Description: Part of the abstract: The Michelson Interferometer for Passive AtmosphericSounding (MIPAS), on-board the European ENVIronmentalSATellite (ENVISAT) launched on 1 March 2002,is a middle infrared Fourier Transform spectrometer measuringthe atmospheric emission spectrum in limb sounding geometry.The instrument is capable to retrieve the vertical distributionMIPAS data were re-processed by ESA using updated versions ofthe Instrument Processing Facility (IPF v4.61 and v4.62) andprovided a complete set of level-2 operational products (geolocatedvertical profiles of temperature and volume mixingratio of H2O, O3, HNO3, CH4, N2O and NO2). MIPAS operated in its standard observation mode for approximately two years, from July 2002 to March 2004. MIPAS data were re-processed by ESA using updated versions of the Instrument Processing Facility (IPF v4.61 and v4.62) and provided a complete set of level-2 operational products (geolocated vertical profiles of temperature and volume mixing ratio of H2O, O3, HNO3, CH4, N2O and NO2). MIPAS operated in its standard observation mode from July 2002 to March 2004, covering the altitude range from the mesosphere to the upper troposphere with relatively high vertical resolution (about 3 km in the stratosphere). In this paper, we report a detailed description of the validation of MIPAS-ENVISAT operational ozone data, that was based on the comparison between MIPAS v4.61 (and, to a lesser extent, v4.62) O3 VMR profilesand a comprehensive set of correlative data, including observations from ozone sondes, ground-based lidar, FTIR and microwave radiometers, remote-sensing and in situ instruments on-board stratospheric aircraft and balloons, concurrent satellite sensors and ozone fields assimilated by theEuropean Center for Medium-range Weather Forecasting. A clear indication of the validity of MIPAS O3 vertical profiles is obtained for most of the stratosphere, where the mean relative difference with the individual correlative data sets is always lower than ±10%. Furthermore, these differences always fall within the combined systematic error (from1 hPa to 50 hPa) and the standard deviation is fully consistent with the random error of the comparison (from 1 hPa to 3040 hPa).

Description: Because measurements of bromine at high latitudes are scarce, the current understanding of bromine chemistry is largely based on model calculations. In order to help quantify the amount of bromine in the atmosphere, we measured BrO columns with two ground-based UV-visible spectrometers at the Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka, Nunavut, Canada (80oN, 86oW) in spring 2008. One of these instruments, the UT-GBS (University of Toronto Ground-Based Spectrometer), has been deployed at Eureka during polar sunrise since 1999. The other instrument, the PEARL-GBS (PEARL Ground-Based Spectrometer), was installed permanently in Eureka in August 2006 for year-round operation.The small signal and large diurnal variation of BrO are challenges for ground-based BrO retrievals. With zenith-sky measurements, we can retrieve vertical column densities of BrO, which are primarily sensitive to the stratosphere. We will discuss different methods for these retrievals and will compare our ground-based BrO vertical column density measurements with Ozone Monitoring Instrument on board the NASA Earth Observing System Aura satellite. Additionally, we are working on techniques to retrieve tropospheric partial columns of BrO using a combination of direct-sun measurements and zenith-sky measurements. We will discuss the status of these retrievals and future plans for tropospheric BrO measurements at Eureka.

Description: Despite its low concentrations in the atmosphere, bromine monoxide (BrO) accounts for up to half of springtime catalytic ozone depletion in the stratosphere. In the troposphere, large quantities of BrO can appear suddenly and linger for several days. These bromine explosions have been linked to mercury deposition in the Arctic.Retrieval of BrO is difficult and measurements of bromine species at high latitudes are scarce. Therefore, there are large uncertainties in our knowledge of the amount of bromine in the atmosphere. In order to improve this situation, we measured BrO columns with two ground-based UV-visible spectrometers at the Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka, Nunavut, Canada (80oN, 86oW) in spring 2008. This research is an integral part the larger CANDAC (Canadian Network for the Detection of Atmospheric Change) project at PEARL to study Arctic atmospheric processes through 2007-2009, the International Polar Year (IPY), and beyond.We will discuss the techniques and challenges for ground-based BrO measurements. Furthermore, we will discuss comparisons between the ground-based measurements of BrO above Eureka and those made by the OSIRIS and OMI satellite instruments, distinguishing between tropospheric and stratospheric BrO concentrations.