Mutating ENSO Impact on Northwest Pacific Tropical Cyclones Under Global Warming

A prominent feature of the western North Pacific tropical cyclone genesis frequency (TCGF) anomaly in response to El Nino-Southern Oscillation (ENSO) is a distinct west-east dipole structure in the present-day (PD) climate. Here, large ensemble high-resolution simulations show that the current dipole may transform into a monopole under global warming (GW). In the PD climate, the ENSO-induced dipole effect on TCGF is mainly observed in late autumn. However, GW accelerates this effect into the summer by amplifying atmospheric circulation anomalies. Consequently, this leads to a significant increase in the coastal TCGF during the development phase of El Nino under GW. Meanwhile, it weakens the anomalous anticyclonic circulation during late autumn, leading to an increase in coastal TCGF during the mature phase of El Nino, and vice versa. Therefore, the combined effect suggests a potential trend toward spatial homogenization during ENSO phases under GW. El Nino-Southern Oscillation (ENSO) typically has a dipole impact on tropical cyclone genesis frequency (TCGF) over the western North Pacific (WNP) in the current climate. During the warm phase of ENSO, there is a significant increase in TCGF over the southeastern part of the WNP (open-sea region), but a decrease over its northwestern part (coastal region). The opposite pattern occurs during the cold phase of ENSO. However, under global warming (GW), this dipole pattern could transform into a basin-uniform change in TCGF. In the present climate, ENSO primarily affects TCGF only over the open-sea region during the summer (June to August) but causes a dipole pattern of TCGF anomalies in the autumn (September-November). The summer TCGF over the coastal region is less influenced by ENSO. Hence, the dipole pattern of TCGF anomalies from summer to autumn is mainly contributed by the anomaly in autumn TCGF over the coastal region. However, GW could extend the ENSO impact on coastal TCGF to summer. Therefore, the TCGF anomaly in summer offsets the opposite TCGF anomaly in autumn over the coastal region during the ENSO phase, resulting in a more consistent change in TCGF anomalies across the region under GW. The dipole pattern of tropical cyclone genesis frequency (TCGF) during June-November in response to El Nino-Southern Oscillation (ENSO) over the western North Pacific may transform into a monopole under global warming (GW)The present-day dipole of TCGF anomaly is mainly observed in late-autumn, while GW accelerates this impact to summerGW amplifies cyclonic (anticyclonic) circulation during warm (cold) ENSO phases, causing a basin-uniform TCGF change