CNES Proposal Cover Sheet NASA/CNES Research Announcement SALP-BC-MA-EA-14810-CN

CNES Proposal Cover Sheet
NASA/CNES Research Announcement SALP-BC-MA-EA-14810-CN
Proposal No.
_____________________ (Leave Blank for NASA/CNES Use)
Title: TROPICAL INSTABILITY WAVES AND VORTICES: OBSERVATIONS AND CAUSES
Principals Investigators:
Name: Frédéric MARIN
Institution: __LEGOS/CNRS – UMR5566 (CNRS/CNES/UPS/IRD)___________________
Street/PO Box: _18, av. Edouard Belin_____________________________________
City: __Toulouse__________
State: ___________
Zip: _31401 Cedex 9 ___
Country: _FRANCE__________ E-mail: _marin@notos.cst.cnes.fr _____________
Telephone: _33 5.61.33.30.04____________ Fax: __33 5.61.25.32.05_________________
Name: Christophe Eugène MENKES __________________________________________________
Institution: __LODYC UMR (7617) (CNRS/IRD/UPMC/MHN)___________________
Street/PO Box: _4 Place Jussieu_____________________________________
City: __Paris__________
State: ___________
Zip: _75252 Cedex05 ___
Country: _FRANCE__________ E-mail: menkes@lodyc.jussieu.fr _____________
Telephone: _33 1 44 27 51 57________ Fax: __33 1 44 27 71 59_________________
Co-Investigators:
Name
Yves du Penhoat
Jérôme Vialard
Institution
Telephone
LEGOS – UMR5566 (CNRS/CNES/UPS/IRD)
LODYC – UMR7617 (CNRS/IRD/UPMC)
05-61-33-29-26
91-832-2450474
Budget (for U.S. and French Investigators only):
1st Year: 12.5 kEuros__
2nd Year: 14.0 kEuros __
3rd Year: 9.0 kEuros __
Total: 35.5 kEuros ___
Authorizing Official: _Patrick MONFRAY__
(Name)
__Directeur, LEGOS____
(Institution)
TROPICAL INSTABILITY WAVES AND VORTICES
OBSERVATIONS AND CAUSES
Proposal submitted to the joint NASA/CNES Research Announcement
`The Ocean Surface Topography Science Team’
October 2003
SUMMARY
Satellite observations of sea level anomalies, sea surface temperature or surface cholorophyll
reveal the existence, close to the equator, of large mesoscale undulations in the Atlantic and
Pacific oceans that propagate westward during the boreal summer and fall. These so-called
Tropical Instability Waves (TIWs) are observed to be a significant contributor for the horizontal
heat fluxes in the equatorial oceans, to play an active role in the ecosystem of these regions and
to generate strong local anomalies in the atmosphere just above.
We intend to document, explain the main properties of, and hopefully monitor the TIWs (and
their variability from intra-seasonal to interannual timescales) from long time series of combined
satellite data (T/P-JASON, TMI, SeaWiFS), in situ observations (buoy arrays TAO/PacificPIRATA/Atlantic, XBT from merchant ships, individual cruises) and realistic simulations
(CLIPPER/Atlantic and ORCA05/Pacific + MERCATOR data assimilated simulations). The
main questions we plan to address are: why are TIWs so different north of the equator, right at
the equator and south of the equator? what are the relative impacts of local processes
(instabilities, coupling) and distant processes (equatorial oceanic waves) for the lifecycle and the
variability of TIWs? And what is the precise influence of TIWS over the general structure of
equatorial oceans including the structure of the surface ecosystem? This proposal complements
two in situ observation programs that have been submitted to French program committees to be
carried out in the next years in the Pacific (MOTIV – Multiple Observations of a Tropical
Instability – in the program MATI – Multiple Aspects of Tropical Instabilities) and in the
Atlantic (EGEE – Etude du Golfe de Guinée – in the multidisciplinary program AMMA –
African Monsoon Multidisciplinary Analysis).
In this proposal, we plan (i) to build a coherent high-resolution dataset that combines available
satellite observations, (ii) to infer the main dynamical/thermodynamical/phytoplankton balances
at the location of the TIWs from realistic ocean simulations and to develop (iii) new methods to
estimate the high-resolution surface circulation on the equatorial oceans from satellite data, (iv) a
new tool to analyze the stability of the time-dependent structure of the equatorial oceans and (v)
a simple coupled model to study the coupling process associated with the TIWs.
TABLE OF CONTENTS
I SCIENTIFIC OBJECTIVES
II PROPOSED WORK
a) combining high-resolution satellite data
b) in situ observations
c) estimating the surface horizontal circulation of equatorial oceans
d) dynamical and thermodynamical processes at the location of TIWs
e) stability analysis of the time-dependent structure of equatorial oceans
f) impact of the ocean TIW dynamics on ecosystem
g) impact of the air-sea coupling of TIWs properties
III REFERENCES
IV MANAGEMENT PLAN
V COST PLAN
VI BIBLIOGRAPHICAL INFORMATIONS
I SCIENTIFIC OBJECTIVES
Sea-Surface Temperature (SST) data obtained from satellites show the coexistence, between
8ºS and 8ºN, of large-scale temperature fronts at seasonal timescales (associated with the
existence of a cold tongue near the equator and of warmer waters north and south of the equator)
and of mesoscale structures of order 1000km at monthly timescales in the central and eastern
parts of equatorial basins (Fig. 1a). These mesoscale structures are commonly called “Tropical
Instability Waves” (TIWs) and have first been detected in current meter records in the Atlantic
(Duing et al., 1975) and in satellite infrared images in the Pacific (Legeckis, 1977). The TIWs
structure and intensify the upwelling fronts south and north of the equator into spectacular
undulations that propagate westward, north and south of the equator, with periods of 20-40 days
and phase speeds of 30-60 cm/s. They are observed in boreal summer and fall, and experience an
important interannual variability, being the strongest during La Niña years where both the
surface currents and the large-scale SST front are the most intense in the Pacific; the interannual
variability of TIWs is not as well documented in the Atlantic ocean. They also have a significant
signature in the surface field of chlorophyll (Fig. 1b). They play an active role in the biology of
these regions (Chavez et al., 1999; Murray et al., 1994) up to trophic levels (tuna for instance)
(Menkès et al., 2002).
These structures are associated with intense coherent eddies north of the equator (Flament et
al., 1996; Menkès et al., 2002) where they have a strong altimetric signature (Weidman et al.,
1999; Kennan and Flament, 2000; Chelton et al., 2001). Right at the equator, they behave like
north-south undulations of surface currents in the eastern part of the basin (Weisberg and
Weingardner, 1988; Halpern et al., 1988; Qiao and Weisberg, 1995, 1998; Kennan and Flament,
2000), with a weak altimetric signature probably due to the thinness of the mixed layer in this
region. South of the equator, they are poorly documented, even though they are associated with a
SST front that can be as intense as north of the equator; in this region, they are not located at the
same longitude as their northern counterparts (Fig. 1a) and are barely seen in altimetric signals
(Fig. 1c). Note also that the lifetime of TIWs is observed to be greater in the Pacific (about 7
months) than in the Atlantic (about 4 months).
These structures are essentially three-dimensional and are mainly confined to the mixed-layer
and the upper part of the thermocline. They can however generate some variability in the
thermocline and in the subsurface layers down to 500 meters, as can be seen in the TAO data in
the Pacific. They are also the location of local upwelling/downwelling with vertical velocities
reaching 50-500m/day at the base of the thermocline, i.e. more than 10 times greater than the
mean vertical velocities of the equatorial upwelling (Poulain, 1993). Besides they are seen, from
drifters data, as a heat source for the equatorial zone (Hansen and Paul, 1984; Baturin and Niiler,
1997; Swenson et al., 1999; Kennan and Flament, 2000) of order of the seasonal atmospheric
heat flux. Numerical simulations suggest that they also lead to important heat and momentum
exchanges between the surface and the deep ocean (Cox, 1980; Donohue and Wimbush, 1998;
Jochum et al., 2003).
Fig.1 Sea-Surface Temperature from TMI (a), chlorophyll from SeaWiFS (b) and sea level anomaly from T/P (data from
JPL/NASA) (c) for 10/28/1999. Geostrophic velocities (lower) are computed from T/P out of the equator.
These structures result from complex mechanisms that involve tropical instabilities. There is
however no consensus about the precise instability mechanisms that create TIWS (Vialard et al.,
2002): TIWs may result either from the barotropic (or inertial) instability of the surface currents
(Philander, 1976, 1978) or from the baroclinic instability of the large-scale SST front or of the
meridionally shoaling thermocline (Yu et al., 1995). There is no consensus either about the
factors that generate the discrepancies in the properties of TIWS north of the equator, right at the
equator and south of the equator (Kennan and Flament, 2000; Vialard et al., 2002). Besides,
while the most intense TIWS are believed to be anticyclonic eddies north of the equator (Flament
et al., 1996; Menkès et al., 2002; Vialard et al., 2002), it may not be the case for the moderate
undulations or for TIWs in formation.
TIWs are associated with atmospheric structures of the same scale, both propagating
westward together, suggesting a strong coupling between the ocean and the atmosphere at these
spatial scales (Fig. 2). Wind anomalies are observed above TIWs, as a consequence of the
changes in the vertical mixing within the atmospheric Planetary Boundary Layer (PBL) across
SST fronts (Wallace et al., 1989). These wind anomalies, that can reach 2m/s, influence the airsea momentum exchanges and also change the evaporative flux above TIWs, thus modifying the
air-sea heat flux at the TIW scales. In parallel, the formation of clouds over warm SSTs will also
affect the heat budget of TIWs through their impact on the shortwave radiation. How this
atmospheric response to TIWS can influence in return the TIWs is not known although initial
experiments (Pezzi et al., 2003) have started to explore the air-sea momentum coupling.
(Hashizume et al., 2002)
Thus a large number of questions concerning the TIWs still needs to be addressed:
1. Why are TIWs so different north of the equator, right at the equator, south of the equator?
More generally, what sets the longitudinal, latitudinal and temporal dependence of TIWs?
2. What are the relative impacts of local processes (instabilities, coupling, dissipation) and
distant processes (large-scale oceanic and atmospheric structures, equatorial oceanic
waves) for the birth, the life and the death of TIWs?
3. What is the exact influence of TIWs over the general structure of equatorial oceans
(horizontal versus vertical fluxes of momentum, heat, salt and phytoplankton)
The main objectives of this proposal are the following:
1. to build a coherent high-resolution (both in time and space) dataset of satellite data to
identify the main correlations between TIWs and sea level, SST, chlorophyll, wind stress,
heat fluxes from seasonal to interannual timescales.
2. to use in parallel in situ observations in order to infer the three-dimensional structure of
TIWs and to document the possible influence of distant/external forcings for their
formation and variability.
3. to develop new methods (based either on altimetric data and/or high-resolution SST and
ocean color images) to estimate the surface high-resolution (both in time and space)
horizontal circulation associated with the TIWs that cannot be deduced from satellite or
buoys data.
4. to use realistic high-resolution numerical simulations in order to compute the main
dynamical and thermodynamical balances at the location of TIWs.
5. to describe the stability of the temporally-dependant structure of currents and temperature
in the equatorial oceans in a non-normal framework.
6. To infer within coupled dynamical-biological modeling how phytoplankton and upper
trophic levels is structures by the TIW dynamics
7. to infer, within ocean/atmosphere coupled models, how the ocean-atmosphere coupling
may affect the properties of TIWs (timing of the onset and of the termination,
propagation, amplitude).
II PROPOSED WORK
A) Combining high-resolution satellite data
Satellites are the best tool to study TIWs systematically insofar as they can now provide
high-resolution (both in time and space) simultaneous data of sea level, sea surface temperature,
chlorophyll (and soon sea surface salinity) from which the surface properties of TIWs can be
followed. Most recent observational studies combining these high-resolution satellite data
focused on the second half of the year 1999 (Chelton et al., 2001; Liu et al., 2001), which was a
La Nina year in the equatorial Pacific and thus a period of particularly active and intense TIWs.
It is now possible and necessary to use the long-term (more than 4 years at present) series of
these data to infer the interannual variability of TIWs properties.
For this proposal, we plan to use, besides the altimetric data from T/P-ERS and JASON, the
high-resolution SST observations from the TRMM Microwave Imager (TMI) and AVHRR
(Advanced Very High Resolution Radiometer), the sea color measurements from the Seaviewing Wide Field-of-view Sensor (SeaWiFS) and from the ENVISAT Medium Resolution
Imaging Spectrometer (MERIS), and the wind data from SSM/I, ERS1-2 and QuikSCAT. Unlike
AVHRR, TMI has the advantage to provide high temporal resolution measurements even under
non-precipitating clouds, which will be particularly useful in the Guinea Gulf and in the eastern
equatorial Pacific where cloud cover is important. However, one potential advantage of AVHRR
data is to reach very high spatial resolutions needed to monitor the fronts associated with TIWs.
We will make use of the complementary strengths of TMI and AVHRR data sets. New heat flux
products from Abderrahim Bentamy (CERSAT) and Denis Bourras (CETP) will also be used.
As a first step, a coherent dataset of these satellite fields at a temporal resolution of 3 days
and a spatial resolution of ¼ degre will be constructed from all these satellite data. This dataset
will be validated versus in situ observations and will be constantly updated. This dataset will be
used first to document the relationship between TIWs and oceanic/atmospheric anomaly fields
(from intra-seasonal to interannual timescales), then to estimate the high-resolution ocean surface
circulation associated with TIWs (see section c) and finally to validate the various numerical
simulations that we will use in this proposal (see section d).
The time period beginning in September 2002 will be studied with a particular interest since
data from both T/P and JASON (with parallel orbits) are available at that time, leading to a
reduced inter-track distance (157km) at the equator. While the gridded data sets allow to infer the
large signals viewed north of the equator in the Pacific (Busalacchi et al., 1994) and in the
central Atlantic, the weak signal to the south is not readily visible in the gridded data sets (Fig.
1c). Thus we will use the high-resolution along-track data from this period to give new insight in
the altimetric signature of TIWs at the equator and south of the equator. A retrospective analysis
over the longer period encompassed by the coherent datasets (1999-on) will then be constructed.
B) in situ observations
Since satellites provide only measurements of surface fields, in situ observations are required
to document the full three-dimensional structure of TIWs. In situ observations that will be used
for this proposal are temperature, salinity and current measurements from buoy arrays (PIRATA
in the Atlantic and TAO in the Pacific), current measurements from drifters, temperature
measurements from XBT and thermosalinograph from ships of opportunity, and all the data
collected during individual cruises (PICOLO, EQUALANT-1999, EQUALANT-2000, FOCAL2001, EGEE in the Atlantic and TIWE, MOTIV in the Pacific).
In complement to this proposal, two in situ observation programs have been submitted to
French programs committees to be carried out in the next years. First, a cruise is proposed in the
Pacific in the second half of 2004 to provide direct observations of the three-dimensional
structure of a TIW, of its coupling to the ecosystem and of the involved air-sea heat fluxes above
it, in the framework of MOTIV (Multiple Observations of a Tropical Instability Vortex) in the
program MATI (Multiple Aspects of Tropical Instability). Secondly, several cruises are proposed
in the Guinea Gulf in 2005-2006 to study the circulation and the air-sea interactions in this
region, in the framework of EGEE (Etude du Golfe de Guinée) in the program AMMA (African
Monsoon Multidisciplinary Analysis).
These in situ observations will be first used for intercomparison with satellite data and to
validate the numerical simulations that will be used in this proposal. They will also be used, in
complement to the numerical simulations and theoretical studies described hereafter, to
document the three-dimensional structure and life cycle of the TIWS, and their possible
interaction with propagating equatorial waves.
C) estimating the surface horizontal circulation of equatorial oceans
Satellites cannot provide any direct measurement of surface velocities. The sparse surface
measurements then come from buoy arrays or drifters (with a high temporal resolution, but a
poor spatial resolution) or from individual observation cruises (with a high spatial resolution, but
a poor temporal resolution). Indirect methods must then be used to estimate high-resolution (both
in time and space) maps of the surface circulation.
In this work, two different methods for the computation of surface horizontal velocities in
equatorial oceans from satellite data will be tested:
(i)
Surface horizontal velocities will be first estimated from altimetric data. An estimate
of the mean sea level is required in addition to the sea level anomalies that are
measured by T/P and JASON. An estimate of the large-scale mean sea level can
already be obtained from the static gravity geopotential derived from the CHAMP
mission, and a higher-quality product is expected from the GRACE mission. The
limitation of this method is that only the geostrophic component of the surface
velocities can be directly computed from the dynamic height data, while Ekman
currents are known to be important (Lagerloef et al., 1999).
(ii)
Surface horizontal velocities will be then estimated from high-resolution SST images
following Vigan et al. (2000a)’s method that was originally applied to AVHRR SST
images in the Confluence region. This method is based on the minimization of a
mixed-layer integrated form of the heat balance equation. In this method, some terms
(vertical advection, heat fluxes, diffusion) have to be either neglected or
parameterized; besides, additional constraints (on the divergence and vorticity of the
surface circulation, for instance) are required so as to select a unique solution to the
minimization problem. In the equatorial oceans, TMI give high-resolution SST data
with a good spatial cover, which should allow to use this method in this region.
However, this method may be difficult to apply to the equatorial oceans and to the
TIWs problem in particular: first what should be the best additional constraints in the
equatorial oceans? second, terms to be neglected or parameterized in the heat budget
equation prove to be important in this region (upwelling/downwelling for the cold
tongue and the TIWs, heat fluxes and dissipation for the mesoscale eddies). A
combination of SST images and other satellite images (sea color or altimetry) may
therefore be necessary to solve the problem.
These two methods will be compared together and will be validated against current
measurements from in situ buoy arrays, drifters and individual cruises. They should allow, in the
future, to provide a high-resolution description of the time evolution of the surface currents in the
equatorial oceans and to monitor TIWs from satellite data.
D) dynamical and thermodynamical processes at the location of TIWs
Both satellite and in situ observations cannot document extensively the full threedimensional structure of TIWs at a high resolution both in time and space. Realistic numerical
simulations have to been used in order to carry out precise diagnostics of momentum, heat and
salt fluxes that are associated with the TIWs. In particular, there is a need to clarify the
respective roles of horizontal advection/flux versus vertical advection/flux in the momentum and
heat equations for the equatorial oceans.
To do so, it is required to perform careful diagnostics of momentum and heat fluxes in highresolution ocean circulation models forced with realistic winds. In the Atlantic, we will use
CLIPPER/DRAKKAR simulations (A.M. Tréguier) of the tropical Atlantic Ocean which have a
resolution of 1/6 degrees and are forced with ERS and QSCAT winds. In the Pacific and also in
the Atlantic, ORCA ½ degrees will be used forced by ERS+QSCAT stress and ECMWF heat
flux analyses covering the 1992-now period.
These diagnostics will quantify the importance of the momentum fluxes associated with the
TIWs, when compared to the wind stress and/or heat flux forcings. They will also allow to
identify which terms are dominant in the momentum and heat equations, and how the possible
spatial variations (especially in latitude between the equator, north of the equator and south of
the equator) of these terms may explain the observed discrepancies between these regions.
Besides these diagnostics, these simulations should give new insight on the possible role of
distant forcings (equatorial waves forced by the seasonal cycle and/or wind bursts, for instance)
for the onset and the variability of TIWs. In particular, we will analyze how the propagation of
equatorial waves may trigger or prevent equatorial instabilities by changing the surface velocity
shear (that provides the forcing for barotropic instabilities) and how propagating equatorial
waves (besides dissipation processes) may dampen already-formed TIWs. If there is no way in
these forced simulations to decouple local and distant forcings for the atmosphere, there is an
obvious way to decouple local and distant forcings in the ocean: local forcings will be due to
local instabilities, wind convergence/divergence and/or heat flux whereas distant forcings will be
due to the propagation of equatorial waves that will have their main signature in subsurface in
the thermocline depth or the integrated heat content (above 600 meters, for instance). The
relation between the propagating equatorial waves and the TIWs will thus been studied.
Thirdly, we will examine the dynamical and thermodynamical balances of TIWs in
assimilated runs from MERCATOR to compare and understand how assimilation may modify
the main balances associated with the TIWs scales. We wish to estimate also if the assimilated
runs do a better job in representing these scales that are crucial for the equatorial upwelling
regions.
E) stability analysis of the time-dependent structure of equatorial oceans
TIWs are commonly believed to result from equatorial instabilities. The stability problem of
the equatorial oceans have till now mainly been addressed in a normal modes framework (study
of the growth rate of exponential modes) in linearized models where the basic state is chosen to
be zonally- and time-independent (generally corresponding to the oceanic structure of the
equatorial oceans in boreal summer). This approach seems to be valid at first order insofar as the
birth of tropical instability waves occurs quickly (in a few weeks) at that time. However, given
the amplitude of the seasonal and decadal (El Nino/La Nina) variability of the equatorial oceans,
an approach that considers the full time-dependent structure of the equatorial oceans would be
preferable to study the full time-dependent formation of TIWs. More specifically, it would allow
to study how the local formation of TIWs may depend upon longitude and time and how the
propagating/advected TIWs may be altered as the mean oceanic state changes in space and time.
Farrel and Ioannou (1996) have developed a theory to study the stability of non-autonomous
(i.e. time-dependent) flows in a non-normal context. A version of this tool is available for
oceanic circulation models (Vialard, personal communication), allowing to diagnose the
instability processes associated with the time-dependent three-dimensional oceanic structure of
equatorial Atlantic and Pacific oceans as obtained from the numerical simulations described
above. This study is expected to give new information about the instability mechanisms (and
their temporal and spatial variability, especially in latitude) that are involved in the TIWs and
their sensivity to local versus distant forcings.
F) impact of the TIW dynamics on phytoplankton and marine ecosystem
Retrieval of surface currents at the TIW scales should provide means by which to evaluate
horizontal phytoplankton budgets on seasonal to interannual time scales which have not been yet
been assessed from observations. In addition to these surface properties, the use of a coupled
dynamical-biogeochemical model ORCA05 coupled to the ecosystem model PISCES (Aumont
et al., 2002) over the ERS-QSCAT period (Gorgues, 2003) will allow to determine more
precisely how the dynamic modulates the ecosystem from nutrients to micronekton.
The Pacific ocean is an HNCL (High Nutrients Low Chlorophyll) area which is iron limited
while the Atlantic ocean is not . Thus the ecosystem should respond differently in both oceans on
TIW scales. In particular, the strong regions of upwelling associated with the vortices, off the
equator should provide a secondary source of nutrients (e.g iron) to the photic layer and thus be
an analog for iron fertilization (Strutton et al., 2001). It is expected that the ecosystem be
structured differently within the two ocean TIWs with large diatom species and large
zooplankton developing in the vortices in the Pacific while a smaller size structure ecosystem
should be developing the Atlantic (Menkès et al., 2002).
We thus aim at exploring how the ecosystem types evolve spatially and temporally in
response to TIW forcings to be able to understand the biological budgets on seasonal to
interannual time scales.
G) impact of the air-sea coupling of TIWs properties
Recent observations based on satellite data and in situ measurements give evidence that the
presence of oceanic TIWs induces a strong local response in the atmosphere just above. Beside
the clouds that form preferentially on the warm sides of the TIWs (Deser et al., 1995), wind
anomalies are the result from local changes in the vertical momentum mixing within the
Planetary Boundary Layer (PBL) across SST fronts (Wallace et al., 1989). Namely, when winds
cross a SST front to warmer sea surface, vertical mixing intensifies, thus bringing fast-moving
air down and accelerating the surface flow; conversely, the surface flow is decelerated when
winds cross a SST front to colder sea surface.
A preliminary study (Pezzi et al., 2003) has used a simple air-sea momentum coupling (i.e. a
statistical linear relationship between SST anomalies at TIWs scales) to show that the oceanic
properties of the TIWs were weakly affected by the coupling. This initial study should be
complemented by more detailed studies and, in particular, one needs to explore the full air-sea
momentum and heat couplings. We plan to study the impact of this atmospheric response on the
TIWs, i.e. the full coupled problem for TIWs, by continuing the previous study in an idealized
coupled ocean-atmosphere model framework for which the ocean model will be a simplified
layered model of barotropic/baroclinic instability and the atmospheric mechanism described
above will be parameterized from the satellite observations of the wind and heat flux anomalies
structure above the TIWs. We will study, in this simple configuration, in which conditions this
coupling process may trigger/damp the TIWS and/or modify the properties of oceanic-forced
TIWs. Second, we plan to move the full ocean-atmosphere coupling strategy using the
OPA/Hawaii regional model for the Pacific region (in collaboration with K. Richards, IPRC) and
the coupled CLIPPER/LMD coupled simulations developed by Arnauld Jouzeau at LODYC.
This latter action is however envisioned as a perspective given the work load already presented
here.
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Montel, A. Morlière, A. Lebourge-Dhaussy, C. Moulin, G. Champalbert et A. Herbland, 2002. A whirling
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Tropical Instability Waves to Initial Conditions. J. Phys. Oceanogr., 33, 105–121.
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IV MANAGEMENT PLAN
Schedule
-
(A) Construction and validation of the combined satellite dataset : end 2004
(B) Cruises in the Atlantic (EGEE, 2005-2006) and in the Pacific (MOTIV, 2005)
(C) Reconstruction of the equatorial surface circulation : 2004-2005
(D) Diagnostic of momentum and heat fluxes from numerical simulations : 2004
(E) Stability analysis of the time-dependent structure of equatorial oceans : 2005
(F) Analyses of chlorophyll budgets from ocean color and coupled dynamical-biological
models 2004-2006
(G) Conception of the idealized coupled model for TIWs : 2004-2005
+ Regular update of the combined satellite dataset every six months
Organization
Frédéric Marin (LEGOS) (40%) :
- analysis of dynamical and thermodynamical balances in numerical simulations
- stability analysis of the time-dependent structure of equatorial oceans
- conception of the idealized coupled model of TIWs
Christophe Menkès (LODYC) (40%)
- analysis of dynamical and thermodynamical balances in numerical simulations
- analysis of phytoplankton distribution and coupled dynamical-biological simulations
- estimates of surface circulation from satellite data
- programs MOTIV and MATI in the Pacific
Yves du Penhoat (LEGOS) (30%)
- Conception of the combined satellite dataset
- Program EGEE in the Atlantic
Jérôme Vialard (LODYC) (30 %)
- analysis of dynamical and thermodynamical balances in numerical simulations
- stability analysis of time-dependent equatorial oceans
PhD students
Anne-Charlotte Peter (LEGOS) (40%)
- analysis of heat budget in the equatorial Atlantic
Thomas Gorgues (LODYC) (80%) :
- analysis of dynamical and thermodynamical budgets in numerical simulations (Pacific)
- analysis of phytoplankton distribution and coupled dynamical-biological simulations
- estimates of surface circulation from satellite data
- programs MOTIV and MATI in the Pacific
Collaborators
Yves Gouriou, Bernard Bourlès (LEGOS)
- program EGEE in the Atlantic
Gurvan Madec (LODYC), Anne-Marie Tréguier (LPO)
- diagnostic of heat and momentum fluxes in numerical simulations
Cyril Moulin (LSCE)
- interpretation of sea color measurements from SeaWiFS and MERIS
Denis Bourras (CETP)
- interpretation of heat flux products
Lionel Gourdeau (LEGOS)
- reconstruction of surface velocities from T-P/JASON and CHAMP/GRACE
Sean Kennan (Nova University, Florida)
- estimates of surface circulation from satellite data
Pierre Dutrieux and Pierre Flament (University of Hawaii)
- diagnostic of heat fluxes in numerical simulations in the Atlantic ocean
Kelvin Richards (University of Hawaii)
- GCM coupling in the Pacific ocean
Alban Lazar (LODYC)
- temporal variability of the Atlantic N-E tropical upwelling system (proposal JASON)
V COST PLAN
Costs per year
- 4 round trips Paris-Toulouse or Paris-Brest per year :
2000 euros
- 1 trip for an international meeting from LEGOS per year :
1000 euros
- 1 trip for an international meeting from LODYC per year :
1000 euros
- 1 participation to SWT for the organization team per year:
2000 euros
- 1 publication per year :
1500 euros
Total per year : 7500 euros per year.
Additional costs
2004
- 1 PC (Thomas Gorgues, LODYC):
3000 euros
- 1 mission to Nova University, Florida (collaboration S. Kennan) :
2000 euros
- 1 PC (LEGOS, construction of the satellite dataset) :
3000 euros
- 1 mission to Nova University, Florida (collaboration S. Kennan) :
2000 euros
2005
- 1 trip to University of Hawaii (collaborations K. Richards, P. Flament) : 1500 euros
2006
- 1 trip to University of Hawaii (collaborations K. Richards, P. Flament) : 1500 euros
Total cost (for the whole 2004-2006 period) : 35500 euros
A 1-year fellowship (CDD) will also be asked to CNES, CNRS or IRD to construct and validate
the combined satellite dataset.
VI Biographical Informations
Principal investigators
Frédéric Marin
Scientist at LEGOS (Laboratoire d’Etudes en Géophysique et Océanographie Spatiales), IRD
(Institut de Recherche et de Développement), Toulouse, France.
Major areas of interest : large-scale oceanic circulation, equatorial oceanography, instability
processes, idealized models of the equatorial ocean-atmosphere coupling.
PhD in Oceanography, Université Pierre et Marie Curie (Paris), 2001.
Publications:
B. L. Hua, F. Marin and R. Schopp, 2003. Three-dimensional dynamics of the subsurface countercurrents
and equatorial thermostad. Part I : Formulation of the problem and generic properties. J. Phys.
Oceanogr., in press.
F. Marin, B. L. Hua and R. Schopp, 2003. Three-dimensional dynamics of the subsurface countercurrents
and equatorial thermostad. Part II : Influence of the large-scale ventilation and of equatorial winds. J.
Phys. Oceanogr., in press.
S. Arnault, G. Eldin, B. Bourlès, Y. Du Penhoat, Y. Gouriou, A. Aman, R. Chuchla, F. Gallois, E.
Kestenare and F. Marin, 2003. In situ and satellite data comparison in the tropical Atlantic during the
EQUALANT99 experiment. International Journal of Remote Sensing, in press.
F. Marin, L. Hua and S. Wacongne, 2000. The equatorial thermostad and subsurface countercurrents
in the light of the dynamics of atmospheric Hadley cells. J. Marine Research, 58, 405-437.
F. Marin and Y. Gouriou, 2000. Heat fluxes across 7°30’N and 4°30’S in the Atlantic Ocean. Deep
Sea Research part I, 47, 2111-2139.
F. Marin, Y. Gouriou and B. Bourlès, 1998. Heat flux estimates across A6 and A7 WOCE sections.
International WOCE Newsletter, 31, pp.28-31.
Christophe Menkès
Scientist at LODyC (Laboratoire d’Océanographie Dynamique et du Climat), IRD (Institut de
Recherche et de Développement), Paris, France.
Major area of interest : equatorial ocean dynamics.
PhD in Oceanography, Université Pierre et Marie Curie (Paris), 1994.
Publications:
Boulanger, J.-P., C. Menkès and M. Lengaigne, 2003. Role of high-frequency wind variability and other
potential mechanisms in the onset, growth and termination phases of the 1997-1998 El Niño, Clim.
Dyn., accepted.
Boulanger, J.-P., S. Cravatte and C. Menkès, 2003. Role of the western Pacific in the ENSO delayed
action oscillator. J. Geophys. Res., in press.
Boulanger, J.-P., E. Durand, J.-P. Duvel, C. Menkès, P. Delecluse, M. Imbard, M. Lengaigne, G. Madec
and S. Masson, 2001. Role of non-linear ocean processes to westerly wind events: new implications
for the 1997 El Niño onset. Geophys. Res. Letters, 28, 1603-1606.
Boulanger, J.-P. and C. Menkès, 1999. Long equatorial wave reflection in the Pacific Ocean during the
1992-1998 TOPEX/POSEIDON period. Clim. Dyn., 15, 205-225.
Boulanger, J.-P. and C. Menkès, 2001. The TRIDENT Pacific model. Part II: The thermodynamical
model and the role of long equatorial wave reflection during the 1993-1998 TOPEX/POSEIDON
period. Clim. Dyn., 17, 175-186.
Lebourge-Dhaussy, A., E. Marchal, C. Menkès, G. Champalbert, B. Biessy, 2000. Vinciguerria Nimbaria
(micronekton) environment and tuna : their relationships in the eastern tropical Atlantic.
Oceanologica Acta, 23, 515-528.
Lehodey, P., J.-M. André, M. Bertignac, A. Stoens, C. Menkès, L. Mémery and N. Grima, 1998. Tuna
and environment: predicting skipjack forage distributions in the Equatorial Pacific using coupled
dynamical biogeochemical models. Fisheries Oceanography, 7:3/4, 317-325.
Lengaigne, M., J.-P. Boulanger, C. Menkès, S. Masson, P. Delecluse and G. Madec, 2003. Ocean
response to the March 1997 westerly wind event. J. Geophys. Res., in press.
Masson, S., P. Delecluse, J.-P. Boulanger and C. Menkès, 2003. Part I : Seasonal variability and
formation mechanisms of barrier layer in the eastern equatorial Indian ocean. J. Phys. Oceanogr., in
press.
Masson, S., C. Menkès, J.-P. Boulanger and P. Delecluse, 2003. Part II : The termination of the Wyrtki
jet. J. Phys. Oceanogr., in press.
Masson, S., J.-P. Boulanger, C. Menkès, P. Delecluse and T. Yamagata, 2003. Impact of salinity in the
1997 Indian Ocean Dipole in a numerical experiment. J. Geophys. Res., in press.
Menkès, C., J.-P. Boulanger and A. J. Busalacchi, 1995. Evaluation of TOPEX and basin-wide TOGATAO sea surface topographies and derived geostrophic currents. J. Geophys. Res., 100, 25087-25099.
Menkès, C., S. C. Kennan, P. Flament, Y. Dandonneau, E. Marchal, B. Biessy, G. Eldin, S. Masson, A.
Lebourges, C. Moulin, G. Champalbert, J. Grelet, Y. Montel, A. Herbland and A. Morlière, 2003. A
whirling ecosystem in the equatorial Atlantic. Geophys. Res. Letters, 29, 10.1029/2001GL014576
Picaut, J., M. Ioualalen, C. Menkès, T. Delcroix and M. J. McPhaden, 1996. Mechanism of the zonal
displacements of the Pacific warm pool: implications for ENSO. Science, 274, 1486-1489.
Radenac, M.-H., C. Menkès, J. Vialard, C. Moulin, Y. Dandonneau, T. Delcroix, C. Dupouy, A. Stoens
and P.-Y. Deschamps, 2001. Modeled and observed impacts of the 1997-1998 El Niño on nitrate and
new production in the equatorial Pacific. J. Geosphys. Res., 106, 26879-26898.
Stoens, A., C. Menkès, M.-H. Radenac, N. Grima, Y. Dandonneau, G. Eldin, L. Mémery, C. Navarette,
J.-M. André, T. Moutin and P. Raimbault, 1998. The coupled physical-biogeochemical system in the
tropical Pacific ocean in sept.-nov. 1994. J. Geophys. Res., 104, 3323-3339.
Stoens, A., C. Menkès, Y. Dandonneau and L. Mémery, 1998. New production in the equatorial Pacific :
a coupled dynamical-biogeochemical model. Fisheries Oceanography, 7, 311-316.
Vialard, J., C. Menkès, D. L. T. Anderson and M. Balsameda, 2003. Sensitivity of Pacific Ocean Tropical
Instability Waves to initial Conditions. J. Phys. Oceanogr., 33, 105-121.
Vialard, J., P. Delecluse and C. Menkès, 2002. A modeling study of salinity effects in the tropical Pacific
ocean during the 1993-1998 period. J. Geophys. Res., in press.
Vialard, J., C. Menkès, J.-P. Boulanger, P. Delecluse, E. Guilyardi, M. J. McPhaden and G. Madec, 2001.
Oceanic mechanisms driving the SST during the 1997-1998 El Niño. J. Phys. Oceanogr., 31, 16491675.
Vialard, J., C. Menkès, D. L. T. Anderson and M. Balsameda, 2003. Phase locking of tropical instability
waves. J. Phys. Oceanogr., in press.
Other publications of the organization team
Bourlès, B., M. D‚Orgeville, G. Eldin, R. Chuchla, Y. Gouriou, Y. du Penhoat, and S. Arnault, 2002. On
the thermocline and subthermocline eastward currents evolution in the Eastern Equatorial Atlantic,
Geophys. Res. Lett., 29, 16.
Bourlès, B., C. Andrié, Y. Gouriou, G. Eldin, Y. du Penhoat, S. Freudenthal, B. Dewitte, F. Gallois, R.
Chuchla,, F. Baurand, A. Aman and G. Kouadio, 2002. The Deep Currents in the Eastern Equatorial
Atlantic Ocean, Geophys. Res. Letters, 30, 5, 8002, 10.1029/2002GL015095.
Dandonneau, Y., A. Vega, H. Loisel, Y. du Penhoat and C. Menkes, 2003. Rossby waves acting as a “hay
rake” for ecosystem floating by-products. Science, accepted.
Dewitte B., D. Gushchina, Y. duPenhoat and S. Lakeev, 2002. On the importance of subsurface
variability for ENSO simulation and prediction with intermediate coupled models of the Tropical
Pacific: A case study for the 1997-1998 El Niño. Geoph. Res. Letters, 29 (14), Art. No. 1666.
du Penhoat, Y., G. Reverdin and G. Caniaux, 2002. A Lagrangian investigation of vertical turbulent heat
fluxes in the upper ocean during TOGA-COARE, 2002, J. Geophys. Res., 107, C5,
10.1029/2001JC00926.
Illig S., B. Dewitte, N. Ayoub, Y. du Penhoat, G. Reverdin, P. De Mey, F. Bonjean and G.S. E. Lagerloef,
2003: Interannual Long Equatorial Waves in the Tropical Atlantic from a High Resolution OGCM
Experiment in 1981-2000. J. Geophys. Res., accepted.
Vauclair, F. and Y. du Penhoat, 2001. Interannual variability of the upper layer of the tropical Atlantic
ocean from in situ data between 1979 and 1999. Climate Dynamics, 17, 527-546.
Vauclair F., Y.du Penhoat and G. Reverdin, 2003. Heat and mass budgets of the warm upper layer of the
tropical Atlantic Ocean in 1979-1999. J.Phys.Oceanogr., accepted.
Vega A., Y. duPenhoat, B. Dewitte and O. Pizarro, 2003. Equatorial forcing of interannual Rossby waves
in the South eastern Pacific. Geoph. Res. Lett., 30 (5), 1197-1200.
Vauclair F., Y. du Penhoat and I. Wainer, 2003. Interannual to decadal variability of mass and heat
budgets simulated in the equatorial Atlantic between 1948 and 2000. Submitted to Climate
Dynamics.