Measurements of the vertical distribution of atmospheric mercury are rare,because airborne measurements are expensive and labour intensive.Only during 13 campaigns vertical mercury profiles have been reported since the 1970th.The latest European vertical profile was measured in 1996,when the CARIBIC measurements from 6 km upward(Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container)are not considered.Within the Global Mercury Observation System project(GMOS)from August 19th to 22nd 2013 five vertical profiles were flown over different locations in Slovenia and Germany.Each vertical profile consists of at least seven 5 minute horizontal flight sections from 500 m above ground to 3000 m a.s.l..During all flights the gaseous elemental mercury concentration(GEM)was measured with a Tekran 2537X analyser(resolution: 150 s)and a Lumex RA-915-AM(resolution: 1 s).Another Tekran was operated as backup instrument,measuring the total gaseous mercury concentration(resolution: 150 s).Additionally,gaseous oxidized mercury(GOM)was sampled onto 8 denuders(one for each profile,three during the transfer flights,and two blanks).All denuders were analysed after the flights in laboratory.In addition to the mercury measurements,the research aircraft,a CASA-212 with a custom-built air inlet,measured SO2,CO,O3,NO,NO2,as well as basic meteorological parameters(pressure,temperature,relative humidity).For the two profiles over the GMOS master sites Iskraba/Slovenia and Waldhof/Germany additional ground based speciated mercury measurements are available.Four of the five vertical profiles cover the planetary boundary layer and the lower free troposphere.Only during the first profile over Iskraba the boundary layer top was not reached.No vertical gradient was found inside the well mixed boundary layer(variation by less than 0.1 ng/m?)at different sites with GEM varying from location to location between 1.4 and 1.6 ng/m?.At all locations GEM dropped to 1.3 ng/m? when entering the lower free troposphere and remained constant at higher altitudes.The combination of the vertical profile,measured on August 21th over Leipzig/Germany with the CARIBIC measurements during ascent and descent to Frankfurt airport in Germany at approximately the same time provide a unique central European vertical profile from inside the boundary layer(550 m a.s.l)to the upper free troposphere(10500 m a.s.l.).The highest GOM concentrations of up to 60 pg/m?(denuder samples)were found above the boundary layer during the transfer flights.