SEMINAR: REMINDER - TODAY AOML SeminaR -2:00 p.m.- Dr. Greg Foltz - “Interaction between the Atlantic meridional and Nino modes during 2009 ”

["Aoml.Receptionist" <Aoml.Receptionist@noaa.gov>]

AOML  Seminar

DATE :                Monday, March 8, 2010

 TIME :                 2:00 p.m. - refreshments at 1:45 p.m.

LOCATION :     AOML First- Floor Conference Room       

     SPEAKER :         Dr. Greg Foltz

                             University of Washington JISAO

                 

TITLE :              “Interaction between the Atlantic meridional and Nino modes during 2009 ”

Abstract:
During the first half of 2009 sea surface temperatures (SSTs) were anomalously cold in the northeastern tropical Atlantic and anomalously warm in the central and eastern equatorial Atlantic. Associated with this anomalous meridional dipole in SST was a southward displacement of the ITCZ and extreme flooding in Northeast Brazil. In this study a combination of observations and a linear equatorial wave model is used to investigate the mechanisms responsible for the evolution of anomalous conditions in the equatorial Atlantic during 2009. It is found that anomalous cooling in the northeastern tropical Atlantic began in January, driven by stronger than normal wind-induced latent heat loss. The atmospheric response to anomalously cold SSTs included anomalous northwesterly surface winds along the equator and Ekman pumping to the north (3N-5N). The Ekman pumping in turn led to further anomalous cooling in the 3N-5N band and further strengthening of the meridional SST dipole during boreal spring. Along the equator, weaker than normal westward winds led to an anomalously deep thermocline and surface warming during boreal spring and early summer. The transient response to the anomalous equatorial wind forcing was a downwelling equatorial Kelvin wave and an upwelling equatorial Rossby wave. The Rossby wave reflected off the western boundary and propagated eastward along the equator as a Kelvin wave in June-July, raising the thermocline and putting an abrupt end to the developing equatorial warm event. These results highlight the role of ocean dynamics and air-sea coupling in the development of SST anomalies in the eastern ITCZ region and identify the equatorial Rossby wave as a potential link between the boreal spring meridional mode and the boreal

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