Geography Reference
In-Depth Information
Figure 9-8:
Conditions asso-
ciated with El
Niño (top) and La
Niña (bottom).
Living Under Pressure
You're under pressure all the time — atmospheric pressure, that is. Just about everybody has
seen a weather map with big “H's” and “L's” here and there. And just about everybody knows
that they respectively stand for: high pressure and low pressure. But just about nobody under-
stands what exactly they mean, except maybe that lows are associated with cloudy, rainy (or
snowy) days, and highs usually are associated with pleasant, sunny days.
A
low-pressure system
is an area of relatively warm, moist ascending air. A
high-pressure system
is
an area of relatively cool, dry descending air (see Figure 9-9). In general, therefore, you can think of
low pressure as being a rainmaker, and high pressure as a drought-maker.
