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Abstract:

The isotopic composition of stratospheric water vapour depends on the sources of water vapour and the temperature and precipitation history of the stratospheric air. Isotopic measurements therefore have potential to aid invesigation of dehydration in the polar vortex, of stratospheric/tropospheric exchange, of upward transport in the tropics and of subsidence at polar latitudes. Here we compare measurements of H2¹⁶O, HDO and H2¹⁸O from two satellite limb-sounding instruments: the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), an infra-red limb sounder on Envisat, and the Sub-Millimetre Radiometer (SMR), a microwave limb sounder on board the Odin satellite.

Abstract:

There are two level 2 data resources provided by ESA for MIPAS users. These are the Near Real Time (NRT) and Offline data sets. We investigate the differences observed between these products over a large number of profiles, to assist in validating their mutual consistency and determining the effect of the differing data processing routes.

Abstract:

Monthly mean profiles have been calculated for the MIPAS Near-Real-Time Level 2 products (temperature, H2O, O3, HNO3, CH4, N2O and NO2) from July 2002 until March 2004. The Level 2 profiles have been split into six latitude bands (90S-65S, 65S-20S, 20S-0, 0-20N, 20N-65N, 65N-90N) for the calculation of the means. Here we compare these monthly means with reference climatologies for each of the Level 2 products to provide an overview of the quality of these products over the timescale that MIPAS has been operating. The reference climatologies used in these comparisons are the COSPAR International Reference Atmosphere (CIRA) (2) for temperature and the IG2 dataset (1) (used in the construction of the initial guess for MIPAS retrievals) for the gases.

Abstract:

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is a polar orbiting high resolution mid-infrared emission stratospheric limb sounder with a nominal vertical resolution of 3 km. Work to extend the list of interesting, routinely retrieved species led to the examination of SF6, a potent greenhouse gas and a useful tracer species. We demonstrate the feasibility of profile retrievals in the range 6-30 km based on single scans. Additionally, we investigate latitudinal variation using coaddition to improve signal-to-noise. A mean mid-latitude profile shows tropospheric (4.32 +/- 0.03 pptv, 6-12 km) and stratospheric (3.50 +/- 0.03 pptv, 21-30 km) regimes, in September 2002, similar to accepted values. The global mean contains an interhemispheric variability of the order of 0.3 pptv in the lower stratosphere, in line with age of air. Finally, the continuation of acknowledged global trends in atmospheric concentration, is estimated at +0.28 pptv yr(-1) (6.5 +/- 1.3% yr(-1)).