STRAPOLETE : Studying summer polar stratosphere.

Abstract

International audienceThe polar stratosphere in the summertime remains largely unexplored. Dynamical conditions are characterizedby large scale transport and mixing between air masses of higher and lower latitude origins. Understanding theseexchanges is crucial since they have a large impact on the distribution of trace gases and aerosols at polar latitudes,and thus on the stratospheric ozone budget. Ozone change affects the radiative balance, the coupling betweentroposphere and stratosphere, and therefore the climate.In the framework of the International Polar Year, the STRAPOLETE project starts on January 2009. It is associatedwith a successful balloon borne campaign which took place close to Kiruna (Sweeden) from 2 August 2009 to12 September 2009 with eight balloon flights. During this campaign the main characteristics of the summertimearctic stratosphere have been captured. The data set obtained using UV-visible and infrared instruments, remoteand in situ sensing embarked spectrometers provided detailed information on vertical distributions of more thanfifteen chemical tracers and reactive species from the upper troposphere to the middle stratosphere. A number of insitu optical aerosol counters, a UV-visible remote spectrometer for the aerosol extinction and a photopolarimeterprovided information on the nature and size distribution of the stratospheric aerosols. These balloon measurementswith high precision and high vertical resolution are relevant to qualify the dynamical processes occurring in thisregion during summertime, the aerosols variability, the bromine abundance and establish a reference state of thepolar summer stratosphere. The data set is completed by satellite data offering large spatial coverage of the regionof interest. Data analysis is made using relevant dynamical (trajectory calculations, contour advection model) andchemistry-transport models (CTM) to highlight major mechanisms that control the distribution of tracers, aerosolsand bromine.An overview of the project, its scientific issues, the measurement campaign and some balloon measurementsobtained will be presented, as well as preliminary comparisons between measurements and models outputs