Wednesday, June 13, 2018

The following message has been forwarded to all registered PO.DAAC users on behalf of the KNMI Scatterometer Team. Please direct all related inquiries to

Dear wind product user,

We are planning to upgrade the near-real time OSI SAF and EARS ASCAT 25 km and 12.5 km winds in September of this year. The current products are still being produced with the previous CMOD5n geophysical model function and the products contain real 10m ECMWF background model winds as auxiliary data. We will upgrade the processing and start using the CMOD7 geophysical model function. CMOD7 was developed to take out incidence-angle dependent effects in CMOD5n. It improves the consistency of the scatterometer retrievals across the instrument swath. Moreover, the products will contain stress-equivalent ECMWF winds, which are known to better resemble the scatterometer winds. 

Until the operational products will be upgraded in September (the exact date will be communicated later), we will be providing a parallel data stream on the KNMI FTP server, so that you can evaluate the products. The product improvement is stated as follows in the validation report: looking at the global bulk statistics as obtained from comparisons with ECMWF model winds and buoy winds, the new products show a slight improvement as compared to the old ones. However, the improvements when looking at specific regions, colder and warmer areas, and certain wind speed domains are more distinct.                                                                                                       

The parallel test products (25 and 12.5 km) can be found in these directories at the KNMI FTP server ( /scat/ascat_a_osi_cmod7_test (Metop-A) and /scat/ascat_b_osi_cmod7_test (Metop-B). If you don't have access to this server (yet), please send a request to and we will provide you with the credentials. The data formats will not change.                                                                                                            

The updated user documentation can be found here:

ASCAT wind validation report:

ASCAT Wind Product User Manual:

Algorithm Theoretical Basis Document for the OSI SAF wind products:

The assets of CMOD7 and stress-equivalent model winds have been published in peer-reviewed papers:

Stoffelen, A., J. Verspeek, J. Vogelzang and A. Verhoef, The CMOD7 Geophysical Model Function for ASCAT and ERS Wind Retrievals

IEEE Journal of Selected Topics in Applied Earth O, 2017, 2123-2134, doi:10.1109/JSTARS.2017.2681806.

De Kloe, J., A.C.M. Stoffelen and A.H. Verhoef, Improved Use of Scatterometer Measurements by Using Stress-Equivalent Reference Winds

IEEE Journal of Selected Topics in Applied Earth O, 2017, 10, 5, 2340-2347, doi:10.1109/JSTARS.2017.2685242.

Please don't hesitate to contact us at if you have any further questions.

Best regards,

Anton Verhoef

KNMI Scatterometer Team

For global wind products:

EUMETSAT Ocean and Sea Ice SAF

For scatterometer processing software:

EUMETSAT Numerical Weather Prediction SAF

For timely ASCAT regional wind products:


For other scatterometer matters contact: