teleconnections and height patterns: comparing recent winters
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Teleconnections and height patterns: comparing recent winters. Richard H. Grumm and Robert Hart V_3.0 17 March 2004 27 Feb 2003 26March 2002. Snow in Israel-Snow in DC Late Feb 2003 is there a connection. Jerusalem. Road to Damascus. Introduction. What are teleconnections? - PowerPoint PPT PresentationTRANSCRIPT
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Teleconnections and height patterns:
comparing recent winters
Richard H. Grummand
Robert HartV_3.0
17 March 200427 Feb 2003
26March 2002
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Snow in Israel-Snow in DCLate Feb 2003 is there a connection
Jerusalem Road to Damascus
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Introduction• What are teleconnections?• Brief History of teleconnections• Using Teleconnections
– long-term forecast aspects– short-term forecast aspects– Flow regimes
• Good old fashion teleconnections• New concepts and applications
– nodes and antinodes– A 2003-2004 perspective
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Teleconnectons defined Wallace and Gutzler MWR 1981
• Definition: significant simultaneous correlations between temporal fluctuations in meteorological parameters at widely separated points on the earth. – Provide evidence of transitory behavior of
planetary waves– show evidence of fluctuations with times scales
on order of weeks.– Suggest preferred region of standing wave
nodes and antinodes. (nodes-similar sign)
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Similar definition O’Connor 1969
• Definition: the favored modes for coupling large-scale abnormalities of the atmospheric circulation as determined statistically or empirically.– Rossby’s centers of action (1939) concept proved
teleconnections had a physical basis. (nodes)– Found great use to improve forecasts based on
patterns and centers of action (nodes)– developed teleconnection maps correlating an
anomalous trough/ridge at a 10x10 Lat/Lon region to other anomalies and anti-anomalies around the hemisphere. (nodes and antinodes)
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The well known El Nino Teleconnection
the temporal fluctuation about globe associated with El Nino
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How El Nino Teleconnects
Walker Circulation impacts
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Teleconnectons Wallace and Gutzler MWR 1981
• Implications:– A standing wave in one location favors the
existence of a wave downstream at a known location. Therefore,
– there exist, preferred trough/ridge locations• may be referred to as nodes and antinodes
– Their existence allows the use of indices to quantify or measure flow patterns associated with these features.
• The NAO correlates the flow over the Atlantic Basin• The ENSO sign has its own teleconnections in the
both northern and southern hemispheres• other known indices (EP,AO etc, etc…)
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Teleconnectons Wallace and Gutzler MWR 1981
• Things to consider:– wave patterns and flow can be measured and
teleconnected.– ocean indices can be measured and teleconnected– the indices are teleconnected, typically by
regression, to a favored mode of weather conditions at a location.
– Not all correlations are one-to-one• negative correlations too, ANTINODES
– These correlation’s have direct forecast applications, especially on the scale of weeks and months.
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Teleconnecton’s A History Perspective
• Southern Oscillation (SO), identified and documented in 1897.– Connecting weather and long term wet/dry
periods in India and Australia.
• Walker and Bliss (1932) improve SO documentation.
• Association of weather patterns in western Europe to eastern United States– trough in western Europe correlates well with trough in
eastern North America. NODES– A ridge in western Europe ~ ridge in eastern North
America
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Known North Hemisphere Teleconnection Patterns
• North Atlantic Oscillation (NAO)– Negative phase: cold eastern NOAM/Europe– Positive phase: warm wet Europe / eastern NOAM– We shall show how eastern US nodes/antinodes fit into
the NAO and PNA pattern nicely.
• North Pacific Oscillation (NPO)
• Pacific North American Pattern (PNA)– PNA > 0 similar to NAO <0
• The zonally symmetric seesaw/ Quasi-Biennial Oscillation (QBO)
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Cutting to the Chaseanomaly correlation showing nodes and
antinodes
Correlation point
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Winter 2003-2004
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North Atlantic Oscillation (NAO)
• Statistical correlation’s:– negative correlation severity of winters in
Greenland and Labrador and northwestern Europe.
– Negative correlation between MSLP at Iceland and the eastern Atlantic
– Winter temperatures were used to determine severity
– Deep Icelandic Low: Positive NAO• cold advection over Labrador and Greenland• warm southwesterly flow into Europe and southern
flow into eastern North America.
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Pacific North American Pattern (PNA)
• There are clearly 2 preferred flow patterns over North America
• relate upper air pattern mid-Pacific to eastern North America with two preferred modes:– Positive Mode
• Ridge along west coast with negative nodes• southeastern US (35N/75W)• near 45 N in the mid-Pacific (40N/150W)• so called Postive PNA
– Negative Mode• more zonal flow across north America• lack of Pacific Ridge, can flood US with Pacific air.
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PNA > 0
Positve Yellow
Negative Blue
Nodes/Antinode
Nodes
antinode
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Teleconnection Mapsrelate flow pattern
• Initial teleconnection’s used operationally– maps of anomalies in 10x10 Lat/Lon bands– relate a known height anomaly (Lat/Lon) with
other associated anomalies– For example
• Compute height anomaly at 30 N and and 40W• see what the mean anomalies are around the
hemisphere when this anomaly exists• often find centers of action
– correlation centers– low off eastern US correlates well with ridge over
northern Atlantic– negative nodes typically have downstream preferred
location of next negative node
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Teleconnection Map Example(O’Connor)30N/40W Negative in Winter
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Teleconnection Map Example(O’Connor)30N/50W Negative in Winter
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Teleconnection Map Example(O’Connor)30N/60W Negative in Winter
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Teleconnection Map Example40N70W: Winter Positive (~PA)
TrofTrof Ridge
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Nodes and Antinode
• Centers of action from re-analysis data
• Use eastern US to compare to previous 40/75W box
• Examine impacts on past three winters– Note how our PA node correlates well with
the preferred nodes of the PNA and NAO.
• A forecast tool?
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Autocorrelation JA-FE-MA 01correlation point 40N/75W
PA Node
European Node
Pacific Node
AntiNode
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Winter 01 Explanationnodes-antinodes show why PNA evolved
• Correlation point is 40W/75W– see white dot correlation to self is 1– high correlation about point hot colors– Positive Nodes:
• coast of Europe (~0.6)• Gulf of Alaska/mid Pacific (~0.6)
– Negative Nodes (antinodes)• western North America (~-0.6) (South of
2001) position• southern Atlantic (~0.6) west of 2001
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Jan-Mar 2001 Jan-Mar 2000
Centers of action for 40/75 some year-year variability
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Cold US Decembers1989 and 2000
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DEC 1989
Anomaly and Standardized
anomalyNodes and mean 500
hPa heights
COLD
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DEC 2000
Anomaly and Standardized
anomalyNodes and mean 500
hPa heights
WARM
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DEC 2001
Anomaly and Standardized
anomalyNodes and mean 500
hPa heights
WARM
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Jan 2002
Anomaly and Standardized
anomalyNodes and
mean 500 hPa heights
WARMnote +NAO
Pattern
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Feb2002
Anomaly and Standardized
anomalyNodes and
mean 500 hPa heights
WARM
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2003 Summer
• Wet eastern US• Warm and dry
western Europe– Record warmth
Italy Jun – Record warm UK-
FR-GDR August
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NOAM and Europe Flow
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Autumn 2003
• Correlation and nodes expand southward
• More notes of value
• Good Eastern US and western Europe correlation centers
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Autumn Patterns
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Winter 2003-2004
•Big node over eastern US
•Some correlation to western Europe
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Winter Patterns 2003-2004
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NOAM Winter 2003 verse 2004
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Conclusions
• Teleconnections ~ weather to flow– Rossby waves dictate location of
troughs/ridges– specific mean wavelengths imply existence
of preferred nodes and antinodes• these preferred locations led to some of the
well-known indices (PNA)•Can produce these for any Lat/lon box on
globe
– relate weather to anomalies of heights- • mean trough~cold or mean ridge~warm• forecast tools on the order of weeks
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Conclusion-Indicesnow your a “node-it-all”
• NAO: – North-South Dipole– teleconnect’s well with weather in
Europe, Greenland and western North America
• PNA – quadrapole (nodes and antinodes)– teleconnects well with NOAM weather– Trough in eastern US correlates with
trough in Europe-relates PNA to NAO
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References
• Namias, J., 1978: Multiple Causes of the North American Abnormal Winter 1976-77. Mon. Wea. Rev., 106, 279-295.
• O’Connor, J.F. 1969: Hemispheric Teleconnections of Mean Circulation anomalies at 700 millibars. ESSA Technical report WB10, US Dept.Commerce.
• van Loon, H., and J. C. Rogers, 1978: The seesaw in winter temperatures between Greenland and northern Europe. Part I: General description. Mon. Wea. Rev., 106, 296-310.
• Wallace, J., and D. Gutzler, 1981: Teleconnections in the Geopotential Height Field during the Northern Hemisphere Winter. Mon. Wea. Rev., 109, 784-811.
• Burroughs, W.J, 2002: Climate Change. Cambridge Univ. Press, 1-298.
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Computing the PNAknow the sign of the anomaly at center of action
• Base on Anomalies (nodes and antinodes)– 4 Locations– SMidPac (SMP) = 20N/160W– NMidPac (NMP) = 45N/165W– WNOAM (NNM) = 55/115W– SERNUS (SUS) = 30N/85
– PNA= (SMP - NMP + NNM - SERNUS)/4PNA > 0 : Strong Ridge along western CanadaPNA < 0 : Trough or zonal flow along western
Canada
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The zonally symmetric seesaw
• Lorenz (1951) first identified this seesaw effect in the MSLP fields
• A similar patten has been associated with the Quasi-biennial oscillation (QBO)– pressure changes associated with sudden
warming’s (mainly in polar regions)– effect most notable in Stratosphere (20-30 km)– QBO has been related to surface pressure
changes too and may have long term forecast skill on monthly/seasonal level.
– NH winters may related to phase of QBO at 50 hPa in the tropics
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Quasi-Biennial Oscillation(QBO)
• 20-30km in Stratosphere• Measured near 30 hPa• Wind reversal over equatorial regions
every ~27 months• Easterly to westerly• Teleconnects to weather patterns
– Correlated to some temperature records– And behavior of ENSO,– Hurricane activity in the Atlantic
• Related to upward propagating easterly Kelvin waves and westerly Rossby waves.