Clear-sky far-infrared measurements observed with TAFTS during the EAQUATE campaign, September 2004

Abstract

Observed clear-sky far-infrared (FIR) radiances measured by the Tropospheric Airborne Fourier Transform Spectrometer (TAFTS) are presented. These measurements were taken when flying on board the Facility for Atmospheric Airborne Measurements British Aerospace 146 aircraft over the UK on 18 September 2004 in the upper troposphere between 8.3 and 9.2 km altitude, during the European AQUA Thermodynamic Experiment (EAQUATE). Upwelling clear-sky measurements from the TAFTS short-wave channel (330 to 500 cm−1) are shown and these measured radiances are compared to model radiances where various dropsonde data are incorporated. The variations in the water vapour profiles below the aircraft are explored in terms of the FIR spectra. The downwelling measurements from TAFTS long-wave channel (90 to 230 cm−1) are also compared to model spectra, produced in this case from the UK Met Office (UKMO) mesoscale model. The variation in the UKMO mesoscale modelled downwelling radiance over the flight leg is seen to have a standard deviation of 0.5 to 2 mW (m2 sr cm−1)−1, that is of the order of TAFTS detection limit in this particular campaign. Copyright © 2007 Royal Meteorological Society