Satellite Winds
Tracking Clouds
Here is a fun exercise to experiment with deriving winds by tracking cloud features
between two visible satellite images.
Instructions: Below applet diplays two images that are 30 minutes
apart. You can switch between the two images by using the step button below the images
(yellow indicates which image you are on). You can also tell which image you are on
by the color of the markers, yellow indicates which target indentifier (cross or X)
will be moved, and blue indicates the other target indentifier marked on the other
image that's not being displayed.
The "cross" and "X" are your target identifiers. You can move these markers by placing
your cursor over them and holding down the left mouse button and drag until you find
a cloud feature to track. You could also simply click on a cloud feature to move the
active marker (in yellow) over.
At the top of the image are listed three variables:
Time: This gives the time of the image you are currently viewing.
Bearing: This gives the compass orientation between the cross and X, and thus
will give your wind direction.
Distance: This gives you the distance between the cross and X, and can be used
to calculate wind speed (if you chose your targets correctly).
Computing wind speeds: You can compute the wind speed by dividing the
distance between targets by the time between the images. Be sure to check your units!
(Do you want your speed to be in miles per hour, kilometers per hour, or kilometers
per minute?)
Note that at each station, the current weather (symbol) and visibility (in miles) are plotted.
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