1. Atmospheric Structure and Weather Variables

2. Do Now using page 14 ESRT : Ms
Do Now using page 14 ESRT : Ms. Mowbray jumped out of a plane at 13,500 ft above sea level…yup *1 mile= 5,280 ft How many miles up did I jump? What layer of the atmosphere was I in?

3. *Note altitude is in km on left side of scale and miles on the right 

4. What am I going to wear today?!
Should I go to the mall on Saturday or go for a run?

5. I. Weather is the condition of the atmosphere at any point in time
I. Weather is the condition of the atmosphere at any point in time. (What’s going on NOW!)
A. Weather Variables are individual pieces of information that describe specific conditions of the atmosphere
-Temperature
-Pressure
-Dew Point
-Humidity
-Relative Humidity
-Cloud Cover
-Wind Velocity

6. Weather stations record weather variables (data)
 Synoptic Weather maps provide a picture of the conditions of the atmosphere at a moment in time.
Forecasting – is making predictions based upon current conditions of the atmosphere

7. II. The atmosphere A. is a mix of gases, held in by gravity
Our atmosphere is primarily Nitrogen and Oxygen
Pg. 1
of ESRT gives ATM comp by %

8. III. Atmospheric Divisions
What do you already know about the atmosphere?
“What Dew you Know”
Complete using page 14 of ESRT

9. Main Atmospheric Relationships
B. The levels of the atmosphere.
The troposphere has the greatest concentration of H20 and highest Pressure.
T and P ↓ with ↑ altitude
All weather occurs here (No H20, no weather!)
The stratosphere contains ozone, which absorbs ultraviolet (uv) rays, causing T to ↑
O3=Ozone (smog at ground level)

10. Now Let’s talk about Weather Variables
1.) Air pressure :is the weight of air at any particular point. It is also called barometric pressure.
The units are given in the ESRT in millibars (mb), and inches of mercury, and as atmospheres (atm).
A barometer is a device used to measure pressure.
Air pressure depends on how tightly packed the molecules are and how heavy they are.

11. Types of Barometers As P ↑, it pushes the Hg upwards
As P ↑, a spring presses down on the guage

12. Pressure: pg. 13 of ESRT
Converting MbInches of Hg Practice: 1.)how many Mb of pressure is 29” of Hg equivalent to? _________mb 2.) How many inches of Hg are 1033 mb equivalent to? ____________ 3.) According to this, what is sea level pressure? (Where there is one atmosphere on top of you!) _______mb OR _______ inches of Hg

13. How does P change with altitude?

14. Air Pressure Relationships of Pressure: 1.) Temperature Change
a.) as T↑ P↓
Why? Air expands when warm (D ↓)
b.) As T ↓ P ↑
Why? Air contracts when cold (D ↑)
Ex: Balloon Demo in H20

15. Pressure changes with humidity
2.) Water Vapor added to air ↑ Humidity
WATER VAPOR IS LESS DENSE THAN AIR!
Why? _________________________________
a.) As humidity of air ↑ the P ↓
(b/c H20 molecules replace N molecules)
b.) As Humidity of air ↓ the P ↑
(b/c as H20 is lost, denser N molecules replace them and weight of air ↑ )
Key Concept:
*That’s why low pressure is always associated with storms/rainy and warmer weather and high P with clear/dry and cooler weather*

16. 2.) Air temperature
Temperature is the measure of KE of the molecules. ↑Heat causes molecules to move faster and expand.
Measured in F, C, and K.
Liquid thermometers measure T
Explain how a thermometer works:
______________________
_____________________

17. Evaporation rates in USA Contributing factors: Humidity and Temp

18. Evaporation Rate and Air Temp
Water vapor enters Atm through evaporation from surface water and ice.
Energy is required for evaporation, which takes heat away from the surface.
SO KEY FACTS:
Warm air has more energy, and can therefore cause more evaporation (why your clothes dry on a hot day)
Cold air cannot cause as much evaporation, so the water vapor tends to condense (You wouldn’t hang your clothes out on a cold day would you?)
*Condensation releases heat back into the air.

19. Evaporation Rate and Wind Speed
Question: Why would you want to put wet clothes to dry on a fan? Key Relationship *Evaporation ↑ with greater wind speed

20. Evaporation Rate & Surface Area
Question: Two lakes in NY have the same volume of water in them; however lake #1 is 100 feet deep and has a smaller surface area then Lake #2 which is 50 ft. deep with larger surface area. Assuming they are the same temperature and have equal air movement on top, which lake will lose more water to evaporation over the course of 1 day?

21. 3.) Dewpoint Temperature
temperature at which water vapor will CONDENSE to become drops of water or ice crystals.
It indicates how humid air is.
The air must be cooled for this to happen.
The dewpoint temperature depends on:
the amount of water vapor in the air.
***It DOES NOT depend on the air temperature***
A high dewpoint indicates a high concentration of water vapor.
(Dry=low DP, Wet=high DP)

22. Where are the highest DP temps?

24. Why is there not any “dew” on my seltzer can today?

25. So how do we measure Dew Point?
Using a Psychrometer
This will yield two temperatures:
A “dry-bulb” temperature
A “wet-bulb” temperature
The Wet-Bulb Depression is the difference between these two temperatures
(Dry T-Wet T)

26. The “Dry Bulb” Don’t let it fool you. It is just a thermometer.
It measures the air temperature.
Duh!
20°C

27. The “Wet Bulb” Has a little wet booty tied to the bottom. Wet Booty
12°C
Wet Booty

28. On a Dry Day… A lot of moisture will evaporate.
The wet bulb will be a lot cooler than the dry bulb.
20°C
20°C
14°C
12°C
8°C
Difference between wet bulb & dry bulb is 12 °C

29. On a Humid Day… A little bit of moisture will evaporate.
The wet bulb will not be much cooler than the dry bulb.
24°C
21°C
Difference between wet bulb & dry bulb is 3 °C,

30. Page 12 of your ESRT!
Warning #1: Be sure to READ the correct chart: DPT or RH
Warning #2: Dew Point Temperature IS NOT “Difference between wet bulb and dry bulb”.
Warning #3: The wet bulb temp IS NOT the DPT.

31. How to find the Dew Point
14°C
10°C
14-10=4
Dew Point = 6°C

32. Try These… 17 °C Dry Bulb Wet Bulb Dry-wet DPT 26°C 20 °C 6 °C 5 °C

33. Dew Point temperature and current air temperature determine the altitude at which water vapor will condense to form clouds in the sky…

34. 22ºC Dry
D.P 16ºC

35. Cloud Base Altitude
Is the minimum altitude at which clouds will start to form
Clouds are made of LIQUID WATER DROPLETS
(NOT WATER VAPOR)
phase change must occur:
water vapor(g)liquid droplets (l)
(cooling)
Scientifically:
--it’s the altitude where the air temp and dew pt temp become the same due to the air temp cooling to the dew pt temp

37. -so if the dewpoint temperature is very low, then the height of the cloud base increases or is higher (cirrus clouds)
-Conversely if dew point temperature is higher (more humid air), height of cloud base is lower (cumulous clouds…)
*As air rises, the temperature and pressure decrease and the air can hold less and less water so water vapor condensescloud droplets

38. Relative Humidity Relative humidity is a percent (%)
It compares the amount of water vapor in the air, (indicated by the dewpoint temperature), to the amount the air can hold at the present air temperature.
Indicates :
likelihood of dew or frost or fog forming.
100% RH =air is saturated with H20 (g)
indicates that fog is probably forming.
Clouds are always at 100% RH.

39. Relative Humidity Practice ESRT
1.)What is the RH if the dry bulb temperature is 10 ˚ C and the wet bulb is 8˚C? ________ 2.)If the wet bulb depression is 6 C˚, what is the Dry bulb temperature if the RH is 41 %? _________ 3.) What is the wet bulb depression if the RH is 70% and the Dry bulb temp is 4 C˚? ________

41. Comparing RH with Temp Changes
If T ↓ the RH will ↑ (if % water vapor or Absolute Humidity remains the same)
Remember cooler air can hold LESS H20
If T ↑ the RH will ↓ (again if absolute humidity
stays the same)
- Remember: warmer air can hold MORE H20
Question Checkpoint:
How do you think relative humidity changes over the course of the day?....

43. Relationship of time of day and Temperature to R.H.

44. Q: What time of day could you expect it to rain in Syracuse?

45. E. Wind speed and direction
Wind is the horizontal movement of air.
Wind occurs because of uneven heating on earth.
The greater the difference in air pressure, the faster the wind speed. Speed is given in mph or in knots.
Wind is named for the direction
from where it comes
An anemometer measures wind speed 
Socks can tell u direction (or undies!)

46. WARM AIR RISES
Click for Interactive
COOL AIR MOVES INLAND

48. COOL AIR OVER THE LAND PUSHES OUT TO SEA
WARM AIR RISES

49. Air Flow Air flows from High to Low Pressure
And is faster where the pressure gradient is the largest (∆P/Distance)

51. Where would you expect wind speeds to be the fastest on this isobar map?

52. Wind is represented on weather maps using: 1
Wind is represented on weather maps using: 1.) Barbs with feathers and knots to indicate speed 2.) direction of barb is where wind is COMING FROM

53. Comparing Air with Weather Variables
Heavy Air: (high pressure)
1)cooler: because the molecules are packed in closer together (Vibrate less)
2.)Dry- air dries out as it sinks (descends) (Temp and DP are further from one another, RH ↓)
Calm, because all air moves away from high pressure areas elsewhere
Light Air: (low pressure)
warmer; the molecules have more energy by “bouncing” off one another (Vibrate more)
Humid,- light air rises, cools and condenses (Temp cools to dew point ) *lighter air also because water vapor weighs less than N
Windy, because air flows from other areas high to low pressure areas,