Answer
What are cloud drift winds?
Geostationary satellites track winds in the upper atmosphere by observing the movement of
image features in time. The distance traveled by a feature in the time between images is the speed.
The height of the feature is often determined from its temperature. We reference features, because
while clouds are easy to track by our eyes, features in water vapor imagery are easier to track
with a computer and provide information on upper level winds in the absence of clouds. Examples
of operational cloud drift winds are available on the
NESDIS website.
How do I access NCDC-archived cloud drift wind files?
What is the format of the NCDC-archived cloud drift wind files?
Data are stored in flat-binary files. Data records contain information for one wind observation and the
number of records per file is deduced from the file size. A record is 200 bytes which consists of 18 4-byte
integers containing data followed by 32 4-byte integers containing zeros. The following table describes
the data within the first 18 integers.
The information in this table is provided as guidance and is not to be considered the final documentation
of the data. This was derived from page 165 of the GOES Satellite Derived Winds Processing System (HD WINDS)
Programmer Maintenance Manual.
0 |
Date of observation |
YYYYMMDD |
1 |
1 |
Time of observation |
HHMM (UTC) |
1 |
2 |
Date created |
YYYYMMDD |
1 |
3 |
Time created |
HHMM (UTC) |
1 |
4 |
Pressure Level of the Obs. |
mb |
10 |
5 |
Temperature |
Kelvin |
1 |
6 |
Latitude |
Degrees North |
100 |
7 |
Longitude |
Degrees West |
100 |
8 |
Wind Direction |
Degrees East of North |
1 |
9 |
Wind Speed |
meters / second |
10 |
10 |
Unknown |
|
|
11 |
Unknown |
|
|
12 |
Unkown |
|
|
13 |
Unknown |
|
|
14 |
Unknown |
|
|
15 |
Unknown |
|
|
16 |
Unknown |
|
|
17 |
Unknown |
|
|
To convert the integer value to the actual value, divide by the scale.
An IDL routine is also available which will read the data.
|