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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Chemical spill Charleston WV
http://www.nytimes.com/2014/01/12/us/the
-wait-continues-for-safe-tap-water-in-west-
virginia.html?ref=us&_r=0http://www.nytimes.com/2014/01/12/us/the
-wait-continues-for-safe-tap-water-in-west-
virginia.html?ref=us&_r=0 What is MCHM
http://www.csmonitor.com/USA/USA-
Update/2014/0110/W.Va.-chemical-spill-
Is-more-regulation-needed-for-toxic- substances
http://www.csmonitor.com/USA/USA-
Update/2014/0110/W.Va.-chemical-spill-
Is-more-regulation-needed-for-toxic- substances
https://maps.google.com/
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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 Fetter, Applied Hydrology Recharge
Discharge Recharge Discharge
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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 = S i S f + P + I D
S i = initial soil water storage S f = 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
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Worlds deserts tend to occur near 30 o N and S latitudes
Rainforests at the equator Global Air Currents
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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 23.5 o 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 CO 2 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
Ice cores from ancient times sometimes contain trapped bubbles
of atmospheric air that can be analyzed for CO 2 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 (CO 2 ), water vapor, methane, ozone, nitrous oxide
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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-pollution-
beyond-crazy-bad/#slide/1
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Scientific Consensus? IPCC
http://www.ipcc.ch/http://www.ipcc.ch/ Web of Science
http://thomsonreuters.com/web-of-science-
core-collection/http://thomsonreuters.com/web-of-science-
core-collection/ Peer-reviewed articles on climate change
http://thecontributor.com/why-climate-deniers-
have-no-scientific-credibility-one-pie-charthttp://thecontributor.com/why-climate-deniers-
have-no-scientific-credibility-one-pie-chart Google Scholar
http://scholar.google.com/http://scholar.google.com/
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 97 o F in the Persian Gulf Minimum 28 o F in the polar seas
Temperature extremes occur in mid- continents Maximum 136 o F
Sahara Desert (Libya) Minimum -126 o F 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 1 o F 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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Wicklow Mountains, Ireland Orographic Lifting
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Cascade Mountains orographic rainfall and rain shadow
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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/w xinfo/intersat/satellite_ gallery
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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/colora
do-river-drought-forces-a-painful-reckoning-
for-states.htmlhttp://www.nytimes.com/2014/01/06/us/colora
do-river-drought-forces-a-painful-reckoning- for-states.html
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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