Equatorial total column of nitrous oxide as measured by IASI on MetOp-A: implications for transport processes

Abstract

Abstract. In this paper we use the total columns of nitrous oxide (N2O) as retrieved from the radiance spectra as measured by the Infrared Atmospheric Sounding Interferometer (IASI) instrument aboard the MetOp-A platform and distributed by the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) during the March–May (MAM) 2008 period. Since the total column of N2O reflects concentrations in the middle troposphere, cloud-free columnar N2O measurements are used to assess transport processes in the equatorial band (10° S–10° N). We compare the measured data set with the outputs produced by the 3-D chemical-transport model MOCAGE during the period MAM 2002–2004. To reflect MAM 2008 concentrations, MOCAGE results have been scaled by a factor 1.25% in order to represent the change in concentration of N2O since 2004. IASI N2O equatorial measurements show a maximum over Africa (4.96×10−3 kg m−2) and a minimum over South America (4.86×10−3 kg m−2) in very good agreement with the outputs from MOCAGE despite the fact that emissions of N2O are more intense over America than over Africa. The amplitude of the longitudinal variation of total column N2O along the equatorial band is twice as intense in the measurements (~1.6%) than as in the model calculations (~0.8%), and much greater than the IASI mean random error (0.16–0.33%). A difference between the two data sets is observed above the Western Pacific (110° E–150° E) with a marked minimum in IASI compared to MOCAGE. Recent theoretical studies (Ricaud et al., 2007, 2008) have shown the potentially important effect of the Walker and the Hadley cells on the tropospheric distribution of N2O in producing a local maximum in N2O above Africa. Based on equatorial total columns of N2O measured by IASI, we provide measurement evidence that Africa is a zone of convergence of airmasses coming from different convective regions whilst Western Pacific behaves more like a divergence zone.

Monitoring of atmospheric composition using the thermal infrared IASI/MetOp sounder

“…The retrieval of their concentration from IASI observations requires very specific methods, which are not reported in this paper. Additional information can be found in Crevoisier et al (2009a) and Ricaud et al (2009) for CO 2 and N 2 O, respectively. A similar situation is observed for the weakly absorbing chlorofluorocarbons CFC-11 and CFC-12, which still exhibit significant absorption signatures in IASI spectra despite being regulated by the Montreal protocol.…”

Measurement of trace gases in East Asia from satellite infrared radiometer

“…MetOp-A/IASI, Envisat/SCHIAMACHY and ADEOS/IMG). The spectral region used for the retrieval N 2 O to be in the range of 2165-2245 cm -1 with mainly peaking 2190-2240 cm -1 in response to pressure between 300 and 700 hPa [7] [8]. In this study, we challenged to select the channels for the N 2 O retrieval in an appropriate with TES observation.…”

Operational Monitoring of Trace Gases over the Mediterranean Sea

“…Within the context of Tikhonov theory [28], the regularization of the problem (7) (hence (1)) improves for > 1. From (10) it is also seen that the amount of smoothing (regularization) is independent of the details of S and S , provided that they have inverse (so that we can define the operator G). This is an important aspect of the inverse problem (1) because normally both S and S are model approximations of the truth.…”

“…The subject of remote sensing of atmospheric minor and trace gases from nadir-looking instruments on board polar satellites is not a new subject. Instruments used for this objective include the Japanese IMG (Interferometric Monitor for Greenhouse Gases) [5], the American AIRS (Atmospheric Infrared Radiometer Sounder) [6][7][8], the European IASI [9][10][11][12][13][14][15][16][17], and the Japanese GOSAT (Greenhouse Gases Observing Satellite) [18].…”