Multi-timescale Variabilities and Interactions in the Global Monsoon

Abstract A long-standing question in atmospheric science concerns how, and to what extent, climate variabilities across different timescales interact to shape global weather and climate extremes. Here we address this issue through a quantitative framework that integrates both large-scale climate controls and upscale feedback processes. Coherent co-variability across multiple timescales appears throughout the global monsoon (GM) domain. Land precipitation on the interannual timescale exhibits a coherent in-phase relationship across all the sub-monsoon systems, largely governed by El Niño-Southern Oscillation (ENSO). Meanwhile, Madden-Julian Oscillation (MJO)-related precipitation accounts for about 30–65% of total intraseasonal precipitation variability across the sub-monsoon regions. Significant positive correlations are found between the interannual variability (IAV) and the intensity of the intraseasonal oscillation (ISO) and between the ISO and the intensity of synoptic-scale variability (SSV) across the entire GM domain, indicating a large-scale control of lower-frequency modes to higher-frequency variabilities. It is further demonstrated that higher-frequency variabilities (e.g., SSV and ISO) exert marked upscale feedback to lower-frequency modes through nonlinear rectification of condensational heating. About 90% of extreme precipitation days occur during the active phase of the ISO across the GM domain, laying a foundation for sub-seasonal prediction of weather and climate extremes weeks and even months ahead.