资源环境科技发展态势分析平台

The atmospheric perturbation potential energy (PPE) over the tropical Pacific is calculated and analyzed in a composite ENSO cycle. The PPE over the tropical Pacific troposphere increases during El Nino and decreases during La Nina, displaying two centers symmetrical about the equator and delaying the central-eastern Pacific SST anomaly by two months. Generated from atmospheric diabatic heating, the smaller part of PPE in the lower troposphere varies synchronously with the central-eastern Pacific SST through sensible heating, while the larger part of PPE lies in the mid-and upper troposphere and lags the central-eastern Pacific SST about one season because of latent heat release. As the tropical Pacific PPE peaks during the boreal late winter in an El Nino event, two anticyclones form in the upper troposphere as a result of the Gill model response. More PPE is converted to atmospheric kinetic energy (KE) above the central-western Pacific, but less over the eastern Pacific, leading to intensified Hadley circulations over the central-western Pacific and weakened Hadley circulations over the eastern Pacific. The strengthened Hadley circulations cause surface easterly wind bursts through KE convergence in the western equatorial Pacific, which may trigger a La Nina event. The reverse situation occurs during La Nina. Thus, the response of the Hadley circulations in the central-western Pacific provides a negative feedback during the ENSO cycle.