HR: 0800h
AN: GC51A-0165    [Abstracts]
TI: Role of Wind-Evaporation-Sea Surface Temperature (WES) Feedback in Internal and Forced Tropical Variability
AU: Saravanan, R
EM: sarava@tamu.edu
AF: Department of Atmospheric Sciences, Texas A & M University, College Station, TX 77840,
AU: * Mahajan, S
EM: salilmahajan@tamu.edu
AF: Department of Atmospheric Sciences, Texas A & M University, College Station, TX 77840,
AU: Chang, P
EM: ping@ocean.tamu.edu
AF: Department of Atmospheric Sciences, Texas A & M University, College Station, TX 77840,
AB: Tropical climate variability is known to be governed by atmosphere-ocean coupled interactions. The Wind- Evaporation-Sea surface temperature (WES) feedback is one such mechanism that has been hypothesized to play a significant role in the deep tropics. The WES feedback is conjectured to amplify the inter-hemispheric gradient mode variability in the deep tropics. While the WES feedback amplifies the internal atmospheric variability, such as that associated with the North Atlantic Oscillation (NAO), it also potentially enhances the response to remote forcings. Observational studies backed by modeling studies reveal a strong influence of El- Nino Southern Oscillation (ENSO) on tropical Atlantic variability. The response of the tropical Atlantic to ENSO has been hypothesized to be enhanced by local air-sea interactions, possibly via the WES feedback and air-sea temperature and humidity differences. It is challenging to identify individual impacts of the role of individual impacts of these phenomena in observations or even in coupled models, as their effects are super-imposed on each other. Presented here is a report on experiments using a modified version of an atmospheric GCM (AGCM), where the WES feedback is deliberately suppressed in the bulk aerodynamic formulation for surface fluxes. A comparison of coupled integrations using the modified AGCM to those carried out using the control AGCM could isolate the role of the WES feedback. Preliminary analysis suggests that WES feedback intensifies the natural inter-hemispheric gradient mode in the tropics. Experiments with forced ENSO cycle also suggest that WES feedback amplifies the surface heat flux anomalies related to ENSO in the deep tropical Atlantic, probably through the influence of local winds. It is also found that WES feedback reinforces the tendency of the ITCZ to stay north of the equator over the Atlantic during El-Nino events.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1620 Climate dynamics (0429, 3309)
DE: 4215 Climate and interannual variability (1616, 1635, 3305, 3309, 4513)
DE: 4504 Air/sea interactions (0312, 3339)
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting