19.2 Pressure Centers & Winds

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?