Teleconnections and height patterns:

Meteorology 415Fall 2011

Snow in Israel-Snow in DCLate Feb 2003 is there a connection

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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

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)

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

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.

Teleconnection’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) improved 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

Northern Hemisphere Teleconnection Patterns

• North Atlantic Oscillation (NAO)– Negative phase: cold eastern NOAM/Europe– Positive phase: warm wet Europe / eastern

NOAM

• 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

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.

NAO-Positive Phase

NAO-Negative Phase

Pacific North American Pattern (PNA)

• There are clearly two 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.

Pacific North American Patten

• Flow Pattern over North America and adjacent pacific ocean

• referred to as the PNA• The standard one is from Wallace and

Gutzler (1981) where they defined the index as being: z=zonal component of wind

time(year)=[z(20N,160W)-z(45N,165W)+z(55N,115W)+z(30N,85W)]/ 4

PNA Description• The PNA pattern is one of the most prominent

modes of low-frequency variability in the Northern Hemispheric extra-tropics– appearing in all months except June and July.

• The PNA pattern reflects a quadripole pattern of height anomalies, – anomalies of similar sign located south of the Aleutian

Islands and over the southeastern United States.

• Anomalies with sign opposite to the Aleutian center are located in the vicinity of Hawaii, and over the intermountain region of North America (central Canada) during the Winter and Fall (Spring).

PNA in recent times

Positive PNA-January

Deep troughs

Ridges

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

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

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-Indices

• NAO: – North-South Dipole– teleconnects 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 zonal 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 be 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.