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Intraseasonal SSS varia.ons in the
northeastern tropical Pacific (NETP)
fresh Pool
10th Aquarius / SAC-D Joint Science Team Meeting 17-19 November
2015, Buenos Aires, Argentina
Audrey Hasson and Tony Lee NASA Jet Propulsion Laboratory,
California Institute of Technology
Pasadena, California, USA
Frederick Bingham University of North Carolina at Wilmington,
NC., USA
J. Thomas Farrar
Woods Hole Oceanographic Institution, MA, USA
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Background & Mo.va.on
November 17-‐19th, 2015 10th Aquarius
/ SAC-‐D Joint Science Team
Mee.ng
• NASA’s SPUR2 field campaign –
to understand salinity processes in
the NETP fresh pool, focusing
on intraseasonal to seasonal
variability.
• Satellite obs provide large-‐scale
context for SPURS2. • Intraseasonal
variability in the NETP has
been studied using SST, SSH but
not SSS.
170oE 170oW 150oW 130oW 110oW 90oW 70oW 20oS
10oS
0o
10oN
20oN
(a) Salinity − Aqua
32.833.233.63434.434.835.235.636
170oE 170oW 150oW 130oW 110oW 90oW 70oW 20oS
10oS
0o
10oN
20oN
(d) Temperature − Ostia
212223242526272829
170oE 170oW 150oW 130oW 110oW 90oW 70oW 20oS
10oS
0o
10oN
20oN
(c) Density − Ostia − Aqua
20.1520.7521.3521.9522.5523.1523.7524.3524.95
170oE 170oW 150oW 130oW 110oW 90oW 70oW 20oS
10oS
0o
10oN
20oN
(b) Salinity std between 50 and 200 days − Aqua
0.020.060.10.140.180.220.260.3
170oE 170oW 150oW 130oW 110oW 90oW 70oW 20oS
10oS
0o
10oN
20oN
(a) Salinity − Aqua
32.833.233.63434.434.835.235.636
170oE 170oW 150oW 130oW 110oW 90oW 70oW 20oS
10oS
0o
10oN
20oN
(d) Temperature − Ostia
212223242526272829
170oE 170oW 150oW 130oW 110oW 90oW 70oW 20oS
10oS
0o
10oN
20oN
(c) Density − Ostia − Aqua
20.1520.7521.3521.9522.5523.1523.7524.3524.95
170oE 170oW 150oW 130oW 110oW 90oW 70oW 20oS
10oS
0o
10oN
20oN
(b) Salinity std between 50 and 200 days − Aqua
0.020.060.10.140.180.220.260.3
Sept. 2011-‐ Dec. 2014 Average and
standard deviaOon of SSS (pss)
from Aquarius, average SST (ºC)
from OSTIA and following Density
(-‐1000 kg.m-‐3).
SSS std
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Data
November 17-‐19th, 2015 10th Aquarius
/ SAC-‐D Joint Science Team
Mee.ng
Objectives
• Dominant space-‐Ome scales of
intraseasonal SSS in the NETP.
• Coherence of SSS signals with
SSH & SST (if any).
• Influence of local horizontal
advecOon (e.g., by NEC &
NECC), precipitaOon,
eddy propagaOon on SSS.
• Aquarius, V4.0, level-‐3 SSS. •
OSTIA level-‐4 SST. • AVISO SSH. •
OSCAR ocean surface current. • GPCP
precipitaOon. • Fields from ECCO-‐2
18-‐km ocean model.
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Wavenumber-frequency spectra at 10ºN
November 17-‐19th, 2015 10th Aquarius
/ SAC-‐D Joint Science Team
Mee.ng
SSS SSH SST
Modeled SSS • SSH spectrum suggests westward
intraseasonal propagation (e.g., 50- 150 days).
• A slight hint in observed SSS & SST. • ECCO2 SSS shows
more prominent
westward propagation of SSS (is it right?) ECCO2 SSH spectrum
(not shown) similar to AVISO.
Log10 of the Zonal-wavenumber-frequency power spectral density
from a 2DFFT between 100-150ºW and averaged over 9-11ºN.
ECCO2 SSS
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Observed intraseasonal (50-150d) SSS, SST, & SSH anomalies
at 10ºN
November 17-‐19th, 2015 10th Aquarius
/ SAC-‐D Joint Science Team
Mee.ng
SSS (pss) SST (ºC) SSH (m)
• Westward propagation evident in all observed fields.
• Most coherent in SSH’. • Large SSS’ in the 1st half of
2013
associated with SSH’, probably related to subsurface processes
(±SSS’ ~ ±SSH’).
• Weak signal in SST’ because of
weak gradient there.
Averaged between 9 and 11oN and
30 of longitude to reduce the
noise
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Intraseasonal (50-150d) SSS budget 10ºN
E-P Forcing
Zonal Advection
SSS Tendency
Meridional Advection
∂tSSSSSS.Tendency! =
E −P( )H
⋅SSS
E−P.Forcing! "## $##
− u ⋅∂xSSSZonal.Advection! "# $#
− v ⋅∂ySSSMeridional.Advection! "# $#
+ [...]Other.Processes!
• Salinity tendency shows both the
propagaOng signal and larger-‐scale
standing padern.
• Standing padern largely due to
E-‐P. • PropagaOon significantly
affected by
zonal adevcOon in the 1st half
of 2013 • Meridional advecOon
important in the
2nd half of 2013.
• VerOcal processes (not resolved) are
probably also important, as hinted
by ±SSS’ ~ ±SSH’ shown earlier.
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Date Goes Here Name of
presentaOon or other info goes
here 8
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Date Goes Here Name of
presentaOon or other info goes
here 9
Summary
Intraseasonal SSS variaOon in the
northeast tropical Pacific is
influenced by • OscillaOon of
precipitaOon with large zonal scale.
• Zonal advecOon by the NEC and
NECC and their meridional movement.
• Westward propagaOng eddies with
associated SSS anomalies (the nature
of which need to be studied).
• VerOcal processes are also believed
to be important.