1. Earth’s Weather and Climate
EVSC 1300
Earth’s Weather and Climate

2. Composite Surface Maps
warm
fronts
cold
stationary
occluded
Precipitation
type and intensity
isobars
pressure
wind direction
wind speed

3. Scales of Motion (pp. 230-231) Page: 230
FIGURE 9.1 Scales of atmospheric motion. The tiny microscale motions constitute a part of the larger mesoscale motions, which, in turn, are part of the much larger synoptic scale. Notice that as the scale becomes larger, motions observed at the smaller scale are no longer visible.
(pp )

4. Scales of Motion Increasing size Increasing duration (pp. 230-231)
Page: 231
FIGURE 9.2 The scales of atmospheric motion with the phenomenon’s average size and life span. (Because the actual size of certain features may vary, some of the features fall into more than one category.)
(pp )

5. Scales of Motion (pp. 230-231) Page: 231
FIGURE 9.2 The scales of atmospheric motion with the phenomenon’s average size and life span. (Because the actual size of certain features may vary, some of the features fall into more than one category.)
(pp )

6. Mercury Barometer Page: 203
FIGURE 8.6 The mercury barometer. The height of the mercury column is a measure of atmospheric pressure.

7. Aneroid Barometer
Page: 203
FIGURE 8.7 The aneroid barometer.

8. Barograph or Recording Barometer
Page: 205
FIGURE 8.8 A recording barograph.

9. Time of frontal passage
Barograph Trace
Charlottesville
Jan. 5–10, 2009
Time of frontal passage
(4–6 p.m., Jan. 7)

10. Surface Map; Jan. 7, 2009; 7 a.m. EST

11. Surface Map; Jan. 7, 2009; 7 p.m. EST

12. Time of frontal passage
Barograph Trace
Charlottesville
Jan. 5–10, 2009
Time of frontal passage
(4–6 p.m., Jan. 7)

13. Sea-level pressure variations Page: 203
FIGURE 8.5 Atmospheric pressure in inches of mercury and in millibars.

14. resulting map of sea-level
Station
vs.
Sea-level
Pressure
station pressure—barometer measurement
correction factor for elevation
FIGURE 8.9 The top diagram (a) shows four
cities (A, B, C, and D) at varying elevations above
sea level, all with different station pressures. The
middle diagram (b) represents sea-level pressures of
the four cities plotted on a sea-level chart. The
bottom diagram (c) shows sea-level pressure
readings of the four cities plus other sea-level
pressure readings, with isobars drawn on the chart
(gray lines) at intervals of 4 millibars.
resulting map of sea-level
pressure variations
(surface map)

15. Sea-level Pressure Map Influence of topography (elevation) on pressure
has been removed
(pp. 200–207)

16. Change of Air Pressure and Density with Height
Page: 11
FIGURE 1.9 Both air pressure and air density decrease with increasing altitude. The weight of all the air molecules above Earth’s surface produces an average pressure near 14.7 lb/in.2

17. Earth’s atmosphere is thin relative to the size of the planet.

18. Change of Air Pressure with Height
atmosphere’s
mass above
100 mb
Page: 12
FIGURE 1.10 Atmospheric pressure decreases rapidly with height. Climbing to an altitude of only 5.5 km, where the pressure is 500 mb, would put you above one-half of the atmosphere’s molecules.
100 mb
90% of
atmosphere’s
mass below
100 mb

19. 500 mb Map
(pp. 10–12)
Upper air map showing winds and other variables at the “mid-point” of the atmosphere.

20. Quick Pressure Summary:
pressure is the weight of the atmosphere per unit horizontal area
pressure variations determine wind (speed and direction)
High vs. low pressure determine clear vs. stormy weather
pressure drops rapidly with height from sea level
average surface pressure is about 1000 mb ( mb)

21. air molecules Number of air molecules determine surface pressure
Page: 200
FIGURE 8.1 A model of the atmosphere where air density remains constant with height. The air pressure at the surface is related to the number of molecules above. When air of the same temperature is stuffed into the column, the surface air pressure rises. When air is removed from the column, the surface pressure falls. (In the actual atmosphere, unlike this model, density decreases with height.)
Number of air
molecules determine
surface pressure
(Note: Unrealistic
example...constant
density and fixed top)

22. TWO BAROMETERS L SAME TEMPERATURE D E N S Low Pressure High Pressure
Air Column
Air Column D E N S L
SAME
TEMPERATURE
Low Pressure
High Pressure
Barometer
Barometer
At same temperature, dense air has higher pressure than less dense air

23. Impact of Heating and Cooling on Pressure
Reference Level
denser
less
dense
Page: 201
FIGURE 8.2 Illustration of how variations in temperature can produce horizontal pressure forces. (Note that for simplicity, this model assumes that the air density is constant with height, whereas in the actual atmosphere, density decreases with height.) (a) Two air columns, each with identical mass, have the same surface air pressure. (b) Because it takes a shorter column of cold air to exert the same surface pressure as a taller column of warm air, as column 1 cools, it must shrink, and as column 2 warms, it must rise. (c) Because at the same level in the atmosphere there is more air above the H in the warm column than above the L in the cold column, warm air aloft is associated with high pressure and cold air aloft with low pressure. The pressure differences aloft create a force that causes the air to move from a region of higher pressure toward a region of lower pressure. The removal of air from column 2 causes its surface pressure to drop, whereas the addition of air into column 1 causes its surface pressure to rise. (The difference in height between the two columns is greatly exaggerated.)
Warming or cooling air can induce pressure changes.
Pressure change can produce air motion—wind!

24. Pressure and Density Same temperature at both locations
Page: 204
FIGURE 1 Air above a region of surface high pressure is more dense than air above a region of surface low pressure (at the same temperature). (The dots in each column represent air molecules.)
Same temperature at both locations
Denser air produces higher surface pressure
(Chap. 8; pp. 200–207)

25. Wind Direction (16-point compass)
Page: 255
FIGURE 9.43 Wind direction can be expressed in degrees about a circle or as compass points.
Wind is defined based on the direction from which it is coming.

26. Surface High = ANTICYCLONE
Cyclones and Anticyclones
Page: 223
FIGURE 8.35 Winds and air motions associated with surface highs and lows in the Northern Hemisphere.
Surface Low = CYCLONE
(counter-clockwise winds)
Surface High = ANTICYCLONE
(clockwise winds)
(N. Hemisphere)

27. Cold vs. Warm Air Parcels
Page: 32
FIGURE 2.1 Air temperature is a measure of the average speed (motion) of the molecules. In the cold volume of air, the molecules move more slowly and crowd closer together. In the warm volume, they move faster and farther apart.
Cold air is denser that warm air (at the same pressure)

28. Surface Air Temperature Variations (pp. 32–34) Page: 34
FIGURE 2.2 Comparison of Kelvin, Celsius, and Fahrenheit scales, along with some world temperature extremes.
(pp. 32–34)

29. Quick Summary—Ideal Gas Law:
relates pressure, temperature, and density
with 3 variables, you can’t determine how one will affect another unless the third variable is held constant
cold air is denser than warm air (at the same pressure)
temperature changes can induce pressure changes between two locations (pressure “gradients”) that cause the wind

30. Composition of Atmosphere
Permanent
Variable
Greenhouse Gases
TABLE 1.1 Composition of the Atmosphere near the Earth’s Surface

31. (removal from atmosphere)
SOURCE
(to atmosphere)
SINK
(removal from atmosphere)
Fixed by (incorporated into) soil bacteria
Fixed by ocean phytoplankton
Lightning N2
Denitrification by anaerobic
bacteria in wet soil
Aerobic bacterial processes
Combustion
Respiration (oxidation: food to energy) O2
Ocean phytoplankton
Photosynthesis
Vis. light
6 CO H2O
C6H12O6 + 6 O2
Photosynthesis
Fixation by ocean phytoplankton
Dissolved directly into ocean surface
CO2
Respiration
Combustion
STORAGE: limestone sediments, marine shells, fossil fuels

32. (removal from atmosphere)
SOURCE
(to atmosphere)
SINK
(removal from atmosphere)
Anaerobic processes
(wetlands, rice paddies)
Bovine flatulence
Termites
Biomass burning
Interaction with hydroxyl in atmosphere
Soils
CH4
CH4 + OH
CH3 + H2O
Bacteria in soils/oceans
(nitrification)
Combustion (cars, biomass)
Fertilizers
Stratospheric photochemistry
(converted to NOx)
N2O
O2 + O O3
O3 + uv
O2 + O O3
Also chlorine, bromine, NOx
Evaporation from open water
Sublimation (from ice)
Transpiration (through plants)
Condensation onto surfaces
Precipitation
Deposition
H2O
(pp. 6–10)

33. Average vertical temperature structure of atmosphere (pp. 12–17)
Page: 13
FIGURE 1.11 Layers of the atmosphere as related to the average profile of air temperature above Earth’s surface. The heavy line illustrates how the average temperature varies in each layer.
(pp. 12–17)

34. Variation of Tropopause Height by Latitude
Page: 275
FIGURE Average position of the polar jet stream and the subtropical jet stream, with respect to a model of the general circulation in winter. Both jet streams are flowing from west to east.
Tropopause is higher over equator and lower over poles