The near 50GHz sea ice emissivity product (OSI-404-a)
In the context of the third Continuous Development and Operation Phase (CDOP-3), the sea ice emissivity product is upgraded in the Ocean and Sea Ice SAF product's portofolio. It is based on satellite SSMIS microwave radiometer data.
The spatial resolution is about 50 km. However it is provided on daily grids where the grid-point spacing is 10km or 25km. All swath data from one day are combined and resampled to the grid using nearest neighbor. The model for computing the emissivities is described in the ATBD. It uses the brightness temperatures at 19v, 37v and 37h measured by the conically scanning SSMIS. It also provides the effective temperature based on 6v and 10v brightness temperatures taken from AMSR data.
1. Introduction and FAQ
How should I cite this dataset?
This dataset shall be referred to as the The near 50GHz sea ice emissivity product of the EUMETSAT Ocean and Sea Ice Satellite Application Facility (OSI SAF, www.osi-saf.org).
Which satellite sensors are processed?
The brightness temperatures at 19v, 37v and 37h measured by the conically scanning SSMIS.
What is the spatial resolution of this product?
The spatial resolution of the product is about 50km. similar to the 19GHz channel on the SSMIS.
What is the time-span of this product?
One day (24 hours).
There are 4 different layers in the NetCDF file, which one should I use?
The R and S coefficients are input to the emissivity model in equation 1 and 2 of the PUM. Provided with these coefficients it is possible to compute the near 50GHz sea ice emissivity at vertical and horizontal polarisation and a angles between nadir and about 60 degrees.
The emissivity at vertical polarisation and at 50 degrees, ev, is compatible with the SSMIS sounding channels 1-5 configuration.
The nadir emissivity, e, is compatible with the mid-swath AMSU configuration.
The emissivity near the edges of the swath will be lower than the nadir emissivity.
Which new features should I be aware of?
- The effective emitting layer temperature in addition to the emissivity. The variable name is Effective Temperature (teff). The sea ice self emission brightness temperature is the product of the emissivity and the effective temperature. The effective temperature is computed using an empirical algorithm and the 6 and 10 GHz data from the AMSR2 instrument.
- Spatially and temporally varying uncertainties to the emissivity product. The variable name is Uncertainties (u). Uncertainties are provided for the user to estimate the quality of each individual data point.
- We also updated the emissivity algorithm coefficients. This was done to minimize biases between the new daily and continuous validation methodology and the emissivity product.
Today's product file is empty or has large data gaps, what happened?
There are two possible reasons for missing data:
- In case of interrupted data link with the satellite operating centres, no input swath data are available for processing of sea ice drift data inside the time constraints, resulting in an empty grid.
- The data point values are outside of model range.
What is the legend used for the quicklooks?
Quicklooks for the product can be viewed from this page.
Where can I find the emissivity for Antarctic regions?
The product is global and covers sea ice and ice shelves in the Arctic and the Antarctic.
I do not fancy NetCDF, do you have other formats?
The processing chain is currently only producing NetCDF files. Please let us know (contact) if you need another format.
Validation of OSISAF can be found in the product specific validation report, also referred to in Documentation and links, below.
4. Documentation and links
The following documentation is available, further describing the OSI-404 sea ice emissivity product.
Quicklooks for this dataset can be accessed from this page.