Data Set ID:

NOAA/NSIDC Climate Data Record of Passive Microwave Sea Ice Concentration, Version 4

This data set provides a Climate Data Record (CDR) of sea ice concentration from passive microwave data. The CDR algorithm output is a rule-based combination of ice concentration estimates from two well-established algorithms: the NASA Team (NT) algorithm (Cavalieri et al. 1984) and NASA Bootstrap (BT) algorithm (Comiso 1986). The CDR is a consistent, daily and monthly time series of sea ice concentrations from 25 October 1978 through the most recent processing for both the north and south polar regions. All data are on a 25 km x 25 km grid.

Notice: The Version 3 Sea Ice Concentration CDR data will continue to be available through December 2021. You can access the Version 3 data from the Version 3 Sea Ice Concentration CDR data set landing page.

Note: A near-real-time version of this data set also exists to fill the gap between the time that this data set is updated through to the present. The data set is called the Near-Real-Time NOAA/NSIDC Climate Data Record of Passive Microwave Sea Ice Concentration (

This is the most recent version of these data.

Version Summary:

* CDR now begins 25 October 1978
* NSIDC-produced daily and monthly NASA Team (NT) and NASA Bootstrap (BT) variables are new included
* Four variables in the daily files and four variables in the monthly files have been renamed.
* Goddard-produced variables were removed
* Yearly aggregated files containing daily data and period-of-record aggregated files containing monthly data are available in addition to the daily and monthly NetCDF files.
* Gap filling implemented using spatial and temporal interpolation
* Arctic pole hole filled by spatial interpolation
* NSIDC’s BT algorithm has been updated to use Goddard’s BT version 3.1 algorithm
* Updated the NASA Team weather filter threshold for the Southern hemisphere instruments.
* In addition to the BT weather and land spillover filters, the NT filters are now also applied.
* Individual land masks have been merged into one composite land mask.

COMPREHENSIVE Level of Service

Data: Data integrity and usability verified; data customization services available for select data

Documentation: Key metadata and comprehensive user guide available

User Support: Assistance with data access and usage; guidance on use of data in tools and data customization services

See All Level of Service Details

Data Format(s):
  • NetCDF
Spatial Coverage:
N: 89.84, 
N: -39.36, 
S: 31.1, 
S: -89.84, 
E: 180, 
E: 180, 
W: -180
W: -180
Platform(s):DMSP 5D-2/F11, DMSP 5D-2/F13, DMSP 5D-2/F8, DMSP 5D-3/F17, Nimbus-7
Spatial Resolution:
  • 25 km x 25 km
Sensor(s):SMMR, SSM/I, SSMIS
Temporal Coverage:
  • 25 October 1978 to 31 December 2020
Temporal Resolution1 day, 1 monthMetadata XML:View Metadata Record
Data Contributor(s):Meier, W. N., F. Fetterer, A. K. Windnagel, and J. S. Stewart.

Geographic Coverage

Would you like to receive updates and notifications regarding this data set? Subscribe below and stay informed. PLEASE NOTE: You only need to fill this form out once.

FTP data can be downloaded through a Web browser (Firefox or Edge are recommended) or command line via FTP. For help downloading data through an FTP client, go to the How to access data using an FTP client support page.

As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.

Meier, W. N., F. Fetterer, A. K. Windnagel, and J. S. Stewart. 2021. NOAA/NSIDC Climate Data Record of Passive Microwave Sea Ice Concentration, Version 4. [Indicate subset used]. Boulder, Colorado USA. NSIDC: National Snow and Ice Data Center. doi: [Date Accessed].

It appears your Web browser is not configured to display PDF files. Download adobe Acrobat or click here to download the PDF file.


Descriptions of and Differences between the NASA Team and Bootstrap Algorithms
NSIDC currently archives passive microwave sea ice concentration products based on two algorithms: the NASA Team algorithm and the Bootstrap algorithm. Both algorithms were developed by researchers at the NASA Goddard Space Flight Center in the 1980s. Provided below are two short summaries of the... read more

How To

How to access NOAA@NSIDC data sets in PolarWatch
Currently three NOAA@NSIDC data sets are available in NOAA's PolarWatch Data Catalog. Please note that in the catalog the Climate Data Record (CDR) data sets are split up into Antarctic and Arctic data sets: NOAA/NSIDC Climate Data Record of... read more