Teleconnections and height patterns: comparing recent winters
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Transcript of Teleconnections and height patterns: comparing recent winters
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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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
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)
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)
The well known El Nino Teleconnection
the temporal fluctuation about globe associated with El Nino
How El Nino Teleconnects
Walker Circulation impacts
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…)
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.
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
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)
Cutting to the Chaseanomaly correlation showing nodes and
antinodes
Correlation point
Winter 2003-2004
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.
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.
PNA > 0
Positve Yellow
Negative Blue
Nodes/Antinode
Nodes
antinode
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
Teleconnection Map Example(O’Connor)30N/40W Negative in Winter
Teleconnection Map Example(O’Connor)30N/50W Negative in Winter
Teleconnection Map Example(O’Connor)30N/60W Negative in Winter
Teleconnection Map Example40N70W: Winter Positive (~PA)
TrofTrof Ridge
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?
Autocorrelation JA-FE-MA 01correlation point 40N/75W
PA Node
European Node
Pacific Node
AntiNode
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
Jan-Mar 2001 Jan-Mar 2000
Centers of action for 40/75 some year-year variability
Cold US Decembers1989 and 2000
DEC 1989
Anomaly and Standardized
anomalyNodes and mean 500
hPa heights
COLD
DEC 2000
Anomaly and Standardized
anomalyNodes and mean 500
hPa heights
WARM
DEC 2001
Anomaly and Standardized
anomalyNodes and mean 500
hPa heights
WARM
Jan 2002
Anomaly and Standardized
anomalyNodes and
mean 500 hPa heights
WARMnote +NAO
Pattern
Feb2002
Anomaly and Standardized
anomalyNodes and
mean 500 hPa heights
WARM
2003 Summer
• Wet eastern US• Warm and dry
western Europe– Record warmth
Italy Jun – Record warm UK-
FR-GDR August
NOAM and Europe Flow
Autumn 2003
• Correlation and nodes expand southward
• More notes of value
• Good Eastern US and western Europe correlation centers
Autumn Patterns
Winter 2003-2004
•Big node over eastern US
•Some correlation to western Europe
Winter Patterns 2003-2004
NOAM Winter 2003 verse 2004
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
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
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.
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
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
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.