Regional daily sea level maps from Multi-mission Altimetry using Space–time Window Kriging

Abstract

In this study, we present a gridding approach using Window Spatio-temporal Kriging applied to multi-mission, along-track Sea Level Anomalies (SLAs) to produce daily regional Level-4 gridded datasets. The method was tested in two distinct regions: the California region, selected for its extensive tide gauge coverage, and the Southwestern Atlantic Continental Shelf, known for complex coastal dynamics where existing gridded products have shown performance issues. We selected unfiltered along-track SLAs within a  ± 5-day window centered around the prediction day to capture short-term spatio-temporal variability. An experimental variogram for each day was constructed and fitted using a sum-metric spatio-temporal variogram model. This model was then incorporated into a Kriging system, which utilizes Ordinary Kriging to predict SLAs at unsampled locations based on the spatial and temporal covariance structures. We produced a daily gridded dataset covering 2018 on a 1/4° grid and compared it against SLAs from independent along-track data, tide gauges, and Glorys12v1 model reanalysis. The resulting grid demonstrated improved correlation with in situ tide gauges, increasing by 10.7% in California and 17.5% in the Southwestern Atlantic Continental Shelf region while reducing the Root Mean Square Deviation by 12.7% and 13.8%, respectively. We also reported a notable improvement (from 58 to 34 days) in terms of effective temporal resolution estimated against independent in situ data, while spatial effective resolution compared to independent along-track data is equal compared to CMEMS SLAs in the study region of California.