WHAT IS DROUGHT? Drought is a common feature of climate, occurring in areas all over the globe: it is the result of too little rainfall over an extended period of time, often causing water shortages. What exactly constitutes a drought depends in part on what is normal for the region: a drought in the Amazon rainforest may occur after only a week without rain, whereas the Sahara desert can go for weeks with no rainfall and still not be considered to be afflicted with drought.
HOW A DROUGHT COMES ABOUT: Drought doesn't have a single cause; rather, it happens as several contributing factors converge all at once. But the most immediate cause is high atmospheric pressure. When the air sinks, producing high pressure, this keeps clouds from forming, so there is less humidity and therefore less rainfall. This is often seasonal in many regions of the world, but the Sahara and Kalahari deserts in Africa, and Asia's Gobi desert, for example, experience high pressure for most of the year. How long a drought lasts depends on how the air and sea interact to transfer moisture to the air, and how much moisture the soil retains in a given region, among other factors.
PREDICTING A DRY SPELL: Because there are so many factors that come into play, scientists can't really predict a drought in a particular region more than a month or so in advance. To make a prediction, they need to be able to forecast both rainfall (precipitation) and temperature, yet climate patterns change all the time as the result of the slightest shifts in conditions.
TIPS FOR SAVING WATER:
- Turn off the faucet while shaving or brushing your teeth
- Wash only full loads of dishes and laundry
- Fix dripping and leaking faucets and toilets
- Take shorter showers
- Wash cars less frequently
- Keep fire hydrants closed
- Water lawns and gardens on alternate evenings, not every day
- Raise your lawn mower blade height; longer grass needs less water
The American Geophysical Union contributed to the information contained in the TV portion of this report.