High‐wind‐speed evaluation in the Southern Ocean

Abstract

[1] Space-based scatterometer instruments provide crucial surface wind measurements with high resolution over global oceans. Midlatitude regions in the Southern Ocean are unique places to evaluate scatterometer winds at high-wind bands because these regions host the strongest wind fields at the ocean surface. The objective of this study is to evaluate high wind speeds observed by Quick Scatterometer (QuikSCAT) wind measurements and produced by simulation models and compare them with weather station data in the Southern Ocean. The occurrence and intensity of high-wind events in scatterometer measurements are compared with that of reanalysis winds, and the spatial and seasonal variability of high-wind characteristics is examined. The results show that the speeds of scatterometer winds are similar to model simulations in the monthly mean field but consistently stronger than both European Centre for Medium-Range Weather Forecasts and National Centers for Environmental Prediction/National Center for Atmospheric Research winds in high-wind bands. When scatterometer winds are compared with the weather station observations at Macquarie Island, the present study finds no systematic bias at high-wind bands across all months. However, both weather station and QuikSCAT winds are higher than the model simulations in high-wind bands most of the time. This suggests that model simulations may underestimate surface wind strength in high-wind bands. Such underestimation would lead to up to an 80% reduction in energy flux between the atmosphere and ocean. Even though high winds occur only sporadically and the reanalysis underestimation in high wind speed is not in itself of great magnitude, they have a significant impact on global climate.

Trends in ship wind speeds adjusted for observation method and height

“…Comparisons of the NCEPR and ERA40 near-surface winds with satellite, buoy, research-vessel and land station winds showed that reanalysis near-surface winds were biased low, particularly in tropical latitudes and for high wind speeds (Swail and Cox, 2000;Smith et al, 2001;Kubota et al, 2002;Caires and Sterl, 2003;Goswami and Sengupta, 2003;Wu and Xie, 2003;Yuan, 2004;Jiang et al, 2005).…”

Mapping High Sea Winds from Space: A Global Climatology

“…The speed threshold corresponds to Beaufort scale 9 (strong gale). Without applying any temporal or spatial averaging to the RSS dataset, our analysis captures more high-wind events than Yuan (2004) and Risien and Chelton (2006), who use some smoothing in space/time. The dominant direction of high winds is determined at each grid point by averaging the velocity vectors exceeding the speed threshold.…”

“…Based on 5-yr QuikSCAT observations, Risien and Chelton (2006) calculate the probability distribution in wind speed-direction space and present the results in wind rose plots on a 0.5° x 0.5° grid. Based on smoothed QuikSCAT data, Yuan (2004) reports that high winds (>20 m s _1 ) occur about 0.7% of the time in the 2000 austral winter over the Southern Hemisphere (SH) south of 30°S. She does not map the spatial distributions of high-wind occurrence, however.…”

Evaluation of the sectional aerosol microphysics module SALSA implementation in ECHAM5-HAM aerosol-climate model

“…Australia, South-America and East-Coast of Africa, indicating transports inland. Sea salt burden is the highest in the Southern Ocean, which has reportedly very high windspeeds (Yuan, 2004) producing large amounts of sea salt. By comparing sea salt and aerosol water burdens in Fig.…”