Download Lectures for weeks 3-5

BESC 320 – Water and Bioenvironmental Science
(Week 3-5; 30 Jan - 17 Feb 2017)
ALERT: Week 6 20-Feb
Mon Exam 1 (water science & technology)
Atmospheric components of hydrologic cycle (Water, weather, energy transport)
Evaporation, sublimation, transpiration, volcanic release – send water into the
atmospheric component. (Sublimation – direct change in water phase from solid
to gas)
Humidity - Amount of water vapor in the air
Relative humidity – Amount of water vapor in the air expressed as a percentage of
the maximum amount that can be held at that temperature. Air holds more
water at higher temperatures, and higher pressure.
Saturation point – Point where the air contains the maximum amount of moisture
given its temperature (i.e., 100% relative humidity). At this point water must
condense onto solid surfaces such as atmospheric dust (forming clouds), or
terrestrial surfaces (forming dew).
Dew Point - Temperature at which condensation occurs for a given amount of
water.
Condensation nuclei – Atmospheric particles that facilitate condensation (e.g.:
smoke, dust, salt mist, spores, large molecules like dimethylsulfide, DMS)
Influence of terrestrial topography
 air sweeps up windward side of a mountain
 pressure decreases, air cools, saturation point surpassed, moisture
condenses
 rain falls on the windward side and mountaintop (if it is cold enough at the
higher altitudes the precipitation becomes snow—that is why snow-capped
peaks are such a common occurrence)
 cool, dry air descends other side of
mountain, warms, absorbing moisture
from other sources making for very
dry leeward sides of the mountain
and desert valleys, called a rain
shadow.
Another look (more detail):
Colliding air masses
A similar phenomenon to the “mountain effect” described above happens when
two air masses of different density run into each other:
• Cold air is more dense and will push
under warmer (less dense) air
• Warm air then gets vaulted into
the stratosphere
• The vaulting air cools and loses
pressure
• Saturation point may be
exceeded
• Condensation (clouds) and
precipitation may occur
We speak of this as “frontal weather”. A front is a region of contact between
dissimilar air masses. Scandanavian scientists came up with the analogy between
weather fronts and war "fronts" of WWI. Dissimilar air masses "battle" at weather
fronts, especially at cold fronts. The front is named (warm or cold) for the faster
moving of two colliding air masses. Cold fronts are especially likely to produce
severe weather.
This collision effect can also
happen when air masses of like
properties collide. The
Intertropical Convergence Zone
(ITCZ) is the region where NE and
SE Tradewinds converge near the
Equator:
Convection
 Hot (less dense) air rises,
creating an area of low pressure
under the column of rising air.
 The low pressure area draws
in cooler (denser) air, resulting in
vertical convection currents
 Simultaneously transports air,
water and energy (heat)
Sun not only heats the landscape and air above it, but the heat also vaporizes
water, which carries with the rising air. Energy is stored in water vapor as latent
heat.
 Rising hot air creates an area of relatively high pressure at the top of the
convection column
 If condensation nuclei are present, temperatures lowers enough, and
pressure is high enough, condensation will form clouds and potentially create
precipitation
 Air flows out of high-pressure zone towards areas of low-pressure, where
cool, dry air is subsiding
 Also, the risen air will be shedding its energy (radiating heat to space), and
will then itself cool
 Subsiding air is compressed as it approaches the earth’s surface where it
piles up and creates an area of high pressure at the surface
 Air flows out of this region back towards low pressure, closing the cycle:
relative left-right
relative left-right
Look at this process at a larger scale. Recall, evaporation is driven by heat (mostly
solar) input, which is highest near the equator
 air at the equator rises, cools, and falls as rain (forming rainforests)
 cooler, drier air descends along Tropics of Cancer and Capricorn
 causes evaporative losses and creates deserts
Convection Cells and Prevailing Winds
As air warms at the equator, rises, and moves northward, it sinks and rises in
several intermediate bands, forming circulation cells.
Surface flows do not move straight North and South, but are deflected due to
Coriolis Effect.
 Major zones of subsidence occur at
about 30° north and south latitude
 Where dry, subsiding air falls on
continents, it creates broad,
subtropical desert regions.
 Winds directly under regions of
subsiding air are often light and
variable.
 Doldrums and horse lattitudes
 Think of the pattern depicted in this
figure and how it is reflected in the
former figure.
If the global latitudinal pattern produces north-south gradients, how can there be
longitudinal (east-west) patterns in the US and prominently, in Texas?
Energy Balance
 Solar energy is unevenly distributed
 Earth’s axis is tilted
 Compare:
CITY
Jan.
Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.
Bogotá
11:53 11:59 12:05 12:13 12:20 12:23 12:22 12:16
12:08
12:00 11:55 11:52
Barrow
0:00
14:45
11:03
4:05
9:20
14:13 19:44 24:00 24:00 24:00
5:52
0:00
 at the equator day length (hence radiation) is consistently 12 hours; off
equator things can reach the extremes (complete day or night).
credit: Wikipedia
 Energy imbalance is smoothed out by movement of air and water vapor in
the atmosphere and by liquid water in rivers and ocean current
 Interaction of energy disequilibrium and motion of planet creates large-scale
upper airflows known as “Jet Streams”. Usually two over NA. Wind speeds
often 200km/hr.
Cyclonic Storms
When rising air is laden with water vapor, latent energy released by condensation
intensifies convection currents and draws up more warm air and water vapor.
Intensification sets up a self feeding synergistic cycle. Low pressure in center of
developing storm draws air in, but the path of incoming air becomes curved due to
the Coriolis effect. (Quick mythbust: the Coriolis effect does not affect toilet flushes)
Storm cell will exist as long as temperature differential exists.
 Hurricanes (Atlantic)
 Typhoons (Western Pacific)
 Cyclones (Indian Ocean)
Tornadoes - Swirling funnel
 Rotation not generated by
Coriolis forces.
 Generated by “supercell”
frontal systems where strong
dry cold fronts collide with
warm humid air.
 Greater air temperature
differences in Spring thus
more tornadoes.
Monsoon – Seasonal reversal of wind patterns caused by differential heating and
cooling rates of oceans and continents, esp. in tropics.
El Niño / La Niña
 Large pool of warm
surface water in Pacific
Ocean moves back and
forth between Indonesia
and
South America.
 Most years, the pool is
held
in western Pacific by
steady equatorial trade
winds.
 Every 3-5 years the
Indonesian low collapses
and
the mass of warm surface
water surges back east.
 During an El Nino year, the northern jet stream pulls moist air from the
Pacific over the US.
 Intense storms and heavy rains.
 During intervening La Nina years, hot, dry weather is often present.
Pacific Decadal Oscillation – Very large pool of warm water moving back and forth
across the North Pacific every 30 years
As emphasized earlier, the water of the Earth ameliorates temperature changes by
storing, gradually releasing and transporting heat. This process moderates global
temperature. Contrast with the moon (212oF during the day; –200oF at night). This
happens in both the atmosphere, and in the hydrosphere per se—the oceans.
Case
study I:
Wetlands
– Florida Everglades (maybe not so much with the “ever” part)
EVER GLADES NATIONAL PARK
(link)
“Spanning the southern tip of the
Florida peninsula and most of Florida
Bay, Everglades National Park is the
only subtropical preserve in North
America. It contains both temperate
and tropical plant communities, including sawgrass prairies, mangrove and cypress swamps,
pinelands, and hardwood hammocks, as well as marine and estuarine environments. The park
is known for its rich bird life, particularly large wading birds, such as the roseate spoonbill,
wood stork, great blue heron and a variety of egrets. It is also the only place in the world
where alligators and crocodiles exist side by side.
Everglades National Park has been designated a World Heritage Site, an International
Biosphere Reserve, and a Wetland of International Importance.”
 Mosaic of freshwater ponds, prairies and forested uplands that support a
remarkable volume and diversity of flora and fauna
 Historically 11,000 square miles of south Florida
 Historic water flow down the Kissimmee River into Lake Okeechobee, then
south by sheet flow through the Everglades marsh to the flats of Florida Bay
 Sheet flow out of Okeechobee called the “River of Grass” for the vast
expanse of sawgrass in the marsh
 The sheet flow spans as much as 60 miles in width, yet is only six inches deep
in some places
 This wetland was degraded severely by water use and diversion for sugar
plantations (strong lobby) and other agriculture
 1905: Gov. Napoleon Bonaparte Broward began systematic effort to drain
the Everglades for agriculture and development. Large tracts were
transformed into farmland, and cities (Miami, Fort Lauderdale) sprang up
and burgeoned.
 With increasing human habitation flood control in this essentially-stillwetland was needed. Fed to the rescue… In 1948, the U.S. Congress
authorized the Central and South Florida Project , which created the largest
water management system in the world. The project involved an extensive
network of man-made canals, levees and water control structures that
channel 1.7 billion gallons of water daily from the Everglades to the ocean.
 The direct water flow to the ocean does not get the filtration that would
have occurred had it flown through the wetlands.
 The loss of water changed the natural characteristics of the marsh. Habitat
loss was due to drying per se, but also to
saltwater intrusions into the marsh from the
ocean. Pollution entered from neighboring
farms and cities. Changes in water quality
stifled the growth of native plants, allowed
exotic plants to take root and fueled the
growth of algae which worsened the loss of
natural habitat. As a result of this cycle continuing for so long the Everglades
today is half the size of a century ago.
 Despite the damage that was done in the
first half of the 20th century, the Everglades is
still considered a national treasure just as
extraordinary as the Grand Canyon, the Great
Lakes or the Redwood Forests. A remarkable
coalition of highly diverse and bipartisan
interests has joined forces to make the
restoration possible.
 To revive and protect this national treasure, Florida is undertaking the largest
environmental ecosystem restoration in the world. It is Florida’s top priority
to improve the quality of life for all south Floridians, provide adequate water
supply for south Florida’s growing population and provide improved flood
control, while preserving America’s Everglades and Florida’s Liquid Heart –
Lake Okeechobee - and protecting natural wildlife and plants for future
generations.
 2000: State funding of the Everglades Restoration Investment Act to fund
Florida’s 50 % (cost-share), complimenting Federal investment, to implement
the Comprehensive Everglades Restoration Plan (CERP)
 FYI—for further interest, here is a well composed, thorough timeline arraying
major events, esp. legislation and actions by Fed and State:
http://www.dep.state.fl.us/evergladesforever/about/timeline.htm
 An economic analysis of the restoration problem, including ecosystem
services is available here: http://www.evergladesfoundation.org/wpcontent/uploads/2012/04/Report-Measuring-Economic-Benefits-Exec-Summary.pdf
How much is the project likely to cost and what is the benefit cost ratio?
(Note CBS news suggests $20b has already been spent)
 Here, graphically, is the plan:
INVASIVE SPECIES
Miami is a port town—deals with imports
of many exotics. Releases and escapes of
exotics have plagued the Everglades. In
some rivers all one may catch in a day
would be (inedible) armored catfish 
Left: Non-natives impact native species. A
dead 6’ American alligator burst forth from this 13’
Burmese python in Everglades National Park. Maybe the
exotic snakes should stick to 5’ alligators. (ASSOCIATED
PRESS/EVERGLADES NATIONAL PARK / October 5, 2005)
Right: Natives fight back—water moccasin (cottonmouth) eating nonnative armored catfish.
“… assorted characters of death and blight…” —?
20% of fisherman in south Florida target exotic species
Good video here