Local

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Local Regional Winds

• The Water Cycle
• Local Winds
• Measuring Winds

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Objectives

• Diagram the movement of the water cycle.
• Discuss the specific conditions that cause the
  different kinds of local winds
• Explain how the surface of the Earth can affect
  surface pressure
• Describe the general movement of weather in the
  US
• Identify how wind speed and direction are
  measured
• Explain the process that leads to and el Niño and
  la Niña describe the effects of both of these
  whether phenomena

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The Water Cycle

• At any one time, only a small percentage of water
  is present in the atmosphere.

This water continually moves between the
atmosphere and Earths surface. The water cycle
is the constant movement of water between the
atmosphere and Earths surface.
Evaporation is the process of water changing
from a liquid to a gas.
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The Water Cycle
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Local Winds

• Local winds- any movement of air produced by a
  locally generated pressure gradient typically
  caused by one of the following
• Topographic effects (mountains/valleys)
• Surface composition (covered with vegetation or
  not, land or water, snow and ice, etc.)

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Land and Sea Breezes

• Due to the uneven heating of land and water,
  coastal areas tend to generate pressure
  differences that cause local breezes.
• Sea breezes occur during the day when land is
  warmed which heats the air above it, causing it
  to expand and rise. Cooler air from the water
  (ocean, lake, etc.) moves in to fill the low
  pressure left behind as the heated air rises.
• Land breezes occur during the night when latent
  heat is released from the water, causing the air
  above it to expand and rise. Air from the land
  moves in to fill the low pressure left behind as
  the heated air rises

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Sea Breezes
L
H
Energy Releasing Land
Energy Absorbing Water
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Land Breezes
H
L
Energy Gaining Land
Energy Releasing Water
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Valley Breeze

• Valley Breezes occur during the day when air is
  heated in a valley and expands. The less dense
  air rises and creates a wind as it moves out of
  the valleys and into the hills/mountains. Cumulus
  clouds are associated with these.

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Mountain Breezes

• Mountain breezes occur at night when air cools
  over the exposed ground. This cool layer of air
  contracts, becomes more dense and flows down into
  the valleys

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Measuring Wind Speed

• When measuring wind speeds, the two most
  important components are speed and direction
• Speed-distance per unit time (km/hr)
• Direction- always measured from the direction the
  wind is blowing

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Measuring Winds

• Prevailing winds- describes a wind that
  consistently blows more often from one direction
  than from any other direction
• In the US, the prevailing wind direction is from
  the west, caused by the westerlies.
• Anemometer (L. Anemowind)- a device that is
  commonly used to measure wind speed.
• Wind Power- a renewable energy source that is
  most commonly generated in areas where
  consistent, relatively high winds are found.

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Wind Power and Anemometers
A wind Farm in Southern California
A cup Anemometer
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El Niño

• El Niño- a weather phenomena that occurs at
  intervals of 3-7 years in which the normal east
  to west, cool water movements of the Pacific
  Ocean reverse and warm, west to east
  countercurrents drive unusual weather patterns in
  N S America
• Often block cooler, nutrient rich waters, causing
  a decline in the oceanic ecosystem fisheries are
  affected. Dry areas often receive higher than
  average rain
• The reversal of water currents causes the polar
  jet stream and the subtropical jet stream to move
  further north over North America

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La Niña

• La Niña- the opposite of el Niño where surface
  temperatures of the Pacific become colder than
  normal Brings colder than normal weather to the
  Pac NW as well as higher than average rainfall.
• Tends to bring nutrient rich waters which
  increase fish populations and increase ocean
  ecosystems

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