Algorithm Input and Output Data Definition (IODD)

In order to process a swath of L2 SIT, the processing starts from a recent SIC map (in swath projection). Land-mask information should be contained in the SIC map. Land is removed before processing and while a flag for ice-free ocean can be used, those pixels would be retrieved as 0 cm in any case. The input for the ice thickness consists of \(T_{b,h}\) and \(T_{b,v}\) at 1.4 GHz and their uncertainties NeΔT which are assumed Gaussian noise in this retrieval. The corresponding output is thickness of thin sea ice up to 50 cm including the uncertainty as described in this document. For retrieved values above 50 cm the output will have the status flag for 50+ cm.

Input data

Field	Description	Shape/Amount
L1B TB	L1B Brightness Temperature at L-band (both H and V polarization)	full swath or section of it (Nscans, Npos)
L1B NeΔT	Random radiometric uncertainty of the channels	full swath or section of it (Nscans, Npos)
sea-ice and land mask	A recent sea-ice concentration field including land information	SIC and land-mask collocated to swath.

Output data

Field	Description	Shape/Amount
L2 SIT	Sea Ice Thickness	full swath or section of it (Nscans, Npos)
SIT uncertainty (4 fields)	Retrieval uncertainties: the total uncertainty as well as the 3 contributions separately.	full swath or section of it (Nscans, Npos)
Status Flag	A flag indicating status of retrieval, e.g. “nominal”, “over land”, “ice-free”, “50+cm”	full swath or section of it (Nscans, Npos)

Note: over land areas, only the status flags will have a valid value, all the others will have “NaN” (_FillValue). Over ice-free ocean, the SIT will be 0 cm.

Auxiliary data

Auxiliary data are used to improve the retrieval. They are not mandatory, but the retrieval will be less accurate without them. This includes the TEC for the transformation from TOA to surface brightness temperature.

Ancillary data

Ancillary data includes the Masks for filling shelf and land areas. While Land areas are assumed fixed, shelf ice is changing over time, in particular pronounced in the Antarctic. The shelf ice mask is used to exclude shelf ice from the retrieval. The land mask is used to exclude land areas from the retrieval.