ENSO Response of Global Atmospheric Energy Conversion and Atmospheric Circulation

The relationship between El Niño-Southern Oscillation (ENSO) response of global atmospheric energies and atmospheric circulation anomalies is investigated using a reanalysis dataset. As the meridional temperature gradient in the troposphere increase in ENSO warm phase, strengthening of subtropical jet, enhancement and narrowing of Hadley circulation, and enhancement of extratropical meridional circulation are observed. Corresponding to the ENSO responses of the circulation anomalies, the zonal mean component of the global energy of the atmosphere increase in the ENSO warm phase, but no ENSO response is seen in the wave energy.

The modulations associated with ENSO are not seen in the global-averaged energy conversion rate. However, the meridional distribution of the energy conversion rates shows some ENSO responses. The latitudinal distribution of the energy conversion rate from zonal-mean available potential energy to zonal-mean kinetic energy shows the two local maxima centered around the subtropics and the midlatitudes. The positions of the maxima move equatorward in the ENSO warm phase, related to the ENSO response of the meridional circulations. The latitudinal distribution of the energy conversion rate from the zonal mean kinetic energy to wave energy shows the maximum values around the subtropical jet. The position of the maximum also moves equatorward in the ENSO warm phase. It is found the ENSO response of the energy conversion rate is due to the response of the barotropic process in the upper troposphere, and the response of the baroclinic process in the lower troposphere. This is consistent with the ENSO response of the Eliassen-Palm flux.