1. Meteorology 12.1 The Causes of Weather 12.2Weather Systems
12.3 Gathering Weather Data
12.4 Weather Analysis

3. The Causes of Weather Weather is the study of atmospheric phenomena.
Greek meaning of meteorology is
Meteor- high in the sky
Clouds, raindrops, snowflakes, fog, dust, and rainbows are types of atmospheric meteors.
ology-the study of
The Causes of Weather

4. Weather vs. Climate Weather Climate Description
Atmospheric phenomena interacting
Long-term variations of weather
Short or long term; measure of variations
Short-term; minutes, hours, days, weeks, or months
Long term; 30 year or more
Weather vs. Climate

5. A question of balance
The sun’s rays hit the surface more directly in the middle of the day as it is overhead.
- The same amount of energy is released during the morning and evening hours, but the Sun’s rays are hitting the surface at an angle and the energy is spread out over a large area.

6. A Balance Act

7. Air Masses Type of Air Masses Source of Air Masses
Weather Associated with Air Mass
Continental tropical
Deserts of Southwest and Mexico
Hot, dry summers
Maritime tropical
Tropical and subtropical oceans
Hot, humid summers
Continental polar
Interior of Canada and Alaska
Frigid winters; cool dry summers
Maritime polar
Cold water of North Atlantic and North Pacific
Heavy rains in winter on West Coast
Arctic
Latitudes over 60 N
Extreme cold
Air Masses

8. Air Masses

9. The Coriolis effect is where moving particles such as air are deflected to the right in the northern hemisphere and to the left in the southern hemisphere.
It combines with the heat imbalance to create distinct global wind systems
These systems transport colder air to warmer areas and warmer air to colder areas.
Weather systems

10. Coriolis effect

11. Global Wind Systems Three basic wind systems Trade winds
Occur at 30o North and South Latitude
Also know as the Hadley cell
Air sinks, warms, and moves toward equator in a westerly direction, it rises again and moves back toward latitude 30 , where it sinks and starts again.
Convergence
Occurs when the trade winds from both hemispheres move together from two different directions and air converges, is forced upward, and creates an area of low pressure.
Global Wind Systems

12. Prevailing Westerlies
Flows between 30o and 60o north and south latitude in a circulation pattern opposite that of the trade winds.
Responsible for much of the movement of weather across the United States and Canada
Move weather in the United States from west to east across the continent.
Polar Easterlies
Lies between 60o latitude and the poles
Characterized by cold weather

13. El Nino describes episodes of ocean warming that affect the eastern tropical Pacific.
La Nina periods occur when the surface temperatures in the eastern Pacific are colder than average.
increase in precipitation
Increase in hurricane activity
El Nino vs. La Nina

14. How would the weather be affected if the jet stream moved north?
If the jet stream dipped south of the north east location, then the colder, arctic air would be dragged down with it.
This would bring colder weather to the north east.
If the jet stream moved north, the warmer weather from the southeast would enter the northeast region.
Jet Streams

15. Jet Stream

16. Fronts Type of front Map Symbol Description of air movement
Associated Weather
Cold Front
Cold air displaces warm air, forces warm air up
Clouds, showers, thunderstorms
Warm Front
Warm air displaces cold air
Very cloudy, precipitation
Stationary Front
Two air masses meet, neither advances
Some-what cloudy, light precipitation
Occluded Front
Fast moving cold air wedges warm air up where it gets trapped between two cold air masses
precipitation
Fronts

17. Cold Front

18. http://www.phschool.com/atschool/phscie xp/active_art/weather_fronts/

19. Pressure Systems Low Pressure Systems High Pressure Systems
Winds move counterclockwise in northern hemisphere
Rising air
Stormy weather
High Pressure Systems
Winds move clockwise in northern hemisphere
Sinking air
Fair weather
Characteristics in Common
Formed by internal forces
Air moves in circular motion
Pressure Systems

20. Pressure Systems

21. Gathering Weather Data
Instrument
What does it measure?
How does it work?
Thermometer
Temperature
Mercury or alcohol expands when warmed
Barometer
Air Pressure
Changes in pressure measured by changes in height of column of mercury
Anemometer
Wind Speed
Cupped arms that rotate as wind blows
Hygrometer
Relative Humidity
Wet- and dry-bulb thermometers
Cellometer
Height and amount of cloud cover
Data collected by ASOS
Gathering Weather Data

22. Upper level weather data is collected by a radiosonde,which is a series of sensors carried by a balloon.
Sensors that measure temperature, air pressure, and humidity are carried.
Measurements are sent back by radio signal.
Tracking is very important when measuring upper-level data because it helps meteorologists determine wind speed and direction.
Upper Level Data

23. Doppler Effect is the change in wave frequency that occurs in energy as the energy moves toward or away from an observer.
Weather Radar

24. Scientist can determine location of precipitation and clouds using
Radar
Tracks precipitation
Satellites
Tracks Clouds
Weather Satellite

25. Infrared imagery detects differences in thermal energy
The temperature of a cloud tells meteorologists about its type and height.
Weather Satellites

26. Isopleths are lines that connect points of equal or constant values.
Isotherm
Represents lines of equal temperature
Used to identify temperature gradients
Isobar
Represents lines of equal pressure
Used to indicate how fast the wind blows
The closer the lines the faster the wind.
Weather Analysis

27. Analog vs. Digital Analog Digital Numerical data
The more data the more accurate will be the forecast
Digital
Monthly or seasonal forecast
Looks at conditions in all levels of atmosphere
Compare current conditions to past.
Analog vs. Digital

28. Long-term forecasting
Factors that impact forecasting
Features like mountains, valleys, rivers, lakes, and cities affect the amount of heat absorbed by the Earth.
This affects the pressure and therefore the wind of that area.
The wind affects the cloud formation and all other aspects of weather.
Long-term forecasting

29. Short vs. Long term forecasting
Short term forecasting
Digital computers calculate the behavior of the fluid-like atmosphere.
More data makes for a more accurate forecast.
More accurate than long term.
Long term forecasting
Analog forecasting is done by studying large patterns through several levels of the atmosphere that have occurred in the past and extrapolating them to the future.
Short vs. Long term forecasting