On the Spatial Scales to be Resolved by the Surface Water and Ocean Topography Ka-Band Radar Interferometer
Year: 2019
Type: article
Abstract: The Surface Water and Ocean Topography (SWOT) mission aims to measure the sea surface height (SSH) at a high spatial resolution using a Ka-band radar interferometer (KaRIn). The primary oceanographic objective is to characterize the ocean eddies at a spatial resolution of 15 km for 68% of the ocean surface. This resolution is derived from the ratio between the wavenumber spectrum of the conventional altimeter (projected to submesoscale) and the SWOT SSH errors. While the 15-km threshold is useful as a global approximation of the spatial scales resolved by SWOT (SWOT scale), it can be misleading for regional studies. Here we revisit the problem using a high-resolution (~2-km horizontal grid spacing) tide-resolving global ocean simulation and map the SWOT scale as a function of location and season. The results show that the SWOT scale increases, in general, from about 15 km at low latitudes to ~30–45 km at mid- and high latitudes but with a large geographical dependence. A SWOT scale smaller than 30 km is expected in the high-latitude energetic regions. The SWOT scale varies seasonally as a result of the seasonality in both the noise and ocean signals. The seasonality also has a geographical dependence. Both eddies and internal gravity waves/tides contribute significantly to the SWOT scale variation. Our analysis provides model predictions for interpreting the anticipated observations from SWOT and guidance for the development of analysis methodologies.
Language: English
Subfield: Oceanography
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: hybrid
Awards: EXPLORING NEW UPPER OCEAN CIRCULATION DYNAMICS THROUGH SYNERGY OF THE SWOT SATELLITE MISSION AND HIGH-RESOLUTION OGCMS THIS PROPOSAL SEEKS PARTICIPAT, THE GOALS OF THIS PROPOSED RESEARCH ARE (1) TO CHARACTERIZE AND UNDERSTAND THE NATURE AND CAUSES OF THE LARGE-SCALE CIRCULATION VARIABILITY IN THE PACIFIC OCEAN ON TIME SCALES FROM INTERANNUAL TO DECADAL AND (2) TO CLARIFY THE INTERACTION OF OCEANIC MOTIONS OF DIFFERENT TIME SCALES AND SPATIAL DOMAINS. AN UNDERSTANDING OF THESE TOPICS WILL LEAD TO INCREASED PREDICTABILITY OF THE OCEAN CIRCULATION AND DENSITY STRUCTURES BOTH OF WHICH ARE IMPORTANT TO THE CLIMATE VARIABILITY ON LONGER TIME SCALES. THE CONCURRENT SATELLITE ALTIMETER MISSIONS FROM THE PAST 2.5 DECADES HAVE HELPED RESOLVE THE ENERGY-CONTAINING MESOSCALE EDDY SIGNALS THAT ARE CRUCIAL FOR THE EQUILIBRATION OF THE LARGE-SCALE OCEANIC GYRE CIRCULATIONS. ALTHOUGH DESCRIPTIONS ABOUT THE MESOSCALE EDDY SIGNALS HAVE IMPROVED SIGNIFICANTLY THANKS TO THE ACCUMULATING ALTIMETER DATA EDDY'S ROLES IN FEEDBACKING TO THE SLOWLY MODULATING LARGER-SCALE CIRCULATION ARE YET TO BE ADEQUATELY QUANTIFIED. WITH THE GROWING TIME SERIES OF THE SATELLITE ALTIMETER DATA THAT RESOLVES BOTH THE MESO- AND LARGE-SCALE SSH SIGNALS THE TIMING BECOMES NOW RIPE FOR ADDRESSING THIS EDDY-MEAN FLOW INTERACTION ISSUE IN AN OBSERVATIONALLY-CONSTRAINED FUNDAMENTAL WAY. THIS STUDY PROPOSES TO CONDUCT CAREFUL ANALYSES OF THE MULTI-DECADE ALTIMETRY DATA FROM ALL AVAILABLE EXISTING/FUTURE MISSIONS. WE PLAN TO FIRST DOCUMENT THE LARGE-SCALE SSH FLUCTUATIONS ON THE DECADAL TIME SCALES. THE OBSERVED SIGNALS WILL BE COMPARED AGAINST OTHER OCEANIC DATA (SUCH AS SEA SURFACE TEMPERATURE AND ARGO PROFILING FLOAT DATA) AND THE ATMOSPHERIC VARIABLES (E.G. THE SURFACE WIND AND BUOYANCY FORCING) WITH THE GUIDANCE OF OUR UNDERSTANDING OF THE OCEAN DYNAMICS. OUR NEXT STEP IS TO CLARIFY THE CAUSES FOR THE OBSERVED DECADAL CHANGES. TO DO SO WE PROPOSE TO USE BOTH SIMPLIFIED DYNAMIC MODELS AND OCEAN GENERAL CIRCULATION MODEL OUTPUTS WITH REALISTIC TOPOGRAPHY AND SURFACE BOUNDARY CONDITIONS. THROUGH COMBINING THE ALTIMETRIC DATA AND THE OCEAN MODELS WITH VARIOUS COMPLEXITY WE SEEK TO IDENTIFY THE ROLES PLAYED BY DIFFERENT PHYSICAL PROCESSES SUCH AS THE INTERIOR OCEAN DYNAMICS THE SURFACE WIND AND BUOYANCY FORCINGS AND REGIONAL NONLINEAR AND INSTABILITY PROCESSES. PARTICULAR ATTENTION WILL BE DIRECTED TO CLARIFY HOW THE OBSERVED TIME-VARYING CIRCULATION SIGNALS OF VARIOUS TIME AND SPACE SCALES MUTUALLY INTERACT. BY COMBINING THE DATA ANALYSIS AND NUMERICAL MODELING THIS PROPOSED RESEARCH WILL DIRECTLY CONTRIBUTE TO THE TWO RESEARCH THEMES SET OUT BY THE JOINT NASA/NOAA/CNES OCEAN SURFACE TOPOGRAPHY SCIENCE TEAM (OSTST): 1) TO SUPPORT STUDIES IN PHYSICAL OCEANOGRAPHY UTILIZING JASON-SERIES MISSION DATA AS WELL AS THE COMBINED 20-YEAR TP/JASON/JASON-2/ JASON-3 DATA PREFERABLY JOINTLY WITH OTHER SATELLITE AND IN-SITU DATA AND/OR MODELS IN SUPPORT OF BOTH BASIC RESEARCH AND OPERATIONAL APPLICATIONS AND 2) TO SUPPORT STUDIES OF HIGH-RESOLUTION MERGED ALTIMETRIC DATA SETS TO EXAMINE THE ROLE OF MESOSCALE EDDIES AND WESTERN BOUNDARY CURRENTS IN THE GENERAL CIRCULATION OF THE OCEAN.
OpenAlex ID: W2910169751