Weather Notes

Weather Data Technology--

1.      weather satellites---

·        orbit Earth, providing images of the movement of clouds, storms, water vapor, air masses

2.      Doppler radar---

·        located on Earth’s surface gather data by sending out radio signals that are reflected off objects such as raindrops, snowflakes, hailstones, or clouds

·        detects the type and amount of precipitation, location, height, and movement of clouds

3.      Government agencies---

·        NOAA (National Oceanic and Atmospheric Association) and NWS (National Weather Service)

·        gather weather data from around the world

·        make computer models and maps that can show and predict weather changes

·        Meteorologists use data to make a forecast for the local area.

·        A weather forecast is a prediction of future conditions based on observations and data.

Earth’s Seasons ---

4.      revolution---movement of Earth around the sun in its orbit (one year)

5.      rotation---Earth takes 24 hours to complete one rotation (one day)

·        Earth spins on its axis

·        An axis is an imaginary line that runs through the center from one pole to the other pole

6.      tilt---The Earth’s axis is tilted from perpendicular to the plane by 23.45°.

·        gives us the four seasons

·        the weather changes through the seasons because the revolves around the sun

·        Earth’s axis tilts different parts of Earth toward or away from the sun at different points in Earth’s orbit.

·        When the Northern Hemisphere is tilted toward the sun, the Southern Hemisphere is tilted away from the sun. It is summer in the hemisphere titled toward the sun. It is winter in the hemisphere tilted away from the sun.

·         solstice---a point in Earth’s orbit when a hemisphere is tilted as far as possible toward or away from the sun. In the Northern Hemisphere---winter solstice is Dec. 21 or 22; summer solstice is June 20 or 21

·         equinox---a point in Earth’s orbit when the planet is tilted neither toward nor away from the sun. The vernal equinox or first day of spring occurs in the Northern Hemisphere on March 20 or 21. The autumnal equinox or first day of fall occurs in the Northern Hemisphere on Sept. 22 or 23.

Climate Zones---

         Earth has three major kinds of climate zones---tropical, temperate, and polar

·   temperature and precipitation are key factors

·   major climate zones are determined by latitude or distance north/south of the equator

a.        tropical zone---closest to equator

Ø      tend to be warm to hot year-round

Ø      receive direct sunlight throughout year

b.      polar zones---farthest from equator

Ø      near Earth’s North and South Poles

Ø      least direct sunlight throughout year

Ø      tend to be cool to cold year-round

c.       temperate zones---located between polar and tropical

Ø      angle at which the sun’s rays strike these regions changes greatly throughout the year

Ø      distinct seasons with very different temperatures

Heat Transfer, Weather, and Wind--

7.      convection current---circular flow of gas or liquid caused by temperature differences

·        heat moves warmer to cooler

·        continuous movement of rising warm air and sinking cool air

·        sun sets currents in motion by heating Earth’s surface unevenly (more heat near equator)

·        When air gets warmer, the molecules move faster and spread farther apart.

·        causes sea and land breezes

·        Higher, cooler air sinks since it is denser than warm air

·        After it sinks, the cooler air is warmed by the hot sand, becomes less dense and rises.

8.      sea breeze---

·        sun warms the land more quickly than water

·        heat moves from land to the air above it so the air expands and rises

·        denser, cooler ocean air moves in over land

·        hot sand warms cool ocean air which will rise and makes room for more air to move in off the ocean

9.      land breeze---

·        cool air over land moves toward the ocean

·        air cools at night

·        cools faster over land

·        cooler, denser land air moves out into the warmer, less dense ocean air

·        cool air pushes the warmer air up and toward the land; then cools and sinks

         Wind--

10.  Global winds---winds created by the heating of the sun and spinning of Earth

·        that blow steadily for thousands of kilometers

·        steer weather in certain direction

·        solar energy absorbed near equator warms air forming large areas of low pressure

·        warm air rises as the colder air near the poles sinks forming high pressure areas

A.     polar easterlies--- cold, dense air moves away from the high pressure areas around the poles and curves west

Ø      extend from the poles to 60° latitude.

Ø      In the Northern Hemisphere, the polar easterlies bring cold arctic air down over the United States. This arctic air brings snow and freezing weather.

B.     trade winds--- warm, rising air at the equator moves away from the equator

Ø      Winds that blow toward the equator from 30° latitude

Ø      Cooler air north and south of the equator moves toward the low pressure area at the equator. This cooler air makes up the trade winds.

Ø      In both hemispheres, the Coriolis effect causes these winds to curve.

C.     westerlies---winds that flow from west to east and toward the poles

Ø      between the polar easterlies and the trade winds

Ø      found between latitudes of 30° and 60°

Ø      The westerly wind belt carries storms across the United States.

11.  Coriolis effect---paths of winds and ocean currents curve due to Earth’s rotation

·        rotation or spinning of Earth on its axis plays a role in wind patterns

·        weather tends to move in curving, circular patterns

·        In the Northern Hemisphere, winds moving north curve to the east and winds moving south curve to the west.

·        Weather forecasters need to know this to predict where winds and air masses are likely to go.

·        At every 30° latitude, the Coriolis effect causes winds to curve in a different direction.

12.  jet streams---high in the atmosphere, flowing from thousands of kilometers from west to east

·        can reach speeds up to 400 kilometers per hour

·        do not follow regular paths around Earth

·        move north and south over time