Study of the Low Level Wind Shear using AMDAR reports Ana Denisa Urlea¹·², Mirela Pietrisi¹·³, Simmons Tascu³ ¹University of Bucharest, Faculty of Physics, P.O.MG-11, Romania ²Romanian Air Traffic Services Administration ³National Meteorological Administration of Romania ARPEGE analysis: , 12 UTC: MSLP and 850 hPa temperature European Geosciences Union General Assembly April, 2015, Vienna, Austria INTRODUCTION: The aim of this work is the study of the effects of the wind shear on aircraft flights, in particularly when it appears on path of take-off or landing phase which is the most troublesome phase. This phenomenon has a lot of generating sources as: convection, frontal surfaces, strong surface wind coupled with local topography, breezes (either sea or mountain originated), mountain waves or low level temperature inversions. The study is dedicated to analysis of Low level wind shear for Bucharest Otopeni airport. OBJECTIVES: wind shear profile evaluation : statistical approach; case studies for convective and inversion weather conditions. RESULTS Otopeni airport wind shear profile Reported wind shear in local routine report between 11:00 UTC and 12:00UTC Warm and relatively dry air mass over southeastern Europe. Over Romania the upper air flow (from south- west) is uncoupled from the southeasterly circulation of the lower troposphere. Bucharest Otopeni meteogram : 21, 00 UTC - 22, 00 UTC SODAR vector plot for LROP 26L: AMDAR SKEW-T zoom ascending sounding Otopeni, :05 UTC Bucharest Otopeni meteogram : strong temperature inversion forming during midday, due to southerly warm advection in the low troposphere SODAR vector plot Otopeni 26L AMDAR SKEW-T zoom descending sounding Bucharest, :00 UTC REFERENCES : (Elizabeth Walls, and Niels LaWhite, SODAR and Extrapolated Tower WindShear Profile Comparison in Various Topographic Conditions, EWEC2009 Marseille, 2009) CASE STUDIES ARPEGE analysis: , 12 UTC: geopotential and 500 Hpa temp. ARPEGE analysis: , 12 UTC: Absolute vorticity at 500 hPaARPEGE analysis: , 06 UTC: Absolute vorticity at 500 hPa reported severe turbulence by an aircraft pilot at 11:30 UTC, 20 ft  extended low surface pressure area over eastern Europe with a corresponding upper trough  CAPE up to 1000J/kg over the Black Sea towards Greece  mesoscale nuclei of absolute vorticity over Romania  storm systems ARPEGE analysis: , 12 UTC: MSLP and 850hPa temperature(top) 500 hPa geopotential and temperature (bottom) ARPEGE analysis: hPa geopotential , 06 UTC (top), 12 UTC (bottom)  mobile Doppler SODAR registrations (PCS Metek) > - the model has a more logarithmic profile; - underestimates the wind shear (systematic error; the lowest error for July 2014 – convective activity) - comparable diurnal cycle Comparison with NWP ALADIN (Alaro version) wind shear profile SHORT THEORETICAL CONSIDERATIONS α power law share exponent describes the shape of the wind shear profile: low α little shear (wind speed does not drastically change) high α large increases in wind speed 3 months period (May-July 2014) a simple method to estimate wind shear profile - AMDAR (Aircraft Meteorological DAta Relay) - SODAR registrations-(SOnic Detection And Ranging system DATAOUTPUTS model from  ALARO for statistical computation and case studies  ARPEGE for case studies