The El Nino-Southern Oscillation Pattern Effect

El Nino-Southern Oscillation (ENSO) variability is accompanied by out-of-phase anomalies in the top-of-atmosphere tropical radiation budget, with anomalous downward flux (i.e., net radiative heating) before El Nino and anomalous upward flux thereafter (and vice versa for La Nina). Here, we show that these radiative anomalies result mainly from a sea surface temperature (SST) pattern effect, mediated by changes in tropical-mean tropospheric stability. These stability changes are caused by SST anomalies migrating from climatologically cool to warm regions over the ENSO cycle. Our results are suggestive of a two-way coupling between SST variability and radiation, where ENSO-induced radiative changes may in turn feed back onto SST during ENSO.

Automated summary

The study reveals that the radiative anomalies induced by El Nino-Southern Oscillation (ENSO) are mainly caused by sea surface temperature (SST) pattern effect, mediated by changes in tropical-mean tropospheric stability. These stability changes are triggered by SST anomalies migrating from climatologically cool to warm regions over the ENSO cycle, suggesting a two-way coupling between SST variability and radiation. The results also indicate that ENSO-induced radiative changes may feedback onto SST during ENSO.