Analysis of G-V Aircraft and Complementary SOCRATES Observations to Understand Clouds, Aerosols and their Interactions Over the Southern Ocean

分析 G-V 飞机和补充苏格拉底观测以了解南大洋上空的云、气溶胶及其相互作用

• 批准号: 1660609
• 负责人: Robert Wood
• 金额: $ 105.75万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-06-01 至 2021-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1660609&HistoricalAwards=false
• 关键词: Analysis; Aircraft; Complementary; SOCRATES; Observations

The Southern Ocean (SO), meaning the global ocean of the high latitude Southern Hemisphere, has a well-deserved reputation as the stormiest place on earth. The remoteness of the SO and its unforgiving conditions have severely limited observations of atmospheric processes occurring above it, including cloud processes in the cyclones traveling along the South Polar front. Yet these processes are of interest for a variety of reasons, including the fact that SO clouds are relatively free from the effects of continental and anthropogenic aerosols, and the region is thus a natural laboratory for the study of cloud behavior under pristine conditions. SO clouds also play a significant cooling role in the energy balance of the planet by reflecting incoming sunlight back to space. There is evidence to suggest that this cooling has a long-range effect on the distribution of the low-latitude rainfall associated with the intertropical convergence zone, and that changes in SO cloudiness due to global climate change will affect the location and strength of the Southern Hemisphere jet stream. One indicator of our lack of understanding of SO cloud processes is the inadequate SO cloud cover found in climate model simulations, which is accompanied by excessive absorption of sunlight by the ocean surface which may in turn cause errors in estimates of climate sensitivity. The deficiency in simulated cloud cover is most pronounced in boundary layer and lower-tropospheric clouds (tops below 3km) in the cold, dry sectors of frontal weather systems traveling along the SO storm track.This project is part of a larger field campaign titled Southern Ocean Clouds, Radiation, Aerosol, Transport Experimental Study (SOCRATES). The primary activity of the campaign is the deployment of a Gulfstream V (GV) research aircraft maintained by the Earth Observing Laboratory of the National Center for Atmospheric Research. The GV will be based in Hobart, Australia and make multiple flights across the South Polar front collecting data on SO clouds and the meteorological conditions in which they occur. The GV is equipped with dropsondes to record ambient meteorological conditions, radar and lidar to observe the clouds, and instruments mounted on the wings or positioned behind inlets to to sample, collect and analyze aerosols and cloud particles (liquid droplets and ice crystals). The SOCRATES campaign is complementary to SO activities planned internationally and by other US agencies, including surface observations taken on ships and on MacQuarie Island, a small uninhabited island at 54 degrees South.Work supported under this award specifically addresses the relatively warm, shallow clouds found at the top of the atmospheric boundary layer, with a specific focus on cloud droplet number concentration, or the number of droplets per unit volume in a cloud. Droplet number concentration is a key parameter for understanding cloud properties and evolution, and in a pristine region like the SO it can be limited by the availability of cloud condensation nuclei (CCN), aerosol particles which absorb water vapor from the air to form droplets. The PIs seek to determine if droplet number concentration can be related to CCN concentration in the local boundary layer or the overlying free troposphere, or if droplet concentrations are more strongly influenced by turbulent cloud motions, removal through precipitation, or other meteorological factors. Previous studies suggest that low clouds in the colder air to the south of the South Polar front have higher mean droplet concentrations than the warmer clouds to the north, a difference which is not presently understood. Possible explanations include increased CCN production in the colder ocean waters to the south (meaning closer to the South Pole), and higher precipitation rates with increased CCN removal to the north.A variety of observations, collected in collaboration with other SOCRATES projects, are used to examine the controls on space and time variability of droplet number concentration in SO clouds:* size-resolved aerosol and CCN concentrations, both above and within the boundary layer, using probes and inlets on the GV at multiple flight levels;* precipitation rates, cloud updraft and downdraft strength, and cloud base and top heights determined from onboard radar and lidar.* near-surface aerosol and CCN concentrations from low-level flight legs, planned to sample as low as 150m above surface;* profiles of ambient temperature, moisture, and wind from dropsondes released from the aircraft.These data are combined to produce integrated datasets including a north-south "SOCRATES curtain" dataset which facilitates comparison with numerical model output. Modeling activities based on these datasets are also planned.The work has broader impacts due to the potentially significant role of SO clouds in determining the sensitivity of global climate to external forcing from greenhouse gas increases and other factors. Data from the campaign will be used to develop better representations of clouds in models used for weather prediction and climate impacts assessments. The data will be made available to the worldwide scientific community, thus the campaign has broader impacts by creating a community resource for basic science research. Outreach to K-12 students and the general public is conducted during the campaign through regular newsletters and blogs, and an interactive "Ask SOCRATES" website. This project provides support to two graduate students, thereby providing for the future workforce in this research area.

南大洋（SO），意思是南半球高纬度的全球海洋，作为地球上风暴最多的地方，有着当之无愧的声誉。SO的遥远和它的恶劣条件严重限制了对它上面发生的大气过程的观测，包括沿着南极锋行进的气旋中的云过程。然而，这些过程由于各种原因而令人感兴趣，包括SO云相对不受大陆和人为气溶胶的影响，因此该地区是研究原始条件下云行为的天然实验室。SO云还通过将入射的阳光反射回太空，在地球的能量平衡中发挥着重要的冷却作用。有证据表明，这种冷却有一个长期的影响，低纬度降水的分布与热带辐合带，和SO云量的变化，由于全球气候变化将影响南半球急流的位置和强度。我们对SO云过程缺乏了解的一个指标是气候模型模拟中发现的SO云量不足，伴随着海洋表面过度吸收阳光，这反过来可能会导致气候敏感性估计的错误。 模拟云量的不足在边界层和低对流层云（顶部低于3公里）中最为明显，这些云位于沿着SO风暴路径行进的锋面天气系统的寒冷干燥区域。该运动的主要活动是部署一架由国家大气研究中心地球观测实验室维护的湾流V（GV）研究飞机。GV将以澳大利亚的霍巴特为基地，在南极锋面进行多次飞行，收集SO云及其发生的气象条件的数据。GV配备了用于记录环境气象条件的下投式探空仪，用于观测云层的雷达和激光雷达，以及安装在机翼上或位于进气道后面的仪器，用于采样，收集和分析气溶胶和云粒子（液滴和冰晶）。SOCRATES活动是对国际上和美国其他机构计划的SO活动的补充，包括在船上和南纬54度无人居住的小岛麦夸里岛上进行的地面观测。该奖项支持的工作专门针对大气边界层顶部相对温暖的浅云，特别关注云滴数浓度，或者云中每单位体积的液滴数量。 水滴数浓度是了解云的特性和演变的关键参数，在像SO这样的原始区域，它可能受到云凝结核（CCN）的可用性的限制，气溶胶颗粒从空气中吸收水蒸气形成水滴。PI试图确定液滴数浓度是否与当地边界层或上覆自由对流层中的CCN浓度有关，或者液滴浓度是否受到湍流云运动、降水清除或其他气象因素的强烈影响。以前的研究表明，南极锋以南较冷空气中的低云比北部较暖的云层具有更高的平均液滴浓度，目前还不清楚这种差异。可能的解释包括在南方较冷的海洋沃茨中CCN的产量增加与SOCRATES其他项目合作收集的各种观测数据被用来检查SO云中液滴数浓度的空间和时间变化的控制：* 在多个飞行高度层，使用GV上的探测器和进气道，测量边界层之上和之内的气溶胶和云凝结核浓度的大小;* 由机载雷达和激光雷达确定的降水率、云上升气流和下降气流强度以及云底和云顶高度。*近地面气溶胶和云凝结核浓度从低空飞行腿，计划采样低至150米以上的表面;* 环境温度，湿度和风的廓线从投放探空仪从飞机上释放。这些数据相结合，以产生综合数据集，包括南北“SOCRATES窗帘”数据集，便于与数值模式输出的比较。 由于SO云在确定全球气候对温室气体增加和其他因素的外部强迫的敏感性方面具有潜在的重要作用，因此这项工作具有更广泛的影响。该活动的数据将用于在用于天气预测和气候影响评估的模型中开发更好的云表示。这些数据将提供给全世界的科学界，因此，该运动通过为基础科学研究创建社区资源而产生更广泛的影响。在运动期间，通过定期通讯和博客以及互动的“问苏格拉底”网站，向K-12学生和公众进行宣传。该项目为两名研究生提供支持，从而为这一研究领域的未来劳动力提供支持。

项目成果

Evaluation of Cloud and Precipitation Simulations in CAM6 and AM4 Using Observations Over the Southern Ocean

使用南大洋观测评估 CAM6 和 AM4 中的云和降水模拟

• DOI: 10.1029/2020ea001241
• 发表时间: 2021
• 期刊: Earth and Space Science
• 影响因子: 3.1
• 作者: Zhou, Xiaoli;Atlas, Rachel;McCoy, Isabel L.;Bretherton, Christopher S.;Bardeen, Charles;Gettelman, Andrew;Lin, Pu;Ming, Yi
• 通讯作者: Ming, Yi

Evaluation of MODIS and Himawari‐8 Low Clouds Retrievals Over the Southern Ocean With In Situ Measurements From the SOCRATES Campaign

• DOI: 10.1029/2020ea001397
• 发表时间: 2021-01
• 期刊: Earth and Space Science
• 影响因子: 3.1
• 作者: Litai Kang;R. Marchand;W. Smith

The hemispheric contrast in cloud microphysical properties constrains aerosol forcing

• DOI: 10.1073/pnas.1922502117
• 发表时间: 2020-07
• 期刊: Proceedings of the National Academy of Sciences of the United States of America
• 影响因子: 11.1
• 作者: I. McCoy;D. McCoy;R. Wood;L. Regayre;D. Watson‐Parris;D. Grosvenor;J. Mulcahy;Yongxiang Hu;F. Bender;P. Field;K. Carslaw;H. Gordon

How Well Do Large‐Eddy Simulations and Global Climate Models Represent Observed Boundary Layer Structures and Low Clouds Over the Summertime Southern Ocean?

大涡模拟和全球气候模型在多大程度上代表了夏季南大洋上空观测到的边界层结构和低云？

• DOI: 10.1029/2020ms002205
• 发表时间: 2020
• 期刊: Journal of Advances in Modeling Earth Systems
• 影响因子: 6.8
• 作者: Atlas, R. L.;Bretherton, C. S.;Blossey, P. N.;Gettelman, A.;Bardeen, C.;Lin, Pu;Ming, Yi
• 通讯作者: Ming, Yi

Wavelet Analysis of Properties of Marine Boundary Layer Mesoscale Cells Observed From AMSR‐E

• DOI: 10.1029/2021jd034666
• 发表时间: 2021-06
• 期刊: Journal of Geophysical Research: Atmospheres
• 作者: Xiaoli Zhou;C. Bretherton;R. Eastman;I. McCoy;R. Wood