Meteorologists use mathematics and statistics to analyze weather data for patterns and deviations. An example of one pattern: people who live in desert areas typically experience bigger daily temperature ranges than people who live in other regions. The Heat Index of how hot it "feels" is mathematically calculated from humidity AND temperature. This supports our observation that a 90° day in the dry Chihuahuan Desert feels cooler than a 90° day in Houston!
Desert weather also involves probability, but what does a forecast of
"70% chance of rain" REALLY mean? It doesn't mean that 70% of the land
will get wet. It is a statement of historical data—that 70% of the days with these
weather conditions resulted in rain. If it does NOT rain tomorrow, that doesn't
mean that the forecaster was WRONG—it's still true that it rains on about 70% of
days with these conditions. Of course, forecasts of 70% chance of rain would be rare in
the desert!
Contributor: Lawrence M. Lesser, Mathematical Sciences, 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.