Although infrequent, it does snow in the Chihuahuan Desert. When exposed to the sun, it usually disappears rapidly; after all, even in the dead of winter, the sun is relatively high in the sky in these southern latitudes. We may be puzzled, though, at how long it takes for snow to melt away in shaded locations, even with air temperatures well above freezing.
The reason is the same as why we use ice cubes to cool summer drinks:
it takes a lot of heat to melt a given amount of ice. Of course, the opposite is true,
too: water has to give up a lot of heat before turning solid. Thus, in lands with a lot
of water, temperature extremes are dampened (no pun intended). In our Southwest,
though, another feature of water is at work: water vapor is a greenhouse gas tending to
hold in heat; when its concentration in the atmosphere is low, heat radiates away
rapidly at night, leaving us with the great temperature differences between night and
day so typical of deserts.
Listen to the Audio (mp3 format) as recorded by KTEP, Public Radio for the Southwest.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.