auxiliary material for salawitch et al., a new

Auxiliary Material for Salawitch et al., Total Column BrO During Arctic Spring 1

Auxiliary Material for Salawitch et al., A New Interpretation of Total Column BrO during Arctic Spring, Manuscript 2010GL043798

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The main body of the paper states “further details of the retrieval … are given in the auxiliary material”. The retrieval uses absorption cross sections for BrO measured by Wilmouth et al. [1999]. The multiple scattering radiative transfer model is based on Spurr et al. [2001]. The a priori for BrO is a stratospheric profile from the model described by McLinden et al. [2006]. The retrieval used in the main body of the paper differs from the OMI operational retrieval in that we have:

a) used a fitting window shifted to shorter wavelengths, 319 to 347.5 nm, compared to the 340.5 to 357.5 nm window used for the operational product b) neglected contributions to absorption from the O2 dimer, which has a small absorption feature near 343 nm c) used surface reflectivity from a geographically varying (0.5°×0.5°), monthly mean climatology based on the first 3 years of OMI observations [Kleipool et al., 2008] compared to the use of a constant surface albedo of 0.1 in the operational product d) calculated BrOVC using a wavelength dependent air mass factor.

The retrievals used in the main body of the paper, which we term here the ARCTAS retrievals, are a candidate to become the new OMI operational retrieval that will eventually be placed on the NASA data server (http://disc.sci.gsfc.nasa.gov/Aura/data-holdings/OMI). In the interim, the retrievals used in this study are available at

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https://www.cfa.harvard.edu/~tkurosu/SatelliteInstruments/OMI/SampleData/BrO. 19

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Figure 2010GL043798-fs01 compares the retrievals of BrOVC used in the main body of the paper to values found using the operational algorithm. Largest differences are observed over snow and ice, with a ~15 to 20% reduction in the new retrieval, due to the use of higher surface reflectivity in the ARCTAS retrieval. The residual of the spectral fit is about a factor of 2 lower for the ARCTAS retrieval compared to the operational retrieval. Values of BrOVC have a similar overall morphology for the two retrievals and the location as well as magnitude of BrO hotspots are quite similar. As noted in the main body of our paper, our conclusions do not depend on which OMI BrOVC product is used.

The retrieval of BrOVC is sensitive to surface albedo. The ARCTAS retrievals rely on a wavelength dependent air mass factor calculated using a stratospheric climatology for BrO. The stratospheric AMF (Air Mass Factor, the ratio of slant column BrO to vertical column BrO) varies with respect to surface albedo (Figure 2010GL043798-fs02). As albedo ranges from 0.0 to 1.0, the stratospheric AMF varies by about 10%. The closer to the surface the BrO layer resides, the more sensitive AMF and BrOVC are to albedo. Much larger sensitivity of BrOVC to surface albedo is found for a purely tropospheric AMF. If most of the BrO resided near the surface, the sensitivity of BrOVC to surface albedo would need to be addressed in the main body of the paper. However, the aircraft and Max-DOAS observations indicate most of the BrO is well above the top of the convective boundary layer. Hence, a central conclusion of our paper, the importance of longitudinal variations in BrOVC due to compression of stratospheric air, is not affected by uncertainty in albedo. The assessment of quantitative closure of the budget for total column BrO may be sensitive to uncertainties in BrOVC due to the vertical distribution of BrO within the troposphere as well as the presence of clouds, which likely have opposite effects on BrOVC. Assessment of these uncertainties is beyond the scope of this investigation; to our knowledge, no prior study of satellite BrO has addressed either of these factors. We intend to quantify these sensitivities in future studies. We devoted considerable attention to whether the strong linear relation of BrOVC and total column O3 could be due to interference from O3 in the retrieval of BrOVC (i.e., whether our primary result could be a retrieval artifact). A capability to retrieve BrOVC was added to a code that had been

http://disc.sci.gsfc.nasa.gov/Aura/data-holdings/OMI

https://www.cfa.harvard.edu/~tkurosu/SatelliteInstruments/OMI/SampleData/BrO


developed to retrieve profiles of tropospheric O3 from OMI radiances [Liu et al., 2010]. Correlation coefficients between elements of the state vector for BrO and O3 were found, for a variety of fitting windows. These coefficients were generally smaller than 0.06, suggesting little interference due to O3 for the retrieval of BrOVC. As noted in the main body of the paper, the relation between BrOVC and column O3 breaks down for SZA ≥ ~85°, as BrO goes into its nighttime reservoirs. The break down of the relation for SZA ≥ ~85° further supports our confidence that the relation between enhanced BrO and elevated O3 is not a retrieval artifact.

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The main body of the paper states “the WAS data are discussed primarily in the auxiliary material” and “the relation of our definition of Bry

VSL to WMO [2007] and justification for our use of 5 and 10 ppt levels of Bry

VSL based on the WAS measurements are discussed in the auxiliary material”. Figure 2010GL043798-fs03 is designed to address these points, which we discuss at length since they are likely to be of interest to a segment of the atmospheric sciences community. Figure 2010GL043798-fs03a compares the total organic bromine content carried by CH3Br, halons, and CH2Br2 (CBry

WAMSLEY) in the tropical troposphere during TC4 to the WMO [2007] specification of CBry

for O3 loss calculations. The TC4 campaign consisted of a series of flight from San Jose, Costa Rica during summer 2007 (http://www.espo.nasa.gov/tc4). Values of CBry

WAMSLEY in the tropical troposphere are larger than assumed by WMO [2007], mainly due to neglect of CH2Br2 by WMO [2007]. Figure 2010GL043798-fs03b shows a profile of organic bromine from all sources (CBry

TOTAL). All data in Figures 2010GL043798-fs03a and 2010GL043798-fs03b were obtained in the troposphere, based on O3 < 120 ppb. The O3 data were acquired with a dual beam UV photometer [Proffitt and McLaughlin, 1983]. Considerable scatter in CBry

TOTAL occurs between 200 and 300 hPa, the region of convective outflow. During the slow ascent to the cold point tropopause (~120 hPa), nearly all source species other than CH3Br, halons, and CH2Br2 decompose.

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Figure 2010GL043798-fs03b suggests the potential for significant, additional supply of Bry to the stratosphere from product gas injection (PGI): i.e., the cross-tropopause transport of inorganic bromine species produced by the decomposition of short-lived organic bromocarbons in the tropical upper troposphere (UT). The excess content of organic bromine observed in the region of convective outflow relative to the UT (highest altitudes shown) suggests that PGI could be as high as 5 to 7 ppt, or much larger if the influence of decomposition products of highly elevated CBry in the tropical marine boundary layer (MBL) is also considered. The highly elevated levels of CBry observed in the tropical MBL during TC4 are consistent with prior ship-board observations [e.g., Butler et al., 2007 and references therein]. Figure 2010GL043798-fs03c shows the relation between CBry

WAMSLEY and CFC-12 measured in the Arctic stratosphere by the DC-8 during ARCTAS (black circles). The baseline value of Bry used in the main paper, denoted by the green lines, was derived using the method of Wamsley et al. [1998]. Figure 2010GL043798-fs03d shows the relation between CBry

TOTAL and CFC-12 for the Arctic stratosphere (magenta circles). Values of Bry inferred from CBry

TOTAL are shown by the magenta crosses; the difference between these data points and the black dashed line provides an estimate for local source gas injection (SGI) of bromine to the Artic lowermost stratosphere (LMS) by VSL bromocarbons. The data suggest SGI of Bry from VSL bromocarbons could provide nearly as much bromine to the Arctic LMS as is provided by CH3Br and halons (i.e., for CFC-12 = 500 ppt, Bry

WMO ≈ 3.5 ppt and BryTOTAL ≈ 7 ppt). Local SGI of bromine in the Arctic LMS is a surprising

finding, since CH2Br2 is the only VSL bromocarbon thought to cross the tropical tropopause and is expected to decompose before reaching the high latitude stratosphere [Wamsley et al., 1998; Schauffler et al., 1999]. An understanding of this transport pathway for bromine to the Arctic stratosphere is needed. Figure 2010GL043798-fs03 supports the plausibility of Bry

VSL lying between 5 and 10 ppt for the Arctic LMS, with contributions originating from local SGI (presumably from air

http://www.espo.nasa.gov/tc4


masses that enter the stratosphere without passing through the tropical tropopause) plus PGI and SGI from air masses that enter the stratosphere in the tropics.

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Within WMO [2007], BryVSL is defined with respect to a baseline that does not include

CH2Br2. The contribution of this compound to stratospheric Bry is included in our definition of the baseline. Our focus is sorting out the relative contributions of stratospheric and tropospheric BrO to the satellite hotspots, rather than quantification of Bry

VSL. It is clear that if many of the satellite hotspots are indeed caused by compression of stratospheric air to high pressure, then a large amount of Bry must be supplied to the lowermost stratospheric by sources other than CH3Br and halons. The uncertainty in the BrO+NO2+M rate constant is particularly acute when attempting to quantify Bry

VSL using measurements of BrOVC at high latitude during spring. This uncertainty has a much larger effect on the quantification of Bry

VSL than is caused by how baseline Bry is defined. Indeed, the green and black lines shown in Figure 2010GL043798-fs03d are quite similar for values of CFC-12 > 480 ppt, which reflects the composition of LMS air masses that drive the BrOSTRAT hotspots shown in the main body of the paper. Consequently, had we used the WMO baseline definition for Bry, our estimate of BrOSTRAT (and Bry

VSL needed to obtain closure with OMI BrOVC) would be quite close to that given in the main body of the paper. Our quantification of Bry

VSL is at the upper end of the estimates given in Chapter 2 of WMO [2007]. Laube et al. [2008] and Dorf et al. [2008] described balloon flights from Teresina, Brazil designed to quantify Bry

VSL. Laube et al. [2008] suggested BryVSL in the tropical stratosphere is less

than 5 ppt, based on measurements of a suite of bromocarbons at and above 15.2 km altitude. However, they did not obtain measurements in the region of convective outflow, which generally lies below 15.2 km and is where most VSL bromocarbons decompose. Dorf et al. [2008] derived Bry

VSL of 5.2 ± 2.5 ppt based on measurements of BrO in the middle and upper stratosphere. They also report a value of 2.0 ± 1.5 ppt for BrO at the tropical tropopause. Since the BrO/Bry ratio is < 0.5 in the tropical UT [Yang et al., 2005], this measurement suggests PGI could be as large as 4 to 7 ppt. More observations of BrO and related species in the region of convective outflow and the tropical UT are needed to better define Bry

VSL. The main body of the paper states “Retrievals of BrOVC from OMI compare extremely well with estimates from ground-based instruments located in Harestua, Norway (60.2°N, 11°E) and Lauder, New Zealand (45.0°S, 169.7°E). The ground-based and satellite measurements agree within 15%, with no discernable bias … Further details of the retrieval and these comparisons are given in the auxiliary material.” The ground-based measurements are described by Schofield et al. [2004] and Hendrick et al. [2008]. Different spectral windows are used for the ground-based retrievals (336 to 359 nm for Harestua; 342 to 357 nm for Lauder). Both ground-based DOAS retrievals used BrO cross sections from Wilmouth et al. [1999]. Total column BrO is inferred from vertical profiles retrieved by applying the profiling method described in Hendrick et al. [2007]. Figure 2010GL043798-fs04 compares measurements of total column BrO from OMI to measurements of the same quantity from these two well established ground based stations. The ratio of OMI BrOVC to ground based BrOVC is 0.98 ± 0.14 and 0.99 ± 0.15 for the two stations, as indicated. These ratios indicate no discernable bias between OMI BrOVC and values of this quantity recorded at two well-established stations, which provide data that have been compared extensively to prior satellite measurements. The extremely low values of reduced chi-squared (χ2) between OMI BrOVC and the ground based data (0.081 and −0.005 for Harestua and Lauder, respectively) further establishes the accuracy of the OMI ARCTAS retrieval of BrOVC. The main body of the paper states “comparison to aircraft observations (see auxiliary material) demonstrates that modeled CFC-12 is accurate to within ± 4% in the lower stratosphere.” An evaluation of CFC-12 from the GEOS-5 assimilation has been conducted based on data from the NASA DC-8 during ARCTAS and the NCAR GV during START08 [Pan et al., 2010]. Comparisons


for flights of 4 April 2008 (ARCTAS) and 28 April 2008 (START08) are shown in Figure 2010GL043798-fs05. Comparisons for many other flights look as good as those shown in Figure 2010GL043798-fs05. The mean difference between calculated and measured CFC-12 is 3% for all of ARCTAS and START08. When the comparison is restricted to stratospheric air-masses, based on O3 > 120 ppb, the mean difference rises to 4%. Therefore, the impact of uncertainty in CFC-12 on BrOSTRAT is assessed using a ± 4% uncertainty for CFC-12.

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The main body of the paper states “we have computed vertical column tropospheric BrO (BrOTROP) for 29 profiles of BrO measured during ARCTAS and ARCPAC. Further discussion of measurement uncertainty, which approaches the value of BrOTROP, is given in the auxiliary material”. Table 2010GL043798-ts01 provides information for all 29 profiles of BrO, acquired by CIMS (Chemical Ionization Mass Spectrometer) instruments onboard the DC-8 and WP-3D aircraft [Neuman et al., 2010], for which BrOTROP could be defined. The uncertainty in BrOTROP is based on the assessment that individual measurements of BrO are accurate to (±40% + 1 ppt) and that the precision of an individual BrO measurement is 3 ppt for 2 sec time resolution. Precision errors can be reduced by averaging. Therefore, for the N individual measurements used to define a single value of BrOTROP, we assign a total uncertainty to each data point as the root-sum-of-squares combination of the accuracy term (0.4×[BrO]+0.1 ppt) and an averaged precision term (3 ppt/ N 0.5 ). The error bars in Figures 4c and 4d represent the total uncertainty for each point computed this way. The error bar for BrOTROP in Figure 4g represents the impact of these uncertainties on column BrO. Table 2010GL043798-ts01 also includes values of OMI BrOVC associated with each value of BrOTROP. These values are the average of a bi-linear interpolation of the OMI retrieval along the flight track of the aircraft, for the flight segment of each profile. The table gives the mean position of the aircraft for each profile but, again, the OMI retrieval has been averaged along the segment of each profile. Error bars for OMI BrOVC given in the table represent 1σ residuals in the spectral fit of the retrieval; these uncertainties have also been averaged along each flight segment. The main body of the paper states “the importance of BrO above the CBL to BrOTROP is common to all profiles acquired during ARCTAS and ARCPAC (see auxiliary material)”. Figure 2010GL043798-fs06 is a “box and whisker plot” of the all of the profile measurements obtained during ARCPAC and ARTCAS. This plot shows BrO was not especially elevated near the surface and that highest values were observed near 2 km altitude, well above the top of the convective boundary layer during Arctic spring (e.g., see Figure 5 of the main paper). Finally, the main paper states “closure of the budget is supported quantitatively by the ratio BrOMODEL/OMI BrOVC encompassing unity, within the standard deviation of the mean, for these two simulations. Strictly speaking, budget closure is achieved for values of Bry

VSL ranging from ~1.4 to 13.2 ppt (auxiliary material)”. Figure 2010GL043798-fs07 shows a plot of BrOMODEL/ OMI BrOVC versus Bry

VSL, where BrOMODEL = BrOSTRAT+BrOTROP. The gray shaded box denotes the region where the ratio of modeled and measured BrO column lies within one standard deviation of unity, which occurs for a wide range of Bry

VSL, due to the many remaining uncertainties. The “best fit” value for Bry

VSL is 7 ppt, but we have chosen to not emphasize this value in the main paper due to the many attendant uncertainties and the restricted sampling of the 29 aircraft profiles. Figure 2010GL043798-fs07 suggests consistency with OMI BrOVC could be achieved for Bry

VSL as low as ~1.2 ppt. However, the geographic similarity of BrO hotspots observed by OMI and BrOSTRAT from the 5 and 10 ppt models shown in Figure 2 of the main paper, and the lack of appearance of these features in the 0 ppt simulation, reinforces our notion that “short-lived biogenic bromocarbons likely supply between 5 and 10 ppt of bromine to the Arctic lowermost stratosphere” as stated in the abstract. A model with Bry

VSL = 1.2 ppt fails to capture the geographic pattern exhibited by OMI BrOVC, even with addition of a considerably high uniform tropospheric background. Hence, the preponderance of evidence suggests VSL Bry lies between 5 and 10 ppt, with a “best fit” value of 7 ppt.


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Butler, J. H., D. B. King, J. M. Lobert, S. A. Montzka, S. A. Yvon-Lewis, B. D. Hall, N. J. Warwick,

D. J. Mondeel, M. Aydin, and J. W. Elkins (2007), Oceanic distributions and emissions of short-lived halocarbons, Global Biogeochem. Cycles, 21, GB1023, doi:10.1029/2006GB002732.

Dorf, M., A. Butz, C. Camy-Peyret, M. P. Chipperfield, L. Kritten, and K. Pfeilsticker (2008), Bromine in the tropical troposphere and stratosphere as derived from balloon-borne BrO observations, Atmos. Chem. Phys., 8, 7625-7271.

Hendrick, F., M. Van Roozendael, M. P. Chipperfield, M. Dorf, F. Goutail, X. Yang, C. Fayt, C. Hermans, K. Pfeilsticker, J.-P. Pommereau, J. A. Pyle, N. Theys, and M. De Mazière (2007), Retrieval of stratospheric and tropospheric BrO profiles and columns using ground-based zenith-sky DOAS observations at Harestua, 60°N, Atmos. Phys. Chem., 7, 4689-4885.

Hendrick, F., P. V. Johnston, M. De Mazière, C. Fayt, C. Hermans, K. Kreher, N. Theys, A. Thomas, and M. Van Roozendael (2008), One-decade trend analysis of stratospheric BrO over Harestua (60°N) and Lauder (45°S) reveals a decline, Geophys. Res. Lett., 35, L14801, doi:10.1029/2008GL034154.

Kleipool, Q.L., M.R. Dobber, J.F. de Haan, and P.F. Levelt (2008), Earth surface reflectance climatology from 3 years of OMI data, J. Geophys. Res., 113, doi:10.1029/2008JD010290.

Laube, J. C., A. Engel, H. Bönisch, T. Möbius, D. R. Worton, W. T. Sturges, K. Grunow, and U. Schmidt (2008), Contribution of VSL organic substances to stratospheric chlorine and bromine in the tropics, Atmos. Chem. Phys., 8, 7325-7334.

Liu, X., P. K. Bhartia, K. Chance, R. J. D. Spurr, and T. P. Kurosu (2010), Ozone profile retrievals from the Ozone Monitoring Instrument, Atmos. Chem. Phys., 10, 7 2521-2537.

McLinden, C. A., C. S. Haley, and C. E. Sioris (2006), Diurnal effects in limb scatter observations, J. Geophys. Res., 111, D14302, doi:10.1029/2005JD006628.

Neuman, J. A., J. B. Nowak, L. G. Huey, J. B. Burkholder, J. E. Dibb, J. S. Holloway, J. Liao, J. Peischl, J. M. Roberts, T. B. Ryerson, E. Scheuer, H. Stark, R. E. Stickel, D. J. Tanner, and A. Weinheimer (2010), Bromine measurements in O3 depleted air over the Arctic Ocean, Atmos. Chem. Phys., 10, 6503-6514, doi:10.5194/acp-10-6503-2010.

Pan, L. K., K. P. Bowman, E. L. Atlas, S. C. Wofsy, F. Zhang, J. F. Bresch, B. A. Ridley, J. V. Pittman, C. R. Homeyer, P. Romashkin, W. A. Cooper (2010), The Stratosphere-Troposphere Analyses of Regional Transport 2008 (START 2008) Experiment, Bull. Amer. Meteor. Soc., 91, 327-342.

Proffitt, M. H. and R. J. McLaughlin (1983), Fast-response dual beam UV-absorption ozone photometer suitable for use on stratospheric balloons, Rev. Sci. Instrum., 54, 1719-1728.

Schauffler, S. M., E. L. Atlas, D. R. Blake, F. Flocke, R. A. Lueb, J. M. Lee-Taylor, V. Stroud, and W. Travnicek (1999), Distributions of brominated organic compounds in the troposphere and lower stratosphere, J. Geophys. Res., 104, 21513-21535.

Schofield, R., K. Kreher, B. J. Connor, P. V. Johnston, A. Thomas, D. Shooter, M. P. Chipperfield, C. D. Rodgers, and G. H. Mount (2004), Retrieved tropospheric and stratospheric BrO columns over Lauder, New Zealand, J. Geophys. Res., 109, D14304, doi:10.1029/2003JD004463.

Spurr, R. J. D., T. P. Kurosu and K. V. Chance (2001), A linearized discrete ordinate radiative transfer model for atmospheric remote sensing retrieval, J. Quant. Spectrosc. Radiat. Transfer, 68, 689-735.

Wamsley, P.R., P. R., J. W. Elkins, D. W. Fahey, G. S. Dutton, C. M. Volk, R. C. Meyers, S. A. Montzka, J. H. Butler, A. D. Clarke, P. J. Fraser, L. P. Steele, M. P. Lucarelli, E. L. Atlas, S. M. Schauffler, D. R. Blake, F. S. Rowland, W. T. Sturges, J. M. Lee, S. A. Penkett, A. Engel, R. M. Stimpfle, K. R. Chan, D. K. Weisenstein, M. K. W. Ko, and R. J. Salawitch (1998), Distribution of


H-1211 in the UT and LS and the 1994 bromine budget, J. Geophys. Res., 103, 1513-1526. 238

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Wilmouth, D. M., T. F. Hanisco, N. M. Donahue, and J. G. Anderson (1999), Fourier transform ultraviolet spectroscopy of BrO, J. Phys. Chem. A, 103, 8935-8945.

World Meteorological Organization (WMO) (2007), Global ozone research and monitoring project, in Scientific Assessment of Ozone Depletion: 2006, Rep. 50, Geneva.

Yang, X., R. A. Cox, N. J. Warwick, J. A. Pyle, G. D. Carver, F. M. O’Connor, and N. H. Savage (2005), Tropospheric bromine chemistry and its impacts on ozone: A model study, J. Geophys. Res., 110, D23311, doi:10.1029/2005JD006244.


Table 2010GL043798-ts01. Values of BrOTROP and OMI BrOVC and related uncertainties used in Figure 4g of the main paper. Latitude and longitude are the mean position of the aircraft during each profile. Values of OMI BrOVC and the uncertainty in this quantity are averages along the flight track, for the day the profile was obtained. The bold-faced entry corresponds to the highlighted profile in Figure 4c and 4d of the main paper.

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Profile Number

Date, April 2008

Aircraft Latitude °N

Longitude °W

BrOTROP

(1013 cm−2) OMI BrOVC

(1013 cm−2)

1 11 WP-3D 66.59 148.3 0.17 ± 0.85 6.91 ± 0.85 2 12 WP-3D 65.22 147.9 1.91 ± 1.75 6.19 ± 0.87 3 12 WP-3D 70.53 152.6 0.97 ± 1.48 7.55 ± 0.78 4 12 WP-3D 72.59 153.3 0.68 ± 1.19 7.26 ± 0.74 5 12 WP-3D 73.44 153.3 0.86 ± 1.20 7.93 ± 0.77 6 12 WP-3D 75.05 151.5 2.62 ± 1.69 7.38 ± 0.78 7 15 WP-3D 64.79 152.1 −0.03 ± 1.03 5.79 ± 0.81 8 15 WP-3D 67.88 165.0 0.59 ± 1.24 8.21 ± 0.75 9 15 WP-3D 71.87 161.8 −0.06 ± 1.27 8.57 ± 0.84

10 15 WP-3D 69.49 156.9 1.63 ± 1.72 8.50 ± 0.76 11 16 DC-8 69.51 145.1 3.85 ± 2.48 6.97 ± 0.75 12 16 DC-8 71.51 148.1 2.61 ± 1.99 9.12 ± 0.77 13 16 DC-8 73.54 157.0 3.87 ± 2.46 8.62 ± 0.84 14 16 DC-8 72.18 161.6 1.42 ± 1.46 8.42 ± 0.78 15 16 DC-8 66.21 165.7 2.62 ± 1.97 7.79 ± 0.72 16 16 DC-8 65.53 164.8 2.54 ± 1.95 7.42 ± 0.69 17 17 DC-8 70.28 148.8 2.57 ± 2.20 7.45 ± 0.76 18 17 DC-8 71.28 148.3 1.89 ± 2.14 8.18 ± 0.77 19 17 DC-8 76.91 148.4 4.02 ± 2.98 7.58 ± 0.79 20 18 WP-3D 69.92 148.7 0.98 ± 1.27 6.39 ± 0.76 21 18 WP-3D 72.59 140.9 3.59 ± 2.81 7.91 ± 0.87 22 18 WP-3D 70.68 144.5 0.97 ± 1.50 7.18 ± 0.80 23 19 WP-3D 65.21 148.1 4.66 ± 2.86 4.78 ± 0.63 24 19 WP-3D 71.24 156.5 2.42 ± 1.96 6.41 ± 0.76 25 21 WP-3D 64.83 147.5 3.39 ± 2.24 4.44 ± 0.62 26 21 WP-3D 72.83 126.9 1.32 ± 1.75 8.46 ± 0.73 27 21 WP-3D 69.47 136.9 0.66 ± 1.26 6.66 ± 0.59 28 21 WP-3D 69.49 136.6 0.44 ± 0.97 6.80 ± 0.58 29 21 WP-3D 69.18 137.7 2.06 ± 1.67 6.36 ± 0.59


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Figure 2010GL043798-fs01. Comparison of total vertical column density of BrO (BrOVC) found using the OMI ARCTAS retrieval used in the main body of the paper (left hand side) to OMI BrOVC

found using the operational retrieval (right hand side). Values of BrOVC found using the ARCTAS retrieval are analyzed in the main body of the paper. Figure 2010GL043798-fs02. Stratospheric Air Mass Factors as a function of wavelength and albedo for the conventional and current OMI BrO fitting windows. A typical high-latitude case for SZA=70° is shown. Mean and median AMFs for the current OMI fitting window (window used for the ARCTAS retrievals) are given, as a function of surface albedo (bottom). The numerical values of surface albedo used for the various AMFs are indicated by the legend near the top of the plot. Figure 2010GL043798-fs03. a. Profile of the organic bromine content of CH3Br, halons, and CH2Br2 (denoted CBry

WAMSLEY) in the tropical troposphere during TC4 for air samples acquired by the University of California, Irvine (UCI) (black dots) and University of Miami (blue circles) Whole Air Samplers (WAS) onboard the DC-8 and WB-57, respectively. Instrumentation details are given in Schauffler et al. [1999]. CBry from WMO [2007], found using surface values of CH3Br and halons for 2008, is also shown (dashed line). b. Same as panel a, except for the bromine content of all species measured by the WAS analysis (CH3Br, halons, CH2Br2, C2HBrClF3, CHBr2Cl, CHBrCl2, CHBr3, C2H5Br, n-C3H7Br). Data shown in panels a and b were obtained in the troposphere (O3 < 120 ppb filter applied to the WB-57 measurements; no filter needed for DC-8 measurements) for DC-8 flights conducted from San Jose, Costa Rica stating 13 July 2007 and ending 10 August 2007 and for WB-57 flights from the same location starting 3 August 2007 and ending 13 August 2007. c. Relation between CBry

WAMSLEY and CFC-12 for stratospheric air masses sampled by the UCI WAS during ARCTAS (all data obtained for O3 > 130 ppb) for DC-8 flights from Fairbanks, Alaska starting 1 April 2008 and ending 19 April 2008. Baseline Bry was found using the method of Wamsley et al. [1998], for tropospheric values of bromocarbons scaled to year 2008 (green curves). Black crosses are an estimate of Bry

WAMSLEY, found by subtracting CBryWAMSLEY data from 19.31 ppt, the

tropopause value. The BryWMO relation is based on surface values of CH3Br and halons for 2008 from

WMO [2007]. Relations for BryVSL of 5 and 10 ppt are found by adding these amounts to baseline Bry.

d. Same as panel c, except magenta circles represent CBryTOTAL, the sum of all bromine bearing

organics sampled during ARCTAS. Magenta crosses provide an estimate of Bry in the Arctic stratosphere due to local SGI of all sources, found by subtracting CBry

TOTAL from 22.1 ppt (tropopause value). The values of CBry

WAMSLEY and CBryTOTAL observed in the Arctic tropopause are

close to average values of these quantities in the region of convective outflow in the tropical UT. Figure 2010GL043798-fs04. Measurement of BrOVC from OMI over the location of ground based instruments at Harestua, Norway (60.2°N, 11°E) and Lauder, New Zealand (45.0°S, 169.7°E) obtained during March and April 2008 compared to measurements of BrOVC from instruments at these locations. Figure 2010GL043798-fs05. Comparison of CFC-12 from the GEOS-5 assimilation to measurements of CFC-12 obtained by Whole Air Sampler (WAS) instruments onboard the NASA DC-8 aircraft during ARCTAS (top panel) and onboard the NCAR GV aircraft during START08 (bottom panel). The WAS instruments are described by Schauffler et al. [1999].


Figure 2010GL043798-fs06. Box and whisker plot of BrO volume mixing ratio measured by CIMS instruments on board the WP-3D and DC-8 aircraft during ARCTAS and ARCPAC. The data are placed in altitude bins 0.5 km wide; the middle bar of each box is the median value of the data, the edges of the box define the median of the upper half and lower half of the data, and the length of each line defines the extrema of the data within each altitude bin. The data represent the 29 profiles acquired on 8 days during April 2008 (Table 2010GL043798-ts01).

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Figure 2010GL043798-fs07. Plot of the ratio BrOMODEL/OMI BrOVC versus Bry

VSL, where BrOMODEL = BrOSTRAT+BrOTROP (see Figure 4 of main paper), for the 29 aircraft profiles for which BrOTROP can be defined. Error bars denote the standard deviation about the mean of the ratio. The gray shaded box denotes the region where the ratio of modeled and measured BrO column lies within one standard deviation of unity.

Salawitch et al. Total Column BrO During Arctic Spring

Figure 2010GL043798-fs01

auxiliary material for salawitch et al., a new

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