Gridded segments of sea-ice or snow surface elevation and freeboard from helicopter-borne laser scanner during the MOSAiC expedition flight 20200717_01, version 1

This data set is a higher-processing-level version of Geolocated sea-ice or snow surface elevation point clouds from helicopter-borne laser scanner during the MOSAiC expedition, version 1 (Jutila et al., 2022; doi:10.1594/PANGAEA.950509), where the surface elevation point cloud has been converted to freeboard using automatic open water detection scheme and projected onto a regular 0.5-meter grid. The data were collected using a near-infrared, line-scanning Riegl VQ-580 airborne laser scanner (hdl:10013/sensor.7ebb63c3-dc3b-4f0f-9ca5-f1c6e5462a31 & hdl:10013/sensor.7a931b33-72ca-46d0-b623-156836ac9550) mounted in a helicopter along the MOSAiC drift from the north of the Laptev Sea, across the central Arctic Ocean, and towards the Fram Strait from September 2019 to October 2020. The flights are both small scale, ~5x5 km grid patterns mainly over the central observatory, and large scale, few tens of km away from RV Polarstern, triangle patterns, or transects. The gridded data are stored in 30-second along-track segments in netCDF format. For the small scale grid flights, the data are drift corrected using the position and heading data of RV Polarstern and elevation offset corrected using overlapping segments to overcome degraded GPS altitude data >85°N. Open water points are identified to derive a freeboard estimate from the surface elevations. For the flights with degraded GPS altitude quality, we provide only a freeboard estimate (grid pattern flights) or no freeboard (transects). The gridded 30-s segments include as data variables: surface elevation, freeboard (estimate), freeboard uncertainty, estimated sea surface height, surface reflectance, echo width, and number of points used in the interpolation. In addition, list of detected open water points and an overview figure of each flight is provided.

本数据集为MOSAiC北极气候多学科漂流科考任务（MOSAiC expedition）版本1的进阶处理成果，其原始数据为直升机搭载激光扫描仪采集的地理定位海冰/雪面高程点云（数据引用：Jutila et al., 2022; doi:10.1594/PANGAEA.950509）。该数据集通过自动开阔水域识别算法将表面高程点云转换为海冰干舷（freeboard），并投影至规则0.5米网格。本数据集采用搭载于直升机的近红外线扫描Riegl VQ-580机载激光扫描仪（hdl:10013/sensor.7ebb63c3-dc3b-4f0f-9ca5-f1c6e5462a31 与 hdl:10013/sensor.7a931b33-72ca-46d0-b623-156836ac9550）采集，采集时段为2019年9月至2020年10月，沿MOSAiC科考漂流路线，从拉普捷夫海北部出发，横跨北冰洋中部，最终抵达弗拉姆海峡。飞行作业包含两种尺度：小尺度作业以约5×5千米的网格模式为主，主要覆盖中部观测站区域；大尺度作业则以距离极星号（RV Polarstern）科考船数十千米的三角模式或断面模式开展。网格化数据以沿轨30秒分段的形式存储，格式为netCDF。针对小尺度网格飞行作业，数据采用极星号科考船的位置与航向数据进行漂流校正，并通过重叠分段进行高程偏移校正，以解决北纬85°以上区域GPS高程数据质量下降的问题。通过识别开阔水域点，可从表面高程数据推导出海冰干舷估算值。对于GPS高程数据质量不佳的飞行作业，仅提供海冰干舷估算值（网格模式飞行）或不提供海冰干舷数据（断面飞行）。该30秒沿轨分段的网格化数据包含以下数据变量：表面高程、海冰干舷（估算值）、海冰干舷不确定性、估算海表高度、表面反射率、回波宽度以及插值所用的点数。此外，数据集还附带已识别的开阔水域点列表，以及每一次飞行作业的概览图。