A Global Study of the Correlation Properties of Wind and Rain
Quartly, Graham1; Shutler, Jamie1; Woolf, David2
1Plymouth Marine Laboratory, UNITED KINGDOM; 2Heriot-Watt University, UNITED KINGDOM
Both wind and rain have major impacts on the surface ocean, but in many cases their contributions are treated independently, parametrizing the output of processes as separate components dependent upon the mean fields of wind speed and rain rate, without regard for any interaction terms. Here we make use of the two decades of dual-frequency altimetry, which provide simultaneous measurements of wind speed and rain rate. Whilst the primary Ku-band channel is sensitive to both wind and rain, the secondary frequency (S-band for Envisat; C-band for Topex, Jason-1 and Jason-2) is relatively unaffected by rain, permitting the effects of rain and wind on the altimeter record to be separated.
Data are subdivided into key oceanographic regions and the conditional probability of rain calculated for different wind speed conditions. Whilst in many cases rain is associated with strong winds in storms, in lower latitudes convective rain predominantly occurs in calmer conditions. We quantify these effects and discuss their relevance for sound generation at sea (where wind can diminish the signal due to rain) and the flux of greenhouse gases between atmosphere and ocean.