Assessing the Controversy between Altimetry, Radiometry, and Scatterometry: Satellite Observation Requirements for Trends in Extreme Winds and Waves

Abstract:

A recent study (Young et al. 2011) investigated recent global trends in mean and extreme (90th- and 99th-percentile) wind speed and wave height. Wentz and Ricciardulli (2011) have criticized the study, citing the methodology solely employing data collected from a series of altimetry missions and lack of adequate verification of the results. An earlier study (Wentz et al. 2007) had differing results using data from microwave radiometers and scatterometers. This study serves as a response to these studies, employing a similar methodology but with a different set of data. Data collected from the QuikSCAT and ADEOS-2 SeaWinds scatterometers, SSMI(S), and TOPEX/POSEIDON and JASON-1 altimetry missions are used to calculate trends in the mean, 90th-, and 99th-percentile wind speed and wave height over the period 1999—2009. Linear regression analyses from the satellite missions are verified against regression analyses of data from the ERA-Interim reanalysis dataset. Temporal sampling presents the most critical consideration in the study. The scatterometers have a much greater independent temporal sampling (about 1.5 observations per day per satellite) than the altimeters (about 1 observation per 10 days). With this consideration, the satellite data are also used to sample the wind speeds in the ERA-Interim dataset. That portion of the study indicates the sampling requirements needed to accurately estimate the trends in the ERA-Interim reanalysis.

Wentz, F.J., L. Ricciardulli, K. Hilburn, and C. Mears, 2007: How much more rain will global warming bring? Science, 317, 233-235.

Wentz, F.J. and L. Ricciardulli, 2011: Comment on “Global trends in wind speed and wave height.” Science, 334, 905.

Young, I.R., S. Zieger, and A.V. Babanin, 2011a: Global trends in wind speed and wave height. Science, 332, 451-455.