Enhanced Efficacy Contributes to Tropical Cyclone Intensification in Warmer Climates via Stronger Storm-Scale Radiative Feedbacks

Abstract

Tropical cyclones (TCs) are expected to intensify in a warming climate as sea surface temperatures (SSTs) rise. Potential intensity (PI), the thermodynamic upper limit on storm strength, has long been used to assess how environmental conditions constrain TC intensity. However, a storm’s realized strength also depends on the efficacy in approaching its PI. Using a high-resolution (25 km) global TC-permitting model, we show that uniform SST warming strengthens TCs through concurrent increases in PI and efficacy, leading to a substantial rise in the frequency of Category 3–5 storms. The increased efficacy persists even when changes in wind shear and ventilation effects are accounted for, indicating that changes in TC ventilation are not a primary driver of this response. Instead, the enhanced efficacy is associated with stronger coupling between radiation and moist static energy at the storm scale. This combined increase in thermodynamic limits and storm-level efficacy underscores the importance of considering both PI and efficacy when projecting future TC risks, as focusing on PI alone may underestimate the degree of intensification under warming. Storm-level radiative feedbacks should therefore be incorporated into projections to improve the predictability of TC intensity responses to climate change and variability.