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  

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.