MAX-DOAS measurements of bromine explosion events in McMurdo Sound, Antarctica
Reactive halogen species (RHS) are responsible for ozone depletion and oxidation of gaseous elemental mercury and dimethyl sulphide in the polar boundary layer, but the sources and mechanisms controlling their catalytic reaction cycles are still not completely understood. To further investigate thes...
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University of Canterbury. Physics and Astronomy
2010
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Online Access: | https://dx.doi.org/10.26021/8512 https://ir.canterbury.ac.nz/handle/10092/5394 |
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Open Polar |
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Antarctica absorption spectroscopy MAX-DOAS radiative transfer model optimal estimation sea ice ozone depletion halogens BrO bromine IO iodine mercury McMurdo Sound |
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Antarctica absorption spectroscopy MAX-DOAS radiative transfer model optimal estimation sea ice ozone depletion halogens BrO bromine IO iodine mercury McMurdo Sound Hay, Timothy Deane MAX-DOAS measurements of bromine explosion events in McMurdo Sound, Antarctica |
topic_facet |
Antarctica absorption spectroscopy MAX-DOAS radiative transfer model optimal estimation sea ice ozone depletion halogens BrO bromine IO iodine mercury McMurdo Sound |
description |
Reactive halogen species (RHS) are responsible for ozone depletion and oxidation of gaseous elemental mercury and dimethyl sulphide in the polar boundary layer, but the sources and mechanisms controlling their catalytic reaction cycles are still not completely understood. To further investigate these processes, ground– based Multi–Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) observations of boundary layer BrO and IO were made from a portable instrument platform in McMurdo Sound during the Antarctic spring of 2006 and 2007. Measurements of surface ozone, temperature, pressure, humidity, and wind speed and direction were also made, along with fourteen tethersonde soundings and the collection of snow samples for mercury analysis. A spherical multiple scattering Monte Carlo radiative transfer model (RTM) was developed for the simulation of box-air-mass-factors (box-AMFs), which are used to determine the weighting functions and forward model differential slant column densities (DSCDs) required for optimal estimation. The RTM employed the backward adjoint simulation technique for the fast calculation of box-AMFs for specific solar zenith angles (SZA) and MAX-DOAS measurement geometries. Rayleigh and Henyey-Greenstein scattering, ground topography and reflection, refraction, and molecular absorption by multiple species were included. Radiance and box-AMF simulations for MAX-DOAS measurements were compared with nine other RTMs and showed good agreement. A maximum a posteriori (MAP) optimal estimation algorithm was developed to retrieve trace gas concentration profiles from the DSCDs derived from the DOAS analysis of the measured absorption spectra. The retrieval algorithm was validated by performing an inversion of artificial DSCDs, simulated from known NO2 profiles. Profiles with a maximum concentration near the ground were generally well reproduced, but the retrieval of elevated layers was less accurate. Retrieved partial vertical column densities (VCDs) were similar to the known values, and investigation of the averaging kernels indicated that these were the most reliable retrieval product. NO₂ profiles were also retrieved from measurements made at an NO₂ measurement and profiling intercomparison campaign in Cabauw, Netherlands in July 2009. Boundary layer BrO was observed on several days throughout both measurement periods in McMurdo Sound, with a maximum retrieved surface mixing ratio of 14.4±0.3 ppt. The median partial VCDs up to 3km were 9.7±0.07 x 10¹² molec cm ⁻ in 2007, with a maximum of 2.3±0.07 x 10¹³ molec cm⁻², and 7.4±0.06 x 10¹² molec cm⁻² in 2006, with a maximum of 1.05 ± 0.07 x 1013 molec cm⁻². The median mixing ratio of 7.5±0.5 ppt for 2007 was significantly higher than the median of 5.2±0.5 ppt observed in 2006, which may be related to the more extensive first year sea ice in 2007. These values are consistent with, though lower than estimated boundary layer BrO concentrations at other polar coastal sites. Four out of five observed partial ozone depletion events (ODEs) occurred during strong winds and blowing snow, while BrO was present in the boundary layer in both stormy and calm conditions, consistent with the activation of RHS in these two weather extremes. Air mass back trajectories, modelled using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model, indicated that the events were locally produced rather than transported from other sea ice zones. Boundary layer IO mixing ratios of 0.5–2.5±0.2 ppt were observed on several days. These values are low compared to measurements at Halley and Neumayer Stations, as well as mid-latitudes. Significantly higher total mercury concentrations observed in 2007 may be related to the higher boundary layer BrO concentrations, but further measurements are required to verify this. |
format |
Article in Journal/Newspaper |
author |
Hay, Timothy Deane |
author_facet |
Hay, Timothy Deane |
author_sort |
Hay, Timothy Deane |
title |
MAX-DOAS measurements of bromine explosion events in McMurdo Sound, Antarctica |
title_short |
MAX-DOAS measurements of bromine explosion events in McMurdo Sound, Antarctica |
title_full |
MAX-DOAS measurements of bromine explosion events in McMurdo Sound, Antarctica |
title_fullStr |
MAX-DOAS measurements of bromine explosion events in McMurdo Sound, Antarctica |
title_full_unstemmed |
MAX-DOAS measurements of bromine explosion events in McMurdo Sound, Antarctica |
title_sort |
max-doas measurements of bromine explosion events in mcmurdo sound, antarctica |
publisher |
University of Canterbury. Physics and Astronomy |
publishDate |
2010 |
url |
https://dx.doi.org/10.26021/8512 https://ir.canterbury.ac.nz/handle/10092/5394 |
geographic |
Antarctic McMurdo Sound Neumayer The Antarctic |
geographic_facet |
Antarctic McMurdo Sound Neumayer The Antarctic |
genre |
Antarc* Antarctic Antarctica McMurdo Sound Sea ice |
genre_facet |
Antarc* Antarctic Antarctica McMurdo Sound Sea ice |
op_rights |
Copyright Timothy Deane Hay https://canterbury.libguides.com/rights/theses |
op_doi |
https://doi.org/10.26021/8512 |
_version_ |
1766068956930506752 |
spelling |
ftdatacite:10.26021/8512 2023-05-15T13:35:41+02:00 MAX-DOAS measurements of bromine explosion events in McMurdo Sound, Antarctica Hay, Timothy Deane 2010 https://dx.doi.org/10.26021/8512 https://ir.canterbury.ac.nz/handle/10092/5394 unknown University of Canterbury. Physics and Astronomy Copyright Timothy Deane Hay https://canterbury.libguides.com/rights/theses Antarctica absorption spectroscopy MAX-DOAS radiative transfer model optimal estimation sea ice ozone depletion halogens BrO bromine IO iodine mercury McMurdo Sound CreativeWork article 2010 ftdatacite https://doi.org/10.26021/8512 2021-11-05T12:55:41Z Reactive halogen species (RHS) are responsible for ozone depletion and oxidation of gaseous elemental mercury and dimethyl sulphide in the polar boundary layer, but the sources and mechanisms controlling their catalytic reaction cycles are still not completely understood. To further investigate these processes, ground– based Multi–Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) observations of boundary layer BrO and IO were made from a portable instrument platform in McMurdo Sound during the Antarctic spring of 2006 and 2007. Measurements of surface ozone, temperature, pressure, humidity, and wind speed and direction were also made, along with fourteen tethersonde soundings and the collection of snow samples for mercury analysis. A spherical multiple scattering Monte Carlo radiative transfer model (RTM) was developed for the simulation of box-air-mass-factors (box-AMFs), which are used to determine the weighting functions and forward model differential slant column densities (DSCDs) required for optimal estimation. The RTM employed the backward adjoint simulation technique for the fast calculation of box-AMFs for specific solar zenith angles (SZA) and MAX-DOAS measurement geometries. Rayleigh and Henyey-Greenstein scattering, ground topography and reflection, refraction, and molecular absorption by multiple species were included. Radiance and box-AMF simulations for MAX-DOAS measurements were compared with nine other RTMs and showed good agreement. A maximum a posteriori (MAP) optimal estimation algorithm was developed to retrieve trace gas concentration profiles from the DSCDs derived from the DOAS analysis of the measured absorption spectra. The retrieval algorithm was validated by performing an inversion of artificial DSCDs, simulated from known NO2 profiles. Profiles with a maximum concentration near the ground were generally well reproduced, but the retrieval of elevated layers was less accurate. Retrieved partial vertical column densities (VCDs) were similar to the known values, and investigation of the averaging kernels indicated that these were the most reliable retrieval product. NO₂ profiles were also retrieved from measurements made at an NO₂ measurement and profiling intercomparison campaign in Cabauw, Netherlands in July 2009. Boundary layer BrO was observed on several days throughout both measurement periods in McMurdo Sound, with a maximum retrieved surface mixing ratio of 14.4±0.3 ppt. The median partial VCDs up to 3km were 9.7±0.07 x 10¹² molec cm ⁻ in 2007, with a maximum of 2.3±0.07 x 10¹³ molec cm⁻², and 7.4±0.06 x 10¹² molec cm⁻² in 2006, with a maximum of 1.05 ± 0.07 x 1013 molec cm⁻². The median mixing ratio of 7.5±0.5 ppt for 2007 was significantly higher than the median of 5.2±0.5 ppt observed in 2006, which may be related to the more extensive first year sea ice in 2007. These values are consistent with, though lower than estimated boundary layer BrO concentrations at other polar coastal sites. Four out of five observed partial ozone depletion events (ODEs) occurred during strong winds and blowing snow, while BrO was present in the boundary layer in both stormy and calm conditions, consistent with the activation of RHS in these two weather extremes. Air mass back trajectories, modelled using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model, indicated that the events were locally produced rather than transported from other sea ice zones. Boundary layer IO mixing ratios of 0.5–2.5±0.2 ppt were observed on several days. These values are low compared to measurements at Halley and Neumayer Stations, as well as mid-latitudes. Significantly higher total mercury concentrations observed in 2007 may be related to the higher boundary layer BrO concentrations, but further measurements are required to verify this. Article in Journal/Newspaper Antarc* Antarctic Antarctica McMurdo Sound Sea ice DataCite Metadata Store (German National Library of Science and Technology) Antarctic McMurdo Sound Neumayer The Antarctic |