Atmospheric Rivers and The Onset of Sea-Ice Melt (ARTofMELT)

大气河流和海冰融化的开始 (ARTofMELT)

• 批准号: NE/X000087/1
• 负责人: Ian Brooks
• 金额: $ 81.48万
• 依托单位: University of Leeds
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FX000087%2F1
• 关键词: Atmospheric; Rivers; Onset; Sea; Ice

Arctic climate is warming much faster than that of the world as a whole. Global models show the general trend of enhanced warming, but generally fail to reproduce the observed dramatic reduction in sea ice. This results in part from significant biases in the surface energy budget. The largest source of uncertainty in the energy budget results from problems in the representation of low level clouds and the resulting solar and infra-red radiation fluxes at the surface, and of turbulent heat fluxes within the near-surface atmosphere. The model biases are greatest under the extreme conditions of strong forcing by warm air intrusions - regional events where warm, humid air is transported in over sea ice, cooling close to the surface to form shallow, stably stratified layers within which fog and cloud form. The shallow layers and steep vertical gradients of temperature, humidity, and turbulence are difficult for global models to resolve. Their evolution with increasing time over the sea ice, as the vertical thermodynamic profiles, cloud liquid and ice water contents, and turbulent structure change, depends strongly on small scale processes that must be parameterized within the models. Existing parameterizations are based on measurements at lower latitudes, and fail to adequately represent polar conditions. The resulting model biases can be 100s of W/m2 during warm air intrusions.ARTofMELT is the first observational study focussed on warm air intrusions. Support for an international project, proposed by our partners at Stockholm University, has been approved by the Swedish Polar Research Secretariat, and a research cruise is scheduled for spring 2023 on the Swedish icebreaker Oden. This provides a unique opportunity to make the measurements needed to provide new understanding of the processes controlling air mass modification during these events, and develop new parameterizations for global models appropriate to polar environments. Building on several previous collaborative projects we will work as a single team with our partners in Stockholm to instrument Oden for extensive in situ and remote sensing measurements of the lower atmosphere, clouds, and the components of the surface energy budget. Directed by dedicated forecasts made at ECMWF, Oden will be positioned to sample warm air intrusions entering the Arctic from the Atlantic or Eurasian sectors. We anticipate sampling 3-5 events during the cruise, and use the observations from outside the event periods as a baseline to evaluate the impact of warm air intrusions on lower-atmosphere structure, clouds, and the surface energy budget. Other participants will assess the response of sea ice to the atmospheric forcing.

北极气候变暖的速度比整个世界的变暖速度要快得多。全球模型显示了变暖加剧的总体趋势，但通常无法重现观察到的海冰急剧减少。这部分是由于表面能量预算的显着偏差造成的。能量预算中不确定性的最大来源是低层云的表示问题以及由此产生的地表太阳和红外辐射通量以及近地表大气中的湍流热通量的问题。在暖空气入侵的强烈强迫的极端条件下，模型的偏差最大——在这种区域性事件中，温暖、潮湿的空气被输送到海冰上方，在靠近表面的地方冷却，形成浅层、稳定的分层层，在其中形成雾和云。温度、湿度和湍流的浅层和陡峭的垂直梯度很难用全球模型来解决。它们随着海冰上时间的增加而演变，如垂直热力学剖面、云液体和冰水含量以及湍流结构的变化，在很大程度上取决于必须在模型中参数化的小规模过程。现有的参数化基于低纬度的测量，无法充分代表极地条件。在暖空气入侵期间，所得模型偏差可能为数百瓦/平方米。ARTofMELT 是第一个专注于暖空气入侵的观察性研究。对我们斯德哥尔摩大学合作伙伴提出的国际项目的支持已获得瑞典极地研究秘书处的批准，并计划于 2023 年春季在瑞典破冰船奥登号上进行一次研究巡航。这提供了一个独特的机会来进行所需的测量，以提供对这些事件期间控制气团改变的过程的新理解，并为适合极地环境的全球模型开发新的参数化。在之前几个合作项目的基础上，我们将作为一个团队与斯德哥尔摩的合作伙伴合作，使用 Oden 仪器对低层大气、云层和地表能量预算的组成部分进行广泛的原位和遥感测量。在 ECMWF 专门预测的指导下，奥登将采样从大西洋或欧亚地区进入北极的暖空气入侵。我们预计在巡航期间对 3-5 个事件进行采样，并使用事件周期之外的观测结果作为基线来评估暖空气入侵对低层大气结构、云和地表能量预算的影响。其他参与者将评估海冰对大气强迫的反应。