1
Q
Air Pressure
A
- air molecules produce pressure
- exerted on all surfaces that air contacts
- sea level atmospheric average is 1 kg/cm^2
2
Q
Air Pressure: Gravity & Altitude
A
- gravity makes air denser at surface
- air pressure decreases with altitude
3
Q
Measurements of Air Pressure
A
- barometer
- mercury: tube counterbalanced by mass of air around it
- exerts equivalent pressure on mercury in vessel
- normal sea level is 1013.2 millibars
4
Q
Air Pressure & Density
A
- pressure and density DECREASE with altitude
- low density, molecules are further apart, less collisions there lower pressure
5
Q
Air Pressure and Temperature
A
- air is heated, activity increases and temp increases
- increased activity, increased space between molecules
- density LOWER, pressure LOWER
- warmer air is LESS DENSE and exerts LESS PRESSURE
6
Q
Wind: General
A
-horizontal motion of air across Earth’s surface
7
Q
Vertical Wind
A
- updrafts
- downdrafts
- micro- and macro-bursts of air turbulence
8
Q
Wind: How?
A
-differences in air pressure from one location to another
9
Q
Wind Speed Measurement
A
- anemometer
- km/h, mph, m/s, knots
- knot is nautical Mph, covers 1 minute of Earth’s arc in an hour
10
Q
Wind Direction Measurement
A
- wind vane
- 10 m from ground
- determined from source direction
11
Q
Isobar
A
line denoting equal pressure
12
Q
Isobaric Maps
A
show weight of atmosphere
help predict aridity and precipitation
13
Q
Pressure Gradient Force
A
air moves from areas of high to low pressure
14
Q
Pressure of North America in January
A
- low pressure over ocean (Pacific & Atlantic)
- high pressure over land
- extreme low temperatures
15
Q
Pressure of North America in July
A
- pressure switch locations
- low pressure over land
- W coast, less precipitation
- E coast, summer showers and high humidity
- land heats rapidly due to low heat capacity
- high pressure over water
16
Q
Coriolis Force
A
- spinning of Earth deflects path of objects
- different latitudes, different speeds
- equator: 1 675 km/h, poles: 0 km/h
17
Q
Coriolis Force: Increased Speed
A
-faster objects create greater deflection
18
Q
Coriolis Force: Wind and Ocean
A
- causes deflection to right in Northern Hemisphere
- causes deflection to left in Southern Hemisphere
19
Q
High Pressure Area
A
Diverging
Descending
20
Q
Low Pressure Area
A
Ascending
Converging
21
Q
Close Isobars
A
- steep PGF
- strong wind, high speeds
22
Q
Spaced Isobars
A
- gentle PGF
- gentle breeze, slow wind speed
23
Q
Equatorial Low Pressure Trough
A
- low pressure band around equator
- lots of energy from the Sun
- warm, light, less dense, ascending & converging
- ITCZ
24
Q
Heating and Converging Air
A
- forces air up
- air is moist & full of latent heat energy
25
Subtropical High Pressure Zone
- hot, dry air
- diverging and descending air at outer end of Hadley cells
- deflected POLE-WARD by Coriolis force
- cloudless, desert regions
- creates ocean gyres
26
Ocean Gyres: Directions
- CW in the Northern Hemisphere
| - CCW in the Southern Hemisphere
27
Divergence of High Pressure Cells
-creates trade winds (easterlies )and westerlies
28
Easterlies and Westerlies
Easterlies
-easterly direction, create ocean currents
Westerlies
-westerly direction, create ocean currents i.e. gulf stream
29
Sub-polar Lows
- Polar Front: cold and dry conditions
- migrating centers of low p, brings precipitation
- winter, there is a shift to the South, rain in mid.latitude
30
Aleutian Low and Icelandic Low
- migratory pressure cells
- SUMMER: high latitudes, bring rain to Pacific NW
- WINTER: lower latitudes, cases cyclonic storms on the West coast of North America and Europe
31
Isobaric Maps: Ridges and Troughs
Ridges are areas of high pressure
| Troughs are areas of low pressure
32
Wind near Maximum Speed
accelerates
| diverges
33
Rossby Waves
westerly geostrophic winds
| -develop along flow axis of a jet stream
34
Jet stream
irregular band of very strong wind
| -occurs in specific locations
35
Land and Ocean Breezes in Day
- land heats faster than ocean
- warm air is less dense
- flow of cool onshore marine air
36
Land and Ocean Breezes at Night
- land cools faster than the ocean
- cool air on land flows offshore
- water remains warmer, warm air is lifted
37
Monsoon Drivers
- size and location of Asian landmass
- proximity to Indian Ocean
- changing ITCZ
38
Gyres: definition and strength
- west gyres stronger than east
- trade winds drive ocean west in a channel
- water piles at the equator, spills north and south
39
Upwelling Definition and Causes
- surface water swept from coast
- Coriolis , surface divergence, or offshore winds
- cool water, nutrient rich, rises from depth
40
Upwelling Locations
- Pacific Coasts of North and South America
| - Subtropical and mid latitude west African coast
41
Four Downwelling Regions
- Labrador Sea
- Icelandic Sea
- margins of Antarctica
42
Downwelling: What
- thermohaline currents generated from downwelling
| - travel extents of ocean basins, carrying heat and salinity
43
Downwelling: How
- cold, salty water sinks in North Atlantic
| - full loop takes 1000 to 2000 years
44
Antarctic Downwelling
-very deep, flows north in Atlantic basin, UNDER other downwelling currents
45
Global Warming and Downwelling
- effect distribution of heat throughout ocean
| - could increase warming
46
Humidity: General
- water vapor content of air
| - changes with temperature of air and temperature of water vapor
47
Relative Humidity
-percentage amount of water ACTUALLY in air (content) and the maximum water vapor possible at a given temperature (capacity)
48
Saturated Air
-contains all water vapor possible at given temperature
49
Condensation
- occurs when further addition of water to saturated air
| - occurs when temperature of saturated air decreases
50
dew point temperature
-temperature a given mass of air becomes saturated
51
Daily Air Temperature Trend
- at dawn, water vapor fills to near saturation
| - during the day, lower relative humidity because air temperature decreases and specific humidity increases
52
Stability of Air Parcels
- tendency of a parcel to either:
- stay as it is
- change initial position by lifting or falling
53
Stable Air
- if it resists displacement
| - returns to initial position
54
Unstable Air
-parcel rises to altitude where surrounding air is similar to its own
55
Two Main Forces acting on Air
- buoyancy force
| - gravitational force
56
Warm Air Parcels
- less dense
| - parcels rise (buoyancy force wins)
57
Cool Air Parcels
- more dense
| - parcels sink (gravitational force wins)
58
Buoyancy, Density, Temperature
- dependent on density, which is dependent on temperature
| - therefore, buoyancy is dependent on temperature
59
Air Mass temperature higher/less dense than surrounding
- rise vertically
- begin to expand due to decreasing pressure
- rise until parcel matches surrounding temperature and density
60
Air Mass Cool
- gravity pulls it down
| - parcel compresses
61
Normal Lapse Rate
- average temperature decrease in altitude increase
- 6.4 degrees Celsius per 1 000 m
- for still, calm air
62
Environmental Lapse Rate
-rate for specific areas and weather
63
Adiabatic
-occurs without loss/gain of heat to surroundings
64
Diabatic
-occurs with exchange of heat
65
Dry Adiabatic Lapse Rate (DAR)
- rate that dry air cools by expansion or heats by compression
- dry air is LESS THAN saturated
- relative humidity is less than 100%
- 10 degrees Celsius per 1 000 m
66
Moist Adiabatic Rate (MAR)
- average rate which moist air heats/cools by compression/expansion
- 6 degrees Celsius per 1 000 m
- can vary from 4 to 10 degrees Celsius per 1 000 m
67
DAR and MAR in Cold Air
-similar, MAR can be the same as DAR
68
Unstable Weather
- atmosphere dominated by warm air
- warm air absorbs moisture available and reaches level of saturation
- parcels may rise vertically, cool, condense, and precipitate
69
Stable Weather
- no vertical movement of air
| - atmosphere remains cool and dry
70
Clouds
- made up of moisture droplets
| - 1 million moisture droplets = one rain drop
71
Cloud Formation: Unstable Condition
- air parcel rises to saturation
| - further cooling produces condensation
72
Facilitation of Condensation
- condensation nuclei
| - come from volcanic ash, dust, combustion
73
Clouds: Above Freezing
- collision coalescence is dominate in clouds
- large drops combine with small ones as falling
- become too heavy for the could to hold (rain!)
74
Ice Crystals in Clouds
- ice crystal + super cooled water drops create rain
- super-cooled drops evaporate faster near ice crystals
- ice crystals grow and fall as rain/snow
75
Basic Cloud Form and Classification
- classified by shape and altitude
- puffy, wispy, flat
- 4 classes, 10 types
- in troposphere
76
Stratiform
- horizontal, flat, layered
| - low level
77
Cumuliform
-vertical, puffy, globular
78
Cirriform
- wispy, composed of ice crystals
| - High altitude
79
Cloud Indications
- atmospheric temperature
- atmospheric pressure
- relative humidity/moisture leve
80
Atmospheric Temp (indicated by clouds)
-shown by altitude clouds form
81
Low Elevation Clouds
- stratus, cumulus
- indicate cool atmosphere
- can lead to precipitation
82
Vertical Clouds
- cumulus, cumulonimbus
| - suggest moist air
83
Fog
- cloud in contact with the ground
- dew point temperature and ground temperature is nearly identical
- visibility reduced to max 1 km
84
Advection Fog
-air migrates to a saturated area
85
Steam Fog
-water molecules evaporate from surface into cold overlying air
86
Radiation Fog
-radiate cooling of surface chills air layer above to dew point
87
Source Regions and Air
-air masses reflect characteristics of source regions
88
Great Lakes Effect
- warm great lakes heat up air
- moisten it
- causes heavy snow fall
89
Adiabatic Lifting
- air cools adiabatically
- reaches dew point and saturates
- condense and forms clouds
- possibly precipitates
90
Convergent Lifting
- occurs along ITCZ
- air flows from high to low pressure
- high, vertical, cumulonimbus clouds
91
Convectional Lifting
- stimulated by local surface heating
| - and difference between land and water temperature
92
Orographic LIfting
-air masses forced over physical barrier
93
Front
-leading edge of air mass
94
Frontal Lifting
- air masses of different temperature and humidity
- interact by jet stream
- cold front displaces warm air (forcing up)
- warm front slides over cool air, forced to rise
95
Cold Front
- denoted by triangles
| - life warm/moist air abruptly
96
Warm Front
- denoted by semi circles
- leading edge cannot displace cold air
- pushes cooler air underneath
97
Orographic Precipitation: Stable and Unstable Air
- stable forced up, may create stratiform
| - unstable produces cumulonumbus
98
Windward Slode
-wetter, air masses passing above mountain absorb moisture
99
Leeward Side
- dry side of mountain
- air masses heated by compression
- hot and dry
100
Cyclonic Storms
- migrating, low pressure center
- converging, ascending
- spiraling
- draws surrounding air in
- born on polar front
101
Cyclonic Storms: Cyclogenesis
- disturbance at polar front
- warm are converges and rises
- > instability
102
Cyclonic Storms: Open stage
- counter clockwise (N. Hemisphere) flow
- pulls warm, most air
- from South into Low Pressure center
103
Cyclonic Storms: Occluded stage
- faster moving cold front overtakes warm front
- wedges, creating occluded front
- warm air forced upward
- precipitation occurs
104
Cyclonic Storms: Dissolving Stage
-dissolves when cold air mass cuts off warm air from energy and moisture
105
Thunderstorms
- tremendous energy release
- violent updrafts and downdrafts
- heavy rain, lightning, thunder, hail, blustery winds
- can cause tornado
106
Lightning
- enormous electrical discharge
- ignites air (15 000 to 30 000 degree Celsius
- violent expansion of abruptly heated air
- shock waves through atmosphere
107
Lightning: Relation to Thunder
-shock waves create sonic bangs, which is thunder
108
Lightning Build Up
- electrical energy between areas within cumulonimbus cloud
- electrical energy buildup between cloud and ground
- 3 seconds/km (time for distance between seeing lightning and hearing thunder)
109
Mesocyclone Formation
- body of air pushes faster at higher altitude than at surface
- creates horizontal rotation
110
Mesocyclone: Diameter, encountering updrafts
- strong updrafts create vertical rotation
| - range diameter of 10 km
111
Mesocyclone: extending vertically and compressing horizontally
- speeds mesocyclone up
| - inward vortex created
112
Mesocyclones Produce:
-heavy rain, hail, winds, lightning
113
Rain Routes: Interception
-rain striking ground cover/vegetation
114
Rain Routes: Throughfall
- rain that falls directly to ground
| - rain that drips to ground from vegetation
115
Rain Routes: Stem Flow
-rain and drains across plant leaves and down stems
116
Rain Route Reaching the Soil
- reaches subsurface through infiltration
| - permeates soil.rock through percolation
117
Potential Evotranspiration (PET)
- amount of moisture that WOULD evaporate and transpire if the moisture were available
- moisture demand
- correspond to temperature and humidity
118
PET Approximation
- mean month air temperature
| - day length
119
Soil Moisture Storage (S)
- amount of water stored in soil and accessible to plants
| - held against gravity
120
Water Budget
- comparing Precipitation P with PET
| - by month determines if there is a net supply (+) or net demand (-) for water
GEOG 272
flashcards
Decks in class (1)
# Cards
