Assessing SARAL/AltiKa near-real time data in the coastal zone: comparisons with HF radar

Ananda Pascual (IMEDEA(CSIC-UIB), Spain)


Arancha Lana (IMEDEA(CSIC-UIB), Spain); Charles Troupin (SOCIB, SPAIN); Simón Ruiz (IMEDEA(CSIC-UIB), SPAIN); Yannice Faugère (CLS, FRANCE); Joaquín Tintoré (IMEDEA(CSIC-UIB) and SOCIB, SPAIN)

Event: 2014 SARAL/AltiKa workshop

Session: Oceanography

Presentation type: Type Poster

We present an initial assessment of SARAL/AltiKa data in the coastal band of the Western Mediterranean Sea. The objective is to process, validate and intercalibrate multi-platform datasets with the final aim of improving our understanding of coastal dynamical processes. We focus on the Ibiza Channel where the north-south water exchanges play a key role in controlling the circulation variability in the Western Mediterranean at a wide range of scales (mesoscale, seasonal and inter-annual). In this area, the track number 16 from SARAL/AltiKa intercepts the domain covered by the coastal high-frequency radar system operated by SOCIB, which provides hourly surface currents surface currents, with a 3 km spatial resolution and a range up to 60 km. Five cycles (June 2013- November 2013) of SARAL/AltiKa along-track data are analyzed and compared with HF radar. Additionally, we evaluate the records from Jason-2 track no. 187, which crosses SARAL/AltiKa track no. 16 over Ibiza Island.
The first insights using the standard AVISO near-real products (filtered with 42 km Lanczos filter and subsampled at a resolution of 14 km) put in evidence the emerging capabilities of SARAL/AltiKa in the coastal zone. Indeed, while SARAL/AltiKa data are retrieved at a distance of only 7 km from the coast, all the available measurements from Jason-2 are located farther than 35 km off Southwest Ibiza. This prevents an exhaustive intercomparison between Jason-2 and HF radar as there are only 2 valid Jason-2 points in the area covered by HF radar. On the contrary, SARAL/AltiKa, with 5-6 valid points, reveals coherent mesoscale features with a high level of temporal variability among the different cycles and with general good agreement with HF radar fields (correlations higher than 0.65).
In summary, this study highlights that: (1) SARAL/AltiKa is providing reliable data very close to the coast, representing a challenge for the new era of satellite altimetry observations and (2) the development of synergic approaches through the combined use of observing systems and model simulations supports the investigation of unresolved scientific questions in the coastal area.

Ananda Pascual