Variability in Sigma0 and Wave Height

Author:

Graham Quartly - (PML)

Co-Investigator(s):

Andrey Kurekin (PML)

Abstract:

This programme of work aims to address the potential challenges in incorporating metocean data from Sentinel-6 within operational analyses and long-term climatologies. The proposed series of studies seeks to characterise the expected sources of variability in σ 0 and Hs on a range of different scales. Firstly there is the "Intra-1 Hz analysis" to determine the covariance in anomalies in various terms caused by fading noise and to provide an "adjustment" particular to the implemented retracker that minimises the variability on the shortest scales. Secondly, there will be a revisit of the 58.77-day variability that has long been noted in σ 0 for altimeters in this particular orbit. The period is the alias of the daily cycle, but the cause may either be an instrumental error due to changes in solar irradiation, or an indication of sea surface roughness changes related to diurnal changes in atmospheric stability. The third aspect looks at the empirical differences between LRM- and SAR-derived estimates, and investigates how these might be combined homogeneously. Finally, the fourth part details the work planned in order to validate Sentinel-6 wind speed and wave height estimates using a series of coastal buoys around the UK. The particular focus on coastal validation is to help demonstrate the expected benefits of SAR altimetry in the coastal zone, and will also act as an early assessment of any long-term drift in the sensor performance.