Open AccessMineral dust and global tropospheric chemistry: Relative roles of photolysis and heterogeneous uptake
Author(s) -
Bian Huisheng,
Zender Charles S.
Publication year - 2003
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2002jd003143
Subject(s) - troposphere , mineral dust , photodissociation , atmospheric sciences , stratosphere , northern hemisphere , chemical transport model , atmosphere (unit) , southern hemisphere , ozone , environmental science , chemistry , climatology , aerosol , photochemistry , geology , meteorology , physics , organic chemistry
We investigate the influence of mineral dust on tropospheric chemistry in the present climate at the global scale. The analysis examines the effects of dust on photolysis and heterogeneous uptake, operating independently and together. In numerical experiments the size‐resolved, time‐varying mineral dust distribution predicted by the global Dust Entrainment and Deposition (DEAD) model perturbs the gas phase species in a global chemical transport model (University of California at Irvine (UCI) CTM). We find that the photolysis perturbation dominates limited regions in the low to middle troposphere, while heterogeneous uptake dominates the rest of atmosphere. Coupling of the photochemical and heterogeneous effects of dust is weak in the global mean but moderate in dusty regions, where coupling is sometimes responsible for more than 20% of local O 3 changes. Ozone and odd‐nitrogen concentrations are perturbed in opposite directions by photolysis and heterogeneous chemistry, resulting in a weak net change. However, both processes decrease the concentrations of OH and HO 2 . The global mean change due to dust is −0.7% for tropospheric O 3 , −11.1% for OH, −5.2% for HO 2 , and −3.5% for HNO 3 . Large seasonal signals are present near dust source regions. Over the North African region and tropical Atlantic Ocean downwind, OH decreases by −66.8%, six times more than the global mean reduction. Interestingly, net photolysis‐induced annual mean O 3 changes are greater in the Southern Hemisphere than in the Northern Hemisphere, where significantly more dust and O 3 precursors reside. In polar regions, O 3 change is dominated by transported O 3 and is not sensitive to local dust concentration. O 3 change due to photolysis depends not only on dust vertical structure but also on the availability of O 3 precursors. O 3 change due to heterogeneous reactions on dust is sensitive to dust vertical structure, mainly through the influence of temperature on uptake rates.