Characterising and Interpreting FLuxes Over Sea-ice (CANDIFLOS)

海冰通量的表征和解释 (CANDIFLOS)

• 批准号: NE/S000690/1
• 负责人: Ian Brooks
• 金额: $ 46.57万
• 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: 2019
• 资助国家: 英国
• 起止时间: 2019 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FS000690%2F1
• 关键词: Characterising; Interpreting; FLuxes; Over; Sea

Interactions between the atmosphere and the surface of the planet are mediated by turbulent fluxes - chaotic mixing that transports momentum, heat, moisture, and trace gases between the two. Turbulent mixing spans scales from millimetres to hundreds of meters - much smaller than the grid scale of numerical models; such sub-grid-scale processes must be parameterized (or represented) in terms of simpler model variables such as mean wind speed, air temperature, humidity, etc. These parameterizations are developed by making direct measurements of the fluxes themselves (a very difficult and expensive undertaking) and then determining their empirical relationships with the simpler (and more easily measured) variables such as wind speed, temperatures etc.This proposal aims to address long-standing issues with the parameterization of turbulent fluxes over sea ice. The remote location and harsh conditions of both Arctic and Antarctic sea ice means that very few direct measurements of the fluxes have ever been made, and models must rely on parameterizations developed at lower latitudes, e.g. over ice-free areas of the oceans. The very different conditions that occur over sea ice - a high degree of spatial variability, strong temperature contrasts between the ice and open water in leads in the ice, and strongly stable atmospheric conditions in winter - mean that the parameterizations developed at lower latitudes are often not appropriate, and models tend to do a poor job of representing the surface fluxes. The current generation of models fails to represent the mean changes in sea ice extent compared to satellite observations over the last 35 years or so, and produce often wildly inaccurate seasonal forecasts of ice extent even just a few months in advance.The growth and melt of sea ice is controlled by the surface energy budget, and the turbulent fluxes between the ice and the atmosphere are a critical component of that budget. The solar and terrestrial radiation fluxes dominate the budget, but the turbulent fluxes control the atmospheric boundary-layer structure, and influence the development of boundary-layer clouds which are the dominant control on the radiation fluxes. So all of these fluxes are inter-linked and consequently a failure to properly represent the air-ice turbulent fluxes has a knock-on influence on the surface radiation balance through their impact on clouds. An accurate representation of turbulent fluxes is thus essential for accurate predictions of weather, sea ice and the climate system.On short timescales the recent reduction of Arctic sea ice, and the accompanying increase in commercial activity in the Arctic (shipping, tourism, petrochemical extraction, etc) means that there is an urgent need for accurate operational forecasts of weather, sea ice and other environmental factors on timescales from days to seasons. Delivering these will require a much improved representation of the surface exchange processes that control the atmospheric boundary layer and properties of clouds within it, and contribute to the surface energy budget, and hence ice melt/freeze, and ice drift.Significant progress has been made over the last 5 years in developing theoretical models of the physical processes that control the surface fluxes, such as form drag at ice edges, ridges, melt ponds, and ice/water temperature contrasts. However there is a need for in situ measurements to test these parameterizations and to evaluate their performance.This project will utilise a very extensive set of surface flux and sea-ice measurements made during two recent (2014 and 2016) cruises in the Arctic Ocean, totalling 18 weeks, to develop state-of-the-art parameterizations for momentum, heat, and water vapour that are tuned to real-world conditions. We will implement these parameterizations within the Met Office Unified Model, and evaluate their impact on the atmosphere, and on the climate system, over a range of timescales.

大气层和地球表面之间的相互作用是由湍流介导的，即在两者之间传递动量、热量、水分和微量气体的混沌混合。湍流混合的尺度从毫米到数百米——远小于数值模型的网格尺度；这种亚网格尺度的过程必须根据更简单的模型变量（例如平均风速、气温、湿度等）进行参数化（或表示）。这些参数化是通过直接测量通量本身来开发的（这是一个非常困难和困难的过程）昂贵的任务），然后确定它们与更简单（更容易测量）的变量（例如风速、温度等）的经验关系。该提案旨在解决海冰上湍流通量参数化的长期存在的问题。北极和南极海冰的偏远位置和恶劣条件意味着很少对通量进行直接测量，并且模型必须依赖于低纬度开发的参数化，例如海洋无冰区域上空。海冰上发生的非常不同的条件 - 高度的空间变化，冰中铅与开放水域之间的强烈温度对比，以及冬季非常稳定的大气条件 - 意味着在低纬度地区开发的参数化通常是不合适，并且模型在表示表面通量方面往往表现不佳。与过去 35 年左右的卫星观测结果相比，当前一代的模型无法代表海冰范围的平均变化，并且即使仅提前几个月，对海冰范围的季节性预测也常常非常不准确。海冰受表面能量预算控制，而海冰和大气之间的湍流是该预算的关键组成部分。太阳和地面辐射通量在预算中占主导地位，但湍流通量控制大气边界层结构，并影响边界层云的发展，而边界层云是辐射通量的主要控制因素。因此，所有这些通量都是相互关联的，因此，未能正确表示空气-冰湍流通量会通过对云的影响而对表面辐射平衡产生连锁影响。因此，准确表示湍流对于准确预测天气、海冰和气候系统至关重要。在短时间内，北极海冰最近减少，以及随之而来的北极商业活动（航运、旅游、石化开采）的增加等）意味着迫切需要对天气、海冰和其他环境因素在从天到季节的时间尺度上进行准确的业务预报。实现这些将需要大大改进地表交换过程的表示，这些过程控制大气边界层和其中云的特性，并有助于地表能量预算，从而促进冰融化/冻结和冰漂移。已经取得了重大进展在过去的五年里，我们致力于开发控制表面通量的物理过程的理论模型，例如冰边缘、山脊、融化池的形状阻力以及冰/水温度对比。然而，需要进行现场测量来测试这些参数化并评估其性能。该项目将利用最近两次（2014 年和 2016 年）北冰洋巡航期间进行的一系列非常广泛的表面通量和海冰测量，总计 18 周，开发最先进的动量、热量和水蒸气参数化，并根据实际条件进行调整。我们将在气象局统一模型中实施这些参数化，并评估它们在一系列时间尺度上对大气和气候系统的影响。

项目成果

Improved simulation of the polar atmospheric boundary layer by accounting for aerodynamic roughness in the parameterisation of surface scalar exchange over sea ice

通过考虑海冰表面标量交换参数化中的空气动力学粗糙度，改进极地大气边界层的模拟

• DOI: http://dx.10.1002/essoar.10512220.1
• 发表时间: 2022
• 作者: Elvidge A

Ship-based estimates of momentum transfer coefficient over sea ice and recommendations for its parameterization

海冰动量传递系数的船基估计及其参数化建议

• DOI: http://dx.10.5194/acp-2021-705
• 发表时间: 2021
• 作者: Srivastava P

Ship-based estimates of momentum transfer coefficient over sea ice and recommendations for its parameterization

海冰动量传递系数的船基估计及其参数化建议

• DOI: http://dx.10.5194/acp-22-4763-2022
• 发表时间: 2022
• 期刊: Atmospheric Chemistry and Physics
• 影响因子: 6.3
• 作者: Srivastava P

Surface Heat and Moisture Exchange in the Marginal Ice Zone: Observations and a New Parameterization Scheme for Weather and Climate Models

边缘冰区的表面热量和水分交换：观测和天气和气候模型的新参数化方案

• DOI: http://dx.10.1029/2021jd034827
• 发表时间: 2021
• 期刊: Atmospheres
• 作者: Elvidge A

Improved Simulation of the Polar Atmospheric Boundary Layer by Accounting for Aerodynamic Roughness in the Parameterization of Surface Scalar Exchange Over Sea Ice

通过考虑海冰表面标量交换参数化中的气动粗糙度来改进极地大气边界层的模拟

• DOI: http://dx.10.1029/2022ms003305
• 发表时间: 2023
• 期刊: Journal of Advances in Modeling Earth Systems
• 影响因子: 6.8
• 作者: Elvidge A