Radio Science, 38, 4, 36-1-8. DOI: 10.1029/2002RS002629 -- Abstract. (BibTeX: camps.etal.2003b)
Keywords: sea salinity, microwave radiometry, multiangular, interferometric radiometer.
Soil moisture and ocean salinity at surface level can be measured by passive microwave remote sensing at L-band. To provide global coverage data of soil moisture and ocean salinity with three-day revisit time, the Earth Explorer Opportunity Mission SMOS (Soil Moisture and Ocean Salinity) was selected by ESA (European Space Agency) in May 1999. SMOS'single payload is a Y-shaped 2-D aperture synthesis interferometric radiometer called MIRAS (Microwave Imaging Radiometer by Aperture Synthesis). SMOS presents some particular imaging peculiarities: variation of incidence and azimuth angles, different radiometric sensitivity and accuracy at each direction (pixels), and geometric polarization mixing. Therefore, the accuracy of the geophysical parameter retrieval depends on the knowledge of the angular dependence of the emissivity over a wide range of incidence and azimuth angles. The accuracy of the sea surface salinity retrievals depends on our capability to correct the wind-induced variation of the brightness temperatures. To better understand wind effects, ESA sponsored the WInd and Salinity Experiment 2000 (WISE-2000) from November 15, 2000, to January 16, 2001, in the Casablanca oil rig, at 40 km off the coast of Tarragona (Spain). This paper is divided into two parts. First, it presents the derived sensitivities of the brightness temperatures at vertical and horizontal polarizations with wind speed, and compares to Hollinger's measurements and numerical simulations. Second, these results are applied to the SMOS sea surface salinity (SSS) retrieval problem for different tracks within the swath. It is shown that, except for low SSS and sea surface temperature (SST), the retrieved SSS has a RMS error of approximately 1 psu in one satellite pass.
Kybernetes, 32, 4, 548-560. -- Abstract. (BibTeX: garciaolivares.2003b)
Keywords: Partial Differential Equations (PDE) Boundary problems Series expansion Decomposition method.
A general method is proposed to approximate the analytical solution of any time-dependent partial differential equation with boundary conditions defined on the four sides of a rectangle. To grant that the approximant satisfies the problem boundary conditions the differential operator is modified with one additional term which takes into account the effect of boundary conditions. Then the new problem can be directly integrated in the same way as an ordinary differential equation. In this work Adomian’s decomposition method with analytic extension is used to obtain the first-order approximant to the solution of a test case. The result is an analytic approximation to the solution which is compatible with both the exact boundary conditions and the accuracy imposed in the whole domain. The solution obtained is compared with the analytic approximation obtained with a Tau-Legendre spectral method.
Kybernetes, 32, 3, 354-368. -- Abstract. (BibTeX: garciaolivares.2003c)
Keywords: Partial Differential Equations (PDE) Boundary problems Series expansion Decomposition method.
Adomian’s method is completed to obtain the analytic solution of any partial differential equation with boundary conditions defined on the four sides of a rectangle. Adomian’s decomposition method is first used to obtain the N-order approximant to the one direction partial solution that satisfies the boundary conditions on that direction. Then the functions obtained are variationally modified in the four sides to make them compatible with a given experimental error. The product of these transformations is an analytic approximation to the solution which is compatible with both the weak norm imposed on the boundaries and the accuracy imposed in the whole domain.
Journal of Geophysical Research, 108, C12, 3376. DOI: 10.1029/2003JC001967 -- Abstract. (BibTeX: ostrovskii.font.2003b)
Keywords: stochastic climate model, SST anomaly, inversion.
Processes contributing to the heat anomaly budget of the upper ocean mixed layer are examined over the North Atlantic in summer season on the basis of the inversion of the sea temperature profiles. The net advection velocity, the subgrid heat diffusivity, and the surface heat flux feedback are estimated. Two inversion strategies are pursued, with and without the explicit parameterization of the entrainment heat flux into the upper mixed layer. The regression estimator is employed for the inversion. The data involved are the compilation of the Comprehensive Ocean-Atmosphere Data Set sea surface temperature (SST) and World Ocean Database 2001 temperature profiles over a 2º latitude x3º longitude grid for sequential 10-day intervals in June-September during 1965-2000. The inversion is constrained by the autocorrelation of the National Centers for Environmental Prediction net air-sea heat flux. The regression estimator allows for prediction of up to 60-70% of the SST anomaly value 10 days in advance by using the regressions on the SST anomalies lagged by two time steps. The SST anomaly transport over the North Atlantic agrees broadly with the known features of the surface circulation, although the quantitative details of the SST anomaly propagation obtained in this inversion have not previously been available. The heat anomaly that originates in the Gulf Stream region near the western boundary either moves northeastward with speed of up to 0.12 m s-1 downstream of the North Atlantic Current and the North Atlantic Drift Current or it turns southeastward and then propagates southwestward along the broad subtropical recirculation; in the subtropics the westward propagation is seemingly reinforced by the effects of the planetary waves. The air-sea feedback is negative with the feedback factor having the average value of 39 W m-2 K-1 with substantial variations throughout the North Atlantic. The entrainment rate is generally about 0.15 m d-1; relatively rapid deepening of the mixed layer by more than 2x10-6 m s-1 occurs near the Gulf Stream.
Journal of the Atmospheric Sciences, 60, 1866-1870. -- Abstract. (BibTeX: viudez.2003b)
The beta term, usually defined as the northward gradient of the vertical planetary vorticity, is here defined and interpreted as the northward planetary vorticity. The beta term in the vorticity equation, relative to a rotating reference frame, is put into an exact correspondence with the planetary vorticity tilting term, which has a meaning independent of the coordinate system. For barotropic, isochoric, horizontal flow there is an exact balance between the rate of change of vertical vorticity and the planetary vorticity tilting term due to the northward components of velocity and planetary vorticity. This interpretation of the beta term in the vorticity equation seems to be simpler than the interpretation based on the northward gradient of the vertical planetary vorticity because it only involves the components, not the derivatives, of the planetary vorticity, and because it is independent of the coordinate system. It is also shown, as a consequence of this new interpretation, that the Sverdrup relation is practically equivalent to the vertical component of the Taylor–Proudman constraint
Fluid Dynamics Research, 32, 141-177. -- Abstract. (BibTeX: viudez.2003d)
Keywords: Fluid flows; Material description; Relative description; Generalized Lagrangian mean; Average theory.
A mathematical framework for describing different flows of the same fluid and their relationships is introduced. This theory, named the Multi-flow Framework (MfF), considers the referential, spatial, and relative descriptions of fields of both pure and mixed distributions. A mixed distribution, as opposed to apure distribution, results when the transformation between descriptions of some quantity in one flow is carried out using the particle or position distributions from another flow. The basic kinematics of the mixed distributions is developed with emphasis on those fields giving the circulation and flux in one flow per unit of length and area of another flow. These fields are called here the relative circulation and the relative flux fields, respectively. The MfF is applied to both the material and the spatial ensemble average theories. The results in the material average framework are then applied to obtain a new formulation and interpretation of the conservation of mass, interms of the mean-flow density, and balance of linear momentum given in the Generalized Lagrangian Mean theory. The MfF puts the GLM mean-flow density into an exact correspondence with the reference mass density, of every flow at the average position, per unit of spatial volume of the average flow relative to the reference (initial) volume. The MfF formulates the GLM momentum equation as the spatial ensemble average of the relative circulation balance of momentum relative to the actual flow in the material average flow, expressed in terms of the rate of change of the relative circulation velocity.
Journal of Fluid Mechanics, 483, 199-223. DOI: 10.1017/S0022112003004191 -- Abstract. (BibTeX: viudez.dritschel.2003a)
An analysis of the vertical velocity field using the full generalized omega equation (ω- equation) in a single mesoscale baroclinic oceanic gyre is carried out. The evolution of the gyre over 20 inertial periods is simulated using a new three-dimensional numerical model which directly integrates the horizontal ageostrophic vorticity, explicitly conserves the potential vorticity (PV) via contour advection on isopycnal surfaces, and inverts the nonlinear PV definition via the solution of a three-dimensional Monge–Ampè---re equation. In this framework the ω-equation comes simply from the horizontal divergence of the horizontal ageostrophic vorticity prognostic equation. The ageostrophic vorticity is written as the Laplacian of a vector potential φ, from which both the velocity and the density fields are recovered, respectively, from the curl and divergence of φ. A new initialization technique based on the slow, progressive growth of the PV field during an initial time interval is used to avoid the generation of internal gravity waves during the initialization of the gyre. This method generates a nearly balanced baroclinic gyre for which the influence of internal gravity waves in the mesoscale vertical velocity field is negligible. The numerical fields obtained are then used to carry out a first numerical analysis of the ω-equation. The analysis shows that, for moderately high Rossby numbers, the local and the advective rates of change of the differential ageostrophic vertical vorticity (ζz′) are of the same order of magnitude as the three largest terms in the ω- equation. There is, however, a large cancellation between these two terms, resulting in the approximate material conservation of ζz′. This might explain the ‘over-applicability’ of the quasi-geostrophic (QG) ω-equation for Rossby numbers larger than 0.1. The QG vertical velocity is only 22% smaller than the total vertical velocity for the case studied (having a Rossby number of −0.5).
Journal of Geophysical Research, 108, C3, 3059. DOI: 10.1029/2002JC001365 -- Abstract. (BibTeX: bouzinac.etal.2003a)
Keywords: Mediterranean, sea level, steric effect, seasonal variations.
In the western Mediterranean Sea, sea level variations are the result of seasonal steric effect, atmospheric forcing and mesoscale circulation activity, particularly in the Alboran and Algerian basins, as well as water mass budget variations including flux variations through the Straits of Gibraltar and Sicily. However, the partition of the magnitude of the sea level variations associated with these different components remains a challenging problem. A better determination of the steric effect component will allow a better knowledge of the other annual components. The aim of this study is to improve the estimation and understanding of the annual sea level variations in the different basins of the western Mediterranean Sea, using sea level anomalies (SLA) derived from TOPEX/ POSEIDON and ERS-1/2 altimeters and sea surface temperatures (SST) derived from NOAA/AVHRR infrared imagery, obtained between 1992 and 1998. The first mode of empirical orthogonal function (EOF) analysis on SLA is annual and represents 63% of the total variance. The first mode of EOF analysis on SST anomalies is also annual and represents 98% of the total variance. The lag between the annual variations of SLA and SST is about 40 days. From these EOF results and a parameterisation of the mixed layer, the seasonal dynamic height and the steric effect are estimated and removed from the SLA. The remaining signal is used to examine the annual cycles of the sea level due to water mass budget variations, mesoscale oceanic variability and atmospheric forcing. INDEX TERMS: 4223 Oceanography: General: Descriptive and regional oceanography; 4275 Oceanography: General: Remote sensing and electromagnetic processes (0689); 4520 Oceanography: Physical: Eddies and mesoscale processes; 4556 Oceanography: Physical: Sea level variations; 4572 Oceanography: Physical: Upper ocean processes.
Journal of Fluid Mechanics, 488, 123-150. DOI: 10.1017/S0022112003004920 -- Abstract. (BibTeX: dritschel.viudez.2003b)
We describe a new approach to modelling three-dimensional rotating stratified flows under the Boussinesq approximation. This approach is based on the explicit conservation of potential vorticity, and exploits the underlying leading-order geostrophic and hydrostratic balances inherent in these equations in the limit of small Froude and Rossby numbers. These balances are not imposed, but instead are used to motivate the use of a pair of new variables expressing the departure from geostrophic and hydrostratic balance. These new variables are the ageostrophic horizontal vorticity components, i.e. the vorticity not directly associated with the displacement of isopycnal surfaces. The use of potential vorticity and ageostrophic horizontal vorticity, rather than the usual primitive variables of velocity and density, reveals a deep mathematical structure and appears to have advantages numerically. This change of variables results in a diagnostic equation, of Monge-Ampère type, for one component of a vector potential ϕ, and two Poisson equations for the other two components. The curl of ϕ gives the velocity field while the divergence of ϕ is proportional to the displacement of isopycnal surfaces. This diagnostic equation makes transparent the conditions for both static and inertial stability, and may change form from (spatially) elliptic to (spatially) hyperbolic even when the flow is statically and inertially stable. A numerical method based on these new variables is developed and used to examine the instability of a horizontal elliptical shear zone (modelling a jet streak). The basic-state flow is in exact geostrophic and hydrostratic balance. Given a small perturbation however, the shear zone destabilizes by rolling up into a street of vortices and radiating inertia-gravity waves.
Journal of Geophysical Research, 108, C5, 3164. DOI: 10.1029/2001JC001239 -- Abstract. (BibTeX: garciagorritz.etal.2003a)
Keywords: inertial currents, tidal currents, acoustic Doppler current profiler, Alboran Sea, Catalan Sea.
The objective of this study is to separate the subinertial, inertial, and tidal fields from vessel-mounted acoustic Doppler current profiler (VM-ADCP) observations acquired during six cruises in the Catalan and Alboran Seas (western Mediterranean Sea). To fulfill this objective we use a method that successfully detects and filters out the main high frequencies that are present in the VM-ADCP data. The resulting near-inertial component has frequencies below the Coriolis frequency f in the Catalan Sea, and above f in the Alboran Sea. The tidal component is consistent with observed and modeled tides in the Catalan and Alboran Seas. The steady component is highly correlated with the geostrophic field. There is also a nonfitted (or residual) component, which represents the misfit between the VM-ADCP data and the model proposed. INDEX TERMS: 4283 Oceanography: General: Water masses; 1255 Geodesy and Gravity: Tides—ocean (4560); 4544 Oceanography: Physical: Internal and inertial waves.
Journal of Atmospheric and Oceanic Technology, 20, 772-778. -- Abstract. (BibTeX: isernfontanet.etal.2003a)
A procedure is presented to detect eddy cores from sea level anomaly (SLA) maps obtained from altimetric measurements. The method is based on finding the sign of Q, which is an invariant of the velocity gradient tensor (u). This parameter, commonly used in studies of two-dimensional turbulence, measures the relative contribution of deformation and vorticity. Vortex cores are associated with regions with large and positive values of Q. It is shown that this parameter is adequate to detect marine eddies in altimetric maps and, when the geometry of streamline contours in SLA maps is unclear, the Q 0 criterion appears to work more consistently. The performance of the methodology is applied, as an example, to altimetric maps of the Algerian Basin in the Western Mediterranean Sea, where two long-lived eddies are tracked. The observed trajectories are in good agreement with Advanced Very High Resolution Radiometer (AVHRR) images.
Journal of Marine Systems, 43, 105-131. DOI: 10.1016/j.jmarsys.2003.08.001 -- Abstract. (BibTeX: salasperez.2003)
Keywords: Open-sea eddies; Coastal eddies; Lagrangian trajectories; Infrared images; Altimeter; Algerian Basin; Mediterranean Sea.
The westward evolution of an open-sea anticyclonic eddy along the western Algerian Basin is shown, for the first time, by means of 15 buoy trajectories and remote sensing observations. For -3 months, the buoy trajectories described several anticyclonic loops in periods of 4–21 days. The eddy’s movement, translation, and rotation were separated with a kinematic model, resulting in a mean translation speed of -2 km/day, which fits the self-propulsion speed predicted on theoretical models for isolated eddies on a beta plane. Fluctuations in translation speed were associated with advection of the mean flow and topographic interactions. Both mechanisms changed the eddy\'s horizontal shape from circular to elliptical, inducing fluctuations in its swirl velocity and solid-body rotation. The initial stage of the eddy is an isolated asymmetric dipole, comprised by a small cyclone and a large anticyclone, the latter generated from a frontal instability, which under the Coriolis term acquires anticyclonic relative vorticity. During its first days of life, the anticyclonic eddy was shallow Ro = 0.9 and small (diameter less than 50 km). Later on, it reached a diameter of -150 km and a vertical structure of 3 km (Ro = 0.1). A retrospective analysis with infrared images shows that the eddy’s generation took place at about 3–4jE. Then, the eddy completed a counterclockwise circuit never before reported in other studies and ended up at the entrance of the Algerian Basin, where the interaction with the topography and the coastal instability induced its decay. The eddy\'s life span was -10 months. Computations of the heating rate following clusters of buoy trajectories show fluctuations throughout the eddy’s journey, induced by advection and a seasonal warming
ESA Bulletin, 115, 41-45. -- Abstract. (BibTeX: berger.etal.2003b)
ESA’s second Earth Explorer Opportunity Mission, the Soil Moisture and Ocean Salinity (SMOS) mission scheduled for launch in early 2007, is currently in the design and development phase. Given that today’s lack of global observations of ocean salinity and soil moisture is holding back progress in many environmentrelated research fields, the mission has broad and ambitious scientific objectives, the validity of which is internationally recognised. The studies and campaign activities undertaken by the Agency to advance the science underlying the ocean-salinity objectives of the mission were presented in,ESA Bulletin No. 111. This article therefore focuses on the activities dedicated to advancing our knowledge of the ‘brightness temperature’ associated with microwave radiation emitted by the Earth’s land surfaces and thereby our ability to retrieve reliable soil-moisture data
Fisheries Research, 60, 321-331. DOI: S0165-7836(02)00139-X -- Abstract. (BibTeX: olivar.etal.2003b)
Keywords: Merluccius merluccius; Hake eggs; Hake larvae; Distribution patterns; NW Mediterranean.
Plankton hauls were conducted on five surveys from November 1998 to November 1999 to study the spatial distribution of eggs and larvae of European hake off Catalonia (NW Mediterranean Sea). Also CTD casts to record hydrographic parameters were carried out on a closely spaced station grid. Merluccius merluccius eggs and larvae appeared mainly in late spring, summer and autumn surveys and were very scarce in winter. Strong differences in terms of egg and larval densities were observed between the two November surveys, which could be attributed to the anomalous hydrographic situation during November 1998. M. merluccius egg and larvae were mainly distributed over the continental shelf, with peak abundances between the 100 m isobath and the edge of the shelf. On the evidence of larval size frequency distributions in the different sampling sectors and the closely overlapping distribution patterns for the eggs and the adult spawning stock, drifting of hake eggs and larvae was not a major factor. The larval distribution extended only slightly further offshore than the egg distribution. Using the hydrographic information and the larval distribution data, an attempt was made to relate the different seasonal productivity levels over the spawning period and the distribution of the larvae.
Estuarine, Coastal and Shelf Science, 56, 609-619. DOI: 10.1016/S0272-7714(02)00210-X -- Abstract. (BibTeX: olivar.etal.2003a)
Keywords: Sardina pilchardus; eggs and larvae; distribution patterns; Northwestern Mediterranean.
The influence of environmental conditions on the spatial distribution patterns of the early stages of Sardina pilchardus off the Catalan coast (Northwestern Mediterranean) during November 1998, February 1999 and November 1999 was investigated. As a general rule, eggs were found on the continental shelf, while larvae displayed a wider cross-shelf distribution. The local circulation during autumn-winter 1998-1999 was dominated by an anticyclonic eddy of new Atlantic Water that remained stationary at the centre of the Catalan Sea from September 1998 to the end of February 1999. Such a situation is very infrequent and the influence of these waters extended to the continental shelf zone, modifying the slope current by diverting the flow and even reversing the direction of the flow. On the third cruise, carried out at the beginning of the spawning season of 1999 (November), the circulation and water mass distribution in the region was typical, with the old Atlantic Water occupying the whole region. Abundance of pilchard eggs and larvae during this last cruise was higher than in the previous surveys. In November 1998, the abundance of pilchard eggs and larvae was relatively low in the zones affected by the new Atlantic Water. The most interesting result of these surveys was the very low concentrations of eggs and larvae found in February 1999, possibly due to the anomalous situation created by the eddy, which had remained almost stationary during the 1998-1999 spawning season.
SP-525-EuroSTARRS, WISE, LOSAC Campaigns, . Ed. P. Wursteisen, P. Fletcher. ESTEC. ESA Publications Division. 17-26. Noordwijk (The Netherlnads). ISBN: 92-9092-835-2. ISSN: 0379-6566 (BibTeX: camps.etal.2003c)
In: SP-525- EuroSTARRS, WISE, LOSAC Campaigns, Ed. P. Wursteisen, P. Fletcher. ESTEC. ESA Publications Division. 73-80. Noordwijk (The Netherlnads). ISBN: 92-9092-835-2. ISSN: 0379-6566 (BibTeX: emelianov.etal.2003a)
PhD thesis. Director/es: J. Font, E. García-Ladona (ICM-CSIC). Barcelona. -- Abstract. (BibTeX: isernfontanet.2003c)
La mar Mediterrània es caracteritza per l'entrada d’aigües poc salades procedents de l'Atlàntic a través de l'estret de Gibraltar. El ux sovint es inestable i genera vòrtex coherents, amb longituds característiques compreses entre els 50 i 150 km i temps de vida de mesos fins i tot anys, que afecten fortament el transport a la conca. L'objectiu principal de la tesi es estudiar i caracteritzar les propietats dels vòrtex coherents a la Mediterrània. Des dels inicis dels anys 90 l’ús intensiu d'alt__metres a proporcionat dades sobre la superfície lliure de l'oceà, que, recentment, han estat assimilades a sistemes de predicció oceànica de la Mediterrània. Aquest fet proporciona un conjunt de dades de la superfície lliure forca gran. La presencia d'estructures coherents fa que les observacions de mesoescala de l'oceà s'assemblin a la turbulència bidimensional. Aquestes similituds suggereixen que els darrers avenços en turbulència bidimensional es podrien fer servir com a punt de partida per investigar els vòrtex Mediterranis. Un vòrtex coherent es defineix com la regió simplement connexa amb valors del paràmetre d'Okubo-Weiss W < 0:2_W, on _W _es la desviació estàndard espaial de W, i el mateix signe de la vorticitat. Quan un vòrtex es identificat les seves propietats tals com, mida, energia cinètica o amplitud es poden calcular. En aquest estudi, aquesta definició s'ha aplicat als mapes d'anomalies del nivell del mar (SLA) del període octubre 1992-setembre 1999 i a simulacions numèriques de la Mediterrània pel període setembre 1999 a abril 2003. Els resultats de l'altimetria mostren que la Mediterrània es caracteritza per una distribució de vòrtex aproximadament homogènia. De tota manera, algunes de les propietats dels vòrtex com l'energia o l'amplitud tenen distribucions irregulars amb valors més alts en regions on estaven documentada la presència de vòrtex de mesoescala. Aquest fet suggereix que una classificació basada en l'amplitud podria permetre separar aquests vòrtex de les altres estructures. L'anàlisi de la dependència de l'amplitud de la mida mitjana dels vòrtex mostra un comportament asimptòtic que tendeix cap als a radis d'uns 40 km. Aquests resultats suggereixen la classificació heur_stica de les estructures coherents en vòrtex intensos (caracteritzats per valors de l'amplitud menors de 2_w) que tenen la mida dels vòrtex de mesoescala, i vòrtex febles que es corresponen amb estructures sorolloses i estats poc energètics dels vòrtex de mesoescala. Aquesta separació d'estructures permet seguir amb facilitat de mapa a mapa els vòrtex i, per primera vegada, construir una imatge completa dels Camins preferencials que segueixen. Per altra banda també s'han analitzat les distribucions de probabilitat de la velocitat (PDF) derivades dels mapes de SLA. S'ha dividit la Mediterrània 7 regions depenent de la geometria i la distribució vòrtex intensos. Per cada regió s'han calculat les PDF de la velocitat geostròfica. Les formes de les distribucions observades es caracteritzen per tenir un nucli gaussià amb cues exponencials. De tota manera, la mida del nucli i les cues canvia d'una regió a una altra depenent de la distribució de vòrtex intensos. La descomposició del camp de velocitats en: un camp de fons, un camp induït pels vòrtex febles i un camp induït pels vòrtex intensos mostra que els dos primers es caracteritzen per tenir distribucions semblants a una gaussiana, mentre que el tercer té una distribució propera a una exponencial. L'aplicació a les simulacions numèriques mostra resultats equivalents amb la diferència que conté més estructures petites.
In: SP-525- EuroSTARRS, WISE, LOSAC Campaigns, Ed. P. Wursteisen, P. Fletcher. ESTEC. ESA Publications Division. 51-59. Noordwijk (The Netherlnads). ISBN: 92-9092-835-2. ISSN: 0379-6566 (BibTeX: font.etal.2003a)
In: Building the european capacity in operational oceanography, Elsevier Oceanography Series. Vol. 69. Ed. H. Dahlin, N.C. Flemming, K. Nittis, S.E. Patersson. Elsevier oceanography . Chap. Cap.113. 186-189. Amsterdam (The Netherland). ISBN: 0-444-51550-X. ISSN: 0422-9894 -- Abstract. (BibTeX: font.etal.2003d)
Keywords: Salinity, remote sensing, microwave radiometry, ESA.
The European Space Agency SMOS (Soil Moisture and Ocean salinity) mission is scheduled for launch in early 2007. SMOS will exploit an innovative instrument designed as a 2D interferometer acquiring globally brightness temperatures at L-band (1.4 Ghz) to retrieve soil moisture fields over the land surfaces and ocean salinity fields over the oceans. Considering the exploratory nature of the salinity measurement with SMOS, the GODAE open ocean requirement (0.1, salinity scale, over 200 km every 10 days) represents a technically challenging objective that has been set as a goal for the mission
Proceedings IEEE Inter. Geoscience and Remote Sensing Symposium IGARSS 2003, . IEEE Publications. 7, Piscateway (USA). ISBN: 0-7803-5045-6 (BibTeX: font.etal.2003f)
In: SP-525-EuroSTARRS, WISE, LOSAC Campaigns, Ed. P. Wursteisen, P. Fletcher. ESTEC. ESA Publications Division. 7-13. Noordwijk, The Netherlands. ISBN: 92-9092-835-2 (BibTeX: font.etal.2003e)
In: SP-525- EuroSTARRS, WISE, LOSAC Campaigns, Ed. P. Wursteisen, P. Fletcher. ESTEC. ESA Publications Division. 163-171. Noordwijk (The Netherlnads). ISBN: 92-9092-835-2 (BibTeX: gabarro.etal.2003b)
Proceedings IEEE Inter. Geoscience and Remote Sensing Symposium IGARSS 2003, . IEEE Publications. 7, Piscateway (USA). ISBN: 0-7803-5045-6 -- Abstract. (BibTeX: gabarro.etal.2003e)
Up to now, no space mission has attempted to measure the Sea Surface Salinity (SSS) due to technological challenges. The European Space Agency's SMOS (Soil Moisture and Ocean Salinity) mission, to be launched in 2007, aims at the generation of global SSS maps with a spatial and temporal resolution adequate for climatic and ocean general circulation studies. The sensor aboard SMOS is an L-band interferometric radiometer with full polarimetric capability called MIRAS (Microwave Imaging Radiometer by Aperture Synthesis). At low frequencies the brightness temperature measured by a radiometer presents maximum sensitivity to surface salinity, and optimal conditions are found at L-band (1400 MHz-1427 MHz), which it is a band protected for passive measurements. Even though the sensitivity is maximum at this frequency, it is not very high: 0.5 K/psu for sea temperature of 20ºC, decreasing to 0.25 K/psu for 0ºC. Furthermore, other variables influence the brightness temperature, as the sea roughness (mainly caused by the wind speed), sea foam, and also sea surface temperature. When SMOS will be in orbit it will be necessary to have accurate measurements of the sea roughness and surface temperature as much coincident as possible -both in time and space- to SMOS acquisitions, because errors on these ancillary data produce large errors on the retrieved salinity. This paper presents a study of the effect on the retrieved salinity of inaccuracies in the wind speed and wave height values. It compares the retrieved salinities when using different sources of these ancillary data: satellite measurements and meteorological models. It also investigates the possibility of allowing the algorithm to retrieve an effective wind speed, in addition to the sea surface salinity.
Proceedings IEEE Inter. Geoscience and Remote Sensing Symposium IGARSS 2003, . IEEE Publications. 7, 3055. Piscateway (USA). ISBN: 0-7803-5045-6 -- Abstract. (BibTeX: kerr.etal.2003)
The European Space Agency SMOS (Soil Moisture and Ocean Salinity) mission aims at obtaining global maps of both variables from space for large scale and climatic studies. It uses an L-band microwave interferometric radiometer with aperture synthesis (MIRAS) to measure brightness temperature (TB) emitted by the Earth surface and then compute from it the two geophysical parameters. The retrieval of salinity is a complex process that requires the knowledge of other environmental information and an accurate processing of the radiometer measurements. Here we present the recent results obtained from different studies and campaigns as part of the SMOS mission and highlight the different issues still to be solved.
In: SP-525-EuroSTARRS, WISE, LOSAC Campaigns , Ed. P. Wursteisen, P. Fletcher . ESTEC. ESA Publications Division. 37-47. Noordwijk (The Netherlnads). ISBN: 92-9092-835-2. ISSN: 0379-6566 (BibTeX: lopezbaeza.etal.2003a)
Procceedings ENVISAT Validation Workshop 2002, Frascati (Italy), . ESA. CD. ISBN: 92-9092-841-7 -- Abstract. (BibTeX: roca.etal.2003a)
The EnviSat altimeter, RA-2, is intended to continue an uninterrupted series of measurements of sea-level and ice-sheet elevation started by ERS-1 in 1991. To fully exploit these measurements, an absolute reference in the time series, and a distinction between instrumental artifacts and significant geophysical signals, is necessary. Therefore, the range bias and instrument drift shall be determined with a accuracy of 1 cm and 1 mm/year respectively. Such accuracies can only be achieved by using: • a large number of measurements to reduce random errors; • a diversity of measurement techniques and independent data analysis to reduce susceptibility to systematic errors. Due to the limited temporal sampling of the 35-day repeat orbit of EnviSat, the resulting overall concept is a regional calibration which makes use of the north-western Mediterranean basin as a reference surface, with a number of particular of high-confidence “super-sites”.
Institut de Ciències del Mar - CSIC, 34 pp. pp. (BibTeX: ruiz.font.2003)
In: Building the european capacity in operational oceanography, Elsevier Oceanography Series. Vol. 69. Ed. H. Dahlin, N.C. Flemming, K. Nittis, S.E. Patersson. Elsevier oceanography. 513-518. ISBN: 0-444-51550-X. ISSN: 0422-9894 -- Abstract. (BibTeX: ruiz.etal.2003a)
Keywords: EOF analysis, floats, North Atlantic Ocean.
A three-dimensional Empirical Orthogonal Function analysis is applied to density profiles collected by autonomous floats in the North Atlantic Ocean. Preliminary results reveal that two modes account for most of 90% of the variance of the density field
In: Building the european capacity in operational oceanography, Elsevier Oceanography Series . Vol. 69. Ed. H. Dahlin, N.C. Flemming, K. Nittis, S.E. Patersson. Elsevier Oceanography. 78-86. ISBN: 0-444-51550-X. ISSN: 0422-9894 -- Abstract. (BibTeX: theocharis.etal.2003)
Keywords: Mediterranean, hydrological trends, thermohaline circulation, ocean-atmosphere interaction, long-term network.
During the CIESM workshop (Monaco, 22-24 April 2002) entitled \"Monitoring Hydrological Trends in the Mediterranean\", the review of existing data sets and analyses has revealed important variability in the dynamics and hydrological characteristics, in the past century, ranging from inter annual to decadal time scales. These variations are related mainly to local forcing and larger scale atmospheric parameters (NAO, ENSO, Indian monsoon). Moreover, abrupt events contribute to modification of the Mediterranean conveyor belt, also influencing the biogeochemical environment and the Mediterranean outflow in the Atlantic Ocean. The participating scientist have agreed on the need of a sustained multi-component long-term monitoring system based on both oceanographic and atmospheric observations and modelling. The group also proposed an expansion and strengthening of the on going relevant large operational programs by a \"climatic approach\" component
In: Building the european capacity in operational oceanography, Elsevier Oceanography Series. Vol. 69. Ed. H. Dahlin, N.C. Flemming, K. Nittis, S.E. Patersson. Elsevier Oceanography. 46-56. ISBN: 0-444-51550-X. -- Abstract. (BibTeX: mamaconsortiums.vallerga.etal.2003b)
Keywords: Operational oceanography, Mediterranean, networking, capacity building, awareness, inventories.
Sustainable development requires the intelligent management of the marine environment, to protect the marine ecosystem, minimise the impacts of climate change and anthropogenic influences, and provide benefits for a wide range of users. Routine Ocean monitoring and forecasting based on sound science, long term and adaptive monitoring, and co-operation between nations, is the main tool for such a management. The assets and needs of all countries have to be identified, as well as the constraints impeding data exchange and marine observations in the EEZs. The challenge is to build a monitoring system based on up-to-date science and technology, and adapted to the specifity of the basin for the benefit of different users in all Mediterranean countries. It is necessari to involve all riparian countries in the process of building the Mediterranean monitoring system. A strengthened and dedicated link between the scientific community and the public authorities is moreover necessari to provide a sound scientific background for policy decisions based on environmental monitoring. Building on these concepts the Mediterranean network to Asses and upgrade the Monitoring and forecasting Activity in the region (MAMA), funded under the EESD Programme of the 5th FP, and involving partners from all the Mediterranean countries, aims to establish the multi-national network that will prepare the institutional linkages and regional platform for suc han integrated and sustained monitoring system in the region. The Project builds on the trans-national pooling of scientific and technological resources and provides a concerted basin-scale effort towards the planning and design of the initial ocean observing system in the Mediterranean. The system-wide approach of MAMA is expected to trigger an enhanced motivation on the relevance of systematic marine observations for the sustainable and shared use of the marine resources of the Mediterranean Sea. These catalític ingredients constitute the thrust of MAMA and enabling asset to the future projection into long-term commitments at governmental level.