时间：5月16日早上10点
地点：LAPC多功能厅
报告题目：Chemistry of hydrogen oxide radicals (HOx) in the Arctic
troposphere in spring
报告人： 毛敬秋 （Princeton University/Geophysical Fluid Dynamics
Laboratory）
摘要：We use observations from the April 2008 NASA ARCTAS aircraft campaign
to the North American Arctic, interpreted with a global 3-D chemical
transport model (GEOS-Chem), to better understand the sources and cycling of
hydrogen oxide radicals (HOx ≡ H + OH + peroxy radicals) and their
reservoirs (HOy ≡ HOx + peroxides) in the springtime Arctic atmosphere. We
find that a standard gas-phase chemical mechanism overestimates the observed
HO2 and H2O2 concentrations. Computation of HOx and HOy gas-phase chemical
budgets on the basis of the aircraft observations also indicates a large
missing sink for both. We hypothesize that this could reflect HO2 uptake by
aerosols, favored by low temperatures and relatively high aerosol loadings,
through a mechanism that does not produce H2O2. We implemented such an
uptake of HO2 by aerosol in the model using a standard reactive uptake
coefficient parameterization with γ(HO2) values ranging from 0.02 at 275 K
to 0.5 at 220 K. This successfully reproduces the concentrations and
vertical distributions of the different HOx species and HOy reservoirs. HO2
uptake by aerosol is then a major HOx and HOy sink, decreasing mean OH and
HO2 concentrations in the Arctic troposphere by 32% and 31% respectively.
Better rate and product data for HO2 uptake by aerosol are needed to
understand this role of aerosols in limiting the oxidizing power of the
Arctic atmosphere.
地点：LAPC多功能厅
报告题目：Chemistry of hydrogen oxide radicals (HOx) in the Arctic
troposphere in spring
报告人： 毛敬秋 （Princeton University/Geophysical Fluid Dynamics
Laboratory）
摘要：We use observations from the April 2008 NASA ARCTAS aircraft campaign
to the North American Arctic, interpreted with a global 3-D chemical
transport model (GEOS-Chem), to better understand the sources and cycling of
hydrogen oxide radicals (HOx ≡ H + OH + peroxy radicals) and their
reservoirs (HOy ≡ HOx + peroxides) in the springtime Arctic atmosphere. We
find that a standard gas-phase chemical mechanism overestimates the observed
HO2 and H2O2 concentrations. Computation of HOx and HOy gas-phase chemical
budgets on the basis of the aircraft observations also indicates a large
missing sink for both. We hypothesize that this could reflect HO2 uptake by
aerosols, favored by low temperatures and relatively high aerosol loadings,
through a mechanism that does not produce H2O2. We implemented such an
uptake of HO2 by aerosol in the model using a standard reactive uptake
coefficient parameterization with γ(HO2) values ranging from 0.02 at 275 K
to 0.5 at 220 K. This successfully reproduces the concentrations and
vertical distributions of the different HOx species and HOy reservoirs. HO2
uptake by aerosol is then a major HOx and HOy sink, decreasing mean OH and
HO2 concentrations in the Arctic troposphere by 32% and 31% respectively.
Better rate and product data for HO2 uptake by aerosol are needed to
understand this role of aerosols in limiting the oxidizing power of the
Arctic atmosphere.
