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Chapter 5 Atmospheric Water and Weather

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Title: Chapter 5 Atmospheric Water and Weather


1
Chapter 5 Atmospheric Water and Weather
2
  • Supplemental notes are drawn from Lutgens and
    Tarbuck, The Atmosphere

3
(No Transcript)
4
Significance of Water
  • (1) Vital to all organisms of the Earth
  • (2) Necessary for many Earth system processes
  • (3) Impacts the structure of the Earths surface
    chemically and physically
  • (4) Has definite functions in human activities
  • (5) Can exist in solid, liquid and gaseous states
    under normal Earth atmospheric conditions
  • (6) It is slow to heat / slow to cool

5
Water and Atmospheric Moisture
  • - Water on Earth Location and  Properties  
  • Humidity  
  • - Atmospheric Stability  
  • - Clouds and Fog  
  • - Air Masses  
  • - Atmospheric Lifting Mechanisms  
  • - Midlatitude Cyclonic Systems  
  • - Violent Weather  

6
Ocean and Freshwater Distribution
Figure 5.3
7
Hydrologic Cycle
  • - Closed system movement of moisture in the
    Hydrosphere
  • - Absorption and release of energy (latent
    heatin calories) powers the system
  • - As a proportion, the energy is small, the
    actual amount is significant
  • - Gain-or-loss of energy results in three major
    processes and two minor processes

8
Hydrologic Cycle
  • Evaporation / transpiration
  • Condensation
  • Precipitation
  • Sublimation
  • Deposition
  • In general terms, precipitationevaporation
    worldwide
  • --- in reality,
  • too much, too little, too bad
  • issues of frequency and dependability
  • Continents precipitationgtevaporation
  • Oceans precipitationltevaporation

9
Waters Heat Energy Characteristics
Figure 5.6
10
  • Moisture in the hydrologic cycle is most
    frequently locked in H2O vapor
  • It is a small but, highly variable percentage of
    the atmosphere by volume
  • This H2O vapor is concentrated in the lower
    18,000 of the atmosphere

11
  • There are limits to the volume of H2O that the
    atmosphere can hold in suspension
  • temperature is the primary factor
  • As a general rule, the warmer the air, the
    greater the volume of water vapor that air can
    hold

12
Saturation and Dew Point
  • saturation or point of saturation
  • - Achieved by
  • (1) dropping temperature
  • (2) increasing moisture
  • Temperature of saturation is called dew point
  • After saturation, additional cooling or addition
    of moisture results in condensation

13
Humidity
  • - General term for the measure of the volume of
    H2O present in the air at a given temperature
  • --- reported as
  • absolute relative specific
  • - We are interested in relative humidity
  • Ratio of H2O in the atmosphere at a given
    temperature, to the volume of H2O the air can
    hold at that temperature
  • (H2Oobserved / H2Opossible) x 100

14
Relative Humidity
Figure 5.7
15
Humidity Patterns
Figure 5.10
16
Atmospheric Stability  
  • - Adiabatic Processes  
  • --- Dry adiabatic rate (DAR) 10oC/1000m
  • --- Moist adiabatic rate (MAR) 6oC/1000m
  • --- Stable and unstable atmospheric
    conditions

17
Condensation
  • Process by-which gaseous H2O is changed to a
    liquid (600 cal release)
  • clouds fog dew frost
  • though frost is technically different
  • Requires (1) air cooled beyond saturation
  • (2) a surface on-which to condensation
  • (condensation nuclei)

18
Fog
  • Simplest a cloud with base at ground level
  • (1) cooling
  • radiation
  • advection
  • upslope fog
  • ice fog
  • (2) evaporation fog
  • steam fog
  • frontal fog

19
Clouds
  • Buoyant masses of visible H2O or ice crystals
  • Visible sign of atmospheric stability or
    instability
  • Product of any process encouraging air movement
  • vertical
  • convection
  • convergence
  • subsidence
  • horizontal
  • advection
  • frontal lifting

20
Cloud Forms
  • Classed by altitude and appearance
  • - Altitude families
  • High cirro
  • Middle alto
  • Low strato
  • Clouds of vertical formation

21
Cloud Forms, cont
  • - Appearance
  • stratus - sheet, layer (stability)
  • cumulus globular, pillowy (instability)
  • cirrus high, white, thin (stable, ice)
  • We also make use of the prefix / suffix
  • nimbo or nimbus to designate precipitation-bearin
    g clouds

22
Cloud Types and Identification  
Figure 5.18
23
Cumulonimbus Development
Figure 5.19
24
Airmasses
  • Large masses of air characterized by
  • (1) common properties of humidity and
    temperature at a given altitude
  • (2) characteristics of their source
    region

25
Source Region
  • Region whose terrestrial and atmospheric
    conditions create airmasses
  • (1) extensive and uniform in area
  • (2) area of atmospheric stagnation

26
Airmasses are classified by
  • (1) Latitude of source region
  • (gives temperature)
  • A P T E AA
  • (2) Surface area below the airmass (gives
    humidity)
  • continental c low moisture
  • marine m high moisture
  • k and w are added for stability indices

27
Airmass Classification, cont
  • cA continental Arctic
  • cP continental Polar ()
  • cT continental Tropical ()
  • mT marine Tropical ()
  • mP marine Polar ()
  • mE marine Equatorial
  • cAA continental Antarctic
  • consistently influence North America

28
Air Masses
Figure 5.24
29
Front
  • Surface or zone of contact / conflict /
    discontinuity between airmasses
  • Coined by Norwegian meteorologists in WWI Polar
    Front Theory
  • Norwegian Cyclone Model
  • links cloud patterns, precipitation, wind,
    barometer, flow aloft, etc

30
  • Frontal lifting occurs when one airmass is forced
    to rise/ride above the other
  • Passing through a front frequently brings weather
    change
  • temperature dew point spread wind speed /
    direction atmospheric pressure

31
Atmospheric Lifting Mechanisms 
  • Convectional Lifting  
  • Orographic Lifting  
  • Frontal Lifting
  • ---Cold fronts
  • ---Warm fronts
  • --- Occluded fronts
  • --- Stationary fronts

32
Atmospheric Lifting Mechanisms 
Figure 5.27
33
Cold Front
Figure 5.31a
34
Warm Front
Figure 5.32
35
Midlatitude Cyclone
Figure 5.33
36
Average and Actual Storm Tracks
Figure 5.34
37
Thunderstorms
  • Best known disturbance weather pattern not
    strictly cyclonic flow
  • Worldwide approx 16 million annually
  • Product of warm, moist air lifted to
    condensation most are tropical almost unknown at
    the Poles
  • - may be convectional orographic
  • frontal

38
Thunderstorms
Figure 5.36
39
Thunderstorms, cont
  • Characterized by thunder/lightning
  • torrential rainfall/hail strong
  • up-and-downdraft winds release of latent heat
  • Stages
  • (1) cumulus
  • (2) mature
  • (3) dissipation

40
Tornadoes
  • From the Spanish tornar to turn
  • Intense center(s) of low pressure
  • pressure gradient winds may exceed 300 mph
  • a whirl-pool like column of air vortex
    downward from a cumulonimbus cloud
  • A funnel of condensed H2O, funnel colored by what
    the tornado contacts

41
Tornado Development and Occurrence
  • - Often produced in association with mid-latitude
    cyclones
  • - lt 1 of thunderstorms produce tornadoes
  • - Typically North American (3/4) and spawned in
    cP-mT air collisions
  • --- 700 annually North America dominates

42
Twister!
Figure 5.38
43
Tornadoes
Figure 5.39
44
  • Life Stages
  • Though a tornado may have a life of only
    minutes, each will go through some combination of
    the following stages
  • (1) Funnel cloud
  • (2) Tornado
  • (3) Mature Tornado
  • (4) Shrinking Tornado
  • (5) Decaying Tornado

45
Tornado Destruction
  • Millions of stories about what tornadoes can do
  • Destruction from
  • (1) high winds - strong updrafts
  • (2) high speed projectiles
  • (3) subsidiary vortices /
  • down blasts

46
Tornado Destruction, cont
  • No one has accurately measured the windspeed of a
    tornado
  • We rate tornadoes by extent of damage the Fujita
    Scale (F-Scale)
  • Tornado Watch and Tornado Warning

47
Hurricanes
  • Tropical cyclone with windspeed in excess of 200
    mph
  • Lowest pressure recorded in the Western
    Hemisphere
  • Name from Huracan Carib Indian god of evil

48
Hurricane Development and Occurrence
  • Giant heat engines taking energy from oceanic
    latent heat
  • Form over tropical waters 5o to 20o
  • but not all the tropical waters
  • inside of 5o no Coriolis
  • So. Atlantic cold water currents
  • The notable exception to a lack of So. Atlantic
    hurricanes is Hurricane Catarina (2004)

49
Hurricane Development and Occurrence, cont
  • Three stages of development
  • (each can be an end in itself)
  • (1) tropical depression
  • (2) tropical storm
  • (3) hurricane
  • --- wind swirl/rain bands
  • --- eyewall winds to 200 mph
  • --- eye winds approx 25 mph

50
Profile of a Hurricane
Figure 5.42
51
Destruction
  • Damage from tropical hurricanes range from
    complete devastation, caused by the passage of
    the eyewall of a very intense hurricane along the
    coast, to a minor nuisance, produced by a weak
    hurricane whose effects resemble those of a
    strong thunderstorm
  • Annually nearly every portion of the US is
    effected directly or indirectly by hurricane
    activity

52
Destruction
  • Forms
  • (1) wind
  • (2) storm surge
  • (3) inland flooding
  • eye wall may produce 10 rainfall
  • (4) ancillary vortices (tornadoes)
  • function of ground speed
  • Saffir-Simpson Hurricane Intensity Scale
  • Hurricane Watch/Hurricane Warning

53
Some Interesting Ones
  • No Name Galveston Bay,TX 1900
  • No Name Okeechobee, FL 1928
  • Camille 1969
  • Agnes 1972
  • Hugo 1989
  • Gilbert 1994
  • Dennis, Floyd, Irene 1999
  • Andrew 1992
  • Katrina 2005
  • Catarina 2004
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