CFC-11, CFC-12 and HCFC-22 ground-based remote sensing FTIR measurements at Reunion Island and comparisons with MIPAS/ENVISAT data.

Zhou, Minqiang; Vigouroux, CCorinne; Langerock, Bavo; Wang, Pucai; Dutton, Geoff; Hermans, Christian; Kumps, Nicolas; Metzger, Jean-Marc; Toon, Geoff; De Mazière, Martine

Profiles of CFC-11 (CCl3F), CFC-12 (CCl2F2) and HCFC-22 (CHF2Cl) have been obtained from Fourier transform infrared (FTIR) solar absorption measurements above the Saint-Denis (St Denis) and MaÃ'do sites at Reunion Island (21° & S, 55° & E) with low vertical resolution. FTIR profile retrievals are performed by the SFIT4 program and the detail retrieval strategies along with the systematic/random uncertainties of CFC-11, CFC-12, and HCFC-22 are discussed in this study. The FTIR data of all three species are sensitive to the whole troposphere and the lowermost stratosphere, with the peak sensitivity between 5 and 10 & km. The trends derived from the combined St Denis and MaÃ'do FTIR time-series are -0.86 & ± & 0.12 & % and 2.75 & ± & 0.12 & % for CFC-11 and HCFC-22, respectively, for the period 2004 to 2016, and -0.76 & ± & 0.05 & % for CFC-12 for 2009 to 2016. These measurements are consistent with the trends observed by the National Oceanic and Atmospheric Administration (NOAA) Global Monitoring Division's (GMD) Halocarbons & other Atmospheric Trace Species Group (HATS) measurements at Samoa (14.2° & S, 170.5° & W) for CFC-11 (-0.87 & ± & 0.04 & %), but slightly weaker for HCFC-22 (3.46 & ± & 0.05 & %) and stronger for CFC-12 (-0.60 & ± & 0.02 & %). The ground-based FTIR data have also been compared with the collocated Michelson Interferometer for Passive Atmospheric Sounding (MIPAS/ENVISAT) data, and found to be in good agreement: the observed mean relative biases and standard deviations of the differences between the smoothed MIPAS and FTIR partial columns (6-30 & km) are (-4.3 & % and 4.4 & %), (-2.9 & % and 4.6 & %) and (-0.7 & % and 6.0 & %) for CFC-11, CFC-12, and HCFC-22, respectively, which are within the combined error budgets from both measurements.

REMOTE-sensing images; FOURIER transform infrared spectroscopy; AEROSPACE telemetry

Atmospheric Measurement Techniques Discussions, 2016, p1

1867-8610

Academic Journal

10.5194/amt-2016-235