“…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].…”