Abstract. Land-based coastal high-frequency (HF) radar systems provide operational measurements of
coastal surface currents (within 1–3 m depth) with high spatial
(300 m–10 km) and temporal (≤1 h) sampling resolutions, while the
near-continuous altimetry missions provide information, from 1993 until today,
on geostrophic currents in the global ocean with typical along-track and
temporal sampling resolutions of >7 km and >9 days, respectively. During
the last years, the altimetry community has made a step forward in improving
these data in the coastal area, where the data present lower quality than in
the open ocean. The combination of HF radar and altimetry measurements arises
as a promising strategy to improve the continuous monitoring of the coastal
area (e.g. by expanding the measurements made by HF radars to adjacent areas
covered by the altimetry or by validating/confirming improvements brought by
specific coastal algorithms or new altimeter missions). A first step towards
this combination is the comparison of both data sets in overlapping areas. In this study, a HF radar system and two Jason-2 satellite altimetry
products with different processing are compared over the period from
1 January 2009 to 24 July 2015. The results provide an evaluation of the
performance of different coastal altimetry data sets within the study area
and a better understanding of the ocean variability contained in the
HF radar and altimetry data sets. Both observing systems detect the main
mesoscale processes within the study area (the Iberian Poleward Current and
mesoscale eddies), and the highest correlations between radar and altimetry
(up to 0.64) occur in the slope where the Iberian Poleward Current
represents a significant part of the variability in the circulation.
Besides, the use of an Ekman model, to add the wind-induced current
component to the altimetry-derived geostrophic currents, increases the
agreement between both data sets (increasing the correlation by around 10 %).
The Evaluation of the Result of Post-Processing Envisat Satellite Altimetry Data Used for Coastal Area Potential Flood Mapping (Case Study: Coastal Area of Buleleng Regency, Bali, Indonesia)