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Global Winds AOSC 200 Tim Canty Class Web Site: http://www.atmos.umd.edu/~tcanty/aosc200 Topics for today: Ocean transport Ocean cycles Air Masses Lecture 18 Nov 1 2016 Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 1 Today’s Weather Map http://www.hpc.ncep.noaa.gov/html/sfc2.shtml Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 2 Sea-level pressure in Summer N.H. summer: thermal lows over land, high pressure over ocean Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 3 Ocean Currents Fig 8-6 Meteorology: Understanding the Atmosphere Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 4 Ocean Currents North Atlantic Gyre driven by trade winds and Westerlies Fig 8-8 Meteorology: Understanding the Atmosphere Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 5 Ekman Transport Ocean water pushed by wind but is also affect by Coriolis forces Fig Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 7.39: Essentials of Meteorology 6 Ekman Spiral and Ekman Transport http://www.meted.ucar.edu/fogstrat/ic31/ic313/graphics/comet/ekman.gif Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 7 Ekman Spiral and Ekman Transport Water off the coast of Southern California is cold and teeming with life Great for fishing!!!! Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 8 Ocean Currents Fig 8-6 Meteorology: Understanding the Atmosphere Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 9 Conceptual Model Polar Cell Ferrel Cell http://www.ux1.eiu.edu/~cfjps/1400/circulation.html Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 10 Normal Conditions Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty El Niño: warm water sloshes to the east During an El Nino, easterly trade winds weaken and warm water is Copyright © 2016 University of Maryland transported from western pacific to eastern pacific This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty El Niño Warming of Pacific Ocean off coast of South America near Ecuador and Peru. May lead to variations in weather Fig 8-11 Meteorology: Understanding the Atmosphere Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 13 Multivariate El Niño Southern Oscillation Index Multivariate ENSO Index (MEI): based on observations of sea-level pressure, zonal and meridional components of the surface wind, sea surface temperature, surface air temperature, and total cloudiness fraction of the sky over tropical Pacific http://www.esrl.noaa.gov/psd/enso/mei/ Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 14 Strong El Niño years Global Monthly Temperature Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 15 How does El Niño affect Hurricanes? Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 16 How does El Niño affect Hurricanes? Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty How does El Niño affect global weather? • Western Pacific: less rainfall as warm water moves east. • Shift in rain patterns moves subtropical jet stream from its normal path. • Change in path of sub-tropical jet allows El Niño to affect the weather and climate of the midlatitudes as well as the tropics. • The commodities markets use the NOAA El Niño forecasts to influence buying and selling. Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 17 El Niño: Global Weather Fig 8-14 Meteorology: Understanding the Atmosphere Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 19 La Niña: Global Weather Fig 8-17 Meteorology: Understanding the Atmosphere Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 20 Pacific Decadal Oscillation https://www.ncdc.noaa.gov/teleconnections/pdo/ Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 21 Atlantic Meridional Overturning Circulation http://phys.org/news/2015-03-atlantic-ocean-overturning-today.html Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 22 Atlantic Multidecadal Oscillation Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 23 Strong AMO Global Monthly Temperature Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 24 North Atlantic Oscillation Relative changes in pressure systems Positive NAO: Both the Bermuda High and Icelandic Low strengthen Negative NAO: Both the Bermuda High and Icelandic Low weaken Fig Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 7.28: Essentials of Meteorology 25 North Atlantic Oscillation Positive Phase Negative Phase Shift in atmospheric pressure between polar low near N. Pole and subtropical high over Atlantic Fig 8-18 Meteorology: Understanding the Atmosphere Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 26 North Atlantic Oscillation http://www.cpc.ncep.noaa.gov/products/precip/CWli nk/pna/month_nao_index.shtml Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 27 Air Masses What is an air mass? Large body of air whose temperature and humidity are the same in any horizontal direction Can cover huge areas (hundreds of thousands sq mi) Influenced by the surface over which they form (source region) Longer the air stays over source region the more it takes on characteristics of that region Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 28 Air A ir Masses Mas sses Fig Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 8.1: Essentials of Meteorology 29 Air Mass Source Regions Characteristics of air mass depends on source region Fig 9-3 Meteorology: Understanding the Atmosphere Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 30 Air Mass Source Regions Two main surface categories Maritime (m) Continental (c) Formed over land Formed over ocean Generally dry Generally moist Characteristics of air mass depends on source region Fig 9-3 Meteorology: Understanding the Atmosphere Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 31 Air Mass Source Regions Three main location categories Arctic (A) Formed over Arctic Extreme cold Polar (P) Formed poleward of 60° latitude Cold or cool Tropical (T) Formed between 30S and 30N Hot or warm Characteristics of air mass depends on source region Fig 9-3 Meteorology: Understanding the Atmosphere Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 32 Air Mass Source Regions Remember: Continental = dry Maritime = moist First letter: surface category Second letter: location category cT = continental Tropical Table Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 8.1: Essentials of Meteorology 33 Air Masses that Affect North America Arrows indicate general direction of air flow Fig Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 8.2: Essentials of Meteorology 34 Continental Polar (cP) and Continental Arctic (cA) Air Cold to extremely cold and dry air masses cP air comes from Canada and can head as far south as Florida cA forms over frozen Arctic bringing bitterly cold temperatures Sometimes called “Siberian Express” Strong winds and blowing snow can lead to blizzards Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 35 Continental Polar (cP) and Continental Arctic (cA) Air http://majornews.us/archives/667 Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 36 “Siberian Express” Dec 24 1983 Large high pressure system can bring freezing air down from Arctic Fig Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 8.3: Essentials of Meteorology 37 Madison, Wisconson, Feb 1996 “Normal” Temps Fig 9-7 Meteorology: Understanding the Atmosphere Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 38 Maritime Polar Air (mP) Form over oceans at high latitudes, cool to cold and humid In winter, mP from Pacific begin as cP from Siberia These systems run into west coast mountains and dump lots of snow (orographic forcing) On East coast, mP brings in moist air from Atlantic over land where it meets with cP air Can lead to large snowfalls!!! Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 39 Maritime Polar Air (mP) What could this represent? Table Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 8.7: Essentials of Meteorology 40 Maritime Polar Air (mP) Table Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 8.8: Essentials of Meteorology 41 Maritime Polar Air (mP), Dec 11, 1992 “Nor’easter”: cyclone that moves to the Northeast Table Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 8.U3: Essentials of Meteorology 42 Maritime Tropical Air (mT) Eastern U.S. strongly affected by mT air that forms over Gulf of Mexico, Caribbean Sea, and subtropical western Atlantic Ocean Stable air mass leads to oppressive heat wave Wintertime precipitation over Central and Eastern U.S. due to uplift of mT air over cold air masses Western U.S. strongly affected by mT air from Pacific Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 43 Maritime Tropical Air (mT) “Pineapple Express” Jan 1, 1997 Fig Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 8.9: Essentials of Meteorology 44 Maritime Tropical Air (mT) Upper level winds High pressure brought warm air into Eastern U.S. Fig Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 8.11: Essentials of Meteorology 45 Maritime Tropical Air (mT) Heat wave in 1999 led to 232 deaths Fig 9-8 Meteorology: Understanding the Atmosphere Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 46 Continental Tropical Air (cT) Form over tropical and subtropical deserts and plateaus In North America, formed in southwest and N. Mexico Air mass is hot and dry When cT and mT air meet, contrast between systems is called the “dry line” In summer, large supercell storms often form at dry line, conducive to tornado development Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 47 Continental Tropical Air (cT), July 14-22, 2005 Sinking upper level air (Hadley Cell) is shown (H), leading to hot, dry conditions at surface Fig Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 8.12: Essentials of Meteorology 48 Dry line Rocky Mountains very important in dryline development Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 49 Air Mass Modification Air masses can be modified through lifting and heat exchange with the surface Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 50 Lake Effect Snow Cold Polar or Arcitc blows over warm water and picks up moisture and drops snow on downwind side of lake Snow can fall in distinct bands Fig Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 8.U2: Essentials of Meteorology 51 Lake Effect Snow Fig Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 8.U1: Essentials of Meteorology 52 Lake Effect Snow Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 53 Lake Effect Snow http://www.wunderground.com/blog/JeffMasters/co mment.html?entrynum=2606 Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 54 Lecture Recap • Ocean Currents • Ekman transport • upwelling • El Niño/La Niña • SST • global climate • ENSO • PDO • NAO • Air Masses • Continental, Maritime • Arctic, Polar, and Tropical • Air Mass Modification • Lake effect snows Copyright © 2016 University of Maryland This material may not be reproduced or redistributed, in whole or in part, without written permission from Tim Canty 55
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