Global Variations in Oceanic Evaporation (1958–2005): The Role of the Changing Wind Speed

• DOI: 10.1175/2007jcli1714.1
• Publication Date: 2007-11-12T19:38:20Z
• Authors: Lisan Yu
• Keywords: Climatology; Air-sea interaction; 13. Climate action; Evaporation; Decadal variability; 14. Life underwater; Winds; 551; 01 natural sciences; 0105 earth and related environmental sciences

Abstract Global estimates of oceanic evaporation (Evp) from 1958 to 2005 have been recently developed by the Objectively Analyzed Air–Sea Fluxes (OAFlux) project at Woods Hole Oceanographic Institution (WHOI). The nearly 50-yr time series shows that decadal change global is marked a distinct transition downward trend an upward around 1977–78. Since transition, Evp has up about 11 cm yr−1 (∼10%), low 103 in 1977 peak 114 2003. increase was most dramatic during 1990s. uncertainty ±2.74 yr−1. By utilizing newly datasets and related air–sea variables, study investigated cause Evp. differences between 1990s 1970s indicates occurred over scale had spatially coherent structures. Larger pronounced two key regions—one paths western boundary currents their extensions, other tropical Indo-Pacific warm water pools. It also found enlarged primarily hemispheric wintertime (defined as mean December–February for northern oceans June–August southern oceans). Despite dominant tendency basins, slight reduction appeared such regions subtropical centers maxima well eastern equatorial Pacific Atlantic cold tongues. An empirical orthogonal function (EOF) analysis performed yearly winter-mean variables [i.e., wind speed (U) humidity (dq)]. suggested role forcing both dq. hypothesized impacts ways. first way direct: greater induces more carrying vapor away evaporating surface allow gradients be reestablished faster pace. second indirect: enhanced strengthens wind-driven gyre, which turn drives heat transport currents, warms SST along causes enlarging gradients. EOF annual-mean fields showed three modes account 50% total variance. mode 1 variability represents after 1978 attributable increased U, 2 explains much before correlated dq variability. 3 captures interannual on scales El Niño–Southern Oscillation, with center action Pacific.