The MJO and Arctic Air Temperatures

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The MJO and Arctic Air Temperatures

• Gabriel A. Vecchi and Nicholas A. Bond
• JISAO, University of Washington
• and NOAA/Pacific Marine Environmental Laboratory

• Madden-Julian Oscillation connects to DJF Arctic
  Air Temperatures.
• O(3-10 Degrees C)
• Statistical connection is significant and robust.
• Both radiative and advective processes appear to
  drive air temperature changes.

Vecchi, G.A. and N.A. Bond 2003 The
Madden-Julian Oscillation and Northern Hemisphere
High Latitude Surface Air Temperatures,
submitted to Geophys. Res. Lett.
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Introduction

• MJO is dominant mode of large-scale tropical
  intraseasonal variability.
• Connections have been found to precipitation
  along west coast of USA.
• e.g. Higgins and Mo 1997, Mo and Higgins 1998,
  Jones 2000, Bond and Vecchi 2003.
• There are circulation anomalies in
  high-latitudes.
• e.g. Mo and Higgins 1998, Bond and Vecchi 2003.

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MJO and Pacific NW Precip.
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Composite MJO Z500 Anomaly (m)
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MJO Index

• 850 hPa winds from NCEP/NCAR reanalysis
  (post-1979)
• 1st and 2nd EOFs of Intraseasonal near-equatorial
  wind combined to generate MJO index (based on
  Shinoda et al. 1998, Bond and Vecchi 2003)
• Divide MJO cycle into 8 Phases, based on angle of
  EOF1 and EOF2.
• Index available online at http//ferret.pmel.noa
  a.gov/mjo

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MJO composite
Composite wintertime MJO 850 hPa zonal wind and
OLR anomalies.
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Arctic Air Temperature Data

• Daily minimum temperature data from stations in
  Alaska, Canada and Keflavik, Iceland. (1979-2002)
• Daily mean temperature data from stations in
  former U.S.S.R. (1979-1991)
• Daily mean temperature data from station in
  Sermilik, Greenland (1979-2000).

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Location of station data used in analysis
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MJO and North American SAT

• December-February Alaska, Canada, Sermilik
  (Greenland) and Keflavik (Iceland) data over
  1979-2002.
• Composite for each MJO Phase SAT Anomaly.
• Estimate significance using Students-t test at
  90.
• Also composite NCEP/NCAR extended reanalysis 500
  hPa height and 700 hPa specific humidity
  anomalies.

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Phase 5 Composite
Circulation anomalies consistent with radiative
and advective processes controlling SAT
anomalies. Cool (Warm) SAT under low (high) 700
hPa humidity. Dry (cold) air over Alaska
associated with flow from Siberia. Moist (warm)
air in Canada associated with poleward flow.
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MJO and Global Arctic SAT

• December-February Alaska, Canada, Sermilik
  (Greenland), Keflavik (Iceland), and former USSR
  data over 1979-1990.
• Composite for each MJO Phase SAT Anomaly.
• Estimate significance using Students-t test at
  90.
• Also composite NCEP/NCAR extended reanalysis 500
  hPa height and 700 hPa specific humidity
  anomalies.

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Phase 7 Global Composite
Circulation anomalies consistent with radiative
and advective processes controlling SAT anomalies.
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Phase 2 Composite
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Composites are robust (stationary)
Over N. America composite is generally the same
for periods 1979-2002, 1979-1990 and
1991-2002 Over USSR composites same for 6 year
subperiods of 1979-1990 (not significant)
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There are also circulation anomalies over
northern Europe
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Connection appears limited to northern winter
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Summary

• Madden-Julian Oscillation connects to Arctic Air
  Temperatures.
• O(3-10 Degrees C)
• Statistical connection is significant and robust.
• Both radiative and advective processes appear to
  drive air temperature changes.
• Association between MJO and Arctic SAT could be
  exploited for outlooks in 1-3 week timescale.

Vecchi, G.A. and N.A. Bond 2003 The
Madden-Julian Oscillation and Northern Hemisphere
High Latitude Surface Air Temperatures,
submitted to Geophys. Res. Lett. Contact
bond_at_pmel.noaa.gov or vecchi_at_atmos.washington.edu
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Caveats

• MJO definition used here is diagnostic, not
  prognosticneed to somehow forecast MJO.
• Monitored real-time at CPC.
• Extrapolations from current state being made by
  Matt Wheeler at Australias BOM.
• Limited period of analysis
• 1979-2002 for North America
• 1979-1990 for former USSR)
• Period of analysis dominated by warm ENSO and
  positive PDO conditions

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Future work.

• What mechanisms connect tropics to Arctic?
• What is sensitivity of mechanisms and connections
  to background state?
• Example of Arctic Oscillation

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MJO SAT signal is on same order as AO signal
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AO Appears to impact character of MJO related
signal
Phase 2 Temp and Z500 Composites
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AO Modulates MJO associtations in global Arctic
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Summary

• Madden-Julian Oscillation connects to Arctic Air
  Temperatures.
• O(3-10 Degrees C)
• Statistical connection is significant and robust.
• Both radiative and advective processes appear to
  drive air temperature changes.
• Association between MJO and Arctic SAT could be
  exploited for outlooks in 1-3 week timescale.

Vecchi, G.A. and N.A. Bond 2003 The
Madden-Julian Oscillation and Northern Hemisphere
High Latitude Surface Air Temperatures,
submitted to Geophys. Res. Lett. Contact
bond_at_pmel.noaa.gov or vecchi_at_atmos.washington.edu