Transcript meteo.hawaii.save

Teleconnections and the MJO:
intraseasonal and interannual
variability
Steven Feldstein
June 25, 2012
University of Hawaii
The dominant Northern Hemisphere teleconnection patterns
North Atlantic Oscillation
Pacific/North American pattern
Climate Prediction Center
NORTH ATLANTIC OSCILLATION
University of Hamburg
Earliest NAO observations
Norse (Viking) settlers arrived in Greenland in CE 985. The
Norse, who appeared to be very interested observers of the
weather, also seemed to be aware of teleconnection patterns
in the North Atlantic basin.
There was an anonymous Norwegian book (approx. CE 1230),
entitled the `King's Mirror'. This book, in the form of a
discussion between father and son, wrote that severe weather
in Greenland coincides with warmer weather at distant
locations, and vice versa.
• Danish missionary Hans Egede (1745) wrote:
“In Greenland, all winters are severe,
yet they are not alike. The Danes
have noticed that when the winter in
Denmark was severe, as we perceive it,
the winter in Greenland in
its manner was mild, and conversely.”
Hans Egede map in “History
of Greenland”
• Walker (1932) used correlation analysis to find the dominant
teleconnection patterns, including the NAO.
SEASONAL ROTATED EOFS
seasonal NAO
seasonal PNA
Corr=0.98
daily NAO
Corr=0.97
DAILY ROTATED EOFS
daily PNA
Feldstein (2000)
POWER SPECTRA
 = 9.5 days
101 10 0 10-1 10-2 10-3
Period (years)
An AR(1) process
PNA
 = 7.7 days
Power
Power
NAO
101 10 0 10-1 10-2 10-3
Period (years)
x t = ax t-1 + Ft
Power spectral density function
s x2 (1- a 2 )
f (w ) =
p (1- 2a cosw +a 2 )
Feldstein (2000)
DAILY NAO INDEX & FORECAST (since ~2002)
Climate Prediction Center
Implication for interannual variability?
Feldstein (2002)
Feldstein (2002)
Climate Noise: relationship between daily &
interannual NAO variability
2
2
Snao
/SAR(1)
=1.09
Most interannual NAO variability is from Climate Noise
Physical processes of the NAO
Streamfunction tendency equation
Projections
NAO
Feldstein (2003)
NAO DRIVING MECHANISMS
¶y /¶t =
Linear
+
Nonlinear
NAO AMPLITUDE
Nonlinear
Linear
High-frequency eddies
Vorticity Advection
Low-frequency eddies
Divergence
Feldstein (2003)
Day 1
Day 4
Day 7
Day 10
Benedict et al. (2004)
Initial perturbation
MODEL SIMULATION
NAO +
NAO -
Area of small potential
vorticity gradient
Franzke et al. (2004)
Physical processes for the PNA
• Both phases of the PNA are excited by
tropical convection
 Tropical convection excites a small amplitude
Rossby wave train via linear dispersion
 In contrast to the NAO, the PNA is dominated by
linear processes: stationary eddy advection.
 Synoptic-scale eddies (remote pos phase;
local neg phase) amplify PNA
OLR anomalies associated with the PNA
300-hPa streamfunction anomalies associated with OLR
PNA Life Cycle
PA
PNA
PNA
Summary of Physical Processes
• Prominent Northern Hemisphere teleconnection patterns have
a timescale of 7-10 days
•Interannual variability of most teleconnection patterns arises primarily from
climate noise
• The NAO is comprised of the remnants of breaking synoptic-scale waves; nonlinear
process
• The PNA wavetrain is excited by tropical convection and then amplified by breaking
synoptic-scale waves;
primarily a linear process
Tropical Convection Associated with
the Madden-Julian Oscillation (MJO)
Phase 1


Dominant intraseaonal
oscillation in the tropics
Phase 2
MJO cycle: 30-60 days
Phase 3

Shading OLR

Time between
phases ~ 6 days
Phase 4
Phase 5
Phase 6
Time between Phases ~
6 days
Phase 7
Phase 8
From Wheeler and Hendon (2004)
20۫°
E
180۫
°
From Wheeler and Hendon (2004)
60۫°
W
Does the MJO affect Arctic surface air temperature?
MJO Phase 1 (neg PNA)
MJO Phase 5 (pos PNA)
Zonal-mean zonal wind and temperature
MJO Phase 1 (neg PNA)
MJO Phase 5 (pos PNA)
Eliassen-Palm Fluxes associated with the MJO
Planetary-scale
(k-1,3)
Synoptic-scale
(k=4,8)
MJO Phase 1 (Phase 5) associated with a reduced
(increased) poleward heat and wave activity flux
Summary of physical processes
(projections onto 7-10 day SAT)
MJO Phase 1 (neg PNA)
MJO Phase 5 (pos PNA)
Mean Meridional Circulation
Negative PNA
Positive PNA
Multi-level primitive equation model calculation of MJOinduced Arctic SAT change (GFDL dynamical core)
Use MJO-like steady heating profiles for MJO phases 1 and 5 (100
MJO phase 5
MJO phase 1
randomly selected ensemble members): Initial value problem
MJO-induced poleward tracer (H20) transport
MJO phase 5
MJO phase 1
Composite evolution of anomalous tracer concentration
Tracer (H20) transported equatorward (poleward) during
MJO phase 1 (phase 5) (Perhaps can explain observed downward IR
associated with MJO)
Sensitivity of midlatitude response to
initial conditions
Projections onto 7-13 day SAT
MJO Phase 1 (neg PNA)
MJO Phase 5 (pos PNA)
Response to MJO convection very sensitive to
intial conditions
Concluding remarks
• Most of the major teleconnection patterns have a time scale of less than 10 days
• Most of the interannual variability of the major teleconnection patterns arises from
climate noise
• The NAO and arises from synoptic-scale wave breaking and the PNA as a Rossby
wave train response to MJO convection followed by amplification by synoptic-scale
wave breaking
•MJO impacts Arctic SAT through changes in the excitation of poleward Rossby
wave propagation (poleward heat flux and eddy-induced adiabatic warming/cooling) :
Poleward Rossby wave propagation is weakened (strengthened) in MJO phase 1
(phase 5) and is associated with less (more) localized tropical convection
•Downward IR (surface sensible and latent heat flux) enhances (weakens) the
impact of the MJO on Arctic SAT
•Anomalous downward IR may be associated with changes in poleward moisture
transport associated with MJO