AG6430_cai ANNALS OF GEOPHYSICS, 56, Fast Track-1, 2013; 10.4401/ag-6340 1 Analysis of new species retrieved from MIPAS Shaomin Cai *, Anu Dudhia University of Oxford cai@atm.ox.ac.uk Abstract The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument which operated on the Envisat satellite from 2002-2012 is a Fourier transform spectrometer for the measurement of high-resolution gaseous emission spectra at the Earth's limb. It operates in the near- to mid-infrared, where many of the main atmospheric trace gases have important emission features. The initial operational products were profiles of Temperature, H2O, O3, CH4, N2O, HNO3, and NO2, and this list was recently extended to include N2O5, ClONO2, CFC-11 and CFC-12. Here we present preliminary results of retrievals of the third set of species under consideration for inclusion in the operational processor: HCN, CF4, HCFC-22, COF2 and CCl4. I. INTRODUCTION he Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), which operated on the Envisat satellite from 2002-2012, is a Fourier transform spectrometer for the measurement of emission spectra at the Earth's limb. It operates in the near- to mid- infrared where many of the main atmospheric trace gases have detectable emission features. The initial operational products were profiles of Temperature, H2O, O3, HNO3, CH4, N2O and NO2, and this list was recently extended to in- clude N2O5, ClONO2, CFC-11 and CFC-12. In this paper the preliminary results of a third set of species, HCN, CFC-14 (CF4), HCFC-22, COF2, CCl4, SF6, OCS, HOCl and C2H6, re- trieved using the Oxford L2 processor, MORSE (Multispectral Optimal Retrievals using Se- quential Estimation), are presented. HCN, OCS and C2H6 are tracers of biomass burning (Rinsland et al., 1998; Li et al., 2000; Notholt et al., 2003; Logan et al., 1981). The rel- atively long lifetimes for HCN and C2H6 make them indicators of how transport redistributes pollutants on a global scale (Rinsland et al., 2005). CCl4, CFC-14, HCFC-22 and SF6 are mainly from anthropogenic emissions. For ex- ample CFC-14 are produced primarily as a by- product during electrolytic aluminum produc- tion and SF6 is mainly from insulating electric- al equipment. SF6 and CF4 are extremely long- lived species and often used as tracers for the ‘age of air’. HOCl is considered to be a reser- voir for active chlorine, ClOx, and odd hydro- gen, HOx, in the stratosphere (von Clarmann et al., 2012). It is produced primarily by the reaction of ClO and HO2 (peroxy radical) and is destroyed mainly by photo-dissociation, which returns OH and Cl radicals (Hickson et al., 2007). Here we also examine fluorine species collec- tively measured by MIPAS. Stratospheric fluo- rine has important effects on the atmosphere, especially fluorine in long-lived greenhouse T ANNALS OF GEOPHYSICS, 56, Fast Track-1, 2013; 10.4401/ag-6340 2 gases. Over the past few decades, the major sources of fluorine in the stratosphere are the man-made chlorofluorocarbons CFCs and HCFCs. Photolysis of these compounds forms COF2. The COF2 molecule has been shown to be the second most abundant stratospheric fluorine reservoir (Kaye et al., 1991). II. ZONAL MEAN DISTRIBUTIONS The Oxford L2 processor MORSE has been used to retrieve these new species with the mi- crowindows shown in Fig.1. Here we analyze these new retrieved species to establish their zonal mean for the period of 2010 March. For each gas, we eliminated those data points that are cloud-affected and where a priori has a significant contribution, in other words, the retrieved random error greater than 50% of the volume mixing ratio (VMR). A 5σ global spike test is then applied to each species to eliminate unrealistic data. The percentage of profiles re- moved by the spike test is shown in Table 1. The largest percentage showed in the table is 21.5% from CFC-14. Reasons for these spike test failures have yet to be investigated. As the total number of profiles for each species for one month is over 32,000, there are still re- maining a large number of profiles, over 25,000 profiles, to have a reliable sample basis for the further study. The remaining profiles are used construct monthly zonal mean together with a standard deviation defined as the standard deviation of profiles contribute to each grid point, which is a combination of random error and atmos- phere variability. Zonal plots of species CCl4, OCS, HCFC-22, SF6, C2H6 and COF2 in Fig. 2 show the expected structure for tropospheric source gases. The Table 1, percentage of removed profiles by 5σ spike test. Species Ratio (%) CCl4 1.9 COF2 12.5 HCFC-22 0.5 HCN 5.2 CFC-14 21.5 SF6 12.3 HOCl 0.03 C2H6 18.7 CFC-11 1.6 CFC-12 2.6 OCS 2.0 Fig. 1, Microwindows for the new species. The upper panel shows the microwindows selected for these new species retrievals. The lower panel show the spectral signatures of these species. ANNALS OF GEOPHYSICS, 56, Fast Track-1, 2013; 10.4401/ag-6340 3 plot of COF2 also well represents the maxi- mum of VMR around the middle of the stra- tosphere over equator. This occurs because COF2 is an intermediate product in the de- gradation of CFCs in the stratosphere, which results in an increase of VMR. Also because COF2 is destroyed by photolysis and reaction Fig. 2, zonal plots and standard deviations of the new species from MIPAS. ANNALS OF GEOPHYSICS, 56, Fast Track-1, 2013; 10.4401/ag-6340 4 VMR of Fluorine Retreived from MIPAS for 2010 March 0 500 1000 1500 2000 2500 VMR of Fluorine (pptv) 1000.0 100.0 10.0 1.0 0.1 P re s s u re ( h P a ) F CFC-11 CFC-12 CFC-14 CFC-22 SF6 COF2 -50 0 50 Latitude 1000 100 10 1 0.1 P re s s u re ( h P a ) Zonal mean of expected HF from MIPAS (pptv) 200.00 200.00 20 0.0 0 400.00 400.00 400.00 4 0 0 .0 0 600.00 600.00 600.00 60 0.0 0 800.00 800.00 800.00 80 0. 00 1000.00 1000.00 1000.00 10 00 .00 1600.00 1600.00 1600.001600.00 2400.00 2400.00 2400.0024 00 .00 Fig. 4, expected zonal plot of HF from MIPAS Fig. 5, zonal plot of HF from ACE-FTS (Jones et al., 2012) with O(1D) in the upper stratosphere, which results in a decrease of VMR. There are some unexpected features in the zonal plots for species CFC-14 and HCN. For example, a maximum VMR of HCN occurs near the stratopause over the equator, which seems unrealistic and requires comparison with other data sets. Similar for CFC-14 there is a maximum in the upper stratosphere over equator, which is unrealistic as well. Due to its complexity, HOCl species need further study before the data could be used for quantitative research. III. Total Fluorine The fluorine species measured by MIPAS are COF2, CFC-11, CFC-12, CFC-14, CFC-22 and SF6 from which the total fluorine can be com- puter as [F] = 2[COF2] + [CFC-11] + 2[CFC-12] + 4[CFC-14] + 2[CFC-22] + 6[SF6]. Mahieu et. al. (2008) show most of the stratospheric fluorine species eventually form Hydrogen Fluoride (HF), which is not measured by MIPAS. Other fluorine containing species are comparable small compared with those measured by MIPAS and HF. Figure 3 shows the vertical profiles of all the fluorine species and total fluorine (F) meas- ured by MIPAS. In the lower stratosphere and upper troposphere, the atmospheric fluorine is mainly contributed by CFC-12. COF2 contri- butes nearly half of the fluorine VMR at 10hPa pressure level, while CFC-14 dominates in the upper stratosphere. The total [F] decreases with altitude as they are eventually formed in- to HF, which is not measured by MIPAS. The expected HF zonal plot for 2010 March is con- structed by the following, [HF] = [Fmax]-[F], where [F] is the total fluorine zonal mean measured by MIPAS and [Fmax] is the maxi- mum value of [F]. This plot (Fig. 4) is further compared with the zonal plot of HF (fig. 5) produced by Jones et al., 2012. Fig 5 is a three- month combined zonal average from ACE-FTS data during September-October-November. Fig4 and Fig 5 is for brief comparison of MIPAS data with ACE-FTS data of HF zonal means. Fig. 3, The vertical profiles of all the fluorine containing species and the total fluorine retrieved by MIPAS. ANNALS OF GEOPHYSICS, 56, Fast Track-1, 2013; 10.4401/ag-6340 5 IV. CONCLUSIONS AND FUTURE WORK Plausible distributions of HCFC-22, COF2, CCl4, SF6, OCS, HOCl and C2H6 retrieved by MIPAS, which CFC-14 and HCN have some anomalies requiring further investigation. However, fur- ther comparison with ACE-FTS, other MIPAS processor and model results are required for further justification. REFERENCES E. Mahieu et al., Validation of ACE-FTS v2.2 measurements of HCl, HF, CCl3F and CCl2F2 using space balloon and ground based instru- ment observations, Atmos. Chem. Phys. Discuss., 8, 3431–3495, 2008 Hickson, K. and L. Keyser et al., Temperature dependence of the HO2 + ClO reaction.2. Reac- tion kinetics using the discharge-flow reson- ance-fluorescence technique, J. Phys.Chem. A, 111, 8126–8138, 2007. Jones, A. and K. A. Walker et al., Technical Note: A trace gas climatology derived from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) data set, Atmos. Chem. Phys., 12, 5207–5220, 2012 Kaye, J. A. and A. R. Douglass et al., Two- dimensional model calculation of fluorine- containing reservoir species in the stratosphere, J. Geophys. Res. ,96, 12,865–12,881, 1991 Li, Q. and D. J. Jacob et al., Atmospheric hy- drogen cyanide (HCN): Biomass burning source, ocean sink?, Geophys. Res. Lett., 27, 357– 360, 2000 Logan, J. A. and M. J. Prather et al., Tropos- pheric chemistry: A global perspective, J. Geo- phys. Res., 86, 7210–7254, 1981 Notholt, J. and Z. Kuang et al., Enhanced up- per topical tropospheric COS: Impact on the stratospheric aerosol layer, Science, 300, 307– 310, 2003 Rinsland, C. P. and M. R. Gunson et al., ATMOS/ATLAS 3 infra red profile measure- ments of trace gases in the November 1994 tropical and subtropical upper troposphere, J. Quant. Spectrosc. Radiat. Transfer, 60, 891–901., 1998 Rinsland, C. P. and G. Dufour et al., Atmos- pheric chemistry experiment (ACE) measure- ments of elevated Southern Hemisphere upper tropospheric CO, C2H6, HCN, and C2H2 mix- ing ratios from biomass burning emissions and long-range transport, Geophys. Res. Lett., 32, L20803, 2005 von Clarmann, T. and B. Funke et al., The MIPAS HOCl climatology, Atmos. Chem. Phys., 12, 1965–1977, 2012.