What controls the quasi-decadal variability of tropical cyclone genesis in the western North Pacific in recent decades

Abstract Quasi-decadal variability (QDV) in tropical cyclone (TC) genesis (TCG) over the western North Pacific is a critical yet insufficiently explored aspect of TC climate variability. This study identified distinct QDV in TCG during June–October, characterized by two leading empirical orthogonal function (EOF) modes. The first mode (EOF1) exhibits a north-south dipole pattern and is indirectly modulated by solar variability through circulation anomalies over the mid-latitude North Pacific. The second mode (EOF2) exhibits a west-east dipole pattern and is driven by internal variability linked to the Pacific Quasi-decadal Oscillation (PQDO), represented by sea surface temperature anomalies (SSTa) in the tropical central Pacific (TCP). Both modes strongly correlate ( r > 0.83) with key regional indicators: regional mean 200 hPa geopotential height (150° E–180°, 34° N–44° N) and SSTa (164° E–164° W, 10° S–10° N). The direct influence of solar variability on TCG is weak, primarily due to offsetting effects of solar-associated in-phase SSTa between the mid-latitude North Pacific and the TCP. Solar variability and PQDO affect TCG primarily through dynamic factors, explaining about 85% of TCG changes, with relative vorticity contributing around 30%. These findings highlight the complex interplay between solar and internal forcings in modulating TCG, providing valuable insights for improving long-term TC forecasts.