2012 Aquarius/SAC-D Science Team Meeting
Buenos Aires, Argentina
The first post-launch Aquarius/SAC-D Science Team Meeting was held in Buenos Aires, Argentina in April, 2012. More than 120 scientists and engineers from around the world shared scientific findings along with the status of each observatory instrument and its data. Presentations focused on the first data analysis, including the in-orbit checkout, data processing, calibration, validation and near-term data analysis.
Objectives and Agenda
Aquarius Calibration/ValidationYueh, S. (11-Apr-12). Overview of Aquarius calibration/validation (cal/val) concludes: Aquarius instrument has been performing exceptionally well; on-orbit thermal control meets the design requirement; scatterometer calibration has been very stable; radiometer calibration meets the calibration requirement (0.13K within 7 days); there will be new science products (e.g., ocean surface wind, soil moisture, land surface freeze/thaw, etc.); Aquarius surface salinity accuracy has been rapidly improving; and there are some ongoing challenges for cal/val.
Aquarius Project StatusFeldman, G. (11-Apr-12). Presentation gives details of the transfer of Aquarius project management to the NASA Goddard Space Flight Center (GSFC) on Dec 1, 2011, to begin its "Operations" phase. An overview of the GSFC-operated Aquarius Ground System is also provided, along with status (e.g. V1.3 data products in the operational forward stream and viewable online, etc.).
Aquarius Satellite Salinity Measurements AssessmentLagerloef, G. and Kao, H-Y. (12-Apr-12). Presentation includes these conclusions: Argo buoy measurement differences are about 0.6 psu rms, with sea surface temperature > 0.5C and land fraction < 0.0005; in high-latitude cold water regions, retrievals are biased high and much noisier; in the tropics, values are less than Argo, likely due to rainfall and surface stratification; there are residual quasi-monthly radiometer calibration errors resulting in +/-0.2 psu variations relative to Argo buoys; and ascending / descending passes have different bias trends, which could be a seasonal artifact.
Aquarius Satellite Salinity Measurements; Early Science ResultsLagerloef, G. (11-Apr-12). Presentation includes seven-month mean global Aquarius data and some early scientific findings including: Eastern Pacific "Tropical Instability Waves", Amazon Plume dynamics in the tropical Atlantic, and east equatorial Pacific freshening from the Inter Tropical Convergence Zone. Results from an intercomparison between Aquarius and Argo in-water data are also discussed.
Aquarius Soil Moisture RetrievalJackson, T. Bindlish, R., Cosh, M., Zhao, T., and Holmes, T. (11-Apr-12). Presentation summary includes: initial approach to soil moisture retrieval results are encouraging and consistent with expected spatial patterns, SMOS, and model soil moisture; the algorithm will be implemented in the Aquarius processor to provide a separate soil moisture product; and scatterometer and Microwave Radiometer (MWR) calibrations needed to further investigate vegetation parameterization and land surface temperature.
CONAE's Data Processors & DistributionMarenchino, M. and Bruno, L. (11-Apr-12). Overview of the CONAE data archival system, including: post-launch and nominal working processes; status of data processing and distribution; priorities; and products.
Data Collection System Commissioning ResultsSager, G.E., Carlotto, J.A., Juarez, J.M., and Mercado, G. (11-Apr-12). Overview of SAC-D Data Collection System (DCS) concludes: DCS was turned on for the first time on 31-Aug-11; during months of commissioning, it was subject of many in-orbit tests to assess functionality and performance; tests were performed involving different transmission and reception modes, operational frequencies and parameter adjustments; and DCS is fully functional and ready to collect enviromental data.
Evaluating the Impact of Ocean Gravity Wave Variability On Aquarius Satellite MeasurementsVandemark, D. and Fent, H. (12-Apr-12). Presentation includes these early conclusions: Soil Moisture and Ocean Salinity (SMOS) sea surface salinity data able to produce before and after snapshots of plume location associated with tropical cyclone (TC) passage; satellite data yielding accurate sea surface salinity perturbation due to TC as compared to two Argo floats - 0.5 to 1.5 increase in sea surface salinity; and new look at plume - TC interaction with sea surface salinity + sea surface temperature perhaps allows enhanced diagnosis.
First Results of SAC-D MWR Sea Ice Concentration ProductTauro, C., Masuelli, S., Salgado, H., Barreira, S., and Jones, L. (12-Apr-12). Overview includes: feasibility of determining sea ice concentration from Microwave Radiometer (MWR); NASA Team and CONAE algorithms; prototype steps; preliminary results from validation; and comparisons to National Snow and Ice Data Center results.
High Sensitivity Camera (HSC) - Geometric Correction AlgorithmsMadero, F. (11-Apr-12). Presentation includes some known issues with the High Sensitivity Camera (HSC) such as: geolocation errors due to star tracker error from moon interference; and issues with generation of sun and moon position in Earth-Centered, Earth-Fixed (ECEF) reference frame.
High Sensitivity Camera (HSC) - Radiometric CalibrationRaimondo, H. and Marenchino, M. (11-Apr-12). Overview of radiometeric calibration of the High Sensitivity Camera (HSC), including: spectral and radiometric characterization; spectral response; relative and absolute calibration; and offset estimations.
Microwave Observations of La Plata Basin Vegetated Environments: Analysis of AMSR-E, SMOS and Aquarius DataKarszenbaum, H., Grings, F., Carballo, F., Barraza, V., Bruscantini, C., Salvia, M., and Perna, P. (11-Apr-12). Comparison of data from various Argentine soil moisture projects using three satellite instruments: AMSR-E, SMOS and Aquarius. Conclusion regarding retrieval algorithm performance is that, although promising, it is not satisfactory at this time in this region. In terms of the SMOS/Aquarius: different sensor configuration, engineering, and acquisition strategies and temporal characteristics make comparison difficult; too few simultaneous data; and nevertheless, sensitivity to rain events in Chaco forests is observed.
Microwave Radiometer (MWR) Geometric Correction AlgorithmsMadero, F. (11-Apr-12). Presentation includes some known issues with the Microwave Radiometer (MWR) such as: invalid geolocation at high latitudes; geolocation errors due to star tracker error from moon interference; and need to update the version of antenna patterns used by the processor.
Microwave Radiometer (MWR) L1B Brightness TemperaturesJones, L., Gallo, J-C., Rocca, D., Biswas, S., and Hejazin, Y. (11-Apr-12). Presentation give status of preliminary Microwave Radiometer (MWR) L1B Brightness Temperatures algorithm, including: release of Version 4.0 (V4.0) to the Aquarius Cal/Val team; reasonable results have been produced using the V4.0 geophysical algorithm; MWR "smear-effect" discovered and empirical correction algorithm developed; and Version 5.0 algorithm has been tuned to WindSat using "smear-corrected" antenna temperature.
National System of Sea Data (MINCYT)Matheos, S. (11-Apr-12). Overview of the National Sea Data System and its mission to ensure accessibility to data and marine information of the Southwestern Atlantic Ocean and Antarctica. Objectives include: continuous updating of shared marine data and information; consolidating registration and capturing of marine information and for maintaining the databases; and providing access to basic information on the marine environment under defined rules and procedures.
New Infrared Sensor Technology (NIRST) - Geometric Correction AlgorithmsMadero, F. (11-Apr-12). Presentation includes some known issues with the New Infrared Sensor Technology (NIRST) such as: geolocation errors due to star tracker error from moon interference; and issues with generation of sun and moon position in Earth-Centered, Earth-Fixed (ECEF) reference frame.
New Infrared Sensor Technology (NIRST) CommissioningMarraco, H. (11-Apr-12). Early results from New Infrared Sensor Technology (NIRST), including qualitative results, are presented. Issues include striping in data; non uniformity in data; lack of complete barrel temperature distribution; variable gain from pixel to pixel, etc.
Observatory Operations AssessmentOglietti, F. (11-Apr-12). Presentation includes assessment of the Aquarius/SAC-D observatory and orbit dynamics. Conclusions include: orbit acquistion sequence was successfully performed (e.g., correction of launch injection errors, achievement of nominal ground track on 07-Aug-11, etc.); orbit maintenance operations successful (e.g., ground track longitude, descending node height, "frozen orbit" within margins, etc.); and CONAE Orbit Dynamics Services are operational.
Overview of PO.DAAC Support for Aquarius/SAC-DVazquez, J. and Tsontos, V. (11-Apr-12). Overview of the Aquarius data archival system, Physical Oceanography Distributed Active Archive Center (PO.DAAC), located at the NASA Jet Propulsion Laboratory. Conclusions: PO.DAAC is hosting and providing timely access to the full range of Aquarius data sets and a variety of data monitoring and user support services and tools; and plans to continue working closely with the Goddard Space Flight Center to ensure the timeliness and integrity of data transfers for distribution, in addition to providing quality documentation and user support services.
SAC-D/Aquarius First Science DataTorrusio, S. (11-Apr-12). Presentation includes first data results from the SAC-D observatory instruments including: Microwave Radiometer (MWR); New Infrared Sensor Technology (NIRST); High Sensitivity Camera (HSC); Data Collection System (DCS); CARMEN-1 and ROSA.
Simulation of AT-Sensor Radiance Over Volcanoes for NIRST SensorSilvestri, M., Randazzo, D., Buongiorno, M.F., and Musacchio, M. (12-Apr-12). Presentation gives an overview of: Volcanic thermal phenomena characteristics and monitoring capability of current earth-observing missions; first results of simulation data; ten years of thermal analysis of volcanoes; and Italian Space Agency pre-operative project for volcanic risk management.
SMOS and Aquarius: Sea Surface Salinity and Wind EffectBoutin, J., Yin, Martin, N., Dinnat, E., Yueh, S., Reverdin, Coll G., Alory, G., and Gaillard, F. (12-Apr-12). Conclusions include: for Soil Moisture and Ocean Salinity (SMOS) sea surface salinity data, precision at 100x100km^2 over 10 days is about 0.3 in non-rainy tropical-subtropical regions far from land; there is freshening with respect to in-situ sea surface salinty (at 5m depth) in rainy conditions, suggesting a need for surface drifters to validate; Argo is very useful for large-scale validation; ship-borne thermosalinographs are very useful for validating 'small scale' (<200km) variability (gradients) seen by SMOS; etc.
SMOS Salinity Data Processing Status and ResultsGuimbard, S., Font, J., Ballabrera, J., Turiel, A., Martinez, J., Portabella, M., Gourrion, J., and Perez, F. (12-Apr-12). Conclusions include: European Space Agency is being provided Soil Moisture and Ocean Salinity (SMOS) Level 2 sea surface salinity products; Level 3 & 4 products are provided by the Spanish Data Processing Centre & Centre Aval de Traitement des Données (CATDS); at the Barcelona Expert Centre, new data fusion algorithm for Level 4 products based on singularity exponents; and the synergy SMOS/Aquarius can begin.
The Aquarius Salinity Retrieval AlgorithmWentz, F.J., and Meissner, T. (11-Apr-12). Overview of the Aquarius salinity retrieval algorithm concludes: Aquarius and the salinity retrieval algorithm are working well; standard deviation of retrieval salinity versus HYCOM (computer model) is 0.6 psu; standard deviation for monthly averages is 0.4 psu; and there are issues that need to be resolved to achieve the goal of 0.2 psu (e.g., small radiometer pointing errors, radiometer calibration time drifts, revised antenna pattern correction, etc.).
Validation of Aquarius Data Using a Regional Oceanographic Data Base in the Southwest AtlanticGuerrero, R., Fenco, H. Reta, R., Mercado, A., and Cozzolino, E. (12-Apr-12). Overview of validation of Aquarius sea surface salinity (SSS) exercise including: use of Level 2 grid SSS field using Version 1.2.2 and comparing it to Level 3 data; comparison of SSS error to regional climatology; evaluation of error; and focusing on the Rio de la Plata plume.
Working Group A: Calibration and Validation Studies for Aquarius Salinity RetrievalBrown, S., and Misra, S. (12-Apr-12). Presentation summary includes: method developed to track Aquarius radiometer brightness temperature drift over Antarctica and the Amazon; evaluation of v.1.2.3 roughness correction shows little bias with respect to altimeter wind speed but some residual correlation with significant wave height; and highest residuals from scatterometer correction when Aquarius is viewing cross wind.
Working Group A: Evaluating SMOS and Aquarius Against Model and In Situ DataBanks, C.J., Gommenginger, C.P., Srokosz, M.A., and Snaith, H.M. (12-Apr-12). Presentation includes: comparison of different monthly products (e.g., sea surface salinity, sea surface temperature) from European Space Agency's Soil Moisture and Ocean Salinity (SMOS) and Aquarius data at 1x1 degree resolution; and validation of these products against in-situ Argo data and ocean forecast models.
Working Group A: Improved Seawater Model Function and its Comparison with Argo DataLang, R.H., Zhou, Y., Drego, C., Utku, C., and Le Vine, D. (12-Apr-12). Conclusions include the following: more accurate new salinity measurements have an average variance of 0.31 compared with 0.74 in 2008; temperature range has been expanded to include 0 and 5 degrees; initial comparison with in-situ data shows that the slope and variance of retrieved salinity vary with the closest point of approach from Argo buoys.
Working Group A: Near-Surface Variability of Temperature and Salinity: Observations from Profiling FloatsAnderson, J.E. and Riser, S.C. (12-Apr-12). Overview of the surface temperature & salinity (STS) sensors added to Argo-type floats, which allow for high-resolution evaluation of the near-surface layer. Conclusions include: in general, there is little difference in temperature and salinity in the upper 5 meters (about 85-90% of the time); and overall, there is promise in using Aquarius and Argo together to improve knowledge of the freshwater cycle in the ocean.
Working Group A: Observation of Salinity Gradients in the Top Five Meters of the Ocean SurfaceAsher, W., Jessup, A., Branch, R., and Clark, D. (12-Apr-12). Conclusions include: rain generates measurable near-surface (top 0.5 m) salinity gradients that can form at wind speeds up to 10 m/s; these gradients are large enough (in terms of their area-weighted delta-salinity) to affect Aquarius; gradients extend over large enough areas to affect satellite measurements; and the 2- and 3-meter ports on the Research Vehicle Thomson can detect the presence of near-surface salinity gradients relevant for Aquarius.
Working Group A: Ocean Data & Validation - ConclusionsWorking Group A (12-Apr-12). Overview of presentations and conclusions from Session A. The topics of this session include the detectability of rain on satellite and Argo measurements of salinity and temperature, and examining the seasonal salt balance in the mixed layer in the tropics. Calibration and validation results have shown a gain drift over Antarctica, as well as an ascending vs. descending issue for SMOS and Aquarius. A review of work on the dielectric constant measurement was provided.
Working Group B: NIRST, HSC, DCS - ConclusionsWorking Group B (12-Apr-12). Overview of presentations from Session B. The conclusions of this session include specific recommendations for improving Relative Calibration issues, including the creation of a test plan, gather Cold Sky Calibration, look for signs in homogeneous areas of the ocean, and take moon-look views. For the High Sensitivity Camera (HSC), presenters recommended acquiring data as often as possible during Southern Hemisphere winter. Future tasks include finishing and testing transmitters being built at La Plata University, and to design and implement a web system for storage and retrieval of user's environmental data.
Working Group B: Argentine Data Collection System Features and ApplicationsCarlotto, J.A., Juarez, J.M., Sager, G.E. and Mercado, G. (12-Apr-12). Overview of Data Collection System (DCS) primary features and applications, including: data Collection Platform (DCP), a system of gathering information from ground user platforms by satellite; Pre-Processing and Distribution Center, which receives SAC-D Observatory data, processes it and makes available to users; DCP's reliability, low power consumption and low maintenance, designed for location in inhospitable and difficult access areas; and plan to have at least 200 DCPs in Argentina.
Working Group B: New Infrared Sensor Technology (NIRST) Radiometric CalibrationMarraco, H. and Raimondo, H. (12-Apr-12). Presentation includes numerous examples of New Infrared Sensor Technology (NIRST) calibration data sets, including: relative calibration, Fourier filtering and wavelets; and normalized vs. filtered.
Working Group B: New Infrared Sensor Technology/High Sensitivity Camera Geometric Calibration (Discussion)Madero, F. (12-Apr-12). Overview of New Infrared Sensor Technology (NIRST) and/or High Sensitivity Camera (HSC) calibrations, including: geolocation errors; post-launch geometric calibrations; and pointing angle estimations.
Working Group C: Aquarius Data on Carbon and Water ChangesLiu, T.W. and Xie, X. (13-Apr-12). Presentation examines the following: ocean as source and sink of greenhouse gases; ocean's changes in biochemistry and dynamics; and salinity as a rain-gauge and mixing indicator.
Working Group C: Dynamics and Forcing of Sea Surface Salinity (SSS) and the Potential of Satellite-Derived SSS to Constrain Air-Sea Freshwater FluxesVinogradova, N.T. and Ponte, R.M. (13-Apr-12). Objectives of the presentation are to: examine the relationship between sea surface salinity, air-sea freshwater fluxes (F) and ocean transport (O) on time scales from months to years; and analyze the potential of satellite-derived salinity measurements to constrain surface freshwater flux. Conclusions include: variability in salinity can be attributed to both F and O, demonstrating the importance of the ocean's role in evolution of sea surface salinity patterns, particularly through advective fluxes of salt.
Working Group C: Estimates of Rapid Variability in Surface Salinity and Potential for Aliasing in Aquarius MeasurementsPonte, R.M. and Vinogradova, N.T. (13-Apr-12). Conclusions include: rapid sea surface salinity variability can be a significant part of the total variability (20% on average, >50% in some tropical and coastal regions); aliasing impacts are also dependent on sampling characteristics, including irregular sampling times; aliasing errors are relatively small but can be important locally; etc.
Working Group C: Evaluation of Aquarius SSS Space/Time Variability and Biases In the Indian OceanHacker, P., Melnichenko, O., Potemra, J., and Maximenko, N. (13-Apr-12). Presentation includes the following results: Aquarius sea surface salinity (SSS) provides significant value-added information in the tropical Indian Ocean; along-track Aquarius SSS provides improved latitude and time resolution compared to in-situ data products; and regional empirical correction of ascending/descending and inter-beam biases for production of improved Level 3 products appears feasible.
Working Group C: Ocean Processes - ConclusionsWorking Group C (13-Apr-12). Overview of presentations from Session C. Findings introduced: there were large-scale features seen by Aquarius - including differences of .5-1 psu in the Pacific Ocean, and 1-5 psu in the Indian Ocean. The differences between model-based and observation-based estimates of fresh/salt water budgets was discussed.
Working Group C: The Large Scale Salinity Budget in the North Atlantic and a First Look at ENSO from AquariusWillis, J.K. and Hobbs, W.R. (13-Apr-12). Presentation includes the following summary: estimates of annual-mean precipitation from heat and freshwater budgets are reasonable, but somewhat high; for sub-monthly time scales, more work is required to relate salinity data to evaporation minus precipitation to get useful estimates; and El Niño Southern Oscillation (ENSO) variability should be one of the biggest large-scale, climate signals visible in the Aquarius data.
Working Group D: MWR Calibration/Intercalibration - ConclusionsWorking Group D (13-Apr-12). Overview of presentations from Session D. Conclusions include a description of geolocation and geometric correction efforts, as well as on-orbit calibration of the CONAE Microwave Radiometer.
Working Group D: MWR Smear Effect: Analysis and a Possible CorrectionLabanda, M.F., Jacob, M.M., Masuelli, S., Farrar, S., Raimondo, H., and Jones, W.L. (13-Apr-12). Presentation on the Microwave Radiometer (MWR) includes: physical configuration and footprints of MWR: Examples images with "smear effects"; and beams correlation analysis results, including images before and after application of a "coupling percentage" procedure.
Working Group D: On-Orbit Evaluation of Microwave Radiometer (MWR) Instantaneous Field-of-View Geolocation using Land/Water CrossingsMay, C., Jones, L., Madero, F., and Kuba, J. (13-Apr-12). Presentation describes the assessment of geolocation of Microwave Radiometer (MWR) Level 1 brightness temperature (Tb) measurements with MWR Tb images of land using high-resolution maps. Peliminary work indicates that geolocation errors meet MWR specification (< 5 km overall).
Working Group E: Ocean Salinity Open Discussion - ConclusionsWorking Group E (13-Apr-12). Overview of presentations from Session E. This session, lead by Peter Hacker and Yi Chao, explore the possibilities of merging Aquarius and SMOS data with in-situ data as well as further options for intercalibration and harmonization. New working groups were proposed, including a joint U.S. and Eurpoean SPURS group as well as a possible working group to investigate matters of surface straification.
Working Group F: MWR Retrievals - ConclusionsWorking Group F (13-Apr-12). Overview of presentations from Session F. Conclusions include that the accuracy of salinity retrievals from Aquarius are affected by rain and wind-induced surface roughness. For greater consistency in measurements under these conditions, it is recommended that the brightness temperatures should be calibrated using collected WindSat and SSMI/S data.