Modeling chemical and aerosol processes in the transition from closed to open cells during VOCALS-REx
Modeling chemical and aerosol processes in the transition from closed to open cells during VOCALS-REx
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DOI：
10.5194/acp-11-7491-2011
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发表时间：
2011-08
影响因子：
6.3
通讯作者：
J. Kazil;J. Kazil;Hailong Wang;G. Feingold;G. Feingold;A. Clarke;J. Snider;A. Bandy
中科院分区：
文献类型：
--
作者：
J. Kazil;J. Kazil;Hailong Wang;G. Feingold;G. Feingold;A. Clarke;J. Snider;A. Bandy
抽象的。化学和气溶胶过程中的过渡，从封闭到开放的单元环流在遥远的，多云的海洋边界层进行了探讨。以前的研究表明，降水可以引发从封闭到开放的细胞状态的转变，但边界层不能保持这种开放的细胞状态，没有云凝结核（CCN）的补给。云凝结核的潜在来源包括风驱动的海洋海盐生成、气相成核和自由对流层的卷吸。为了研究海洋边界层中的CCN源及其在提供新粒子中的作用，我们在WRF/Chem模型中详细耦合了化学，气溶胶和云过程，并添加了海盐排放和气溶胶成核的最新表示。我们进行数值模拟的海洋边界层的过渡从一个封闭的到一个开放的细胞状态。在东南太平洋边界层的观测结果进行了比较VAMOS海洋-云-大气-陆地研究区域实验（VOCALS-REx）。从闭孔状态到开孔状态的转变通过在反转基底下方形成除云、超净层而产生有利于成核的条件。开放单元上升气流使二甲基硫从海洋表面进入超净层，在那里它在白天被氧化为SO2，随后被氧化为H2SO 4。超净层中的低H2SO 4冷凝汇值允许H2SO 4上升到气溶胶成核产生大量新气溶胶的浓度。观测证实了超净层的存在。我们发现，所观察到的DMS通量从海洋中的VOCALS-REx区域可以支持气溶胶的成核源在开放的细胞，超过海盐排放量的颗粒产生的数量。然而，新成核的纳米尺寸的气溶胶颗粒需要时间来生长到足够大的尺寸以充当CCN。相比之下，近地表风从海洋表面机械产生的颗粒提供了一个稳定的较大颗粒来源，这些颗粒是有效的CCN，其速率超过了维持开孔循环的阈值。卷吸的气溶胶从自由对流层的贡献显着的边界层气溶胶考虑VOCALS-REx的情况下，但小于海盐气溶胶排放。
Abstract. Chemical and aerosol processes in the transition from closed- to open-cell circulation in the remote, cloudy marine boundary layer are explored. It has previously been shown that precipitation can initiate a transition from the closed- to the open-cellular state, but that the boundary layer cannot maintain this open-cell state without a resupply of cloud condensation nuclei (CCN). Potential sources of CCN include wind-driven production of sea salt from the ocean, nucleation from the gas phase, and entrainment from the free troposphere. In order to investigate CCN sources in the marine boundary layer and their role in supplying new particles, we have coupled in detail chemical, aerosol, and cloud processes in the WRF/Chem model, and added state-of-the-art representations of sea salt emissions and aerosol nucleation. We conduct numerical simulations of the marine boundary layer in the transition from a closed- to an open-cell state. Results are compared with observations in the Southeast Pacific boundary layer during the VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx). The transition from the closed- to the open-cell state generates conditions that are conducive to nucleation by forming a cloud-scavenged, ultra-clean layer below the inversion base. Open cell updrafts loft dimethyl sulfide from the ocean surface into the ultra-clean layer, where it is oxidized during daytime to SO2 and subsequently to H2SO4. Low H2SO4 condensation sink values in the ultra-clean layer allow H2SO4 to rise to concentrations at which aerosol nucleation produces new aerosol in significant numbers. The existence of the ultra-clean layer is confirmed by observations. We find that the observed DMS flux from the ocean in the VOCALS-REx region can support a nucleation source of aerosol in open cells that exceeds sea salt emissions in terms of the number of particles produced. The freshly nucleated, nanometer-sized aerosol particles need, however, time to grow to sizes large enough to act as CCN. In contrast, mechanical production of particles from the ocean surface by near-surface winds provides a steady source of larger particles that are effective CCN at a rate exceeding a threshold for maintenance of open-cell circulation. Entrainment of aerosol from the free troposphere contributes significantly to boundary layer aerosol for the considered VOCALS-REx case, but less than sea salt aerosol emissions.