The Hydrologic Cycle, Climate, and Weather

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Chapter 2

• The Hydrologic Cycle, Climate, and Weather

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Chapter Headings

• The hydrologic cycle
• Precipitation
• Runoff
• Surface and groundwater storage
• Evaporation
• Condensation

• Climate and weather
• Climate
• Climate change
• Weather
• Weather modification
• Floods
• Drought

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Chapter Headings

• The hydrologic cycle
• Precipitation
• Runoff
• Surface and groundwater storage
• Evaporation
• Condensation

• Climate and weather
• Climate
• Monitoring climate change
• Weather
• Weather modification
• Floods
• Drought

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Mean annual precipitation
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Modern tipping bucket rain gauge
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http//www.georgiaweather.net/
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Hurricane Charlie 2004 Doppler radar image
Measure of rainfall Counter-clockwise
circulation around a low pressure area
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Hurricane Katrina satellite photo, 5 am Aug 29,
2005
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Chapter Headings

• The hydrologic cycle
• Precipitation
• Runoff
• Surface and groundwater storage
• Evaporation
• Condensation

• Climate and weather
• Climate
• Monitoring climate change
• Weather
• Weather modification
• Floods
• Drought

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Hodler and Schretter, The Atlas of Georgia
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Chapter Headings

• The hydrologic cycle
• Precipitation
• Runoff
• Surface and groundwater storage
• Evaporation
• Condensation

• Climate and weather
• Climate
• Monitoring climate change
• Weather
• Weather modification
• Floods
• Drought

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Lakes and Reservoirs

• Lakes are large inland bodies of water formed
  naturally
• Usually by glaciers or earthquakes
• Reservoirs are manmade lakes formed by damming
  rivers
• Used to store and control water
• From the French verb to reserve reservoir
• All lakes in the southeast are reservoirs
• A reservoir is a long skinny lake

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Great Salt Lake

• Terminal lake with no outlet river extending to
  the ocean
• Broad, shallow terrain
• High salt content because all the water is lost
  due to evaporation leaving the minerals behind
• Geologically, this is the forerunner of a salt
  bed
• Salt content has ranged from 5 (just above sea
  water) to 27 (saturation) depending on water
  level

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Groundwater Storage
Fetter, Applied Hydrology
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Groundwater Storage

• Groundwater recharge
• Water added to groundwater usually through
  percolation down through the soil to the water
  table
• Groundwater discharge
• Water lost from groundwater usually through
  springs, streams, and rivers

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Recharge and Discharge
Recharge
Discharge
Recharge
Discharge
Fetter, Applied Hydrology
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Hodler and Schretter, The Atlas of Georgia
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Chapter Headings

• The hydrologic cycle
• Precipitation
• Runoff
• Surface and groundwater storage
• Evaporation
• Condensation

• Climate and weather
• Climate
• Monitoring climate change
• Weather
• Weather modification
• Floods
• Drought

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Evaporation

• Evaporation loss of liquid water from land and
  water surfaces as it is converted to a gas (water
  vapor)
• Transpiration liquid water moving from soil
  through a plant and evaporating from the leaves
• Evapotranspiration (ET) combination of
  evaporation and transpiration

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Hodler and Schretter, The Atlas of Georgia
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Evaporation

• Soil water balance equation
• ET Si Sf P I D
• Si initial soil water storage
• Sf final soil water storage
• P precipitation
• I irrigation
• D drainage
• All in units of length (inch or mm)

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Example Problem

• In a one week period
• Rainfall 2
• Irrigation 0
• Drainage 1
• Soil water content at beginning of week 5
• Soil water content at end of week 3
• How much water was evaporated or transpired (ET)
  during week?
• ET 5 3 2 - 1 3

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Chapter Headings

• The hydrologic cycle
• Precipitation
• Runoff
• Surface and groundwater storage
• Evaporation
• Condensation

• Climate and weather
• Climate
• Monitoring climate change
• Weather
• Weather modification
• Floods
• Drought

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Condensation

• Condensation cooling of water vapor (gas) until
  it becomes a liquid
• Opposite of evaporation
• As air rises it cools and water condenses forming
  clouds and eventually rain
• As air falls it warms and condensation does not
  occur
• Fog and dew are examples of condensation due to
  cooling

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Chapter Headings

• The hydrologic cycle
• Precipitation
• Runoff
• Surface and groundwater storage
• Evaporation
• Condensation

• Climate and weather
• Climate
• Climate change
• Weather
• Weather modification
• Floods
• Drought

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Climate

• Climate is the long-term average state of the
  atmosphere for a region
• Changes very slowly under normal circumstances
• Example Egypt is hot and dry on average
• Affected by
• Global air currents
• Global ocean currents
• Tilt of the Earths axis

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Climate

• Climate is what you expect, weather is what you
  get
• Dr. Heid Cullen, Weather Channel

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Global Air Currents

• Caused by the uneven heating of the Earth
• Warmer at the equator (rising air)
• Cooler away from the equator (sinking air)
• Coriolis force causes winds to diverge
• To the right in the northern hemisphere
• To the left in the southern hemisphere

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Coriolis force

• Gustave Coriolis, 1792-1843, French mathematician
• The Earth's rotation causes the surface to move
  fastest at the equator... A bird flying away from
  the equator carries this faster motion with
  itor, equivalently, the surface under the bird
  is rotating more slowly than it wasand the
  bird's flight curves eastward slightly. In
  general objects moving away from the equator
  curve eastward objects moving towards the
  equator curve westward. Wikipedia.

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Global Air Currents
calspace.ucsd.edu/virtualmuseum
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Global Air Currents
ITCZ Inter Tropical Convergence Zone
calspace.ucsd.edu/virtualmuseum
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Global Air Currents
Worlds deserts tend to occur near 30o N and S
latitudes Rainforests at the equator
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Global Ocean Currents

• Ocean currents produced by
• Global wind currents
• Tides (gravitational pull of the moon)
• Coriolis effect
• Differences in water density due to temperature
  and salinity
• Ocean currents often temper local climates
• Example Gulf Stream effects on English Isles

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Global Ocean Currents
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Tilt of the Earths Axis

• Tilt of 23.5o
• Causes seasons in temperate zones
• Winter in the northern atmosphere when the North
  Pole is tilted away from the sun
• Summer in the northern atmosphere when the North
  Pole is tilted toward the sun

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csep10.phys.utk.edu/astr161/lect/time/seasons
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Chapter Headings

• The hydrologic cycle
• Precipitation
• Runoff
• Surface and groundwater storage
• Evaporation
• Condensation

• Climate and weather
• Climate
• Climate change
• Weather
• Weather modification
• Floods
• Drought

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Climate Change

• Climate change may now be accelerating due to
  greenhouse gases such as CO2
• No question that the earth is in a warming cycle
• Is it warming faster than normal?
• What is normal?
• Intense interest in determining what the Earths
  temperature record has been

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Climate Change

• Each year, the Earths climate is recorded in
  tree rings, ice, coral, and sediment cores around
  the world
• Dendrochronology the study of tree rings
• Dendro Greek for tree
• Chronology Science that deals with time
• Years with favorable weather produce more
  growth and wider rings
• Calibrated using years with known weather

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Climate Change
web.utk.edu/grissino/images
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Climate Change
www.exploratorium.edu/climate/atmosphere
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Climate Change
Ice cores from ancient times sometimes contain
trapped bubbles of atmospheric air that can be
analyzed for CO2 concentrations to see how they
compare to modern concentrations
news.bbc.co.uk
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Climate Change

• Greenhouse gases in upper atmosphere trap heat
• Allow shortwave radiation from the sun to enter
  the atmosphere
• Do not allow longwave radiation from the earth to
  escape
• Carbon dioxide (CO2), water vapor, methane,
  ozone, nitrous oxide

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www.defra.gov.uk/environment/climatechange
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www.defra.gov.uk/environment/climatechange
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New York Times, Aug 31, 2004
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Chinas industrial growth depends on coal,
plentiful but polluting, from mines like this one
in Shenmu, Shannxi Province, behind a village
store. NY Times Aug 26, 2007. http//blogs.wsj.com
/chinarealtime/2013/01/14/photos-beijings-air-poll
ution-beyond-crazy-bad/slide/1
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Scientific Consensus?

• IPCC
• http//www.ipcc.ch/
• Web of Science
• http//thomsonreuters.com/web-of-science-core-coll
  ection/
• Peer-reviewed articles on climate change
• http//thecontributor.com/why-climate-deniers-have
  -no-scientific-credibility-one-pie-chart
• Google Scholar
• http//scholar.google.com/

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Sea Level Rise

• http//www.nytimes.com/2014/01/14/science/earth/gr
  appling-with-sea-level-rise-sooner-not-later.html

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Sea Level Rise
http//www.npr.org/2014/01/01/258706269/federal-fl
ood-insurance-program-drowning-in-debt-who-will-pa
y
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Chapter Headings

• The hydrologic cycle
• Precipitation
• Runoff
• Surface and groundwater storage
• Evaporation
• Condensation

• Climate and weather
• Climate
• Climate change
• Weather
• Weather modification
• Floods
• Drought

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Weather

• Weather is the local, short-term state of the
  atmosphere
• Determined by
• Temperature
• Air pressure
• Humidity
• Heating and cooling
• Wind speed and direction

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Temperature

• Oceans have a moderating effect on temperature
• Maximum 97oF in the Persian Gulf
• Minimum 28oF in the polar seas
• Temperature extremes occur in mid-continents
• Maximum 136oF Sahara Desert (Libya)
• Minimum -126oF central Antarctica

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Air Pressure

• Weight of atmospheric gases cause air pressure
• Changes with
• Elevation -- highest at sea level, decreases with
  elevation
• Temperature density of gases decrease as
  temperature increases
• Local weather descending air causes a high,
  rising air causes a low

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Humidity

• Relative humidity percentage of water vapor
  (water in the gas form) in the air
• When temperature drops to the dewpoint, air
  reaches saturation and vapor condenses
• Relative humidity 100
• Clouds or fog form or it may rain

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Heating and Cooling

• As air rises it expands and cools
• Adiabatic lapse rate
• Temperature drops 1oF for every 183 ft rise in
  elevation
• If rising air reaches the dewpoint, clouds form
  and it may rain
• This is called orographic effect
• Rising air experiences adiabatic cooling
• Falling air experiences adiabatic heating

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Orographic Lifting
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Orographic Lifting
Wicklow Mountains, Ireland
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Cascade Mountains orographic rainfall and rain
shadow
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Figure H shows precipitation patterns across the
Southeast focusing on the areas around the
Appalachian Mountains. An increase in
precipitation is visible over northern Georgia
and southern North Carolina. In far western North
Carolina, drier conditions are felt around
Asheville compared to areas surrounding western
North Carolina. This is because this area is
sheltered from humid winds from every direction
because of the elevation of the mountains
surrounding Asheville, NC. http//www.nc-climate.n
csu.edu/edu/water/water.SEPrecip
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Heating and Cooling

• Cold fronts occur where cold air masses collide
  with warm air
• Cold air is denser than warm air
• Drives a wedge under warm air and lifts it
• Adiabatic cooling causes clouds and rainfall
  along the front

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www.physicalgeography.net/fundamentals
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Satellite image of cold front moving south over
Hong Kong
www.weather.gov.hk/wxinfo/intersat/satellite_galle
ry
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Wind Speed and Direction

• Wind constantly moves air from areas of high
  pressure to areas of low pressure
• Coriolis force deflects these winds (to the right
  in the northern hemisphere)
• Winds spiral (in northern hemisphere)
• Clockwise away from a high of descending air
• Counterclockwise into a low of rising air

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Hurricane Elena struck Alabama in 1985
www.atmosphere.mpg.de
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Extreme example of vertical motion of air
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Chapter Headings

• The hydrologic cycle
• Precipitation
• Runoff
• Surface and groundwater storage
• Evaporation
• Condensation

• Climate and weather
• Climate
• Climate change
• Weather
• Weather modification
• Floods
• Drought

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Floods

• Some flooding is regular and predictable
• Mississippi River with winter rains
• Colorado River floods with spring snow melt
• Nile River
• Other flooding is erratic and less predictable
• Tigris-Euphrates and Yangtze
• Flash floods occur with little or no warning
• Local weather causes very high rainfall

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Flooding
Hurricane Katrina, New Orleans, Aug 30, 2005
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Flooding

• Flooding is not always bad
• One of the reasons New Orleans is below sea level
  is that it is subsiding at an accelerated rate
• 1 cm per year (10 times average global rate)
• Floodplains built of fine sediment that
  consolidates and subsides over time
• Normally, each flood brings fresh sediment into
  floodplain
• Levees prevent flooding of Mississippi River in
  New Orleans and cut off re-supply of sediment

NY Times article, Aug 30, 2005
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Chapter Headings

• The hydrologic cycle
• Precipitation
• Runoff
• Surface and groundwater storage
• Evaporation
• Condensation

• Climate and weather
• Climate
• Monitoring climate change
• Weather
• Weather modification
• Floods
• Drought

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Drought

• John Steinbeck, The Grapes of Wrath
• And it never failed that during the dry years
  the people forgot about the rich years, and
  during the wet years they lost all memory of the
  dry years. It was always that way
• Drought a period of abnormally dry weather
  which persists long enough to produce a serious
  hydrologic imbalance
• Colorado River
• http//www.nytimes.com/2014/01/06/us/colorado-rive
  r-drought-forces-a-painful-reckoning-for-states.ht
  ml

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Chapter Summary

• Earths water is constantly recycled
• Climate is the long-term average state of the
  atmosphere for a region
• Weather is the local, short-term state of the
  atmosphere
• Dry and wet regions are determined by air
  currents and orographic effects
• Climate change is underway
• Flood and drought cycles are common events