The Properties of Mixed Phase- and Ice Clouds in the Arctic Using a Tethered Balloon System Deployed in Support of the International Polar Year (IPY)

在下个世纪，北极表面温度的上升速度预计将是全球平均水平的两倍(IPCC，2007)。极地冰盖上的浅层低层云的作用可能相当重要，因为它们与可见光和红外波长的辐射能量的相互作用可以不同程度地减少或放大这种变化，净结果在很大程度上取决于这些云的详细微观结构(例如，过冷液态水与其中的冰的相对数量和颗粒大小)。最近有证据表明，春季和夏季云量增加，同时融化速度加快，极地冰盖变薄/退缩，这为我们更好地理解这种联系提供了额外的紧迫性。这里支持的工作体现了史蒂文斯理工学院和SPEC Inc.之间的密切合作，将获得和分析北极云中微物理和辐射特性的低水平测量结果。这些独特的详细数据将通过系留气球系统和挪威支持的科学计划(THORPEX-IPY)在2008年国际极地年期间在NY-Alesund获得，NY-Alesund位于斯瓦尔巴群岛(前身为Spitzbergen)北纬78度，在春季的八周时间里，有利于大范围的低层云层覆盖和相关的地面辐射反馈。观测将使用SPEC开发的复杂的气球载云微物理观测系统来获得，其中包括一台用于对云粒进行成像和对云滴进行计数的仪器，一台由史蒂文斯技术研究所定制的用于监测可见光和近红外辐射能量通量的辐射计，以及获得标准气象观测套装所需的仪器。所有这些数据都将被实时遥测到地面站。使用系留气球平台将允许云结构和辐射/热条件反复和频繁地向下描绘到更接近地表的水平，并且持续时间比使用研究飞机可能的时间长得多(~24小时)，而且成本要低得多。这些信息将被输入到一个综合的辐射传输模型中，该模型能够隔离和量化各种云层特性对底层冰的影响。通过与同期的地面和卫星测量进行比较，该模型将进一步调整和改进，以准确地描述云-冰相互作用。这一改进模型的简化版本最终将被纳入全球规模的卑尔根气候模型，以便利用这些结果来改进对当前气候条件的诊断和更准确的长期预测。

Over the next century, Arctic surface temperatures are predicted to rise at twice the rate of the global mean (IPCC, 2007). The role of shallow low-level clouds over the polar ice sheets is potentially quite important, since their interaction with radiative energy at both visible and infrared wavelengths can variously reduce or amplify such changes, with the net outcome being strongly dependent on the detailed microstructure of these clouds (e.g., the relative amounts and particle sizes of supercooled liquid water vs. ice within them). Recent evidence of increased spring and summer cloudiness accompanied by accelerated melt rates and associated thinning/retreat of polar pack ice lends additional urgency to our improved understanding of such linkages. The work supported here, which embodies a close collaboration between Stevens Institute of Technology and SPEC Inc., will obtain and analyze low-level measurements of microphysical and radiative properties in Arctic clouds. These uniquely detailed data will be obtained via a tethered balloon system operated in conjunction with a Norwegian-supported scientific program (THORPEX-IPY) during the 2008 International Polar Year at Ny-Alesund, located at 78 deg N in the Svalbard (formerly Spitzbergen) archipelago over an eight week period during the spring, when widespread low-level cloudcover and associated surface radiative feedbacks are favored. Observations will be obtained using a sophisticated balloon-borne cloud microphysical observing system developed by SPEC, which includes an instrument for imaging cloud particles and counting cloud droplets, a radiometer custom engineered by Stevens Technical Institute for monitoring radiative energy fluxes in the visible and near-infrared, as well as instruments required to obtain standard suite of meteorological observations. All of these data will be telemetered to a ground station in real-time. Use of a tethered-balloon platform will allow cloud structure and radiative/thermal conditions to be repeatedly and frequently profiled down to levels much nearer the surface and over far longer (~24 h) continuous periods than would be possible using research aircraft, and at considerably lower cost. This information will be input into a comprehensive radiative transfer model capable of isolating and quantifying the impact of variable cloudcover properties on the underlying ice. Through comparisons with contemporaneous ground- and satellite-based measurements, this model will be further tuned and improved to accurately represent cloud-ice interactions. A simplified version of this refined model will ultimately be incorporated into the global-scale Bergen Climate Model so as to leverage these results toward improved diagnosis of current climate conditions and more accurate long-range predictions.