Investigating Convective Processes Underlying ENSO: New Insights into the Fixed Anvil Temperature Hypothesis

Interannual variations provide insight into the sensitivity of convective processes. Thus, CloudSat and ERA5 are used to explore the relationship among convective cores, outflows and environmental conditions during El Niño-Southern Oscillation (ENSO) cycles. Results reveal greater upper-tropospheric stability during El Niño, resulting in a lower level of neutral buoyancy in comparison to La Niña. However, outflow levels remain relatively consistent across ENSO cycles. This suggests that, despite less favorable conditions for deep convection during El Niño, stronger convective intensity is required to achieve outflow levels comparable to those in La Niña. Indeed, our results suggest that convection observed during El Niño tends to have broader cores and lower entrainment rates, translating to greater intensity compared to La Niña. These findings emphasize the importance of considering both large-scale and convective-scale processes, providing an update to the Fixed Anvil Temperature (FAT) and the proportionately higher anvil temperature (PHAT) hypotheses as originally proposed.