Meteorology – the study of weather

1. Weather…Part 1 Meteorology – the study of weather • Here are some variables that are a part of predicting the weather: • Air Temperature – depends on AOI, DOI, and IOI (thermometer) • Air Pressure – the force exerted by the air overhead (barometer) • Humidity – the amount of moisture in the air (hygrometer) • Wind Speed – (anemometer) • Wind Direction – (wind vane or weather vane) • Atmospheric Transparency- how clear the air is (ceiling) • Visibility – how far ahead you can see (in miles) • Wind Chill – how cold it feels (combo of temp. and wind) • Dew Point Temperature – the temp. air needs to cool to, in order for condensation to happen (cloud forms) All of these variables interact in the troposphere. Mrs. Degl

2. People cannot accurately predict weather after 36 hours, b/c there are too many weather variables working and changing at the same time. • The atmosphere gains energy in four ways: • Direct absorption of Insolation from the Sun- Only 19% of the atmosphere’s heat comes from direct absorption. • Change of Phase reactions- Condensation and Sublimation release energy to the atmosphere. • Terrestrial Radiation – the Earth releases heat (Infrared) as it cools off at night. • The Greenhouse Effect – Carbon Dioxide and Water Vapor in our atmosphere trap heat that is trying to escape into space. All of the energy that is gained by the atmosphere is distributed throughout the rest of the atmosphere by Convection Cells orConvection Currents. Mrs. Degl

3. Adiabatic Temperature Change – a change in temperature of the air due to it expanding and contracting, not being cooled or heated. As air rises, it expands (spreads out), it’s volume increases, and it’s temperature decreases after a while of being away from the warmer surface. As air sinks (falls), it contracts (compresses), it’s volume decreases, and it’s temperature increases after a while of being back on the surface of Earth where it is warmer. Memorize this!!!!!!!! Mrs. Degl

4. Mrs. Degl

5. Air (Barometric)Pressure The force exerted by the column of air overhead • Air pressure is influenced by: • Air temperature • Elevation above sea level • How much moisture is in the air. 1. As air temperature increases, air density decreases, so air pressure also decreases. Hot air has a lower air pressure. As air temperature decreases, air density increases, so air pressure also increases. Cold air has a higher air pressure. Mrs. Degl

6. 2. As elevation increases (you get higher above sea level), air pressure decreases, because there is less air over your head. As elevation decreases (you get closer to sea level) air pressure increases, because there is more air over your head. 3. Dry air is made of mostly Nitrogen. As air becomes moister, Water Vapor replaces the Nitrogen. Water vapor is less dense than Nitrogen. So, moist air has a lower air pressure than dry air. Moist air is better and easier to breath. Mrs. Degl

7. We need to learn how to code and un-code air pressure values in order to use and create weather maps. Meteorologists do not put the real air pressure values on the weather maps because the numbers are too long and take up too much space on the map. They use a abbreviation system. • How to read the air pressure numbers on a map: • If the air pressure (in millibars) is below 500, put a 10 in front of the number and a decimal between the last two digits. This number is the real air pressure. • If the air pressure number is above 500, put a 9 in front of it and a decimal between the last two digits. • How to put air pressure numbers onto a weather map: • Remove the 9 or 10 and the decimal in front of the the air pressure number. • Place that number of the weather map in the correct spot. Mrs. Degl

8. Wind – the horizontal (parallel) movement of air. • Facts about wind: • Winds are caused by differences in air pressure between two locations. This difference in air pressure is caused by the differences in temperature between two locations. So, in other words, winds are caused by the unequal heating of the Earth. The larger the difference in pressure, the stronger the wind. • 2. Winds blow from areas of High Pressure to Low Pressure. • Winds blow from areas of Divergence to Convergence. • Winds are named after the direction that they are blowing from, not where they are blowing to. • Surface ocean currents (not tides) are caused by wind direction. • Wind direction is also influenced by the Coriolis Effect (Rotation). Winds curve to their right in the Northern Hemisphere, and to their left in the Southern Hemisphere. Mrs. Degl

9. Landbreezes and Seabreezes During the day, the land heats up faster than the water. The air over the land has a lower density than the air over the water. Because of this, the air over the land rises. There is now an empty spot over the land, so the air over the water fills it in. That is why the breeze always comes off of the water during the day. This is a seabreeze. At night, the land also cools off quicker than the water. This causes the water to have a higher temperature than the land. So, the air over the water now has a lower density and it rises. Now the air over the land must fill the empty spot. This is why the breeze blows from the land to the water at night (it comes from behind). This is a landbreeze. Mrs. Degl

10. Wind and Pressure Belts Areas of Convergence – where the winds collide (0°, 60°N and 60 °S). These latitudes are very wet and have a lower air pressure. Areas of Divergence – where the winds blow away from each other. (30°N, 30°S, 90°N, 90°S) These latitudes are dry (deserts of the world) and have a much higher air pressure. Mrs. Degl

11. Prevailing Winds – zones on the Earth’s surfacewhere winds tend to blow in the same direction over long periods of time. The prevailing winds in NYS are called the southwesterlies (they blow from the SW). See page 14 ESRT’s. Jet Streams – a narrow zone of very strong winds in the upper atmosphere (troposphere). The Jet Streams steer weather systems across the world. The Jet Stream in the USA steers weather from West to East. The Jet Stream tends to migrate north in the summer and south in the winter. Mrs. Degl