Cross calibration of TOPEX, ERS‐I, and Geosat wave heights

Abstract

A method of calibrating estimates of significant wave height (Hs) from satellite altimeters against buoy data is proposed, which compares monthly means in 2° latitude × 2° longitude bins obtained from the satellite data with mean values obtained from hourly buoy measurements. The method is applied to Geosat data, ERS‐1 fast‐delivery and off‐line products and to TOPEX Ku band data. Results for Geosat data are in good agreement with those from earlier work in which individual altimeter and buoy values were compared, lending support to the proposed method. Based upon these results, linear functions are derived for estimating buoy measurements of Hs from ERS‐1 and TOPEX altimeter data. Significant differences are found between the ERS‐I fast delivery and off‐line values. Regression, from 60°S to 60°N, of corresponding 2°×2° mean wave heights for individual months from ERS‐1 and TOPEX confirm that there are significant differences between the data from these satellites. Comparisons of means from ERS‐1 and from TOPEX with those from Geosat for the same calendar month but 5 years apart show wider scatter about the regression line, indicating the between‐year variability in individual 2°×2° bins.

Estimation of extreme wave heights return period from short-term interpolation of multi-mission satellite data: application to the South Atlantic

“…On the other hand, the spatial variability of the return values is similar to description given by Caires and Sterl (2005), who relate this variability to under-sampling within the bins. However, the long data set and the chosen fixed threshold would assure an adequate representation of major spatial features (Caires and Sterl, 2005) The chosen grid size produced results comparable to those obtained by other authors (Cotton and Carter, 1994;Young, 1999;5 Panchang et al, 1999;Woolf et al, 2002;Alves and Young, 2003;Vinoth and Young, 2011), confirming that a mesh element size of 2 • × 2…”

Wave hindcast for the New Zealand region: Deep‐water wave climate

“…Data were excluded where: (1) the record was flagged as being affected by excess atmospheric moisture or rain; (2) significant wave height was identically zero, or exceeded 25 m; (3) the orientation of the satellite altimeter drifted significantly from nadir; or (4) the 1-s sample had a standard deviation exceeding 20% of the mean. Such high variability, greater than expected for open ocean wave fields over the corresponding 7 km track, often occurs adjacent to data gaps (Bauer et al 1992) or where the signal is contaminated by rain (Cotton & Carter 1994). In further processing, the record was divided into 10-s segments, resulting in data points some 60 km apart.…”

Impact of a possible local wind change on the wave climate in the upper Río de la Plata

“…Even though the most important cities and ports, including both capitals (Buenos Aires and Montevideo) and many of the industrial centres and resorts of both countries, are on the RDP margins, a reliable wave climate for the RDP estuary is not available. There are four wave data sources available to build a wave climate: (i) altimeter measurements from ERS-1, ERS-2 and TOPEX instruments (Cotton and Carter, 1994;Woolf et al, 2002); (ii) voluntary observing ships (VOS; Wilkerson and Earle, 1990;Gulev et al, 2003); (iii) wave model hindcasts (Sterl et al, 1998;Cox and Swail, 2001); and (iv) in situ observations (buoys). The first three provide global coverage, but there are serious problems with the data quality.…”