1. Meteorology Part 1
Weather Variables

2. What is Meteorology? What is Weather?
The study of the atmosphere and weather.
What is Weather?
The current atmospheric conditions of a specific place at a specific time.

3. 6 Components of Weather:
Temperature
Air Pressure
Wind
Moisture
Precipitation
Clouds

4. Temperature
Average movement of molecules of a substance. The amount of HEAT!
The faster the molecules move, the higher the temperature.
Instruments used: Thermometer!

5. Conversions Temperature is measured in °Celsius,
°Fahrenheit and Kelvin.
Practice converting these measurements using the ESRT page 13…

6. Energy SUN! The source of energy for the Earth is the
Energy from the Sun heats the Earth by convection, radiation and conduction
SUN!

7. Energy from the Sun heats the Earth by convection…
Heat makes a substance such as air less dense, so it rises.
Cool air sinks because it is more dense.

8. Energy from the Sun heats the Earth by radiation…
Heat moves through space in electromagnetic waves.

9. Energy from the Sun heats the Earth by conduction…
Heat moves from one material to another through direct contact.

11. Other sources of energy…
The decay of radioactive material in the Earth
Geothermal energy: Heat left over from the formation of the Earth.

12. Air Pressure (Barometric Pressure): Instruments used: Barometer
“weight” of air pushing down on the Earth.
Instruments used: Barometer
and Barograph
Measured in millibars (mb)
or inches of mercury

13. High Pressure: Low Pressure:
Heavy air pushes the mercury up HIGH in a barometer.
Air is DRY
Clear skies
Cooler air results
Low Pressure:
Air is light and causes the mercury to be LOW in a barometer.
Air is HUMID
Cloudy skies
Warmer air results

14. How can air be heavy or light??
Composition of the atmosphere:
78% Nitrogen
21% Oxygen
1% other gases

15. Nitrogen (N2)-Nitrogen has an atomic mass of 14
14 x 2 = 28 (weight of N2)
Oxygen (O2)-Oxygen has an atomic mass of 16
16 x 2 = 32 (weight of O2)
1% other gases
~Water vapor: Hydrogen (atomic mass = 1)
H2O = = 18
As water vapor enters dry air, the pressure lowers, because a lighter gas is being added.

16. HEAVY LIGHT Soooooo…dry air is and moist air is
Water vapor is lighter than oxygen or
nitrogen molecules.
Therefore, as the amount of water vapor in the air increases, the air pressure DECREASES!
HEAVY
Soooooo…dry air is
and moist air is
LIGHT

17. How to get an egg into a bottle!

18. Practice some Barometric Pressure Conversions
ESRT pg. 13

19. Wind Caused by uneven heating of the atmosphere
Air moves from high to low pressure
Instruments used:
Wind Vane: Gives wind direction
B) Anemometer: Gives wind speed

20. Wind Named by speed and direction
Direction is always where the wind is coming from.
Ex: North wind blows from the north to the south
Name these winds:
East
South
South West
Draw a NW wind:

21. Moisture: Dew Point & Relative Humidity
Dew point: Temperature at which air is saturated with water vapor.
Condensation-when water vapor, the gas, changes to liquid water.
~Cooling below the dew point produces
condensation on solid surfaces.

22. Dew Point 22°C 17°C 5°C Instrument used: Sling Psychrometer
Dry Bulb Temp: Wet Bulb Temp:
Wet-Bulb Depression:
22°C
17°C
5°C

23. Cold air holds less water vapor than warm air
Practice finding Dew Point using ESRT pg. 12
1.) Dry bulb = 28°C
Wet bulb = 20 °C
Difference =
DP =
8°C

24. This is the dew point temperature!

25. Dew Point Practice… Now try some on your own! 1.) Dry bulb = 28°C
Wet bulb = 20 °C
Difference =
DP =
3.) Dry bulb = -14°C
Wet bulb = -14°C
Difference =
DP =
8°C
0°C
16°C
-14°C
2.) Dry bulb = 4°C
Wet bulb = -2 °C
Difference =
DP =
Now try some
on your own!
6°C
-19°C

26. Relative Humidity
Percent of water vapor in the air compared with the amount of water vapor the air can hold at that temperature.
To find relative humidity, use same process as dew point, just make sure you use the Relative Humidity chart!!!

27. Practice… 1.) Dry bulb = 4°C Wet bulb = -2 °C Difference = RH =

28. This is the relative humidity!

29. Relative Humidity Practice…
1.) Dry bulb = 4°C
Wet bulb = -2 °C
Difference =
RH =
3.) Dry bulb = -14°C
Wet bulb = -14°C
Difference =
RH =
6°C
0°C
14%
100%
Now try some
on your own!

30. Precipitation
Any form of water that is heavy enough to fall from the sky to the ground.
Drops come together until they are heavy enough to fall.
Types: Rain, snow, hail, sleet, freezing rain, virga.

31. Virga

32. Clouds
A cloud is a visible mass of frozen crystals or droplets floating in the atmosphere.

33. What is needed to form a cloud?
Recipe for a cloud:
Water Vapor
Temperatures at the dew point
Dust-condensation nuclei

34. Process of Formation
Moist air rises, pressure decreases & allows air to expand
Air cools to the dew point
Water vapor condenses on condensation nuclei (dust, pollen, ash particles) and forms a cloud

36. Basic Cloud Types
Cumulus
Fair weather
Puffy, cotton ball looking

37. Stratus
Cover entire sky
Gray, low in sky
Bad, rainy weather

38. Cirrus
High, wispy
Ice crystals
Predicts approaching bad weather

39. Identify the following clouds:A B C D E

40. Relationships between weather components:
All of these variables affect each other.
Can you determine how one affects the other?
Can you draw graphs of these relationships?
Well, you soon will!

41. A. Air Temperature & the ability of air to hold water
Warm air expands and can hold more water vapor than cold air which is dry.
Sooo…as temperature increases, ability to hold water increases
Ability to hold water
Temperature

42. B. Air Pressure & Relative Humidity
As relative humidity increases, pressure decreases
WHY???
Water vapor is a light weight gas.
High Pressure: Dry air and low relative humidity
Low Pressure: Humid air and high relative humidity
Air pressure
Relative humidity

43. C. Air Pressure & Temperature
As temperature increases, air pressure decreases
High Pressure: Cool air
Low Pressure: Warm air
Air Pressure
Temperature

44. D. Temperature, dew point and chance of rain
The closer the temperature is to the dew point, the greater the chance of rain, as the air is more humid.
If the two are the same, relative humidity is 100%
Chance of rain
Difference between temperature and dew point

45. Rules to Understand Weather
1. Warm air is less dense and rises.
Cold air is more dense and sinks.
2. Warm air can hold more water vapor than cold air.
3. Humid air weighs less and is low pressure. Dry air is clear, heavy and high pressure.

46. Insolation  Amount of sunlight!
SO…Air temperature changes on a daily basis due to variations in…
cloud cover, humidity, duration and angle of insolation and air pressure.

47. Layers of the atmosphere
~Broken into 4 layers due to changes in temperature
The four layers from the
top to bottom are:
Thermosphere
Mesosphere
Stratosphere
Troposphere
Page 14 ESRT!

48. Station Models—a symbol used on weather map to show a huge amount of data in one very small spot on a map
Data shown includes but is not limited to: temperature, air pressure, dew point, wind speed and direction, cloud cover, precipitation, current weather conditions, etc.
017 63 •
-27 58
1.2
See ESRT page 13!!
Refer to ESRT station model for more information!!

49. As seen in your ESRT:

50. What is the air temperature for each of these 4 cities?
What is the wind speed and direction for each of these 4 cities?
N 10
70ºF
77ºF
75ºF
50ºF
S 15
SE 10
SW 20
Albany
Chicago
Rochester
Atlanta

51. Air Pressure Rule Pressure = _______mb Pressure = _______mb
On the station model…
if the number is 500 or more, add a 9 in front of the number and a decimal before the last number.
if the number is less than 500, add a 10 in front of the number and a decimal before the last number
Pressure = _______mb
Pressure = _______mb

52. Air Pressure Rule On the station model…
if the number is 500 or more, add a 9 in front of the number and a decimal before the last number.
if the number is less than 500, add a 10 in front of the number and a decimal before the last number mb
999.2 mb
998.6 mb mb
Albany
Chicago
Rochester
Atlanta