1. WEATHER & THE ATMOSPHERE

2. Used to measure the 5 major parts of weather observation
Weather Instruments
Used to measure the 5 major parts of weather observation
1. Atmospheric pressure
2. Humidity
3. Precipitation
4. Wind
5. Temperature

3. Tools: Atmospheric Pressure
Barometer:
Measures air pressure, millibars or inches of mercury

4. Tools: Humidity Hair Hygrometer: (Sling) Psychrometer:
Uses hair to measure humidity, hair expands and contracts in response to water vapor content in the air.
(Sling) Psychrometer:
Difference between wet bulb and dry bulb used to determine relative humidity.

5. Tools: Precipitation
Rain Gauge:
Simple funnel with marks

6. Tools: Wind Anemometer – Wind Speed Wind Vane – Wind Direction
km per hour
mi per hour
Wind Vane – Wind Direction
Cardinal units or numerical

7. Measuring Upper-Atmospheric Conditions
Radiosonde:
Carried aloft by a
helium balloon.
Measures upper-atmospheric. conditions: Relative humidity, air pressure, air temperature.
Information sent back to scientists via radio… waves.

8. Not weather satellites, but still cool
Carry cameras
Upper level Cloud speed, direct.
Hurricane observation
Infrared reading of cloud tops
Not weather satellites, but still cool

9. The study of weather = METEROLOGY
Weather is the condition of the atmosphere at any given time or place
Much of weather forecasting and prediction can be accomplished by direct observation
To predict weather, you must make observations of the clouds, wind, temperature, humidity, air pressure and precipitation

10. ATMOSPHERIC VARIABLES
things that can be measured and change from moment to moment
Temperature
Air Pressure
Wind Speed and Direction
Water Content & Humidity
Cloud Cover
Precipitation
Others (dust, transparency, pollen, etc)

11. TEMPERATURE Measures the average kinetic energy of molecules.
Heat enters the atmosphere from the sun as solar radiation (Insolation)
is an average of all of the kinetic energies- hence Average Kinetic Energy

12. 3 ways to Measure temperature:
Fahrenheit
Water freezes at 32°
Water boils at 212°
Celsius
AKA Centigrade (100 levels)
Water freezes at 0°
Water boils at 100°
Makes more sense and is easier to make a thermometer
Kelvin
Same scale as Celsius but 0 means zero energy
No degrees mark for Kelvin
0K means that all atomic vibrations stop.

14. Air Pressure the weight of the air in a certain area
Sinking air pushes down more-
cold air is dense air and brings high pressure
Hot air is less dense air and brings low pressure
Air pressure is measured using an instrument called a barometer
It is measured in inches (height of the mercury column in the barometer), or with the metric units called millibars

15. Air pressure drops with increasing altitude (less air)
Weather maps show sea level air pressure
It ranges from 960mb – 1050mb

16. Air in the Atmosphere Relationships
Air Temperature
Density
Air Pressure
Evaporation
Molecular reaction
Warm
Less Dense
Low Pressure
High evaporation
Loose molecule particles
Moving fast
Cold
More Dense
High Pressure
Low evaporation
Tightly packed molecules

18. Changes in Air Pressure
Temperature- warm air is lighter than cold air!
Humidity- humid (moist) air is lighter than dry air!! Water vapor (H2O) weighs less than the N and O gases that it pushed out
Winds are caused by the unequal heating of the atmosphere (remember that temperature causes changes in air pressure)

19. Water Vapor in the Air
The amount of water vapor in the air depends on the air temperature
The warmer the air, the more water vapor it can hold (think of those hot, humid summer days)

20. Relative Humidity
the amount of water vapor in the air, compared to how much water vapor it could hold at that temperature
Relative humidity is a percent measurement
Air with 100% humidity is said to be saturated
Precipitation will occur

22. Finding Relative Humidity
use an instrument called a hygrometer
One particular type of hygrometer is called a sling psychrometer
This instrument is made of two thermometers attached two a handle
One thermometer has a piece of gauze which is the soaked with water - This is called the WET BULB
The other thermometer is called the DRY BULB
These thermometers are swung in the air for a few minutes, and then the temperatures are recorded (take the wet bulb temperature first)
The wet bulb thermometer should have a lower temperature, since it removes heat from the thermometer as water evaporates from it

23. Interactive Site - http://www. eram. k12. ny

24. Condensation and Dew
remember that air’s ability to hold moisture decreases as the temperature decreases
As the air cools, its relative humidity increases
When the relative humidity reaches 100% (saturated), the water comes out of the air as liquid droplets
The temperature at which this will occur is called the dew point

25. Condensation and Dew
Condensation can only occur if the water has something to condense on
Tiny particles in the air on which water condenses is called condensation nuclei
This can be dust, salts, chemicals from burning fuel, etc.
* Water vapor that condenses on the ground is called dew (think of walking across wet grass in the morning)
If the dew freezes on the ground, it is called frost
Water vapor condensing in the air forms clouds
If the cloud forms close to the ground, it is called fog