Arctic sea ice thermal emission measurements from the Ultra Wideband Microwave Radiometer (UWBRAD) at the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) Expedition in December 2019

The Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) Expedition was conducted to investigate the Arctic processes and evolution of ocean-ice-atmosphere system in the polar region throughout a year. The campaign began in October 2019 when Polarstern moored to an ice floe measuring roughly 2.8 x 3.8 kilometers in the north of the Laptev Sea. The ice floe was estimated to have formed in the north of the New Siberian Islands at the beginning of December 2018, and survived the summer melt during its Transpolar Drift towards the central Arctic. A science camp was established on the drifting ice floe for comprehensive measurements from diverse research groups. The Ultra Wideband Microwave Radiometer (UWBRAD) was also deployed on the ice at the remote sensing site in the camp, and performed measurements over the period December 4-13, 2019. It monitored a refrozen melt pond in oblique angles to measure thermal emission signatures at frequencies 540, 900, 1380 and 1740 megahertz. The instrument was installed on a stationary telescoping mast that can be manually adjusted to different heights. The direction of antenna was controlled by a programmable rotator unit which allowed it both to monitor sea ice from a desired oblique angle and to perform periodic upward looking sky measurements for calibration. The collected data provided the opportunity to investigate the effect of ice evolution in the winter season on the measured wideband brightness temperatures so that the sea ice emission models can be improved for satellite-borne remote sensing instruments.

北极气候研究多学科漂流观测站（Multidisciplinary drifting Observatory for the Study of Arctic Climate, MOSAiC）考察队旨在开展极地地区一整年的北极过程与海-冰-气系统演化研究。该考察活动于2019年10月启动，当时极星号（Polarstern）停泊在拉普捷夫海北部一块约2.8×3.8千米的浮冰上。据估算，这块浮冰于2018年12月初在新西伯利亚群岛北部形成，并在跨北极漂流至北极中部的过程中熬过了夏季融冰期。考察团队在漂流浮冰上建立了科学营地，供多支研究团队开展综合观测。营地遥感站点的冰面还部署了超宽带微波辐射计（Ultra Wideband Microwave Radiometer, UWBRAD），并于2019年12月4日至13日开展观测。该设备以斜角监测一处重新冻结的融冰塘，测量540、900、1380及1740兆赫兹频段下的热辐射特征。该仪器安装在固定式伸缩桅杆上，可手动调节至不同高度。天线方向由可编程旋转单元控制，既可按需求以斜角观测海冰，也可定期向上观测天空以完成校准。所采集的数据为研究冬季海冰演化对实测宽带亮温的影响提供了契机，进而可优化适用于星载遥感仪器的海冰辐射模型。