starpath.com/ascat

We have an extended discussion of how to use ASCAT wind data in our textbook
Modern Marine Weather, 3rd ed.

With internet connections you can obtain these data in graphic format direct from

Ocean Surface Winds Team (OSWT).

The above source has the attractive property of using the same file name for any specific location, which makes it easier to automate the downloads. We can also see the data from the

KNMI Scatterometer Team.

The Metop satellites (A,B, and C) are operated by EUMETSAT and the raw data are provided to both KNMI in the Netherlands to analyze for European agencies and to NOAA/NESDIS for processing here for US use. The basic scatterometer data analysis software used is the same, but each lab has modifications, which may yield slightly different winds ocassionally. The valid times of the data should be the same. We have to check yet on the latency—that is, how long does it take each lab to get the data out. The images below compare the two presentations. You can click the image for a zoomed view.

Left are two US images, stacked one on top of the other; on the right is one from KNMI. The KNMI images are larger and higher resolution, but it remains easier to read actual wind speeds from the US colorbar, noting the wind speeds at which the colors change.

Other ASCAT related resources

• ASCAT Manual from EUMET

• Video: Introduction to ASCAT

• How to get ASCAT graphic data via Saildocs

• Predicting the times of ASCAT (Metop) passes

See also PC program Orbitron, and lizard-tail web page (change the Metop-A number from 29499 to 38771 for Metop-B, or to 43689 for Metop-C)

• How to make an auto-updating overlay of ASCAT data in Google Earth. These KML files can also be imported into qtVlm for comparison with model forecasts in grib format

• Loading auto-updating, georeferenced ASCAT data into qtVlm

• Frequency of ASCAT Data at a Specific Position

• ASCAT data in Grib format: on hold for awhile... maybe gone permanently?

Get ASCAT data in GRIB format directly from NCEP (this service is unfortunately down without promise of when it will be fixed. It is apparently controled by OPC.)

When they were available as GRIB data they could also be downloaded directly from within the few programs that are capable of viewing the data. At last check this was.

LuckGrib (Mac or iOS) video: ASCAT in LuckGrib

Expedition (PC) video: ASCAT in Expedition

(The above commercial products are the most convenient way to obtain and view ASCAT data in GRIB format, but the GRIB data—when available—can be viewed in the public program Panoply, but it takes a bit of patience, as shown in this video.)

At present the fastest way to see this data (meaning nearest time to when the satellite actually went by measuring the winds) at a specific region on earth is to set up the 6 links to get you the graphic data for A, B, and C both ascending and descending. Other scatterometer sources have not been dependable.

Ascending pass above; descending pass below. (Satellite tracks curve west as the earth rotates to the east below the polar orbit.)

The valid universal times (UTC, same as GMT) of these maps are listed in small purple numbers at the bottom of the figures. These samples are from a set of passes that span the time period T1 to T2, where T2 = 0414 Sept. 26, 2012, and T1 is 22 hr earlier, which would be T1 = 0614 Sept. 25, 2012. The pass times for these samples (0704, 0845 and 1931, 2111) would therefore all be for Sept. 25.

The 22-hr data sets are updated every hour, so the 2111 pass is the most recent, being (0414 Sept. 26 - 2111 Sept. 25) about 7h 03m old.

Be aware of the file sizes when downloading the wind maps by satellite phone.