Servei Meteorològic de Catalunya Generalitat de Catalunya Departament de Medi Ambient FORECASTING WEATHER RADAR PROPAGATION CONDITIONS USING NWP MESOSCALE MODEL DATA 25th EWGLAM and 10th SRNWP Meetings. Joint SRNWP/COST 717 Session. Lisbon 8th October 2003 Joan Bech 1, Bernat Codina 2 and Jeroni Lorente 2 1 Servei Meteorològic de Catalunya 2 Universitat de Barcelona

Servei Meteorològic de Catalunya Generalitat de Catalunya Departament de Medi Ambient Index 1. Introduction. 4. Final remarks. 3. NWP Forecasts vs. Observations. Modified Forecasts. 2. Methodology: Vertical Refractivity Gradients & Ducting Index

Servei Meteorològic de Catalunya Generalitat de Catalunya Departament de Medi Ambient ANOMALOUS PROPAGATION (ANAPROP) “ANOMALOUS PROPAGATION (ANAPROP) OF THE WEATHER RADAR BEAM OCCURS WHEN MOISTURE AND TEMPERATURE PROFILES VARY SIGNIFICANTLY FROM NORMAL” SOME OBSERVED EXTREME ANAPROP CASES: MEDITERRANEAN SEA (Battan,1973) INDIC OCEAN (UKMO, 1994) US WEST COAST (Babin,1995) BALTIC SEA (Anderson et al, 1997). Sub refraction Standard refraction Super refraction

Servei Meteorològic de Catalunya Generalitat de Catalunya Departament de Medi Ambient REFRACTIVITY & VRG REFRACTIVITY N&MODIFIED REFRACTIVITY M (Bean and Dutton, 1968) : SUB REFRACTIVE NORMAL SUPER REFRACTIVE (“DUCT”) VERTICAL REFRACTIVITY GRADIENT (VRG)

Servei Meteorològic de Catalunya Generalitat de Catalunya Departament de Medi Ambient (Turton et al., 1988)

Servei Meteorològic de Catalunya Generalitat de Catalunya Departament de Medi Ambient PROPAGATION CONDITIONS AND RADAR BEAM HEIGHT (1) Anaprop leads to differences in expected radar beam heights. Example for PBE radar beam height (0º elevation) with observed subrefractive and superrefractive VRG.

Servei Meteorològic de Catalunya Generalitat de Catalunya Departament de Medi Ambient PROPAGATION CONDITIONS AND RADAR BEAM HEIGHT (2) PBE radar PPI (0.7º elevation) with observed superrefractive VRG (-106 N units/km).

Servei Meteorològic de Catalunya Generalitat de Catalunya Departament de Medi Ambient VRG & DUCTING INDEX VRG =  N /  z ITU (1997) I D = 78  z -  M Johson et al. (1999) November 2002 to February 2003 (183 cases) MASS model refractivity profiles 00 & 12 Z RAOB

Servei Meteorològic de Catalunya Generalitat de Catalunya Departament de Medi Ambient REFRACTIVITY VERTICAL PROFILE (OBS & FOR) Vertical profile of modified refractivity on 13th Novembre 2002 at 12 Z over Barcelona: observation (OBS, thick solid line) and model forecast (FOR, crosses, dotted line).

Servei Meteorològic de Catalunya Generalitat de Catalunya Departament de Medi Ambient VRG & DUCTING INDEX (OBS & FOR)

Servei Meteorològic de Catalunya Generalitat de Catalunya Departament de Medi Ambient DUCTING INDEX (OBS & FOR AVERAGES)

Servei Meteorològic de Catalunya Generalitat de Catalunya Departament de Medi Ambient OBSERVED VRG AUTOC., MAE, ME & RMSE

Servei Meteorològic de Catalunya Generalitat de Catalunya Departament de Medi Ambient DUCTING INDEX MODIFIED FORECASTS

Servei Meteorològic de Catalunya Generalitat de Catalunya Departament de Medi Ambient Final Remarks 1. Four months of NWP derived VRG and ID forecasts have been compared with RAOB diagnosed VRG and ID. 4. Model forecasts were useful to anticipate anaprop conditions but in some aspects RAOB persistency was better. 3. Considering model tendency and previous OBS, new forecasts produced better verification scores. 2. Original model forecasts were biased towards subrefraction (specially ducting index).