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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 26 March 2002
Snow in Israel-Snow in DC Late Feb 2003 is there a connection Jerusalem Road to Damascus
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 • Definitionsignificant 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 • Definitionthe 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 10 x 10 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 the both in 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 eastern US nodes/antinodes into the fit NAO and PNApattern nicely. • North Pacific Oscillation (NPO) • Pacific North American Pattern (PNA) – PNA > 0 similar to NAO <0 • The zonallysymmetric seesaw/ Quasi-Biennial Oscillation (QBO)
Cutting to the Chase anomaly correlation showing nodes and antinodes Correlation point
Winter 2003 -2004
North Atlantic Oscillation (NAO) • Statistical correlation’s: – negative correlation severity of winters in Greenland Labrador and northwestern Europe. – Negative correlation between MSLP at Iceland 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 (35 N/75 W) near 45 N in the mid-Pacific (40 N/150 W) 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 antinode Nodes/Antinode
Teleconnection Maps relate flow pattern • Initial teleconnection’s used operationally – maps of anomalies in 10 x 10 Lat/Lon bands – relate a known height anomaly (Lat/Lon) with other associated anomalies – For example • Compute height anomaly at 30 N and 40 W • 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)30 N/40 W Negative in Winter
Teleconnection Map Example (O’Connor)30 N/50 W Negative in Winter
Teleconnection Map Example (O’Connor)30 N/60 W Negative in Winter
Teleconnection Map Example 40 N 70 W: Winter Positive (~PA) Trof Ridge
Nodes and Antinode • Centers of action from re-analysis data • Use eastern US to compare to previous 40/75 W 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 01 correlation point 40 N/75 W Anti. Node European Node PA Node Pacific Node
Winter 01 Explanation nodes-antinodes show why PNA evolved • Correlation point is 40 W/75 W – 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 Decembers 1989 and 2000
DEC 1989 Anomaly and Standardized anomaly Nodes and mean 500 h. Pa heights COLD
DEC 2000 Anomaly and Standardized anomaly Nodes and mean 500 h. Pa heights WARM
DEC 2001 Anomaly and Standardized anomaly Nodes and mean 500 h. Pa heights WARM
Jan 2002 Anomaly and Standardized anomaly Nodes and mean 500 h. Pa heights WARM note +NAO Pattern
Feb 2002 Anomaly and Standardized anomaly Nodes and mean 500 h. Pa heights WARM
2003 Summer • Wet eastern US • Warm and dry western Europe – Record warmth Italy Jun – Record warm UKFR-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
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 wellknown indices (PNA) • Can produce these for any Lat/ box on globe lon – relate weather to anomalies of heights • mean trough~cold or mean ridge~warm • forecast tools on the order of weeks
Conclusion-Indices now your a “node-it-all” • NAO: – North-South Dipole – teleconnect’s well with weather in Europe, Greenland 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 WB 10, US Dept. Commerce. • van Loon, H. , and J. C. Rogers, 1978: The seesaw in winter temperatures between Greenland 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 PNA know the sign of the anomaly at center of action • Base on Anomalies (nodes and antinodes ) – – – 4 Locations SMid. Pac (SMP) = 20 N/160 W NMid. Pac (NMP) = 45 N/165 W WNOAM (NNM) = 55/115 W SERNUS (SUS) = 30 N/85 – PNA= (SMP - NMP + NNM - SERNUS)/4 PNA > 0 : Strong Ridgealong western Canada PNA < 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 h. Pa in the tropics
Quasi-Biennial Oscillation (QBO) • 20 -30 km in Stratosphere • Measured near 30 h. Pa • 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.