Transcript 19.2 Pressure Centers & Winds / 19.3 Regional Wind Systems

Highs & Lows
0 Cyclones – centers of LP
0 In cyclones, the pressure DECREASES from
the outer isobars toward the centers.
0 In anitcyclones, the isobars INCREASE from
the outside toward the center
Cyclonic & Anticyclonic Winds
0 When Pressure Gradient & Coriolis Effect are
applied to pressure centers in the NH, winds
blow inward & counterclock wise around a
low. Around a high they blow outward &
clockwise
0 2 Most Significant factors that affect wind are
0 Pressure Gradient
0 Coriolis Effect
Weather & Air Pressure
0 Rising air = clouds & precipitation
0 Sinking air = clear skies
Global Winds
0 The atmosphere balances these differences by acting
as a giant heat transfer system.
0 This system moves warm air toward higher latitudes
& cool air toward the equator (BALANCE)
0 Trade Winds
0 Westerlies
0 Polar Easterlies
0 Polar Front
NON ROTATING MODEL
ROTATING MODEL
Influence of Continents
0 ONLY true continuous pressure belt is the
subpolar low in the SH (bc its uninterrupted)
0 Monsoons – seasonal reversal of wind
direction associated with large continents,
esp. Asia
0 Winter = winds blow from land to sea
0 Summer = winds blow from sea to land
Review Questions
0 How do winds blow around pressure centers in the
NH?
0 Compare and contrast cyclone & anticyclone
0 Describe how the atmosphere balances the unequal
heating of Earth’s surface.
0 What is the only TRUE continuous pressure belt?
19.3 Regional Wind Systems
Local Winds
0 Caused by either topographic effects or by
variations in surface composition in the
immediate area
0 Coastal land is heated more than the water
during the day causing air above the land to be
warmer and rising = lower pressure areas
0 On mountains, the air along the slope is
heated more than the same elevation over the
valley
How Wind is Measured?
0 2 Basic Measurements: direction & speed
0 North winds blow from the N to the S
0 East winds blow from the E to the W
0 Instrument used to determine wind direction
= vane
0 In US westerlies are always moving weather
from W to E across the continent
0 Instrument used to measure speed:
anemometer
El Nino & La Nina
0 Southern Oscillations – irregular intervals of 3
– 7 yrs., warm countercurrents become
unusually strong & replace normally cold
offshore waters with warm water from
equator -> El Nino
0 La Nina – opposite – researchers have come to
recognize that when surface temps. In the
eastern Pacific are colder than avg. La Nina is
triggered
Review Questions
0 What are locals winds and what are they caused from?
0 Describe the general movements of weather in the US
0 How is La Nina recognized?