Hysteresis Behaviors in East Asian Extreme Precipitation Frequency to CO2 Pathway

Abstract

AbstractUnderstanding regional hydro‐climatic extreme responses to CO2 pathways is fundamental to climate change mitigation and adaptation. This study evaluates responses of extreme precipitation frequency (R30mm: days with precipitation ≥30 mm) over East Asia to idealized CO2 forcing using the Community Earth System Model (CESM1). Under a symmetric increase (ramp‐up, +1% per year until quadrupling level) and decrease (ramp‐down, about −1% per year back to the present level) of CO2 concentrations, East Asian R30mm shows an asymmetric response with higher frequency during the ramp‐down period. This hysteresis behavior is found to be due to a northwestward propagating wave response to the El Niño‐like warming, which induces a three‐cell (positive‐negative‐positive) R30mm difference pattern from central equatorial Pacific to East Asia. Monthly analysis further reveals that this asymmetry has a seasonal locking, occurring during July–September only, constrained by the background precipitation climatology over the sub‐tropical western Pacific.