Mechanism for formation of super El Ninos
Prof. Tim Li
University of Hawaii, USA
In this talk, I will first discuss distinctive precursor atmosphere-ocean signals prior to El Nino onset between super and regular El Nino group. Then I will further discuss the difference of formation mechanisms between traditional super El Ninos such as those in 1997/98 and 1982/83 and the special 2015 event. A super El Nino was anticipated on the way in early 2014 but failed to materialize toward the end of 2014. Whilst the scientific community was still puzzling about the cause of the aborted El Nino in 2014, the remnants of the decaying warming in late 2014 unexpectedly reignited since February 2015 and grew into a super El Nino by the end of 2015. Our observational analyses and modeling studies demonstrate that the principal difference between the 2015 super El Nino and the traditional ones lies in exceptionally strong and consecutive occurrence of westerly wind burst events that turned around unfavorable ocean thermocline conditions in tropical western Pacific in early 2015, reigniting rapidly the surface warming in the eastern Pacific.