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Medium Resolution Sea Ice Drift product (OSI-407-a)

Two sea ice drift product are part of the Ocean and Sea Ice SAF product's portfolio. A low resolution and a medium resolution product (this product). It is based on visible and infrared data from the Advanced Very High Resolution Radiometer on board a Metop satellite.

The spatial resolution is 20 km on a Polar Stereographic Grid similar to other OSISAF sea ice products. It is an approximately 24 hours ice drift dataset processed four times a day, which means that a product file measuring sea ice motion between e.g. midday on the 16th and 17th of February is available before 18:00 hours on the 17th. The product is based on a Maximum Cross Correlation technique on swath data.

  1. Introduction and FAQ
  2. Algorithms
  3. Validation
  4. Documentation and links

1. Introduction and FAQ

How should I cite this dataset?

This dataset shall be referred to as the Medium resolution sea ice drift product of the EUMETSAT Ocean and Sea Ice Satellite Application Facility (OSI SAF, www.osi-saf.org). Or, just: EUMETSAT OSI-407-a ice drift.

Which satellite sensors are processed?

The sensors and channels used are AVHRR VISible and InfraRed (channel 2 and channel 4) on board EUMETSAT platform Metop-B.

What is the spatial resolution of this product?

The medium resolution sea ice drift product is a gridded dataset. The grid has 20 km spacing on a Polar Stereographic projection mapping. Definitions for the projection parameters can be found in the NetCDF files as well as in the Product User's Manual.

What is the time-span of this product?

One day (24 hours). This is the time delay between the start and the stop time of the motion described by one vector. As the product is based on swath data the valid time between 2 swath, and thus the ice drift period, can vary up to 1 hour.

From the datasets distributed every day, which one should I use?

The medium resolution ice drift product is based on single sensors, either on VIS (channel 2) or on IR (channel 4) data. The IR data are used during the cold period where the temperature difference between water and ice surface typically is large and the VIS data are used during the warm period where the albedo difference between water and ice surface is large. VIS and IR data production cover the month of MJJA and SONDJFMA, respectively.

Today's product file is empty or has large data gaps, what happened?

Three possible answers to missing ice drift data:

  1. In case of interrupted data link with the satellite operating centers, no input swath data are available for processing of sea ice drift data inside the time constraints, resulting in an empty grid.
  2. Clouds and high atmospheric water in general, cause no surface data available for feature tracking.
  3. The ice drift vector filtering routine has excluded drift vectors.
In general - the number of successfully processed ice drift vectors from this product is strongly varying with the time of year, such that the cold winter month is the period of the by far highest number of successful ice drift vectors. This is due to frequent atmospheric opacity in the warmer period. In all cases, the status_flag dataset in the product file indicates the reasons for missing data.

Where can I find the ice motion for Antarctic regions?

This product does not cover sea ice motion in the Southern Hemisphere as the atmospheric conditions there hamper the use of optical data for surface applications. However ice drift in Southern Ocean is monitored by the Low Resolution ice drift product from OSISAF, the OSI-405-c Ice Drift Product.

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 and we will guide you to find a solution.

2. Algorithms

The algorithm used for the medium resolution ice drift product is an ordinary Maximum Cross Correlation (MCC) Technique (See the Algorithm Theoretical Basis Document).

3. Validation

Validation of OSI SAF data can be found in the product specific Validation Report, also referred to in Documentation and links, below. A half yearly validation report is written and can be made available on request. In a Visiting Scientist report the quality of this product is compared with other ice drift products.idation results presented here are taken from the visiting scientist report referred to below. Other validation data 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-407-a ice drift product.
Quicklooks for this dataset can be accessed from this page.