Horizontal profiles of longwave and shortwave radiation components over sea ice near Barrow, Alaska during the 2011 melt

An integrated instrument package for measuring and understanding the surface radiation budget of sea ice is presented, along with results from its first deployment. The setup simultaneously measures broadband fluxes of upwelling and downwelling terrestrial and solar radiation (four components separately), spectral fluxes of incident and reflected solar radiation, and supporting data such as air temperature and humidity, surface temperature, and location (GPS), in addition to photographing the sky and observed surface during each measurement. The instruments are mounted on a small sled, allowing measurements of the radiation budget to be made at many locations in the study area to see the effect of small-scale surface processes on the large-scale radiation budget. Such observations have many applications, from calibration and validation of remote sensing products to improving our understanding of surface processes that affect atmosphere-snow-ice interactions and drive feedbacks, ultimately leading to the potential to improve climate modelling of ice-covered regions of the ocean. The photographs, spectral data, and other observations allow for improved analysis of the broadband data. An example of this is shown by using the observations made during a partly cloudy day, which show erratic variations due to passing clouds, and creating a careful estimate of what the radiation budget along the observed line would have been under uniform sky conditions, clear or overcast. Other data from the setup's first deployment, in June 2011 on fast ice near Point Barrow, Alaska, are also shown; these illustrate the rapid changes of the radiation budget during a cold period that led to refreezing and new snow well into the melt season.

本研究介绍了一套用于测量与解析海冰表面辐射收支（surface radiation budget）的集成仪器套件（integrated instrument package），及其首次野外部署的实测结果。该装置可同步测量上行、下行的长波与短波太阳辐射宽带通量（共四个独立分量），入射与反射太阳辐射的光谱通量，以及气温、相对湿度、地表温度、位置信息（GPS，全球定位系统）等辅助观测数据；同时在每次测量过程中拍摄天空与观测地表的影像。仪器搭载于小型雪橇之上，可在研究区域内多个点位开展辐射收支测量，以探究小尺度地表过程对大尺度辐射收支的影响。此类观测具备多方面应用价值：可用于遥感产品的定标与验证，加深对影响大气-积雪-海冰相互作用并驱动反馈过程的地表过程的认知，最终有望提升海洋冰封区域的气候模拟精度。拍摄的影像、光谱数据与其他观测结果可辅助优化宽带通量数据的分析流程。本研究以某多云天气下的观测为例，展示了该分析方法的应用效果：当日观测到辐射收支因过境云团出现无规则波动，通过该方法可精准估算观测剖面在均匀天空状况（晴天或阴天）下的辐射收支情况。本研究同时展示了该装置2011年6月在阿拉斯加巴罗角附近沿岸固定冰首次部署的其他实测数据，这些数据展现了一段寒冷期内辐射收支的快速变化——该时期甚至在融冰季仍出现了海冰重新冻结与新雪堆积的现象。