Aircraft measurements of spectral downward solar irradiance over Arctic sea ice and ocean during the HALO-(AC)³ campaign in spring 2022

During the HALO-(AC)³ campaign in March and April 2022 spectral solar downward irradiances were measured onboard of the High Altitude LOng range research aircraft (HALO) over the Arctic sea ice and ocean using the Spectral Modular Airborne Radiation measurement sysTem (SMART). The data set gives time series of spectral irradiances measured along the flight path of HALO on 17 days. All flights started from Kiruna, Sweden and headed into the Fram Straight and towards the central Arctic. The goal of the campaign was to study warm air intrusions and cold air outbreaks to and from the Arctic and to follow those air masses over several days with remote sensing instrumentation aboard HALO. The first research flight (RF) was RF02. RF01 was the transfer flight from Oberpfaffenhofen, Germany to Kiruna. The irradiance inlet of SMART was actively stabilized and connected to two spectrometers of which one measured radiation in the visible to near infrared range (VNIR) between 180 and 1014 nm and the other radiation in the shortwave to infrared range (SWIR) between 890 and 2200 nm. The data was merged at 990 nm and cut to 320 to 2100 nm because of high uncertainties at the spectrometer edges. The spectral resolution below 900 nm is 1nm and above 5 nm due to technical limitations of the SWIR spectrometer. The data is corrected for the dark current of the spectrometers and calibrated using in field transfer calibrations connected to a laboratory calibration after the campaign.

2022年3月至4月的HALO-(AC)³科考航次期间，研究人员搭乘高空远程研究飞机（High Altitude LOng range research aircraft，HALO），搭载光谱模块化机载辐射测量系统（Spectral Modular Airborne Radiation measurement sysTem，SMART），在北极海冰与洋面上空完成了下行太阳光谱辐照度的观测工作。本数据集涵盖了17个观测日内沿HALO飞行轨迹采集的光谱辐照度时间序列数据。所有观测航班均从瑞典基律纳起飞，途经弗拉姆海峡后向北极中部空域航行。本次航次的核心研究目标为：探究往返北极的暖空气侵入与冷空气爆发事件，并依托HALO搭载的遥感仪器对相关气团开展多日连续追踪观测。首个科研航班（RF）为RF02，RF01为从德国奥伯法芬霍芬飞往基律纳的转场航班。SMART的辐照度采集入口采用主动稳定设计，并连接两台光谱仪：其中一台用于测量180~1014 nm波段的可见-近红外（visible to near infrared range，VNIR）辐射，另一台用于测量890~2200 nm波段的短波红外（shortwave to infrared range，SWIR）辐射。由于光谱仪边缘波段的测量不确定性较高，数据在990 nm处完成波段融合，并被裁剪至320~2100 nm的有效范围。受SWIR光谱仪的技术限制，900 nm以下波段的光谱分辨率为1 nm，900 nm以上波段的光谱分辨率为5 nm。本数据集已针对两台光谱仪的暗电流完成校正，并采用航次现场传递校准结合航后实验室校准的方案完成定标。