Using Satellite Data to Represent Tropical Instability Waves (TIWs)-Induced Wind for Ocean Modeling: A Negative Feedback onto TIW Activity in the Pacific

Abstract

Recent satellite data and modeling studies indicate a pronounced role Tropical Instability Waves (TIW)-induced wind feedback plays in the tropical Pacific climate system. Previously, remotely sensed data were used to derive a diagnostic model for TIW-induced wind stress perturbations (τ TIW ), which was embedded into an ocean general circulation model (OGCM) to take into account TIW-induced ocean-atmosphere coupling in the tropical Pacific. While the previous paper by Zhang (2013) is concerned with the effect on the mean ocean state, the present paper is devoted to using the embedded system to examine the effects on TIW activity in the ocean, with τ TIW being interactively determined from TIW-scale sea surface temperature (SST TIW ) fields generated in the OGCM, written as τ TIW = α TIW · F(SST TIW ), where α TIW is a scalar parameter introduced to represent the τ TIW forcing intensity. Sensitivity experiments with varying α TIW (representing TIW-scale wind feedback strength) are performed to illustrate a negative feedback induced by TIW-scale air-sea coupling and its relationship with TIW variability in the ocean. Consistent with previous modeling studies, TIW wind feedback tends to have a damping effect on TIWs in the ocean, with a general inverse relationship between the τ TIW intensity and TIWs. It is further shown that TIW-scale coupling does not vary linearly with α TIW : the coupling increases linearly with intensifying τ TIW forcing at low values of α TIW (in a weak τ TIW forcing regime); it becomes saturated at a certain value of α TIW ; it decreases when α TIW goes above a OPEN ACCESSRemote Sens. 2013, 5 2661 threshold value as the τ TIW forcing increases further. This work presents a clear demonstration of using satellite data to effectively represent TIW-scale wind feedback and its multi-scale interactions with large-scale ocean processes in the tropical Pacific.

A Coupled Ocean Physics‐Biology Modeling Study on Tropical Instability Wave‐Induced Chlorophyll Impacts in the Pacific

“…Coupled models are also used to examine the impacts of TIW on the tropical climate. It is demonstrated that TIW‐scale processes can have significant influences on large‐scale air‐sea interaction (An, ; Imada & Kimoto, ; Seo et al, ; Small et al, ; Zhang et al, ).…”

A modulating effect of Tropical Instability Wave (TIW)‐induced surface wind feedback in a hybrid coupled model of the tropical Pacific

“…In this study, α inter =1.3 and α TIW =3.0 were used for all HCM experiments discussed below. As seen in the OGCM simulations [ Zhang et al ., ], α TIW =3.0 can adequately represent TIW‐induced feedback strength in the eastern tropical Pacific when performing the HCM experiments.…”

“…These relationships are well captured in the HCM simulations. Following the previous analyses [e.g., Chelton , ; Zhang et al ., ], TIW activity in the ocean and TIW‐scale coupling were analyzed in terms of standard deviations of the SST TIW and τ TIW fields and the wind stress curl and divergence fields, respectively.…”

“…As was demonstrated by previous ocean‐only experiments [e.g., Pezzi et al ., ; Zhang et al ., ], TIWs in the HCM simulations tended to be weakened when the TIW wind feedback was explicitly taken into account. Furthermore, large‐scale winds and air‐sea coupling affected TIWs and were affected by TIWs in the coupled modeling context [e.g., Seo et al ., 2006; Zhang and Busalacchi , ; Small et al ., ].…”

Impact of tropical instability waves‐induced SST forcing on the atmosphere in the tropical Pacific, evaluated using CAM5.1

“…For example, several previous modeling studies have suggested a negative feedback induced by TIWs (Seo et al, 2007;Imada et al, 2012;Zhang et al, 2013). In a coupled ocean-atmosphere system, the atmospheric boundary layer (ABL) almost simultaneously responds to the presence of TIWs and as a feedback it returns its signal to the oceanic surface, which interacts in an opposite way with ocean surface fields (currents and temperature) that affect the oceanic dynamical and thermo-dynamical features (Polito et al, 2001;Pezzi et al, 2004;Seo et al, 2007).…”