High-Resolution Snow Freeboard Maps from Operation IceBridge (OIB) ATM Measurements

This dataset contains processed snow freeboard (Fs) measurements derived from NASA's Airborne Topographic Mapper (ATM) observations during four April 2019 Arctic campaigns of Operation IceBridge (OIB), with particular focus on the April 8 and 12 flights which were organized into racetracks. This dataset related to article "On the Statistical Relationship between Sea Ice Topography and C-Band Microwave Backscatter – A Study with Sentinel-1 and Operation IceBridge." Specifically, two steps are carried out, as follows.

(1)   Construction of the per-pass 1m-scale Fs map

As the first step, for each OIB pass, we converted OIB ATM samples into the Fs map. Both wide scan and the narrow scan of the OIB ATM are utilized. We first project each ATM sample under the polar stereographic projection according to its geolocation (i.e., its latitude and longitude). Then, we interpolate the samples into a 1m-scale elevation map, using linear interpolation. Afterwards, we apply corrections to the elevation, including the mean sea-surface height (DTU15 MSS model) and the atmospheric and tidal effects. Finally, we treat the corrected elevation as elevation anomalies, and apply the lowest elevation method to retrieve the freeboard. Specifically, the lowest 1‰ of elevation samples within each 10km segment are extracted and interpolated to construct the local water level (also at 1m-scale) using the Inverse Distance Weighting (IDW) method. The final 1m-scale Fs map is further validated with the standard 40m-scale Fs product from IDCSI.

(2)   Collocation between OIB passes and the construction of the merged Fs field

We further merge the three OIB passes to form the Fs map that covers over 1.4km across the flight path. Since the central pass and the left pass were separated by 1∼2 hours, and the central pass and the right pass by 3∼4 hours, the sea ice cover potentially had undergone drift and deformation. Therefore, we first search for corrections between each of the two pairs of OIB passes. For each 3km segment, we maximize the correlation of the overlapping part of the Fs maps of the central and the left (or the right) pass, by adjusting the relative location of the left (or the right) pass with respect to the central pass. After the maximum correlation is attained, we record the corrections in both the along-track and the cross-track directions, and further merge the left and the right pass to the central pass, in order to form a unified Fs map.

For detailed data descriptions, please refer to the manual document.