2. OverviewOverview
WaterWater
DistributionDistribution
PropertiesProperties
HumidityHumidity
Relative HumidityRelative Humidity
Specific HumiditySpecific Humidity
Atmospheric StabilityAtmospheric Stability
Normal and Environmental Lapse RatesNormal and Environmental Lapse Rates
Dry and Moist Adiabatic RatesDry and Moist Adiabatic Rates
Stability and Instability in the AtmosphereStability and Instability in the Atmosphere
Clouds and FogClouds and Fog
3. Global Distribution of WaterGlobal Distribution of Water
SourcesSources
OutgassingOutgassing
TranspirationTranspiration
Combustion and related processes (respiration,Combustion and related processes (respiration,
decomposition)decomposition)
DistributionDistribution
Ocean and Land HemispheresOcean and Land Hemispheres
EustasyEustasy
PercentagesPercentages
Oceans: 97% (Pacific – 50%, Atlantic – 26%, Indian – 20%,Oceans: 97% (Pacific – 50%, Atlantic – 26%, Indian – 20%,
Arctic – 4%)Arctic – 4%)
Freshwater: 3%Freshwater: 3%
Surface water: 2% (1.99% as ice and glaciers)Surface water: 2% (1.99% as ice and glaciers)
Groundwater: 0.6%Groundwater: 0.6%
Soil Moisture: < 0.5%Soil Moisture: < 0.5%
4. Properties of WaterProperties of Water
Polar StructurePolar Structure
Chemical structure gives HChemical structure gives H22O molecules anO molecules an
electrostatic polarityelectrostatic polarity
Unequal sharing of electronsUnequal sharing of electrons
Oxygen has a higher electronegativity thanOxygen has a higher electronegativity than
HydrogenHydrogen
Covalent bondsCovalent bonds
Asymmetrical (bent) shapeAsymmetrical (bent) shape
Positive charge associated H, Negative with OPositive charge associated H, Negative with O
Hydrogen bondingHydrogen bonding
Cohesive force, surface tensionCohesive force, surface tension
Powerful solventPowerful solvent
Affects soil water availability, nutrientAffects soil water availability, nutrient
transporttransport
7. Heat PropertiesHeat Properties
Heat exchanges with water accounts for 30% of energyHeat exchanges with water accounts for 30% of energy
driving atmospheric circulationdriving atmospheric circulation
PhasesPhases
Solid – Ice (also snow, sleet, hail, frost)Solid – Ice (also snow, sleet, hail, frost)
Maximum density at 4CMaximum density at 4Coo
, Density of ice is 0.9 that of water, Density of ice is 0.9 that of water
Hydrogen bonding creates hexagonal crystal structureHydrogen bonding creates hexagonal crystal structure
Liquid – water (rain, dew)Liquid – water (rain, dew)
Hydrogen bonds are fewer, create surface tension, cohesionHydrogen bonds are fewer, create surface tension, cohesion
Gas – water vapor (steam, clouds, humidity)Gas – water vapor (steam, clouds, humidity)
Phase changesPhase changes
Latent Heat – amount of heat released/absorbed in a phaseLatent Heat – amount of heat released/absorbed in a phase
changechange
Latent Heat of Freezing/MeltingLatent Heat of Freezing/Melting
Latent Heat of Evaporation/CondensationLatent Heat of Evaporation/Condensation
Freezing-meltingFreezing-melting
Condensation-evaporation/vaporization (precipitation, dew)Condensation-evaporation/vaporization (precipitation, dew)
The primary means of heat exchange with the environmentThe primary means of heat exchange with the environment
Deposition-sublimation (frost)Deposition-sublimation (frost)
9. HumidityHumidity
Humidity is water content of the airHumidity is water content of the air
Amount of water is directly proportional toAmount of water is directly proportional to
temperaturetemperature
Relative Humidity is the ratio of waterRelative Humidity is the ratio of water
content in the air to its capacity, expressedcontent in the air to its capacity, expressed
as a percentageas a percentage
Capacity varies with temperature over the dailyCapacity varies with temperature over the daily
range of temperaturesrange of temperatures
Content varies with the movement of airContent varies with the movement of air
masses, annual pattern of pressure andmasses, annual pattern of pressure and
oscillationsoscillations
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11.
12. SaturationSaturation
Occurs when relative humidity becomesOccurs when relative humidity becomes
100%100%
Most often occurs when capacity isMost often occurs when capacity is
reduced due to a drop in temperaturereduced due to a drop in temperature
Further increases in content/reduction ofFurther increases in content/reduction of
capacity results in condensationcapacity results in condensation
Clouds, fog, precipitationClouds, fog, precipitation
Dew-pointDew-point
The temperature at which air becomesThe temperature at which air becomes
saturatedsaturated
13. Vapor PressureVapor Pressure
Water vapor is a gas, so it contributes toWater vapor is a gas, so it contributes to
atmospheric pressureatmospheric pressure
Vapor pressure refers to the amount ofVapor pressure refers to the amount of
pressure exerted by water vapor alonepressure exerted by water vapor alone
Expressed in mbExpressed in mb
Varies with temperatureVaries with temperature
Saturation occurs when water moleculesSaturation occurs when water molecules
entering the air are in equilibrium withentering the air are in equilibrium with
those leaving itthose leaving it
Saturation vapor pressureSaturation vapor pressure
The percentage ratio of VP to SVP givesThe percentage ratio of VP to SVP gives
relative humidityrelative humidity
14. At 30At 30oo
C, if the vapor pressureC, if the vapor pressure
is 15mb, then the relativeis 15mb, then the relative
humidity is 33.3%humidity is 33.3%
15mb/45mb (SVP)15mb/45mb (SVP) ×× 100100
15. Specific HumiditySpecific Humidity
Humidity expressed as actual mass ofHumidity expressed as actual mass of
water in the air per mass of air (g/kg)water in the air per mass of air (g/kg)
Maximum specific humidityMaximum specific humidity is the maximumis the maximum
mass of water vapor that the air can hold atmass of water vapor that the air can hold at
any given temperatureany given temperature
Relative humidity is the ratio of SH to MSHRelative humidity is the ratio of SH to MSH
expressed as a percentageexpressed as a percentage
16. At 20At 20oo
C, if the specificC, if the specific
humidity is 5g, then thehumidity is 5g, then the
relative humidity is 33.3%relative humidity is 33.3%
5g/15g (MSH)5g/15g (MSH) ×× 100100
17. Atmospheric StabilityAtmospheric Stability
Storms are caused by atmospheric instabilityStorms are caused by atmospheric instability
Instability is rising air that can produce cyclonic rotationInstability is rising air that can produce cyclonic rotation
Stability occurs when air masses are not risingStability occurs when air masses are not rising
The relative stability of the atmosphere is theThe relative stability of the atmosphere is the
product of two cooling processesproduct of two cooling processes
Environmental Lapse RateEnvironmental Lapse Rate
The rate at which air cools with altitudeThe rate at which air cools with altitude
As measured at any given time.As measured at any given time.
The flow of heat energy through the atmosphere greatly affectsThe flow of heat energy through the atmosphere greatly affects
this ratethis rate
Adiabatic RateAdiabatic Rate
The rate at which air cools as it becomes less denseThe rate at which air cools as it becomes less dense
Based on thermodynamic laws of gases relating temperature toBased on thermodynamic laws of gases relating temperature to
density and pressure – it is the rate of cooling simply bydensity and pressure – it is the rate of cooling simply by
expanding, without the flow of heat energy into or out if it.expanding, without the flow of heat energy into or out if it.
18. If the adiabatic rate exceeds the environmentalIf the adiabatic rate exceeds the environmental
rate, then air will cool more quickly by rising thanrate, then air will cool more quickly by rising than
the surrounding air, and will not risethe surrounding air, and will not rise
If the adiabatic rate is less than the environmentalIf the adiabatic rate is less than the environmental
lapse rate, then rising air will have a higherlapse rate, then rising air will have a higher
temperature than the surrounding air, and willtemperature than the surrounding air, and will
continue to risecontinue to rise
Two adiabatic rates:Two adiabatic rates:
Dry adiabatic rate (DAR) if air is not saturatedDry adiabatic rate (DAR) if air is not saturated
1010oo
C per 1000mC per 1000m
Moist adiabatic rate (MAR) if it is saturatedMoist adiabatic rate (MAR) if it is saturated
66oo
C per 1000mC per 1000m
If a parcel of air rises far enough, it will cool, and itsIf a parcel of air rises far enough, it will cool, and its
capacity for water vapor will decrease, and becomecapacity for water vapor will decrease, and become
saturated. If so, the adiabatic rate for the parcelsaturated. If so, the adiabatic rate for the parcel
changes from DAR to MARchanges from DAR to MAR
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23. Clouds and FogClouds and Fog
An expression of stability in the atmosphereAn expression of stability in the atmosphere
FormationFormation
Air at some point in the atmosphere becomesAir at some point in the atmosphere becomes
saturatedsaturated
Water droplets condense around particles of dust,Water droplets condense around particles of dust,
soot, pollution or sea-saltsoot, pollution or sea-salt
condensation nucleicondensation nuclei
ClassificationClassification
Based andBased and altitudealtitude andand shapeshape
FormsForms
Stratiform: flat and layeredStratiform: flat and layered
Cumuliform: puffy, globular and vertically developedCumuliform: puffy, globular and vertically developed
Cirroform: Wispy clouds (typicaly high altitude)Cirroform: Wispy clouds (typicaly high altitude)
24. Cloud TypesCloud Types
Low clouds (up to 2000 m)Low clouds (up to 2000 m)
Stratus: Dull, gray and featurelessStratus: Dull, gray and featureless
Stratocumulus: puffy stratiform cloudsStratocumulus: puffy stratiform clouds
Nimbostratus: Stratus clouds with drizzling precipationNimbostratus: Stratus clouds with drizzling precipation
Middle clouds (2000 – 6000 m)Middle clouds (2000 – 6000 m)
Altostratus: High, thin stratiform clouds. Sun just visibleAltostratus: High, thin stratiform clouds. Sun just visible
Altocumulus: Patches of “cotton balls” arranged in lines, groups,Altocumulus: Patches of “cotton balls” arranged in lines, groups,
rippling wavesrippling waves
High clouds (6000 – 13,000 m)High clouds (6000 – 13,000 m)
Cirrus: wispy, feathery, hairlike, streaks or plumesCirrus: wispy, feathery, hairlike, streaks or plumes
Cirrostratus: Milky veil of ice crystals – sun and moon halosCirrostratus: Milky veil of ice crystals – sun and moon halos
Cirrocumulus: Tufts, dappled, in lines, groups or ripplesCirrocumulus: Tufts, dappled, in lines, groups or ripples
Vertically developed clouds (0 – 13,000 m)Vertically developed clouds (0 – 13,000 m)
Cumulus: Flat based puffy tops; sharply outlined; fair weatherCumulus: Flat based puffy tops; sharply outlined; fair weather
Cumulonimbus: Cirrus-topped plume blown by upper levelCumulonimbus: Cirrus-topped plume blown by upper level
winds into an anvil-shape; explosive tops; extreme verticalwinds into an anvil-shape; explosive tops; extreme vertical
development; thunderstorms, tornadoes.development; thunderstorms, tornadoes.
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41. FogFog
Stratus clouds sitting on the groundStratus clouds sitting on the ground
Advection FogAdvection Fog
Warm air moving over a cool surface, becoming saturatedWarm air moving over a cool surface, becoming saturated
Cool air moving over a warm surface, saturating itCool air moving over a warm surface, saturating it
evaporation fogevaporation fog
Warm moist air being forced upslope, cooling andWarm moist air being forced upslope, cooling and
becoming saturatedbecoming saturated
Upslope fogUpslope fog
Warm layer of air moving over trapped lower lying cool,Warm layer of air moving over trapped lower lying cool,
saturated air, creating an inversion layersaturated air, creating an inversion layer
Valley FogValley Fog
Radiation FogRadiation Fog
Radiative cooling of a surface saturates the air above itRadiative cooling of a surface saturates the air above it