, Chile. Introduction • Resolution of MM5 model domains: • The GFS model shows better correlation in the Paranal site than Cerro Pachón. • The highest correlation values are in domains 1 and 2 for Cerro Pachón. • The time series for Cerro Pachón shows the accuracy of MM5, due to the close proximity of the lines. This research presents an evaluation of two meteorological models, the Global Forecast System (GFS) and Mesoescalar Model of Fifth Generation (MM5), for three astronomical sites. The first location is Cerro Paranal, found in the second region of Chile, which also hosts the Very Large Telescope (VLT). The second location is Cerro Macón in the Salta region of Argentina, a site which has been short-listed for the construction of the European Extremely Large Telescope (E-ELT). Both instruments are European Southern Observatory (ESO) projects. The third location is Cerro Pachón in the fourth region of Chile, site of the Gemini South observatory. • This model uses sigma high level coordinates. • The boundary conditions are GFS model. Data Cerro Pachón Cerro Paranal • The period studied was during the year 2005, for 2 hours each night (00 and 06 UTC). Data was obtained using an automatic weather station. This was compared to simulated data developed using the GFS and MM5 models. • Variables: • Temperature at 2 meters above ground level. • Relative humidity at 2 meters above ground level. • Atmospheric pressure (but not for Macón due to equipment failure). • Direction and magnitude of the wind at 10 meters above ground level. • Direction and magnitude of the wind at 5 meters above ground level (for Macón). Cerro Macón Cerro Paranal Cerro Pachón Cerro Macón Methodology 1. Bilineal interpolation using 4 points near each site, for extraction of variables from the models. Statistical analysis. Lineal correlations. Models Conclusions • GFS Global Model This poster shows the evaluation of the GFS and MM5 meteorological models for two sites utilized by ESO, and one for Gemini South. The analysis shows that the MM5 model is better than GFS for simulating the temperature near the surface, and the accuracy at 06 UTC is better than 00 UTC. Cerro Pachón features better correlation with the MM5 model, compared with GFS. New techniques are applied to eliminate systematic errors that feature in the simulations. For example, Kalman filter and cubic spline will fix errors resulting from differing altitudes. (www.dfa.uv.cl/astromet/) • Octant P => South America • Resolution of 120 km • 13 levels of pressure • 4 outputs per day Results The results are based on temperatures taken at 2 meters above ground level for both models, to ensure consistency. Linear association using Kalman filter in Cerro Pachón. Green points are Kalman with data measurements from the weather station and red points are GFS model with data measurements, also from the weather station. • MM5 Mesoescale Model Acknowledgements: We wish to thanks to Marc Sarazin (ESO), Julio Navarrete (ESO), and Ruben Diaz (Gemini Observatory) for providing the weather station’s data for this work. We also acknowledge the fianacial support from the Head of the Science of the Gemini Southern Observatory, Dr. Jean Rene Roy; and the Head of ASTELCO, Peter Aniol.