Description
Imagery produced by passive radiometers deployed on geostationary satellites can be used to derive atmospheric wind observations by employing algorithms that track features in a time sequence of images. Wind vectors at low levels can be produced from the visible channel (during daylight hours only); upper and low-level, and some mid-level winds can be generated from the infrared channel, and to improve coverage at mid levels and over cloud free areas, water vapor channels can be used as well.The MADIS satellite wind dataset consists of multiple wind products from different "providers" that are integrated into a single dataset. Currently, these products consist of data from the GOES satellites, including the 3-hour winds that are produced on an operational basis, as well as the rapid scan experimental winds that are produced hourly. Techniques, including quality control, used to derive the hourly winds are (basically) the same as those used to derive the 3-h winds. The main difference in the hourly winds is the geographic coverage. For GOES-E winds the coverage for the hourly, experimental winds is limited to the Continental U.S. (CONUS) scan; for GOES-W the geographic coverage is limited to the Pacific U.S. (PACUS) scan. Use of these scans offers imagery which is separated by 15 minutes, which is very useful for cloud tracking (for IR & VIS). The operational 3-h winds make use of the CONUS & PACUS sectors as well (using the imagery separated by 15 minutes), but also use the Northern Hemisphere (NHEM) and Southern Hemisphere (SHEM) sectors where the imagery is separated by 30 minutes.
Geographic Coverage
GOES-13 is geostationary at longitude 75 W, and provides coverage over the Eastern U.S., Central and South America, and the Atlantic Ocean. GOES-11 is fixed relative to longitude 135 W, to provide coverage over the Western U.S. and the Pacific Ocean.The rapid scan, experimental winds are limited to the continental U.S. (GOES-13) and the Pacific Ocean/Western U.S. (GOES-11).
Data Schedule
The wind products are available on different schedules for the different satellites, and for the different types of wind products. The observation times vary, and the latency ranges from about one and a half to three hours (latency is defined as the time the data are available minus the observation time).In order to get all of the GOES experimental products, you should download the HH:00 file at HH + 15, 25, 35, 75, 85, and 95 minutes, for HH = 00 through 23.
In order to get all of the GOES operational products, you should download files on the following schedule (all times UTC):
Download Time File Time(s) 00:15 23:00 01:25 23:00 01:45 23:00 03:15 02:00 04:25 02:00 05:15 02:00 06:15 05:00 07:25 05:00 06:00 09:15 08:00 10:25 08:00 09:00 12:15 11:00 12:45 12:00 12:55 11:00 12:00 13:25 11:00 15:15 14:00 16:25 14:00 16:35 14:00 16:45 14:00 15:00 18:15 17:00 19:25 17:00 19:35 17:00 18:00 19:45 17:00 18:00 21:15 20:00 22:25 20:00 22:45 20:00 21:00 Volume
Typical daily volume for all MADIS datasets can be seen here.
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