Wave climate observed from satellites: trends and inter-annual variability
Event: 2017 Ocean Surface Topography Science Team Meeting
Session: Science I: Climate data records for understanding the causes of global and regional sea level variability and change
Presentation type: Type Oral
Contribution: PDF file
While the use of altimeters is driven by the sea level community, these data are sufficiently long for climate studies and have high coverage in space and time making them an attractive source of information for wave studies. Altimeters are limited to describing the significant wave height and wind speed. However, important sea state information regarding wavelengths and directions are not possible from altimeters. This is where data from synthetic aperture radars (SAR) is highly valuable since they effectively estimate wavelengths. While GlobWAVE has made significant strides in producing the quality datasets for both altimeters and SARs, these data were not specifically produced for climate studies. This is the main reason, the European Space Agency (ESA) will conduct a climate change initiative on the sea state (CCI-SeaState). The project will focus on producing the better quality data datasets from satellites including altimeters and SARs. There will be emphasis on estimating sea states in the nearshore and in extreme events and most importantly suitable for climate applications.
In this study we explore the GlobWAVE altimeter and SAR datasets to describe the wave climate. The altimeter dataset starts in 1985 with GEOSAT and we have continuous coverage since 1992. The SAR dataset starts in 1995 with ERS2 (1995-1999) and continues with ENVISAT (2002-2012) and the Sentinel-1 missions (2014-present). Using these datasets we describe the inter-annual variability and trends. This 31-year altimeter and 18-year SAR time series have many important applications to better understand the wave climate. We discuss our results within the context of the ESA Sea State CCI and note areas of research that need further efforts to make them suitable for climate studies.