SAC-D Instruments and science results – abstracts

 

SAC-D Instruments and science results

SAC-D/ Aquarius 3rd Year
Contact author: Monica Rabolli, <mrabolli@conae.gov.ar>
All Authors:
Monica Rabolli, CONAE
S. Torrusio, CONAE

After the 3rd year on orbit we are presenting the status of the instruments developed under Argentinian responsibility and of those developed by France and Italy. After a long work we obtained the NIRST calibration, microbolometers flying for the first time. MWR, microwave radiometer, we present the status and the validation of the algorithms developed for estimating wind speed, sea ice concentration, water vapor and rain rate. DCS is monitoring a volcano in Antartica and different sites in our country. We obtained images of Antartica with the High Sensitivity Camera, HSC, which are presented as a gallery for the public access. The French instrument CARMEN 1 is working nominally an bringing important information about radiative particles arriving on the Earth surface. As a scientific result of the scientific production we have more than 50 scientific publication, presentations and posters authored by the staff of the projects of the announcement of opportunities. We contributed with the E&PO Aquarius team in developing material and spreading to the school teachers and students.

NIRST ready for science
Contact author: Hugo Marraco, <hmarraco@conae.gov.ar>
All Authors:
Hugo Marraco, CONAE
Martín Labanda, CONAE
Hector Raymondo, CONAE
Marcelo Colazo, CONAE
Maryse Kalemkarian, CONAE

After considerable work sorting several unforeseen obstacles NIRST is now ready for Science.
Several examples of the camera´s capabilities for revealing land and sea surfaces temperatures distributions with a whole calibrated range are shown. A brief description of the steps leading to this successful goal is also given. This description includes the pitfalls incurred during the camera design, their causes and cures.
NIRST camera can now operate with a NEDT of 0.45K@300K and an uncertainty in the calibration of about 1 K for the brightness temperatures measured by the 10.8 µm camera and slightly larger values for the 11.8 µm camera.

Using Aquarius Radiometer and Scatterometer for generating new soil moisture products (Active, Passive, Active-Passive)
Contact author: C. Bruscantini, CONAE

Assessment of SMOS, Aquarius and AMSR2 Soil Moisture assimilation into hydrological models of a flatland basin
Contact author: Juan Federico Bianchi, <jbianchi@ina.gob.ar>
All Authors:
Juan Federico Bianchi, National Water Institute
Marcelo Uriburu Quirno, National Space Activities Commission
Homero Lozza, National Space Activities Commission
Marc Thibeault, National Space Activities Commission
Danilo Dadamia, National Space Activities Commission
Dora Goniadzki, National Water Institute

The impact on discharge simulation efficiency of satellite soil moisture data assimilation was assessed. Soil moisture estimation products of the instruments SMOS, Aquarius and AMSR2 were assimilated through Ensemble Kalman Filtering into two previously-calibrated conceptual hydrological models of the Gualeguay basin, located in the Argentinian temperate sub-humid flatlands. Data assimilation was used to correct the state variables of the models linearly related to the observed variable taking into account the ratio of their relative errors. The error of the observations was assumed equal to that informed by the data provider, while the error of the model estimates was estimated as the sampling variance of the Kalman ensemble. Variability in the ensemble was forced by adding zero-mean gaussian noise to the model inputs, with variances equal to their estimated observation errors. Each soil moisture product/model combination was assessed separately. Additionally, no-assimilation and discharge data assimilation runs were performed. In each case the model efficiency was computed as the sum of squared errors between observed and predicted discharge assuming different forecast lead times (0 to 3 days) for the period 7-2012 to 4-2014. Results range from minor decrease to no significant change in efficiency for soil moisture assimilation. This may be due to the impact of one or more of the many sources of uncertainty in the soil moisture retrieval techniques and/or a lack of linearity or even correlation between the observed and simulated variables. Further research steps are analyzed and future actions addressed.

AQUARIUS/SAC-D SOIL MOISTURE PRODUCT USING V3.0 OBSERVATIONS
Contact author: Rajat Bindlish, <rajat.bindlish@ars.usda.gov>
All Authors:
Rajat Bindlish, USDA ARS
Thomas Jackson, USDA ARS
Michael Cosh, USDA ARS

Although Aquarius was designed for ocean salinity mapping, our objective in this investigation is to exploit the large amount of land observations that Aquarius acquires and extend the mission scope to include the retrieval of surface soil moisture. The soil moisture retrieval algorithm development has focused on using only the radiometer data because of the extensive heritage of passive microwave retrieval of soil moisture. The Single Channel Algorithm (SCA) was implemented using the Aquarius observations to estimate surface soil moisture. SCA is also the baseline algorithm for the Soil Moisture Active Passive (SMAP) radiometer-only soil moisture product. Ancillary data inputs required for using the SCA are vegetation water content, land surface temperature, and several soil and vegetation parameters based on land cover classes. The Aquarius soil moisture algorithm that was initially implemented with Aquarius V2.0 dataset was modified to account for the adjustments made in v3.0 dataset. Aquarius v3.0 brightness temperature observations are lower than v2.0 observations by about 4-5K over land. The recalibration module to correct for the higher brightness temperatures in Aquarius 2.0 observations was removed from v3.0 soil moisture code.
The resulting global spatial patterns of soil moisture are consistent with the precipitation climatology and with soil moisture from other satellite missions (Advanced Microwave Scanning Radiometer-E and the Soil Moisture Ocean Salinity (SMOS)). Assessments were performed using in situ observations from the USDA Little Washita and Little River watershed soil moisture networks. Results showed good performance by the algorithm for these land surface conditions for the period of August 2011-June 2014 (RMSE=0.041 m3/m3, aRMSE=0.034 m3/m3, Bias=-0.013 m3/m3, and R=0.838). We are currently expanding our in situ observations to extend the validation of the Aquarius soil moisture product to other geographical domains. This radiometer-only soil moisture product will serve as a baseline for continuing research on both active and combined passive-active soil moisture algorithms. The products are routinely available through the NASA data archive at the National Snow and Ice Data Center (NSIDC).
USDA is an equal opportunity employer.

The Salinity Signature of the Cross-Shelf Exchanges in the Southwestern
Atlantic Ocean: Satellite Observations
Contact author: Raul Guerrero, <raul.guerrero@inidep.edu.ar>
All Authors:
Raul Guerrero, INIDEP
Alberto Piola, Hydrographic Service
Harold Fenco, INIDEP
Ricardo Matano, Oregon State University
Vincent Combes, Oregon State University
Yi Chao, Remote Sensing Solutions
Corinne James, Oregon State University
Elbio Palma, Univ. Nacional del Sur
Martin Saraceno, Univ. de Buenos Aires
Ted Strub, Oregon State University

We use sea surface salinity (SSS) data from Aquarius and SMOS to describe the shelf-open ocean exchanges in the western South Atlantic near 35ºS. The satellite data show a well-defined seasonal pattern. During spring and summer low SSS shelf waters expand offshore and are transferred to the open ocean primarily southeast of the river mouth (from 36 ºS to 37º30’S). During fall and winter low SSS waters extend along a coastal plume and the export path to the open ocean distributes along the offshore edge of the plume. The seasonal SSS variations over the shelf are modulated by the along-shelf component of the wind stress over the shelf. However, the combined analysis of SSS, satellite-derived sea surface elevation and surface velocity data suggest that the precise location of the export of shelf waters depends on offshore circulation patterns, such as the location of the Brazil Malvinas Confluence and mesoscale eddies and meanders of the Brazil Current. The satellite data indicate that in summer, mixtures of low salinity shelf waters are swiftly driven towards the ocean interior along the axis of the Brazil/Malvinas Confluence. In winter, episodic wind reversals force the low salinity coastal plume offshore where they mix with tropical waters within the Brazil Current and create a warmer variety of low salinity waters in the open ocean.

The Salinity Signature of the Cross-Shelf Exchanges in the Southwestern Atlantic Ocean: Aquarius observations and models
Contact author: Ricardo Matano, <rmatano@coas.oregonstate.edu>
All Authors:
Ricardo Matano, CEOAS, Oregon State University
Vincent Combes, Oregon State University
Alberto Piola, Hydrographic Service
Raul Guerrero, INIDEP
Elbio Palma, Universidad del Sur
Ted Strub, Oregon State University
Corinne James, Oregon State University
Harold Fenco, INIDEP
Yi Chao, Remote Sensing Solutions
Martin Saraceno, University of Buenos Aires

Sea surface salinity (SSS) data from Aquarius and SMOS and the results of high-resolution numerical model are used to investigate the shelf-deep ocean exchanges in the southwestern Atlantic region, a region characterized by the freshwater discharge from the La Plata River. The satellite data shows strong seasonal variations of the location where the low salinity shelf waters are exported to the deep ocean: to the south of the La Plata River mouth during the summer and to the north during the winter. Analysis of a high-resolution model indicates Analysis of a high-resolution model shows three distinct modes of SSS variability. The first two represent the seasonal variations of the freshwater plumes over the continental shelf. The third mode of SSS variability, which has not been discussed hitherto, represents the salinity exchanges between the shelf and the deep ocean. A sensitivity study indicates that the high frequency component of the wind stress forcing controls the vertical structure of the plumes while the low-frequency component of the wind stress forcing and the inter-annual variations of the RdlP discharge controls the horizontal structure of the plumes. Dynamical analysis reveals that the cross-shelf flow has a dominant barotropic structure and, therefore, the SSS anomalies detected by Aquarius represent net mass exchanges between the shelf and the deep ocean. The net cross-shelf volume flux is 1.21 Sv. This outflow is largely compensated by an inflow from the Patagonian shelf.