climate and global change notes 23-1 hydrologic cycle surface-atmosphere exchange of water water...

Climate and Global Change Notes

23-1

Hydrologic Cycle

Surface-Atmosphere Exchange of Water

Water Cycle

Science Concepts

EvaporationCondensationPrecipitationRunoff


23-2

Hydrologic Cycle

Change in Annual Precipitation


23-3

Hydrologic Cycle

Modeled Environmental Water Scarcity Index• Scarcity is where the amount of water removed from the system puts the

ecosystem at risk by tapping into the environmental water demand, i.e., the

amount of water needed to sustain the integrity of the ecosystem• Areas above 0.4 are under ecosystem environmental stress• Areas higher than 0.8 (orange and red) are highly-stressed environmentally

http://www.iucn.org/themes/wani/eatlas/html/gm16.html


23-4

Hydrologic Cycle

The Water Cycle

• All streams flow into the sea, yet the sea is never full.

To the place the streams come from, there they return again.

Ecclesiastes 1:7 (New International Version)

http://ga.water.usgs.gov/edu/watercycle.html


23-5

TheWaterCycle

Hydrologic Cycle

425Evaporation

71Evapotranspiration

111Precipitation

385Precipitation

40Vapor TransportSurface Runoff

Groundwater FlowPercolation40Return Flow 1012 m3 per year


23-6

Hydrologic Cycle

GOES WaterVapor Image


23-7

Hydrologic Cycle

GOES Visible Image


23-8

Hydrologic Cycle

Mean Global Precipitable Water (cm)

•• Annual AverageAnnual Average

http://isccp.giss.nasa.gov/cgi-bin/browsed2


23-9

Hydrologic Cycle

Mean Global Precipitable Water (cm)(Con’t)

•• Seasonal variabilitySeasonal variability

S.W. Seemann, J. Li, W.P. Menzel – Univ. Wisconsin, NOAAS.W. Seemann, J. Li, W.P. Menzel – Univ. Wisconsin, NOAA


23-10

Hydrologic Cycle

Amazon Seasonal Variability

•• Note seasonal rainfall variabilityNote seasonal rainfall variability

•• Amazon and Tropical seasons revolve Amazon and Tropical seasons revolve around wet/dry not hot/coldaround wet/dry not hot/cold

http://earthobservatory.nasa.gov/Study/AmazonLAI/

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.


23-11

Hydrologic Cycle

Honolulu WSO Airport

• 21° 20’ N, 157° 55’ W

• Elevation = 10 ft

• Averages for10/1/49-3/31/05

0

1

2

3

4

Ave Precip (in) 3.37 2.43 2.59 1.21 0.94 0.38 0.54 0.62 0.66 1.9 2.8 3.3

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

65

70

75

80

85

90

Ave Max Temp (°F)Ave Min Temp (°F)

Ave Max Temp (°F) 80 80.1 81 82.4 84.2 86.1 87.1 88 88 86.4 83.7 81

Ave Min Temp (°F) 65.7 65.8 67.2 68.8 70.4 72.4 73.6 74.4 73.7 72.5 70.5 67.6

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec



Ave. Max. Temp. = 84.0°F

Ave. Min. Temp. = 70.2°F

Ave. AnnualPrecipitation = 20.75 in

http://www.wrcc.dri.edu/cgi-bin/cliMAIN.pl?hihono


23-12

Hydrologic Cycle

Mean January MoistureDewpoint Temperature (°F)

1961-1990

Relative Humidity (%)1961-1990

http://www.nndc.noaa.gov/cgi-bin/climaps/climaps.pl


23-13

Hydrologic Cycle

Mean July MoistureDewpoint Temperature (°F)

1961-1990


Relative Humidity (%)1961-1990


23-14

Hydrologic Cycle

Average Dewpoint Temperature (°F) (1960-1990)


January July

Annual


23-15

Hydrologic Cycle

July Dewpoint Temperature & Diurnal Temperature Range (°F)


Dewpoint Temperature Diurnal TemperatureRange


23-16

Hydrologic Cycle

Average Relative Humidity (1960-1990)


January July

Annual


23-17

Hydrologic Cycle

Average Annual Precipitation (1961-1990)

• Annual

http://www.meted.ucar.edu/broadcastmet/watershed/

media/graphics/unit_6/

nat_atlas_precip.jpg


23-18

Hydrologic Cycle

Surface-Atmosphere Exchange of Water (Con’t)

Saturation ProcessesIncrease VaporCooling

LiftingMixingRadiational Cooling

Condensation TypesDew/FrostFogHazeCloud Droplets

Science Concepts

Dry Adiabatic & Moist Adiabatic

Process


23-19

Clouds and Precipitation

Atmospheric Saturation Processes

• Add moisture - Infrequent (Steam Fog)

• Cool to dewpoint temperature - Usual process

- Lifting

- Mixing

- Radiation


23-20


Cloud Formation

• Condensation process

- Condensation nuclei

> What are they?

‡ Sea salt‡ Combustion products - smoke‡ Dust - Clay from plowed fields

> What is their distribution?

‡ Decrease with height - For Example: 0.1 as many at 3,000 ft as

at surface; 0.01 as many at 14,000 ft as at surface

‡ More over cities than country‡ More over land than ocean - More giant nuclei

over oceans

- Hygroscopic nuclei - Begin to attract water vapor at RHs as low as 70%

> What are they?

‡ Sea salt - Most common

Science quotes of 5th and 6th graders -

I am not sure how clouds get formed. But the clouds know how to do it, and that is the important thing.


23-21

Types of Condensate

• Dew

- Caused by radiational cooling of a surface to the dewpoint temperature of the air

- Typical conditions

> Clear skies> Calm winds (little mixing)> Nighttime

- Dewpoint temperature above 32°F



Dew is formed on leaves when the sun shines down on them and makes them perspire.


23-22


Types of Condensate (Con’t)

• Frost

- Caused by radiational cooling of a surface to the dewpoint temperature of the air

- Typical conditions

> Clear skies> Calm winds (little mixing)> Nighttime

- Dewpoint temperature below 32°F

Quote

“Teg weather report on the car radio had predicted a low of 35 degrees, and Pittmen believed it, seeing frost come out of his mouth.”

David Morrell, "Desperate Measures" (p. 295)

What is wrong with this statement?


23-23


Types of Condensate (Con’t)• Fog

- Defined as a cloud on the ground

- Caused by

> Cooling of the air to its dewpoint temperature

‡ Most common cause‡ Types of “cooling fog”

◊ Radiation fog◊ Advection fog◊ Upslope fog

> Evaporation of enough water to saturate the atmosphere

‡ Least frequent cause‡ Types of “evaporation fog”

◊ Steam fog◊ Warm-rain fog

- Dissipation (“burns-off”) by solar heating the surrounding ground; causes mixing at edges

- Annual average days with fog

In order to save the army during the Revolutionary War Washington retreated from Long Island overnight on Aug. 29, 1776. By sunrise on the 30th not all the troops had been ferried across the river to the NY side. However, a heavy fog had settled over the river so they could continue to cross without being observed by the British troops and war ships. Within an hour after the boats had carried the last of the 9,000 troops safely across, the wind shifted and the fog dispersed. Fog had helped save the army.1776, David McCullough, pp. 186-191


23-24


Radiation and Valley Fog

Note contrails

Bright yellow is fog

Valley fog

AVHRR Satellite - 4 November 1999 - Color enhanced (Visible,

near infrared (~1 micron), infrared (~3.7 micron)

Alabama Rivers


23-25


Types of Condensate (Con’t)

• Haze

- Caused by particles (“large”) that scatter all wavelengths of light equally

- Increases as RH becomes greater than 70% because of hygroscopic nuclei

• Cloud droplets

- Cooling of the air aloft to its dewpoint temperature


23-26

Hydrologic Cycle


Precipitation Physics (Con’t)Cloud Growth Processes

Droplet MultiplicationCascade Effect

Science Concepts

Surface TensionSolute EffectCurvature Effect


23-27


Cloud Droplet Growth Processes

• Solute effect - Solution of water and nuclei material

- Helps droplet grow

- Decreases as droplet becomes larger

- Larger condensation nuclei, larger this effect. Thus,larger nuclei grow larger droplets

• Curvature effect - Caused by surface tension around droplet

- Hinders droplet grow

- Decreases as droplet becomes larger

Cloud Droplet Multiplication Process

• Cascade effect - Large drops break into several smaller drops


To most people solutions mean finding the answers. But to chemists solutions are things that are still all mixed up.


23-28

Hydrologic Cycle


Precipitation Physics (Con’t)Rain Drop Formation

Collision and Coalescence Process

Bergeron Process

Precipitation Types

Science Concepts

Terminal VelocityGravitational ForceDrag ForcePressure Gradient

Force

Supercooled WaterSaturation Over Water Ice


23-29


Forces on a Falling Object

• Terminal velocity ~120 mph

http://cyberbuzz.gatech.edu/skydive/photos/othermisc/ http://www.fcsurplus.ca/army/300745b.gif


23-30


Forces on a Cloud or Rain Drop

• Drag Force => Depends on square of Velocity and Shape of Drop

• Pressure Gradient Force => Depends on Volume of Drop

• Gravitational Force => Depends on the Mass of the Drop

Cloudor

Rain Drop

GravitationalForce

PressureGradientForce

DragForce

D = Cd A V2 / 2

D = Drag forceCd = Drag coefficient

(usually determined

experimentally) = Density of fluid (air) A = Reference area

(includes shape, etc.)V = Velocity


23-31


Atmospheric Particles

Name Diameter (cm) # per cm3 Large Ions 10-6 to 10-5 103 to 104

Smoke and Dust 10-5 to 10-4 variableLarge Condensation Nuclei10-5 to 10-4 102

Giant Condensation Nuclei10-4 to 10-2 1Cloud Droplets 10-4 to 10-2

Rain Drops 10-2 to 1


23-32


Particle Terminal Velocities

Particle Type Diameter (cm) m/s mphCondensation Nuclei 2 X 10-5 1 X 10-7 2 X 10-7

Small Cloud Droplets1 X 10-5 3 X 10-3

Typical Cloud Droplets2 X 10-3 1 X 10-2 2 X 10-2

Large Cloud Droplets 10-2 0.27 0.18

Small Rain Drops 0.1 4.0 8.9

Typical Rain Drops 0.2 6.5 14.6

Large Rain Drops 0.5 9.0 20.1


23-33


Raindrop Growth Process

• Raindrop 100 times larger diameter than cloud drop; 1,000,000 time larger volume

• How does this tremendous growth occur?

- Coalescence process - “Warm” clouds

> Terminal velocity

‡ Gravitational force‡ Pressure gradient force‡ Drag force

> Large drops fall faster than smaller drops

> Large drops collect smaller drops

Did you know -

Houses used to have thatched roofs - thick straw, piled high, with no wood underneath. Because it was the a place animals could get warm, cats and other small animals (mice, bugs) lived in the roof.

When it rained, the thatch became slippery and sometimes the animals would slip off the roof.

Hence, the saying "It's raining cats and dogs."


23-34


Raindrop Growth Process (Con’t)

• Raindrop 100 times larger diameter than cloud drop; 1,000,000 time larger

volume (Con’t)

• How does this tremendous growth occur? (Con’t)

- Bergeron-Findeisen or ice process - “Cold” clouds

> Freezing nuclei

‡ Not enough in the atmosphere‡ “Pure” water may not turn to ice until -40°C

> Between 0°C and -40°C, cloud is mixture of ice and liquid. At

temperatures below (i.e., heights above) -40°C, cloud is all ice.

> Ice crystals grow at expense of liquid drops


23-35


Comparison of Maritime and Continental Rain Clouds

Maritime Continental

Number of Nuclei 940 cm-3 9500 cm-3

Droplet Concentration 50 cm-3 200 cm-3

Median Droplet Diameter17 x 10-6 m 11 x 10-6 m


23-36


Precipitation Classification

• Drizzle

- Small, numerous drops falling out of fog or low layer stratus clouds

- Indicative of stable stratification with little vertical motion

• Intermittent or Continuous Precipitation

- Rain or snow- Falling more or less evenly from altostratus or

nimbostratus clouds- Caused by widespread and slow upward movement of large

masses of air

• Showers (Squalls, Flurries)

- Precipitation with short duration with fair intervals- Caused by cumulus or cumulonimbus clouds, i.e,

convection- Indicative of unstable stratification with fairly

strong upward vertical motion in localized regions


23-37


Types of Precipitation

• Virgae

- Rain that evaporates below cloud base, but before reaching the ground

• Rain

- Lower atmosphere above freezing- Drops large enough to fall relative to

air motions

http://www.ucar.edu/imagelibrary/1600-1650.html

http://www.wrh.noaa.gov/spokane/042700/tstms.htm


23-38



• Freezing Rain

- Ground at 0°C or colder- Very shallow layer of air near the ground

at near 0°C or colder- Layer of air above this shallow layer at

temperatures above 0°Chttp://

ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/prcp/

zr/frz.rxml

http://www.srh.noaa.gov/lzk/html/win121300.htm




23-39



• Sleet, Grauple, Ice Pellets

- Clear ice “drops”- Precipitation is in the form of liquid

drops at sometime as it falls- Deeper layer of air above the ground

at 0°C or colder- Layer of air above this deeper layer at

temperatures above 0°Chttp://

ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/

prcp/slt.rxml




23-40




Types of Precipitation (Con’t)

• Snow- Opaque ice crystals or flakes- Crystals form at temperatures below 0°C

by the process of deposition- No liquid phase- Ground at or near 0°C or colder- Layer of air above the ground at

temperatures below 0°C

http://ww2010.atmos.uiuc.edu/

(Gh)/guides/mtr/cld/prcp/snow.rxml

http://www.noaanews.noaa.gov/stories/s592b.htm

http://www.ucar.edu/imagelibrary/1100-

1133.html


A blizzard is when it snows

sideways.


23-41


Types of Precipitation (Con’t)

• Hail

- Large balls or lumps of ice- Often formed of concentric

rings of clear and opaque ice

- Formed in clouds with strong updrafts, i.e., convective clouds

http://www.eas.slu.edu/Photos/hail.html

http://www.ucar.edu/imagelibrary/1134-1166.html

Record Hail Stone - 7” diameter, 18.75’’ circumference fell in

Aurora, NE, 22 June 2003

climate and global change notes 23-1 hydrologic cycle surface-atmosphere exchange of water water...

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