Chapter 12-Meteorology

1
Chapter 12-Meteorology
2
I. Causes of Weather

• Meteorology is the study of atmospheric
  phenomena.
• 1. Clouds, raindrops, snowflakes, fog, dust and
  rainbows are all types of atmospheric
  meteorology.

3
(No Transcript)
4
(No Transcript)
5
B. Weather and climate

•   1. Weather is the current state of the
  atmosphere.
•  
• 2. Weather is referred mainly to short-term
  variations in the atmosphere.
•  
• 3. These variations could occur over minutes,
  hours, days, weeks, or months.

6

• 4. Long term variations in weather for a
  particular area make u the climate of that area.
•  
• 5. Climate is usually averaged over the course
  of 30 years or more.

7
Weather
8
Climate
9
C. A question of balance

• 1. The suns rays are spread out all over the
  earth.
•  
• 2. There are some areas that have high amounts
  of the suns rays and some areas that have low
  amounts of the suns rays.

10
(No Transcript)
11
D. Air masses

• 1. Air mass is a large body of air that takes
  on the characteristics of the area over which it
  forms.
•  
• 2. Air masses form over land or water.
•  
• 3. Air masses are classified according to their
  regions.

12
(No Transcript)
13

•  4. All five main types of air masses can be
  found in North America because of the continents
  proximity to the source regions associated with
  each air mass.
•  
• 5. Air masses do not stay in one place
  indefinitely. They move.

14
Air mass
15
Weather systems

• Global wind systems.
• 1.  Trade winds occur at 30 degrees north and
  south latitude.
•  
• 2. There, air sinks, warms and moves toward the
  equator in a westerly direction.

16
(No Transcript)
17

• 3. The second wind system, the prevailing
  westerly, flows between 30 degrees and 60 degrees
  north and south latitude in a circulation pattern
  opposite that of the trade winds.

18

• 4. The polar easterlies lies between 60 degrees
  latitude and the poles.
•  
• 5. Similar to the trade winds, the polar
  easterlies flow from the northeast to the
  southwest in the northern hemisphere.

19
B. Jet Streams

• 1. Narrow bands of fast, high-altitude,
  westerly winds called jet streams flow at speeds
  up to 185 km/h.
•  
• 2. Disturbance form along jet streams and give
  rise to large-scale weather systems that
  transport surface cold air toward the tropics and
  surface warm air toward the poles.

20
(No Transcript)
21

•  3. A front is the narrow region separating the
  two air masses of different densities.

22

• 4. Cold fronts dense air displaces warm air
  and forces the warm air up along a step front.

23

•  5. Warm fronts- Advancing warm air displaces
  cold air.

24

•  6. Stationary front- two air masses meet and
  neither advanced into the others territory.

25

•  7. Occluded fronts- Cold air mass moves so
  rapidly that it overtakes a warm front.

26
(No Transcript)
27
C. Pressure systems

•  1. High-pressure systems, air sinks, so that
  when it reaches Earths surface, it spreads away
  form the center.
•  
• 2. Low-pressure systems, air rises.

28
HIGH PRESSURE
29
LOW PRESSURE
30
III. Gathering weather data

• Surface data
• 1. One of the most common weather instruments
  is a thermometer, a device used to measure
  temperature.

31

•  2. Barometers measure air pressure.
•  
• 3. In a mercury barometer, changes in air
  pressure are indicated by changes in the height
  of a column of mercury.

32
(No Transcript)
33

• 4. An anemometer is used to measure wind
  speed.
•  
•  

34
(No Transcript)
35

• 5.      Hygrometer measures relative humidity.
•  

36
(No Transcript)
37

• 6. Ceilometers measure the height of cloud
  layers and estimates the amount of sky covered by
  clouds.

38
(No Transcript)
39
 7. The instrument of choice gathering upper
level data is a balloon- born package of sensors
called a radiosonde.
40
B. Weather radar

•   1. The Doppler effect is the change in wave
  frequency that occurs in energy, such as sound or
  light as the energy moves toward or away from an
  observer.

41
IV. Weather analysis

• Surface Analysis
• 1. Station models provide information for
  individual sits.
•  
• 2. To plot data nationwide or globally,
  meteorologists use isopleths, which are lines
  that connect points of equal or constant values.

42

• 3. Digital forecasting is the main method used
  by modern meteorologists.
•  
• 4. It is highly dependent on the density of the
  data available, basically, the more data, the
  more accurate the forecast.

43

• 5. Another type of forecast, an analog
  forecast, involves comparing current weather
  patterns to patterns that took place in the past.
•  
• 6. Long term forecasts involving months and
  seasons are based largely on patterns or cycles.

44
The end