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Seasonal variation of tropospheric methyl bromide concentrations: Constraints on anthropogenic input
Author(s) -
Wingenter Oliver W.,
Wang Charles J.L.,
Blake Donald R.,
Rowland F. Sherwood
Publication year - 1998
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/98gl02179
Subject(s) - seasonality , troposphere , atmospheric sciences , environmental science , bromide , latitude , climatology , northern hemisphere , ozone depletion , ozone , meteorology , stratosphere , chemistry , geography , geology , statistics , mathematics , organic chemistry , geodesy
Although removal of tropospheric methyl bromide (CH 3 Br) is dominated by the reaction with the seasonally varying hydroxyl (HO) radical concentration, the anticipated corresponding seasonal dependence of CH 3 Br, as found for other gases with major HO sinks, has been sought previously without success [WMO, 1995]. Our observations of northern hemispheric boundary layer CH 3 Br concentrations do reveal substantial seasonal changes. The high latitude CH 3 Br North/South interhemispheric concentration ratio (IHR) varies from a maximum of 1.35±0.04 (1σ) in March–April to 1.10±0.04 in September, with an equal area and seasonally (EAS) weighted average IHR of 1.21±0.03. These observations suggest northern hemispheric emissions are about 15 kilotons/year less than when an IHR of 1.3 is considered [WMO, 1995]. The observed seasonality also partially explains the differences in the IHR reported by several research groups [WMO, 1995] and places needed constraints on the magnitude and seasonality of sources and sinks of CH 3 Br.