Umbert M.,Departament Of Physical And Technological Oceanographyinstitut Of Ciencies Del Mar |
Guimbard S.,Departament Of Physical And Technological Oceanographyinstitut Of Ciencies Del Mar |
Lagerloef G.,Earth and Space ResearchSeattle |
Thompson L.,University of Washington |
And 3 more authors.
Journal of Geophysical Research C: Oceans | Year: 2015
New sea surface salinity (SSS) observations derived from satellite remote sensing platforms provide a comprehensive view of salt exchanges across boundary currents such as the Gulf Stream. The high resolution (45 km spatial resolution and 3 day repeat subcycle) of the Soil Moisture and Ocean Salinity (SMOS) observations allows detection (and tracking) of meander and ring structures of the Gulf Stream from SSS maps. These structures are, however, not resolved by the relatively lower resolution (100 km and 7 day repeat subcycle) of Aquarius observations. A recently developed fusion technique, based on singularity analysis, is applied in this study to reconstruct these mesoscale (from 100 km and 3 days) features in Aquarius-derived products. New quarter-degree SSS maps are obtained by fusing Aquarius data with three different geophysical templates: sea surface height (SSH) from AVISO, SSS from SMOS, and sea surface temperature (SST) from AVHRR. The proposed method exploits the theoretical correspondence among the singularity exponents of different maps of ocean-surface remotely sensed scalar fields. The analysis results over the year 2012 show that merging Aquarius with SSH data provides a series of negative salinity anomalies that better collocate with the position of the cyclonic eddies identified from sea level anomaly maps. This result is consistent with the hypothesis that this SLA derived cyclonic eddies in this area are indeed CCRs shed off the GS. Key Points:: Low spatiotemporal resolution Aquarius L3 maps poorly resolve CCRs A data fusion technique is used to fuse Aquarius with other satellite products Aquarius L4 product fused with SSH best resolves CCR SSS signature and evolution © 2015. American Geophysical Union.
Lagerloef G.,Earth and Space ResearchSeattle
Journal of Geophysical Research: Oceans | Year: 2016
A new high-resolution sea surface salinity (SSS) analysis has been produced using Aquarius satellite observations from September 2011 to June 2015. The motivation for the new product is twofold: to produce Level-4 SSS analysis that is consistent with existing in situ observations such as from Argo profile data, and to reduce the large-scale satellite biases that have existed in all versions of the standard Level-3 Aquarius products. The new product is a weekly SSS analysis on a nearly global 0.5° grid. The analysis method is optimum interpolation (OI) that takes into account analyzed errors of the observations, specific to the Aquarius instrument. The method also includes a large-scale correction for satellite biases, filtering of along-track SSS data prior to OI, and the use of realistic correlation scales of SSS anomalies. All these features of the analysis are shown to result in more accurate SSS maps. In particular, the method reduces the effects of relative biases between the Aquarius beams and eliminates most of the large-scale, space-varying, and time-varying satellite biases relative to in situ data, including spurious annual signals. Statistical comparison between the weekly OI SSS maps and concurrent buoy data demonstrates that the global root-mean-square error of the analysis is smaller than 0.2 pss for nearly all weeks over the ∼4 year period of comparison. The utility of the OI SSS analysis is also exemplified by the derived patterns of regional SSS variability. © 2015. American Geophysical Union.
Kao H.-Y.,Earth and Space ResearchSeattle |
Lagerloef G.S.E.,Earth and Space ResearchSeattle
Journal of Geophysical Research C: Oceans | Year: 2015
This study delineates the salinity fronts (SF) across the tropical Pacific, and describes their variability and regional dynamical significance using Aquarius satellite observations. From the monthly maps of the SF, we find that the SF in the tropical Pacific are (1) usually observed around the boundaries of the fresh pool under the intertropical convergence zone (ITCZ), (2) stronger in boreal autumn than in other seasons, and (3) usually stronger in the eastern Pacific than in the western Pacific. The relationship between the SF and the precipitation and the surface velocity are also discussed. We further present detailed analysis of the SF in three key tropical Pacific regions. Extending zonally around the ITCZ, where the temperature is nearly homogeneous, we find the strong SF of 1.2 psu from 7° to 11°N to be the main contributor of the horizontal density difference of 0.8 kg/m3. In the eastern Pacific, we observe a southward extension of the SF in the boreal spring that could be driven by both precipitation and horizontal advection. In the western Pacific, the importance of these newly resolved SF associated with the western Pacific warm/fresh pool and El Niño southern oscillations are also discussed in the context of prior literature. The main conclusions of this study are that (a) Aquarius satellite salinity measurements reveal the heretofore unknown proliferation, structure, and variability of surface salinity fronts, and that (b) the fine-scale structures of the SF in the tropical Pacific yield important new information on the regional air-sea interaction and the upper ocean dynamics. © 2015. The Authors.