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Chapter 12 Meteorology Section 12.1 The causes of weather Meteorology is the study of atmospheric phenomena. Meteor is Greek for “high in air” Clouds, rain drops, snow flakes, fog, dust and rainbows are known as “meteors” Weather is the current state of the atmosphere (short term) Climate is the long term conditions of the atmosphere in a given region. Average over the course of 30 years. Chapter 12 Meteorology How is the radiation coming to Earth distributed? The continual motion of the air and water distribute the heat energy around the Earth. (nature abhors a vacuum) This difference in temperature creates a pressure difference and therefore a wind (flows from high to low pressure) Chapter 12 Meteorology The Suns rays strike the Earth’s surface at different angles depending on the location and time of year. During the spring and fall equinox (Latin for equal night) the equator receives the Suns direct rays. Chapter 12 Meteorology During the northern hemispheres summer the Sun’s rays are hitting the Earth at 90 degrees at 23.5 degrees North latitude. This is the Tropic of Cancer. In the winter, it is the opposite. The Suns rays will strike the Earth’s surface at 23.5 degrees south latitude. Chapter 12 Meteorology Air mass: A large body of air that takes on the characteristics of it’s source region (area where it develops) Chapter 12 Meteorology The air mass picks up two characteristics from it’s source region. 1. Humidity 2. Temperature Combinations are in your ESRTs! Polar and arctic means cold. Tropical means warm Continental = Dry Maritime = Moist Air mass modification: The air mass begins to take on the characteristics of the region it is traveling over. Front: Boundary between two air masses Section 12.2 Weather Systems Coriolis effect: The wind deflects to the right in the northern hemisphere because the Earth is rotating west to east Section 12.2 Weather Systems Trade Winds: Occur at 30 degrees north and south latitude. Horse latitudes: Region of high pressure and little if any winds. This is an area of wind divergence. *On a side note, sailors who were caught here often tied the horses to their boat to pull them in a desperate effort to escape this windless region. Later, if they were starving, they would resort to eating their cargo (i.e. the horses) Pass the A-1! More sailors lost in the horse latitudes ITCZ (Inter tropical convergence zone): Near the equator the trade winds from both hemispheres come together in an area of convergence. The location of the ITCZ changes with the seasons due to the difference in the angle of insolation (sun light). Here you see the ITCZ shift between January and July These two wind belts flow all the way around the Earth. The Prevailing Westerlies : Wind belts that flow between 30 and 60 degrees North and South latitude The Prevailing Easterlies : Wind belts that flow between 60 degrees and the poles North and south latitude(90 degrees). Jet stream: The narrow band of fast moving (185 km/hr) wind that is high in altitude (10.7-12.2 km) within the westerlies. This diagram is in your ESRTs so you do not have to copy it in your notes! These two wind belts flow all the way around the Earth. The Prevailing Westerlies : Wind belts that flow between 30 and 60 degrees North and South latitude The Prevailing Easterlies : Wind belts that flow between 60 degrees and the poles North and south latitude(90 degrees). Jet stream: The narrow band of fast moving (185 km/hr) wind that is high in altitude (10.7-12.2 km) within the westerlies. So what’s with this picture? You might not believe it the answer! Just read, do not write down... Fugos: Japanese Balloon Bombs of WWII Officially; in the waning days of the Pacific War Japan tried a last ditch ploy to hit the United States with a terror weapon. That weapon was the Balloon Bomb. It was supposed to set fire to the West Coast and drop antipersonnel bombs randomly on the U.S. In research after the war it was found that the Japanese built 15,000 of them but only launched 9,300. A little over 300 Balloon Bomb incidents occurred in the U.S. and Canada. The only casualties were a woman and five kids in By, Oregon on a church picnic, who found and moved one. It exploded, killing them all. Luckily they did not have the technology for the A bomb. Front: Boundary between two air masses. There are four types of fronts. Cold fronts : When a cold air mass pushes into a region of warmer air. They act like a bulldozer and shoves the warm air up and out of the way. The steep slope of the cold front makes the air rise quickly and can generate narrow intense but short lived storms. Cold fronts move twice as fast as warm fronts. After a cold front passes by, cold temperatures are to be expected. Warm front: Advancing warm air displaces cold air creating a gradual slope (unlike the steep slope counter part the cold front). This means air rises slowly and the rain is not as intense but will last a longer period of time over a broader area. After a warm front passes, the area will experience warmer temperatures Stationary Front: Neither the cold front or warm front advances. Rarely intense storms, acts more like a warm front in terms of precipitation patterns. Occluded Front: The front produced when the cold front catches up with the warm front. The precipitation that this causes is often referred to as a “mixed bag”. Warm precipitation then passes through a layer of cold air. Low Pressure systems: Air flows counter clock wise and into a low pressure center, upon converging it rises. What happens to air as it rises??? 1. The temperature decreases 2. The dew point temperature is reached. 3. Water vapor condenses on condensation nuclei 4. Clouds form. If there is enough energy and rapid rising of air storms form 5. If there is enough energy and rapidly rising air, storms form High pressure systems: The direct opposite of low pressure systems. Air flows out, clock wise as air is sinking. If air is sinking, it is stable and increases in air temperature and there fore is getting farther away from the dew point temperature. This results in few if any clouds and cooler temperatures. 12.3 Gathering Weather data Thermometer: Measures temperature Barometer: Measures air pressure (AKA barometric pressure) Anemometer: Measures wind speed Hygrometer: Measures relative humidity. Sling psychrometer: (picture on right) Is a type of hygrometer that uses the wet bulb and dry bulb thermometers 12.3 Gathering Weather data Rain gauge: Collects and measures rain fall amounts Ceilometer: measures the heights of clouds (you will do this with a LCL chart instead) Radiosonde: A weather balloon that carries sensors to determine the air temperature, pressure and humidity at about 30,000 m up Doppler Radar: The change in wave frequency as energy (sound or light) moves towards or away from and observer. Infrared Imagery: Satellites can be equipped to take images based on differences in thermal temperature. The higher the cloud lighter the color. Because storm intensity is related to how high a thunderstorm cloud reaches, this is useful when trying to determine how severe a storm will be. Station Model: A record of weather for a particular site at a given time. This gives you a lot of information and can be found in your ESRT’s. As you are learning, making a station model for your weather journal will get easier and easier. This one has more detail than you need to learn... Iso pleth or Iso line: A line that connects areas of equal value. examples isobars: lines that connect areas of equal pressure. isotherms: lines that connect areas of equal temperature. Accuracy of Forecast declines with time Who has a better chance at predicting a long term forecast? a) The Weather person on TV b) Old people with arthritis c) Your Earth Science teacher d) Miss Cleo The answer is... But if you said Mr.. McGuire you get an “A” and it won’t cost you $3.95 per minute!!! 1. Which of the following is not a front? A. Occluded B. Coriolis C. Stationary D. Cold 2. How does air move in a low pressure system? A. Clockwise, in and down B. Counter clockwise, in and up C. Counter clockwise, down and out D. Clockwise, down and out 3. Where was a continental polar air mass that is affecting the united states most likely developed? A. Mexico B. Gulf of Mexico C. North Pacific D. Northern Canada 4. What are the two characteristics of an air mass? A. Temperature and Humidity B. Temperature and Pressure C. Humidity and Pressure D. Pressure and Density ***Bonus. Draw the Earth in the four positions around the Sun showing the start of each season. Make sure you clearly show the tilt direction and label the correct dates for the beginning of each season. Also make sure to show there is a difference between the distance to the Sun in the summer position compared to the winter position. This can be exaggerated as I am not expecting this to be to scale.