Aliased Tidal Variability in Mesoscale Sea Level Anomaly Maps.

Area of Science:

• Oceanography
• Satellite Remote Sensing
• Geophysics

Background:

• Sea level anomaly (SLA) maps are crucial for monitoring ocean dynamics.
• Satellite altimetry missions have provided continuous data since 1992.
• Recent updates to the Data Unification and Altimeter Combination System (DUACS) enhanced spatial resolution but increased aliased tidal variability.

Purpose of the Study:

• Investigate the magnitude and spatial distribution of aliased tidal signals in SLA maps.
• Assess the impact of DUACS changes on tidal variability.
• Develop and evaluate filtering techniques to mitigate tidal signals.

Main Methods:

• Analysis of SLA data from satellite altimeters.
• Implementation of low-pass and bandpass filters to reduce tidal signals.
• Validation using independent tide gauge data.

Main Results:

• Aliased tidal signals are more pronounced in coastal areas than in the open ocean.
• Phase-locked and phase-variable baroclinic tides cause signals in the open ocean.
• Erroneous tidal corrections and high-frequency variability contribute to coastal signals.
• A specific filter effectively attenuates small-scale and high-frequency components.

Conclusions:

• The developed filtering method successfully reduces aliased baroclinic tidal variability in SLA maps.
• Filtering improves the accuracy of tidal analysis in the open ocean.
• The filter demonstrates acceptable performance in coastal regions, enhancing overall SLA map reliability.