Understanding global secondary organic aerosol amount and size-resolved condensational behavior
Understanding global secondary organic aerosol amount and size-resolved condensational behavior
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DOI：
10.5194/acp-13-11519-2013
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发表时间：
2013-01-01
影响因子：
6.3
通讯作者：
Pierce, J. R.
中科院分区：
文献类型：
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作者：
D'Andrea, S. D.;Hakkinen, S. A. K.;Pierce, J. R.
近期研究表明，二次有机气溶胶（SOA）是超细颗粒增长到与气候相关尺寸的主要贡献者，增加了大陆边界层（BL）内的全球云凝结核（CCN）浓度。然而，关于SOA凝结有三个最新进展，导致了SOA对颗粒增长和CCN浓度贡献的不确定性：（1）虽然许多全球模型仅包含生物源的SOA（年产量一般为10 - 30 Tg yr⁻¹），但近期研究表明，可能需要一个与人为一氧化碳（CO）排放相关的约100 Tg yr⁻¹的额外SOA源才能与测量结果相符。（2）许多模型仅将SOA视为半挥发性物质，这导致SOA的凝结与气溶胶质量分布成正比；然而，近期与实地测量相结合的闭合研究表明，只有假设相当一部分SOA的凝结与福希校正后的气溶胶表面积成正比，才能捕捉到成核模式的增长。这表明凝结蒸汽的挥发性非常低。（3）其他近期关于颗粒增长的研究表明，SOA在小于10 nm的尺寸下凝结，并且需要与尺寸相关的生长率参数化（GRP）才能与测量结果相符。我们使用GEOS - Chem - TOMAS全球气溶胶微物理模型以及全球气溶胶尺寸分布的观测结果来探究这三个发现的重要性。在假设表面积凝结的情况下，与质量分布净凝结相比，边界层内尺寸Dₚ>40 nm的颗粒浓度（N₄₀）的变化导致全球增加11%，但在生物活动活跃区域超过100%。在边界层内，与仅包含生物源SOA排放（19 Tg yr⁻¹）的基础模拟相比，包含额外100 Tg SOA yr⁻¹时N₄₀的百分比变化（两者均假设表面积凝结）导致全球增加13.7%，但在CO排放量大的区域超过50%。在包含额外SOA的情况下，纳入两种不同的GRP均导致N₄₀在全球范围内增加<1%，但在最极端的情况下，在某些地点超过5%。所有模型模拟都与从全球不同地点获得的测量数据进行了比较，结果证实，当假设存在非挥发性SOA并包含额外的SOA时，模型 - 测量偏差减小，并且在比较模拟与测量的CCN数浓度时斜率得到改善。
Recent research has shown that secondary organic aerosols (SOA) are major contributors to ultrafine particle growth to climatically relevant sizes, increasing global cloud condensation nuclei (CCN) concentrations within the continental boundary layer (BL). However, there are three recent developments regarding the condensation of SOA that lead to uncertainties in the contribution of SOA to particle growth and CCN concentrations: (1) while many global models contain only biogenic sources of SOA (with annual production rates generally 10-30 Tg yr(-1)), recent studies have shown that an additional source of SOA around 100 Tg yr(-1) correlated with anthropogenic carbon monoxide (CO) emissions may be required to match measurements. (2) Many models treat SOA solely as semi-volatile, which leads to condensation of SOA proportional to the aerosol mass distribution; however, recent closure studies with field measurements show nucleation mode growth can be captured only if it is assumed that a significant fraction of SOA condenses proportional to the Fuchs-corrected aerosol surface area. This suggests a very low volatility of the condensing vapors. (3) Other recent studies of particle growth show that SOA con-densation at sizes smaller than 10 nm and that size-dependent growth rate parameterizations (GRP) are needed to match measurements. We explore the significance of these three findings using GEOS-Chem-TOMAS global aerosol microphysics model and observations of aerosol size distributions around the globe. The change in the concentration of particles of size D-p > 40 nm (N40) within the BL assuming surface-area condensation compared to mass-distribution net condensation yielded a global increase of 11% but exceeded 100% in biogenically active regions. The percent change in N40 within the BL with the inclusion of the additional 100 Tg SOAyr(-1) compared to the base simulation solely with biogenic SOA emissions (19 Tg yr-1) both using surface area condensation yielded a global increase of 13.7 %, but exceeded 50% in regions with large CO emissions. The inclusion of two different GRPs in the additional-SOA case both yielded a global increase in N40 of < 1 %, however exceeded 5% in some locations in the most extreme case. All of the model simulations were compared to measured data obtained from diverse locations around the globe and the results confirmed a decrease in the model-measurement bias and improved slope for comparing modeled to measured CCN number concentration when non-volatile SOA was assumed and the extra SOA was included.