Abstract
Abstract. Satellite observations have shown large areas of elevated bromine monoxide (BrO) covering several thousand square kilometres over the Arctic and Antarctic sea ice regions in polar spring. These enhancements of total BrO columns result from increases in stratospheric or tropospheric bromine amounts or both, and their occurrence may be related to local meteorological conditions. In this study, the spatial distribution of the occurrence of total BrO column enhancements and the associated changes in meteorological parameters are investigated in both the Arctic and Antarctic regions using 10 years of Global Ozone Monitoring Experiment-2 (GOME-2) measurements and meteorological model data. Statistical analysis of the data presents clear differences in the meteorological conditions between the 10-year mean and episodes of enhanced total BrO columns in both polar sea ice regions. These differences show pronounced spatial patterns. In general, atmospheric low pressure, cold surface air temperature, high surface-level wind speed, and low tropopause heights were found during periods of enhanced total BrO columns. In addition, spatial patterns of prevailing wind directions related to the BrO enhancements are identified in both the Arctic and Antarctic sea ice regions. The relevance of the different meteorological parameters on the total BrO column is evaluated based on a Spearman rank correlation analysis, finding that tropopause height and surface air temperature have the largest correlations with the total BrO vertical column density. Our results demonstrate that specific meteorological parameters can have a major impact on the BrO enhancement in some areas, but in general, multiple meteorological parameters interact with each other in their influence on BrO columns.
Highlights
Bromine (Br) compounds play an important role in atmospheric chemistry in particular with respect to removal of ozone
If the mean meteorological conditions are compared with those during enhanced bromine monoxide (BrO) events, the latter are associated with low pressure systems, cold air temperature, high surface wind speed, and a decrease of tropopause height in both the Arctic and Antarctic sea ice regions
In the case of temperature, surface air temperature is clearly lower during high BrO events in most of both polar regions, but it is slightly higher over the central Arctic and the Antarctic coastal regions
Summary
Bromine (Br) compounds play an important role in atmospheric chemistry in particular with respect to removal of ozone. Stratospheric bromine is predominantly present in its inorganic form, originating from both natural and anthropogenic organic sources. Man-made brominated hydrocarbons (halons) are long lived and are transported to the stratosphere where they release bromine atoms, e.g. Br and bromine monoxide (BrO), through UV photolysis and oxidation. Methyl bromide (CH3Br) released from the ocean by natural processes and used in agriculture is oxidized in the troposphere but so slowly that it is transported to the stratosphere (Harder et al, 2000; Theys et al, 2009a). Organic bromine source gases are converted into inorganic forms of Bry, such as Br, BrO, BrONO2, HOBr, HBr, BrCl, and Br2, either by direct photolysis or by reaction with OH and O (Sinnhuber et al, 2005; Theys et al, 2009b).
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