2017 European Geoscience Union General Assembly

April 23-28, 2017
Vienna, Austria

Aquarius-related papers presented at the 2017 The General Assembly of the European Geosciences Union (EGU) included papers on salniity, atmospheric corrections, and the calibration and validation of L-Band radiometer instruments. The meeting was held at the Austria Center Vienna (ACV) in Vienna, Austria, from 23-28 April 2017, and was open to the scientists of all nations.
Documents (12)
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A Study on the Seasonal Variability of Upwelling and its Effects on Physical Parameters in Arabian Sea
Shukla, R.K., Shaji, C., Ojha, S.P., Kumar, P. (25-Apr-17). The upwelling in Arabian Sea is an important phenomenon, mainly occurring along the southwest coast of India during summer monsoon, which increases the biological productivity in the region. The south west coast of Arabian sea region accounts for about 53% of fish yield of the total fish production in Arabian Sea, thus it is imperative to study and understand the process of upwelling in this region. To study the upwelling features in southwest coast of India, monthly Ekman mass transport is estimated using analyzed wind and derived products from Oceansat-II scatterometer data. Seasonal variability of Ekman mass transport has been analyzed to study the occurrences of coastal upwelling in this region. Results show prominent region of upwelling along southwest coast of India is between 7◦ and 15◦ N.

Consistency of Aquarius Version-4 Sea Surface Salinity with Argo Products on Various Spatial and Temporal Scales
Lee, T. (25-Apr-17). Understanding the accuracies of satellite-derived sea surface salinity (SSS) measurements in depicting temporal changes and the dependence of the accuracies on spatiotemporal scales are important to capability assessment, future mission design, and applications to study oceanic phenomena of different spatiotemporal scales. This study quantifies the consistency between Aquarius Version-4 monthly gridded SSS (released in late 2015) with two widely used Argo monthly gridded near-surface salinity products.

Interannual and Decadal Changes in Salinity in the Oceanic Subtropical Gyres
Bulusu, S. (25-Apr-17). There is evidence that the global water cycle has been undergoing an intensification over several decades as a response to increasing atmospheric temperatures, particularly in regions with skewed evaporation - precipitation (E-P) patterns such as the oceanic subtropical gyres. Moreover, observational data (rain gauges, etc.) are quite sparse over such areas due to the inaccessibility of open ocean regions. In this work, a comparison of observational and model simulations are conducted to highlight the potential applications of satellite derived salinity from NASA Aquarius Salinity mission, NASA Soil Moisture and Ocean Salinity (SMOS), and ESA's Soil Moisture Active Passive (SMAP). We explored spatial and temporal salinity changes (and trends) in surface and subsurface in the oceanic subtropical gyres using Argo floats salinity data, Simple Ocean Data Assimilation (SODA) reanalysis, Estimating the Circulations & Climate of the Ocean GECCO (German ECCO) model simulations, and Hybrid Coordinate Ocean Model (HYCOM).

Intraseasonal to Interannual Sea Surface Salinity Variations in the Tropical Pacific Ocean
Hasson, A., Boutin, J., Puy, M., Reverdin, G., Supply, A., Morrow, R., Lee, T., Bingham, F., and Farrar, T. (25-Apr-17). Sea Surface Salinity (SSS) is one of the key factors influencing the ocean circulation but is also an important indicator of the hydrologic cycle. Understanding processes associated with various SSS regimes is thus crucial to the knowledge of ocean dynamics and of the connection between the ocean and the water cycle. SSS variability is studied between 2010 and mid-2016 in the tropical Pacific Ocean using various datasets such as observations from the satellite missions Soil Moisture Ocean Salinity (SMOS), Aquarius SAC/D and Soil Moisture Active Passive (SMAP); in situ measurements from Argo, voluntary ships and dedicated campaigns; and a forced simulation of the Nemo ocean model. This study focuses mainly on variability north of the Equator, around 10°N. The interannual signal of SSS is particularly intense in this region in 2015, with a very strong and wide freshening and enhanced precipitations.

Near-surface Temperature and Salinity Stratification as Observed with Dual-Sensor Lagrangian Drifters Deployed During SPURS-2 Field Campaign
Volkov, D., Dong, S., Goni, G., Lumpkin, R., and Foltz, G. (25-Apr-17). Despite the importance of sea surface salinity (SSS) as an indicator of the hydrological cycle, many details of air-sea interaction responsible for freshwater fluxes and processes determining the near-surface salinity stratification and its variability are still poorly understood. This is primarily due to the lack of dedicated observations. The advent of satellites capable of monitoring SSS, such as the Soil Moisture and Ocean Salinity (SMOS), Aquarius, and Soil Moisture Active-Passive (SMAP) missions, has greatly advanced our knowledge of SSS distribution and variability. However, the spatial resolution of satellite retrievals is too coarse to study the upper-ocean salinity changes due to patchy and transient rain events. Furthermore, the satellites measure salinity within the upper 1 cm skin layer, which can significantly differ from in situ SSS measured at 5 m depth by most Argo floats.

Quantifying the Impact of Mesoscale Signature on SSS Changes in the Tropical Pacific
Delcroix T., D. Soviadan, A. Chaigneau, and J. Boutin (25-Apr-17). High-resolution ocean model results as well as sporadic observations collected in different regions indicate that mesoscale eddies imprint distinguishable changes in collocated Sea Surface Salinity (SSS) and/or precipitation (P) distribution. This presentation shows this is indeed the case for the tropical Pacific, by collocating 6 years (2010-2016) of SMOS-derived SSS, TRMM-derived P and AVISO-derived sea level anomalies. The main characteristics of mesoscale eddies are first identified in sea-level altimetry maps, and their signature is then determined using concomitant satellite-derived SSS and P data.

Rainfall Effects on the Kuroshio Current East of Taiwan
Hsu, Po-Chun; Lin, Chen-Chih; Ho, Chung-Ru (25-Apr-17). Changes of sea surface salinity (SSS) in the open oceans are related to precipitation and evaporation. SSS has been an indicator of water cycle. It may be related to the global change. The Kuroshio Current, a western boundary current originating from the North Equatorial Current, transfers warm and higher salinity to higher latitudes. It flows northward along the east coasts of Luzon Island and Taiwan Island to Japan. In this study, effects of heavy rainfall on the Kuroshio surface salinity east of Taiwan are investigated.

Recent Advances in the Salinity Retrieval Algorithms for Aquarius and Soil Moisture Active Passive (SMAP)
Meissner, T., Wentz, F., and Lee, T. (25-Apr-17). Our presentation discusses the latest improvements in the salinity retrievals both for Aquarius and Soil Moisture Active-Passive (SMAP) since the last releases. The Aquarius V4.0 was released in June 2015. The final V5.0 release is planned for late 2017. SMAP V 2.0 has been released in September 2016. We will present validation results for both Aquarius V5.0 pre-release and SMAP V2.0 salinity comparing with near-surface salinity measurements from Argo floats. We show that salty biases at higher northern latitudes in Aquarius V4.0 can be explained by inaccuracy in the model used in correcting for the absorption by atmospheric oxygen.

Salinity Changes Relative to the Response to Anthropogenic Forcing and Internal Variability in the North Atlantic
Vinogradova, N., and Buckley, M. (25-Apr-17). Over the past few decades, surface waters in the subpolar North Atlantic have experienced substantial fluctuations, including periods of rapid cooling and freshening alternating with the periods of enhanced warming, salinification, and decreased circulation of the gyre. Since these waters feed the North Atlantic thermohaline circulation, such changes have the potential to impact the global ocean circulation and future climate states. A number of potential causes for the observed changes have been suggested, including those related to the strength of the ocean circulation and heat transports, as well as other factors, such as anthropogenic aerosol forcing or changes in surface fluxes. Here we assess how the observed warming/salinification events fit into the long-term picture, focusing on variations in upper-ocean salinity.

Salinity Signature of Tropical Atlantic Interannual Modes
Awo, M., Alory, G., Da-Allada, C., Jouanno, J., Delcroix, T., and Baloitcha, E. (25-Apr-17). Interannual climate variability in the tropical Atlantic is dominated by two internal modes: an equatorial and a meridional mode. The equatorial mode is partly responsible for sea surface temperature (SST) anomalies observed in boreal summer in the Gulf of Guinea. The meridional mode peaks in boreal spring as an inter-hemispheric SST fluctuation. Previous studies show that these modes affect the migration of the inter tropical convergence zone which drives regional precipitation. In this study, we extracted the Sea Surface Salinity (SSS) signature of these modes from in situ data. 

Surface Drifters Measuring Sea Water Salinity
Reverdin, G., Centurioni, L., Sena-Martins, M., Garcia-Ladona, E., Ballabrera, J., Savador, J., Sommer, A., and Boutin, J. (25-Apr-17). Surface drifters have been introduced in the early 1990s by P.P. Niiler to measure the salinity of the near-surface water as well as its temperature. First, they were deployed to document large scale advection of surface salinity fronts, such as during TOGA-COARE (1991). More recently, salinity drifter data were used for three purposes: 1 - provide in situ data coverage for validation of sea surface (SSS) products, such as provided by band-L microwave radiometry from satellite missions, Aquarius, SMOS, SMAP 2 - provide data for better understanding upper ocean response to air-sea interactions, such as during rainfall, or near-surface warming during low wind events 3 - provide estimates of surface advection of salinity features and their contribution to ocean freshwater budget We will review the drifters that have been deployed and where data were collected, the challenges encountered in correcting the data, ongoing plans and future developments.

The Role of Sea Surface Salinity in ENSO Related Water Cycle Anomaly
Tang, W., and Yueh, S. (25-Apr-17). This study investigates the role of sea surface salinity (SSS) in the water cycle anomaly associated with El Niño Southern Oscillation (ENSO). The 2015-16 El Niño, one of the strongest ENSO events observed in centuries, coincident with unprecedented coverage of spacebased remote sensing of SSS over global oceans. We analyze three SSS data sets: from the NASA's missions of SMAP and Aquarius, and the ESA's Soil Moisture and Ocean Salinity (SMOS). One typical characteristics of an ENSO event is the zonal displacement of the Western equatorial Pacific Fresh Pool (WPFP). The edge of the pool extends eastward during El Niño, retreats westward during La Niña. For super El Niño, the eastern edge of WPFP extends much more east across the equatorial Pacific. Indeed, SSS from SMAP reveals much stronger eastward migration of WPFP starting in April 2015.