Introduction to Oceanography Chris enze, NASA Ames, Public Domain, http://people.nas.nasa.gov/ ~chenze/fvgcm/frances_02.mpg Redistribution of Solar eat Energy ecture 11: 2, Atmospheric water vapor map, April 10 May 10, 2017. Data from http://www.ssec.wisc.edu/data/comp/wv/ POES EQUATOR Convective heat transfer moderates Earth climate eated air expands & rises, then cools & sinks Adapted from image at http://www.yourhome.gov.au/technical/images/62a.jpg, Public Domain? Atmospheric Circulation Without Rotation Cold, more dense air sinks near the Poles Background image from Smári P. McCarthy, Creative Commons A S-A 3.0, http:// commons.wikimedia.or g/ wiki/file:earth_equator _northern _hemisphere.png Warm, less dense air rises near the Equator The Coriolis Effect on Earth Surface velocity increases from pole to equator Points on the equator must move faster than points near the poles to go around once a day atitude velocity differences lead to curving paths Example: Merry-go round Cold, more dense air sinks near the Poles National Snow and Ice Data Center, free for educational use, http://nsidc.org/arcticmet/factors/winds.html To an Earthbound observer (i.e., us): Northern emisphere: Earth s rotation causes moving things to curve to their right Moving things: Air masses, oceanic flows, missiles, anything with mass The Coriolis Effect But wait why do storms (including hurricanes and cyclones) go backwards? Northern emisphere: urricane Isabel (2003) NASA, Public Domain, http://visibleearth.nasa.gov/view_rec.php? id=5862 Southern emisphere: Earth s rotation causes moving things to curve to their left National Snow and Ice Data Center, free for educational use, http://nsidc.org/ arcticmet/factors/winds.html Questions Southern emisphere: Cyclone Drena (1997) NASA, Public Domain, http://www.ngdc.noaa.gov/dmsp/hurricanes/ 1997/drena.vis.gif (now moved)? 1
Atmospheric Circulation including Coriolis Actual forecast of surface winds Pacific surface wind forecast-hindcast, National Weather Service Environmental Modeling Center/NOAA, Public Domain, GIF by E. Schauble using EZGif Figure from NASA, Public Domain, http://sealevel.jpl.nasa.gov/overview/climate-climatic.html Atmospheric Circulation including Coriolis 3 convection cells in each hemisphere Each cell: ~ 30 o latitudinal width Vertical Motions Rising Air: 0 o and 60 o atitude Sinking Air: 30 o and 90 o atitude orizontal Motions Zonal winds flow nearly along latitude lines Zonal winds within each cell band DUE TO DEFECTIONS BY CORIOIS! Atmospheric Circulation including Coriolis 3 Cells per hemisphere: Polar Active (updraft on hot side, downdraft on cold side) Ferrel Passive (downdraft on hot side!) adley Active ADEY FERRE POAR UCA figure background image unknown. Atmospheric Circulation including Coriolis atitudinal winds: 0-30 o : Trade s 30-60 o : Westerlies 60-90 o : Polar Easterlies Atmospheric Circulation including Coriolis Cell Boundaries: 60 o : Polar Front 30 o : orse atitudes orse atitudes Doldrums 0 o : Doldrums Vertical air movement (up at Polar Front and Doldrums, down at orse atitudes) Polar Front Figure by astings, Wikimedia Commons, Creative Commons A S-A 1.0 Generic, http://en.wikipedia.org/wiki/file:atmosphcirc2.png Figure by astings, Wikimedia Commons, Creative Commons A S-A 1.0 Generic, http://en.wikipedia.org/wiki/file:atmosphcirc2.png 2
Questions ocal Meteorology of Southern California Marine layer against the Southern California mountains Photo by Dr. Jonathan Alan Nourse, CalPoly Pomona, http://geology.csupomona.edu/janourse/storms,%20floods,%20andslides.htm Figure from NASA, Public Domain, http://sealevel.jpl.nasa.gov/overview/climate-climatic.html Mediterranean Climate A: Subtropical latitude, abutting ocean Subsiding flow: sinking air Clear most of the year Effects of coast: igher humidity--- thermal buffer Winter Storms Pole-equator temp difference larger in winter Speeds up jet stream, big storms get pushed our way Ocean surface temperature changes slowly. Air displaces less dense rising air on land. Sea Breeze Result wind from sea towards land and warms fastest during the day. Air expands and rises Jesús Gómez Fernández, Wikimedia Commons, Creative Commons A S-A 3.0, http://commons.wikimedia.org/ wiki/file:diagrama_de_formacion_de_la_brisa-breeze.png Ocean surface temperature changes slowly. Air is pushed away and up by cooler denser land air. and Breeze and cools fastest at night. Air contracts and sinks Marine ayer Cold waters, warm air: thin cloud layer on ocean surface Subtropics: pressure, regional subsidence Cloud layer flows onto land at night Evaporates over land by day Result wind from land towards sea Adapted from Jesús Gómez Fernández, Wikimedia Commons, Creative Commons A S-A 3.0, http:// commons.wikimedia.org/wiki/file:diagrama_de_formacion_de_la_brisa-breeze.png AND OCEAN UCA figure 3
UCA Marine ayer Santa Ana s Canada: Chinook Colorado: Downslope s Germany: Foehn s France: The Mistral Southern CA: Santa Ana s Time lapse -- Sept. 23, 2003(?), J. Aurnou, UCA Santa Ana s Winter: Canadian cold air pushes down into Southwestern US igh pressure pushes dry desert air downslope, to sea Compression of sinking air causes heating eating lowers humidity Speeds: up to ~ 70mph 115 km/hr Funneling effect through canyons Feeds dangerous brush fires Weaker in summer Adapted from N. Short Remote Sensing Tutorial/NASA, Public Domain, http:// rst.gsfc.nasa.gov/sect14/katabatic.jpg Piotr Flatau, Wikimedia Commons, Public Domain, http://en.wikipedia.org/wiki/file:santa_ana_wind1.jpg igh Plateau Mojave Desert San Gabriel/Bernardino Mtns. os Angeles NASA image, Public Domain, http://photojournal.jpl.nasa.gov/catalog/pia03892 Santa Ana s ~ 30 mph ~ 500 km Santa Ana s Santa Ana s Santa Ana s: dry & warm, Encourage destructive fires Fertilize ocean? Porter Ranch Fire, Oct. 14 2008, NASA image, Public Domain, http://www.nasa.gov/mission_pages/fires/main/ usa/califires_20081014.html Canada: Chinook Colorado: Downslope s Germany: Foehn s France: The Mistral Southern CA: Santa Ana s 4
UCSD GOES-10/NASA, Public Domain, http://meteora.ucsd.edu/cap/images/junegloom_16jun2004.gif s Questions? The Gulf Stream, Winslow omer (1899), Metropolitan Museum of Art (NY). Public Domain, https://commons.wikimedia.org/wiki/file:winslow_omer_004.jpg s in the Ocean What is a current? A current is a flow of material MASS IS TRANSPORTED Ocean currents transport water is a current of air Map by Ben Franklin, 1787 s in the Ocean Two Types: Surface and Deep Driving Forces Surface s: -driven Deep s: Density-driven Ben Franklin, 1769, Map of the Gulf Stream, Public domain. American Meteorological Society, http://oceanmotion.org/images/ ocean-verticalstructure_clip_image002.jpg Surface s Caused by: Stress Pressure Gradients Coriolis Effects Friction -Driven s accelerates ocean currents Frictional Drag Atmosphere Drag Gene Paull, UT Brownsville, Public Domain(?), http://upload.wikimedia.org/wikipedia/commons/0/06/corrientes-oceanicas.gif Ocean SIDEVIEW Map View TOPVIEW 5
Pressure-Driven s North Atlantic Surface s drives ocean currents s run into continents and can t continue UNIKE ATMOSPERIC FOWS Water piles up ---Pressure Gradients form Atmosphere Ocean Drag SIDEVIEW TOPVIEW Westerlies Trades 60ºN Westerlies 30ºN Trades Equator Simple picture winds push surface currents, water piles up where wind blows onto coastlines (e.g., Atlantic coast of S. America). BUT: Coriolis acts on currents! Background image: U.S. Government, extracted from PDF version of the Vol 26-4 2004 DISAM Journal (direct PDF UR [1]), Public Domain, http://commons.wikimedia.org/ wiki/file:globe_atlantic.svg Coriolis & currents s are affected by Earth s ROTATION! This is called the Ekman response Ekman Spiral V. Walfrid Ekman (Sweden) Surface deflection 45 o right of wind (in N. emisphere) Deflected further right with depth Atmosphere Drag Net (i.e., average) effect of Ekman spiral: Transport 90º to the right of the wind direction in the northern hemisphere eft of wind in the southern hemisphere Ocean s SIDEVIEW s TOPVIEW NOAA image, Public Domain, http://www.windows.ucar.edu/tour/link=/earth/water/ ekman.html&edu=elem s ~60ºN Drag from the wind on surface water WESTERIES WESTERIES orse atitudes ~ 30 o N orse atitudes ~ 30 o N Equator 6
-dragged & Basin-Edge s Final result: a loop of current, a Gyre WESTERIES orse atitudes ~ 30 o N N. Atlantic Gyre Gene Paull, UT Brownsville, Public Domain(?), http:// upload.wikimedi a.org/wikipedia/ commons/0/06/ Corrientesoceanicas.gif One subtropical gyre is found in each hemisphere in each ocean. Gyres rotate clockwise in the N. emisphere, counterclockwise in S. emisphere. Coriolis Geostrophic Response Coriolis Geostrophic Response WESTERIES orse atitudes ~ 30 o N Mean 1992-2002 dynamic ocean topography, Nikolai Maximenko (IPRC) and Peter Niiler (SIO), Public Domain, http:// apdrc.soest.hawaii.edu/ projects/dot/ 1992-2002MDOT.jpeg Average satellite-measured hill of water at western side of gyre. Why isn t the high pressure in the center of the ocean? QUESTIONS? Major Systems 1. North Atlantic gyre 2. South Atlantic gyre 3. North Pacific gyre 4. South Pacific gyre 5. Indian Ocean gyre 6. Antarctic Circumpolar Not a gyre! Gene Paull, UT Brownsville, Public Domain(?), http://upload.wikimedia.org/wikipedia/commons/0/06/corrientes-oceanicas.gif 7