Observing Weather

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I) Observing Weather

A) Properties of the Atmosphere

1) Mixture of gases

(a) Nitrogen

(b) Oxygen

(c) Carbon dioxide

(d) Ozone

(e) Other trace gases

2) Reaches from Earth’s surface to edge of space

3) Resource

(a) Life

4) Protection

(a) Radiation

(b) Temperature extremes

5) Layers of atmosphere

(a) Troposphere

(1) Closest to ground

(b) Stratosphere

(1) Contains ozone

(i) Blocks harmful radiation

(c) Mesosphere

(1) Temperature decreases

(i) Coldest spot in atmosphere

(d) Thermosphere

(1) Warmed by ultraviolet light

(2) Ionosphere

(i) Region where molecules have absorbed so much ultraviolet energy they become ionized

B) Observing the Weather

1) Instruments

(a) Temperature

(1) Thermometer

(b) Wind

(1) Wind vane

(i) Direction

(2) Anemometer

(i) Speed

(c) Pressure

(1) Barometer

(d) Humidity

(1) Hygrometers

(i) Relative humidity

1. amount of water vapor in the air compared to the greatest amount the air can hold

(e) Cloud cover

(1) Measure as a percentage of the amount of sky covered by clouds

(f) Precipitation

(1) Precipitation gauge

(i) Rain, snow, hail, sleet

2) Other instruments

(a) Computers

(b) Radiosonde

(1) Measures weather conditions high above the ground

(c) Radar

(d) Satellites

C) Reading Weather Data and Weather Patterns

1) Isobars

(a) Lines connecting places of equal pressure

2) Isotherms

(a) Lines connecting places of equal temperature

3) Air Masses

(a) A large region of air with similar properties throughout

(1) Maritime Polar

(i) Cool and moist

(2) Continental Polar

(i) Cool and dry

(3) Maritime Tropical

(i) Warm and moist

(4) Continental Tropical

(i) Warm and dry

4) Fronts

(a) Boundary between two different air masses

(1) Cold front

(i) Cold air moves in, pushing warm air above it

(2) Warm front

(i) Warm air moves in, pushing out cold air

(3) Occluded front

(i) One cold front overtakes a warm front and joins with another cold front

(4) Stationary front

(i) Front that does not move

 

Percentage of Various Gases in Air

Life protecting layers of O, O2, and O3 in the atmosphere absorb lethal ultraviolet radiation.

 

The variation of temperature with altitude in the atmosphere

The atmosphere is divided into four temperature zones.  The outermost zone, the thermosphere, continues to an altitude of about 700 km.

The Atmosphere and Earth-Space Interface

Thermometer
An instrument that measures the temperature of a system in a quantitative way
 
Temperature
The temperature of an object is that which determines the sensation of warmth or coldness felt from contact with the object

Parts of a thermometer

Barometer

Measures the air pressure of the air that's pressing in all directions at ground level.  The air's pressure is caused by the weight of all the air above the ground pressing down (caused by gravity).  At sea level, air has a pressure of 14.7 pounds per square inch.  Instead of using pounds per square inch, barometers in the U.S. measure the pressure in inches of mercury.  This is how high pressure would push mercury into a tube that has the top sealed off from the air.  A reading of 29.92 inches of mercury is the same as 14.7 pounds per square inch.

Anemometer

Measures wind force and velocity

Wind Vane

Measures wind direction

    

Hygrometer

Measures relative humidity (amount of water vapor in the air compared to the greatest amount of water vapor it can hold)

Precipitation Gauge

Measurement of rain, snow, sleet and hail

    

Radiosonde

 An instrument carried aloft, chiefly by

 balloon, to gather and transmit

 meteorological data.  That's Eddie

 Friedmen (friend of mine) letting a

 weather balloon with a radiosonde

 loose.

Meteosat

A European weather satellite orbiting above the equator at an altitude of 23,000 miles.  It takes a photo of the Earth every 30 minutes as well as sending back weather information and gathering data on the environment.

EOS Spacecraft

This spacecraft repeats its ground track every 16 days.  It provides atmospheric measurements over virtually every point on Earth in a repeatable pattern.  This permits an ongoing assessment of atmospheric phenomena changes in the same geographic locations.

         

Various Radar Pictures

Weather Map showing relative humidity

Weather Map showing temperature change

 Weather Map showing Isobars

Fronts

Zone of transition between two different air masses.  Zone may be 20 miles across or 100 miles across.  Significant different properties from one side of the front to the other include temperature, dew point, wind direction, cloud cover and on-going weather.

Air Masses

Weather Map indicating Wind Speed

         

Cold Front

Cold air moves in, pushing warm air above it.

Characteristics of Cold Fronts

bulletusually bring in cooler weather, clearing skies and a sharp change in wind direction
bulletslope of a typical cold front is 1:100 (vertical to the horizontal)
bullettend to move faster than all other types of fronts
bullettend to be associated with the most violent weather
bullettend to move the farthest while maintaining their intensity
bullettend to be associated with cirrus well ahead of the front and a broad area of clouds immediately behind the front
bulletfast moving fronts may be mostly clear behind the front
bulletassociated with squall lines (lines of strong thunderstorms parallel to and ahead of the front)
bulletduring winter, cold fronts move into Oklahoma mainly from the Canadian prairies but sometimes from the Artic Circle or the eastern Pacific

         

Warm Front

Warm air moves in, pushing out cold air

Characteristics of Warm Fronts

bullet

slope of a typical warm front is 1:200 (more gentle than a cold front)

bullet

tend to move slowly

bullet

typically less violent than cold fronts

bullet

although they can trigger thunderstorms, warm fronts more likely to be associated with large regions of gentle ascent, stratiform clouds and light to moderate continuous rain

bullet

usually preceded by cirrus first (1000 km ahead). then altostratus or alto cumulus (500 km ahead), then stratus and possibly fog

bullet

behind warm front, skies are relatively clear (but change gradually)

bullet

associated with a frontal inversion (warm air overrunning cooler air)

bullet

on weather map, warm front will be northeast of cold front and to the east of a surface low pressure area

bullet

clouds and precipitation prevalent to the north of the warm front (result from low-level southerly winds in the "warm sector" of the cyclone rise up and over the cooler, more dense air at the surface located north of the warm front.  This lifting leads to saturation, cloud formation and to some form of precipitation)

bullet

in Oklahoma, warm fronts are rare in the winter and non-existent in the summer

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Occluded Front

Formed when a cold front moves faster than a warm front;  cold front catches up to and overtakes the warm front.

Characteristics of Occluded Fronts

bullet

indicative of mature storm systems (storm about to dissipate)

bullet

most common type of occlusion in North America is a cold-front occlusion (occurs when the cold front forces itself under the warm front; the weather ahead of the cold occlusion is similar to that of a warm front while that along and behind the cold occlusion is similar to that of a cold front

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Stationary Front

Does not move or barely moves

Characteristics of a Stationary Front

bulletbehaves like warm fronts, but are more quiet
bulletwinds on both sides of a stationary front are parallel to the front
bullettypically form when polar air masses are modified significantly so as to lose their character
bulletcold fronts which stall

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