1. ESS 111 – Climate & Global Change
Week 1
Weather vs Climate
Structure of the Atmosphere
Global Wind Belts

2. Weather is the state of the atmosphere at a given place and time
Weather is the state of the atmosphere at a given place and time. For example, right now, the temperature in Huntsville, AL is 90°F with Partly Sunny skies.

3. Climate is the average condition of the atmosphere (such as temperature or precipitation) over a long period of time.
For example, the average annual temperature over the past 30 years for Huntsville is 62°F. The average annual precipitation is 54 inches.
Climate is the average of weather conditions in a place.

4. Just as the weather differs from day to day, the climate differs from place to place.
Seattle, WA Houston, TX Phoenix, AZ Barrow, AK
Cool Warm Hot Cold
Moist Moist Dry Dry

5. Two important elements of weather and climate are: precipitation and temperature
Precipitation includes all forms of moisture falling to the surface of the earth. (Examples: rain, sleet, snow, hail)
Temperature is how warm or cool the air is outside.
* For this class, mean temperature/precipitation is the same as average temperature/precipitation.
Mean=Average

6. Climograph
A graph that indicates average temperature and precipitation for an area.
These graphs can answer the following types of questions:
How much rain is there in a particular location?
When is it dry?
Is it wet when it’s cool?
What vegetation can grow there?

7. How to Read a Climograph
Look at the title to see what location’s climate is being described by the graph.
The numbers on the left show you the amount of precipitation. Make sure you check to see if the precipitation is measured in millimeters or inches.
The numbers on the right show you the temperature. Make sure you check to see if the temperature is measured in degrees Fahrenheit of Celsius.
The letters at the bottom show you the months of the year.

8. In case you’re not great at interpreting Celsius temperatures…
30° is hot
20° is nice
10° is cold
0° is ice
**Remember: This is for Celsius, not Fahrenheit!

9. How to Read a Climograph
The bar graph measures the average precipitation for each month. The numbers that measure it are on the left side of the graph.
The line graph shows you the average temperature for each month. The numbers that measure it are on the right side of the graph.

10. Tropical Wet and Dry Location
One factor that effects the temperature of a place is the amount of sunlight it receives.
Notice how the temperature line on the climograph is almost level? This location is near the equator. It receives the same amount of sunlight all year which results in an almost straight temperature line.
Tropical Wet and Dry Location

11. Humid Subtropical Location
The second location is further from the equator. The curved temperature line shows that the amount of sunlight this location receives varies with the seasons.
Humid Subtropical Location

12. Study the two climographs below.
Can you pick out the one that depicts a tropical climate? How do you know?
Is it a tropical wet or a tropical wet and dry climate? How do you know?
Climate A
Climate B

13. Where is the atmosphere?
Everywhere!
Completely surrounds Earth
Held to Earth by gravitational attraction

14. What makes up the atmosphere?

15. Water Vapor Location of this in the atmosphere is highly variable
Significantly influences climate & weather
How?

16. Atmospheric Thickness
No defined top to the atmosphere
The atmosphere is very shallow—and is less than 2% of the Earth’s thickness
Over 90% of
atmosphere in
the lowest 16km
& is where nearly
all weather occurs

17. Temperature Basics
Temperature – measure of average kinetic energy (motion) of individual molecules in matter
Three temperature scales (units): Kelvin (K), Celsius (C), Fahrenheit (F)
All scales are relative
degrees F = 9⁄5 degrees C + 32
degrees K = degrees C

18. Temperature Layers Due to Solar winds, Cosmic rays
Due to ozone absorption of sunlight
Temperature decreases with height in the Troposphere
Due to surface heating (Longwave, Latent heat, Sensible heat)

19. Density & Pressure

20. Density & Pressure
Lower layers of atmosphere are compressed by air above it
This compression increases pressure & density of the lower layers of the atmosphere

21. What is atmospheric pressure?
Weight of the overlying air
Taller the column of air above an object, the greater the air pressure exerted on that object

22. Standard Atmospheric Pressuremb
hPa
29.92 inches of Hg

23. The Layers of the Atmosphere
Thermosphere

24. Troposphere Lowest region of the atmosphere
Contains ½ of the Earth’s atmosphere
density
density

25. Troposphere

26. Depth of tropopause
Between the Troposphere & Stratosphere is the tropopause
Height is variable – Thermal expansion & contraction

27. How do we determine where the tropopause is located?

29. Stratosphere Temperature increases with an increase in altitude
What is this called?

30. Why is there a temperature inversion in the stratosphere?
Temp Inversion – temperature warms with height instead of cooling w/ height
Ozone
Gas that absorbs ultraviolet (UV) solar energy
Increases the temperature of the air surrounds ozone

31. Mesosphere Temperature decreases with an increase in altitude
Where meteors burn up while entering the Earth’s atmosphere

32. Thermosphere
First exposed to the Sun's radiation and so is first heated by the Sun
Air is so thin that a small increase in energy can cause a large increase in temperature

33. Vertical Structure of the Atmosphere

34. Space shuttle Endeavour straddles mesosphere & stratosphere

35. Planetary Winds
Well-defined pressure patterns exist across the Earth that induce the global wind patterns on the planet

36. Idealized Single-Cell Convection Model for a Planet
Features of the
circulation pattern:
horse latitude
trade winds
doldrums
prevailing westerlies
polar easterlies
polar front

37. The Three-Cell Model Polar cell -- northeasterly winds at surface
Ferrel cell -- southwesterly winds at surface
Subtropical high -- Air subsides (dry climate)
Hadley cell -- tropical convection cell
Intertropical convergence zone (ITCZ) -- surface low pressure with clouds and rain

38. Observed Distribution of Pressure and Winds
(a) An imaginary uniform Earth with idealized zonal (continuous) pressure belts
(b) Actual planetary winds belts on Earth taking into account continents and ocean currents

39. Idealized Pressure Belts
Equatorial Low- warm air rising creates cell of low pressure.
Intertropical Convergence Zone (ITCZ)- referred to as the
convergence zone because this region is where the trade winds
converge. Ascending air leads to cloud formation which makes this
region clearly visible on satellite imagery.
Subtropical Highs- These zones are caused primarily by Coriolis
deflection which restricts upper-level winds from moving poleward.
Subsiding air and divergent winds at the surface cause warm, cloud-
free weather (many large desert areas are located along this
latitudinal belt). Subtropical Highs tend to persist throughout the
year, with the center of the high migrating, and are regarded as
semi-permanent pressure systems.

40. Idealized Pressure Belts (cont.)
Subpolar Low – located around 50 to 60  latitude. Associated
with the polar front. The belt of low pressure is formed by the
interaction (convergence) of the polar easterlies and the westerlies
Polar Highs – located over the poles! The process which produces
the polar highs is different than the process which produces the
subtropical highs. Surface cooling is the principle reason the
polar high.

41. The ITCZ is a band of clouds across the tropics

42. The three-celled model vs. reality:
Hadley cells are close approximations of real world equatorial winds
Ferrel and polar cells do not approximate the real world winds very well at all
Model is unrepresentative of westerly flow aloft
Continents and topographic irregularities cause significant variations in real world wind patterns compared to the model

43. Northern hemisphere semi-permanent cells
Semi-Permanent Pressure Cells are large areas of higher or lower atmospheric pressure than the surface average
They may be thermally induced (rising warm air or subsiding cold air) or they may be caused dynamically by converging or diverging wind patterns)
They fluctuate seasonally
Northern hemisphere semi-permanent cells
The Aleutian, Icelandic, and Tibetan lows
Siberian, Hawaiian, and Bermuda-Azores highs
ITCZ (low)

44. Vertical structure and mechanisms
Polar Cell (thermal):
Driven by heating at 50 degree latitude and cooling at the poles
Ferrel Cell (dynamical): Dynamical response to Hadley and polar cells
Hadley Cell (thermal): Heating in tropics  forms surface low and upper level high  air converges equatorward at surface, rises, and diverges poleward aloft  descends in the subtropics

45. Average atmospheric air pressure and wind patterns in January

46. Average atmospheric air pressure and wind patterns in July