Atmospheric manifestation of tropical instability wave observed by QuikSCAT and tropical rain measuring mission

Abstract

Abstract.Observations from two new spaceborne microwave instruments in 1999 clearly reveal the atmospheric manifestation of tropical instability waves north of the Pacific equatorial cold tongue. A unique zonal-temporal bandpass filter enables the isolation of the propagating signals and the determination of their phase differences. The phase differences between the propagation of wind and sea surface temperature (SST) signals observed from space and the vertical wind profiles measured from a research ship are consistent with the hypothesis that the coupling between wind and SST is caused by buoyancy instability and mixing, which reduces the wind shear in the atmospheric boundary layer. The coupling causes higher evaporative cooling over the warm phase and infers a negative thermal feedback.

The influence of salinity on tropical Atlantic instability waves

“…While equatorial Rossby and Kelvin waves affect large-scale ocean-atmosphere coupling associated with El Niño-Southern Oscillation through the effect of basin-scale zonal SST gradient on the Walker Circulation, TIWs also affect smaller-scale air-sea interaction to regulate the tropical climate variability. In particular, TIW-related SST anomalies influence the (vertical) turbulent mixing in the marine atmospheric boundary layer, causing anomalies in ocean surface wind stress and wind stress curl that propagate westward in association with the downwind and crosswind SST anomalies of the TIWs [e.g., Liu et al, 2000;Chelton et al, 2001;Polito et al, 2001;Hashizume et al, 2001;Chelton, 2005].…”

“…Thousand kilometer zonal scale propagating waves with typical periods of tens of days have been observed in the tropical Pacific and Atlantic Oceans, affecting the physical and biogeochemical properties of the ocean and its interaction with the atmosphere [e.g., Legeckis, 1977;Legeckis and Reverdin, 1983;McPhaden et al, 1984;Hayes et al, 1989;Luther and Johnson, 1990;Yoder et al, 1994;Qiao and Weisberg, 1995;McPhaden, 1996;Xie et al, 1998;Chelton et al, 2000;Liu et al, 2000;Polito et al, 2001;Lee et al, 2012]. These tropical instability waves (TIWs) are generated from barotropic and baroclinic instabilities associated with the horizontal and vertical shear of equatorial current systems and related density gradients [e.g., Philander, 1978;Weisberg and Weingartner, 1988;McCreary and Yu, 1992;Masina et al, 1999;Grodsky et al, 2005;Jochum et al, 2004;Lyman et al, 2007;von Schuckmann et al, 2008].…”

“…They are also stronger and last longer in the Pacific than the Atlantic Ocean due to the stronger equatorial current shear and density gradients in the Pacific [e.g., Chelton et al, 2000]. TIWs are important to ocean dynamics such as eddy-mean flow interaction and mixed-layer processes [e.g., Baturin and Niiler, 1997;Grodsky et al, 2005;Jochum and Murtugudde, 2006;Menkes et al, 2006;Kim et al, 2007], ocean-atmosphere interactions [Hayes et al, 1989;Xie et al, 1998;Liu et al, 2000;Chelton et al, 2001;Yu and Liu, 2003;Pezzi et al, 2004], and marine biogeochemistry [e.g., Feely et al, 1994;Strutton et al, 2001;McCain et al, 2002;Gorgues et al, 2005;Evans et al, 2009].…”

SMOSSea Surface Salinity signals of tropical instability waves

“…They are also larger during La Niña conditions when the cold tongue and the related current shear are more intense than those during a normal year. TIWs are found to play important roles in mixing and cross-equator transport of sea water [Jochum and Murtugudde, 2006;Menkes et al, 2006], the modulation of the heat budget of the ocean mixed layer [Swenson and Hansen, 1999;Vialard et al, 2003], air-sea coupling [Liu et al, 2000;Yu and Liu, 2003], and marine biogeochemistry [Boutin et al, 1999;Gorgues et al, 2005;Evans et al, 2009].…”

Ocean bottom pressure waves predicted in the tropical Pacific

“…[4] Abundant prior work has studied the surface properties of equatorial currents in general, and of tropical instability waves and their associated eddies in particular [Flament et al, 1996]; for example the interactions of TIWs with the atmosphere [Liu et al, 2000]. However, those studies focused on these features as upper-ocean phenomena.…”