ICE-IMPACT: International Consortium for the Exploitation of Infrared Measurements of PolAr ClimaTe

远红外（FIR）被定义为波长大于15微米的电磁波谱区域。远红外辐射在地球的能量平衡中起着重要作用，占地球及其大气层向空间发射的全球平均量的大约一半。基础物理学意味着远红外辐射将在影响脆弱的极地地区气候变率和变化方面发挥更重要的作用。在这些位置发现的非常冷的表面温度意味着在较长的波长处发现更大部分的发射表面能量。此外，通常在极地地区发现的相关的非常低的水蒸气浓度有效地打开了FIR中的“窗口”，使得有可能从地面看到比通常在这些波长下可能看到的更远的大气层。根据同样的论点，在这些波长下发射的更多的表面能量能够逃逸到太空中。最近的工作表明，我们用来预测气候的许多最先进的模型（称为地球系统模型）中对FIR表面特征的假设意味着它们可能遗漏了一个重要的极地气候反馈过程。这可能导致到21世纪30年代北极表面再升温2 K，预计这将影响冰融化和海平面上升的速度。被称为“冰发射率”反馈的机制取决于这样一个事实，即在相同温度下，雪和冰在FIR波长上比海水发射更多的能量。目前的地球系统模型通常假设所有表面在FIR中具有相同的发射率，因此不包括这种反馈过程。这些模型也很难与极地地区大气层发出的下行辐射的地面观测相匹配，这一缺陷被认为主要是由于极地云的代表性不足。然而，到目前为止，对极地辐射预算的详细评估一直受到阻碍，因为缺乏跨越整个红外线的专门观测，包括FIR。该项目旨在解决这一缺陷，召集了一个FIR研究和气候建模方面的国际专家小组，以开发一套基于观测的工具，用于评估模型性能并推动未来的改进。在这项工作过程中，我们将首次从格陵兰高原上空的现场空中观测中得出远红外表面发射率的评估结果;对南极上空的红外表面辐射收支进行分析，并评估在一系列时间尺度上导致那里变化的气象过程;评价用于从天基观测中得出合成远红外测量结果的方法;并开始在两个主要的地球系统模型中量化冰发射率反馈的过程。

The Far infra red (FIR) is defined as the region of electromagnetic spectrum found at wavelengths greater than 15 microns. FIR radiation plays a major role in the Earth's energy balance, accounting for approximately half of the emission to space from the Earth and its atmosphere in the global mean. Fundamental physics implies that FIR radiation will play an even more important role in influencing climate variability and change in the fragile polar regions. The very cold surface temperatures found in these locations means that a greater fraction of the emitted surface energy is found at longer wavelengths. Moreover, the associated very low water vapour concentrations typically found in polar regimes effectively open up 'windows' in the FIR, making it possible to see further into the atmosphere from the ground than would normally be possible at these wavelengths. By the same argument, more of the surface energy emitted at these wavelengths is able to escape to space.Recent work has suggested that assumptions about FIR surface characteristics made in many of the most advanced models that we use to predict climate - termed Earth-system models - mean that they may be missing an important polar climate feedback process. This could lead to an additional Arctic surface warming of up to 2 K by the 2030s which would be expected to affect the rate of ice-melt and sea-level rise. Termed the 'ice-emissivity' feedback, the mechanism depends on the fact that snow and ice emit more energy at FIR wavelengths than sea-water at the same temperature. Current Earth-system models typically assume that all surfaces have the same emissivity in the FIR and so do not include this feedback process. These same models also struggle to match surface observations of the downwelling radiation emitted by the atmosphere in polar regions, a shortcoming that is believed to be principally due to inadequacies in the representation of polar clouds. However, up to now a detailed evaluation of the polar radiation budget has been hampered by a lack of dedicated observations spanning the entire infrared, including the FIR. This project seeks to address this deficiency by bringing together a team of international experts in FIR research and climate modelling to develop a suite of observationally based tools which will be used to assess model performance and drive future improvements. In the course of this work we will derive the first ever assessment of FIR surface emissivity from in-situ airborne observations over the Greenland plateau; characterise the infrared surface radiation budget over Antarctica and assess the meteorological processes driving variability there over a range of time-scales; evaluate approaches used to derive synthetic FIR measurements from space-based observations; and begin the process of quantifying the ice-emissivity feedback in two leading Earth-system models.