Monday, May 20, 2013

The Universe of Cumulus

For lovers of clouds, you don't get many days better than today.  Some probably like big cumulonimbus clouds, but I prefer a mixture and today we have just about everything from the cumulus humilis (a.k.a. cumulus patheticus) over extreme northwest Utah and northeast Nevada to cumulus congesus over northeast Utah.  There's also evidence of cloud bands downstream of the Great Salt Lake.

Watching this look you can learn a lot about the wind structure today.  Track the clouds to ascertain the wind direction.  You can find easterlies near the Uinta Mountains and North–Northeasterlies over and south of the Great Salt Lake.  You can also infer a lot about the temperature of the lakes of northern Utah.  The Great Salt Lake appears to be contributing to the initiation of cloud bands, whereas there is a clear cloud hole over and downstream of Bear Lake for much of this loop.  Presumably the Great Salt Lake is warm enough to destabilize the atmosphere, whereas Bear Lake is colder and thus the atmosphere is more stable over and downwind of it.

Meteorologists have developed computer programs that track cloud elements to infer the wind.  Using the cloud toop temperature derived from infrared satellite imagery, one can also estimate the height of the wind.  Here's an example of cloud track winds over the eastern Pacific today, with the color coding providing an estimate of the layer of the inferred wind.

Source: Naval Research Lab
These winds can be assimilated into computer models to improve their initial conditions.  Some day we may have space borne laser-based systems to further aid wind measurement, but until then, we'll squeeze all we can out of the available observations.  

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