Equatorial Annual Cycle Shang-Ping Xie IPRC/Met, University of Hawaii Ocean University of China owerPoint file available at http://iprc.soest.hawaii.edu/~xie/ppt/annual.ppt References Mitchell, T.P. and J.M. Wallace, 1992: The annual cycle in equatorial convection and sea surface temperature. J. Climate, 5, 1140-1156. Xie, S.-P., 1994: On the genesis of the equatorial annual cycle. J. Climate, 7, 2008-2013.
31
Embed
Equatorial Annual Cycle Shang-Ping Xie IPRC/Met, University of Hawaii Ocean University of China PowerPoint file available at xie/ppt/annual.ppt.
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Equatorial Annual Cycle
Shang-Ping XieIPRC/Met, University of Hawaii
Ocean University of China
PowerPoint file available at http://iprc.soest.hawaii.edu/~xie/ppt/annual.ppt
References
Mitchell, T.P. and J.M. Wallace, 1992: The annual cycle in equatorial convection and sea surface temperature. J. Climate, 5, 1140-1156.
Xie, S.-P., 1994: On the genesis of the equatorial annual cycle. J. Climate, 7, 2008-2013.
SST165W, 20N
90W, Eq
Galapagos SST and Precipitation
Calendar Month
Nino3 std dev
ENSO’s Seasonal Phase Locking
u vT
Equatorial Annual Cycle
Why annual? Why Strong in the east? Why propagate westward?
Lukas and Firing (1985, J. Phys. Oceanogr.)
x x
yy
= A(x) ei[ t - (x) ]
A(x) (x)
cf. Horel (1982, Mon. Wea. Rev.)
Mar-Apr
Aug-Sept
SST, Precipitation and Surface Winds
August-May Difference
Sea surface height (cm)
cf. Mitchell and Wallace (1992)
Sept-Mar SST & Wind Diff (COADS)
Buoy Measurements at 110W, Eq.
From Xie (1994, JC)
Why is the annual cycle in h small in the Eq Pacific?
h
TwρQ/c
tT ep
ρc
2TWe
p
3* Q
gh
mu
22* VUCu a
D
1D Ocean
x
TU
'
'
U2H
aμc εT'V'
H
Va'
t
T'2
x
Tc
(coupling)
Simple Theory of Equatorial Annual Cycle
Linearization 22'*
''
VU
VVUUCu a
D
εT')V'VU'U(H
a
t
T'2
How to make this coupled equation unstable? Hint: atmospheric model.
Northward displaced ITCZ ( >0) Annual frequency (V’);
Tilt of the thermocline H(x) Stronger annual cycle in the east;