arXiv subjects

Wuqiushi Yao

Publications and source records attributed to Wuqiushi Yao.

3 recordsLinked to original sources

arXiv2026

Modulation of the tropical meridional circulation by the Madden-Julian Oscillation

The Hadley circulation is Earth's dominant tropical overturning circulation, regulating atmospheric energy transport, tropical rainfall, and subtropical aridity. Although its variability has been extensively studied on seasonal to decadal climate-change timescales, its subseasonal behaviour remains poorly understood. Here we show that the Madden-Julian Oscillation (MJO), the leading mode of tropical intraseasonal variability, systematically modulates the Hadley circulation and influences global hydroclimate variability. Using reanalysis data and dynamical diagnostics, we identify a robust hemispherically asymmetric Hadley circulation anomaly associated with active MJO events, with amplitudes comparable to the climatological intraseasonal variability of the Hadley circulation. Breaking down the dynamical components reveals that the response is primarily maintained by latent heating associated with moist convection, while the overturning strength is driven by interhemispheric moisture gradients. Lead-lag analyses further show that the Hadley circulation lags the MJO by 4-15 days, indicating that MJO convection may drive overturning adjustments on subseasonal timescales. This coupled MJO-Hadley circulation state reveals a previously overlooked pathway linking tropical intraseasonal oscillations, meridional circulation and the hydrological cycle.

physics.ao-ph↗

arXiv2025

Predictability of Storms in an Idealized Climate Revealed by Machine Learning

The midlatitude climate and weather are shaped by storms, yet the factors governing their predictability remain insufficiently understood. Here, we use a Convolutional Neural Network (CNN) to predict and quantify uncertainty in the intensity growth and trajectory of over 200,000 storms simulated in a 200-year aquaplanet GCM. This idealized framework provides a controlled climate background for isolating factors that govern predictability. Results show that storm intensity is less predictable than trajectory. Strong baroclinicity accelerates storm intensification and reduces its predictability, consistent with theory. Crucially, enhanced jet meanders further degrade forecast skill, revealing a synoptic source of uncertainty. Using sensitivity maps from explainable AI, we find that the error growth rate is nearly doubled by the more meandering structure. These findings highlight the potential of machine learning for advancing understanding of predictability and its governing mechanisms.

physics.ao-ph↗

arXiv2025

Rotational Flow Dominates Abrupt Seasonal Change in Zonally Asymmetric Tropical Meridional Circulation

The seasonality of the tropical meridional circulation evolves differently across different regions, governs the onset and retreat of monsoons and migration of tropical precipitation, thereby influencing agricultural productivity and disaster preparedness in the tropics and subtropics. By defining a pseudo meridional overturning streamfunction (Ψpseudo) and defining a new vector-type, dual-component index (ASCI), we diagnose zonally asymmetric abrupt seasonal change (ASC) of tropical meridional circulation. Ψpseudo converges to traditional, meridional overturning streamfunction (Ψm) after being averaged over a zonal circle around any latitude. By applying the Helmholtz decomposition to horizontal velocity fields so as to decompose Ψpseudo into rotational and divergent components, we quantitatively compare the contributions of horizontally rotational and divergent flows to the abrupt seasonal change. We find that the zonal sectors associated with strong deep convection exhibit the most pronounced ASC of tropical meridional circulation, and all of subregions exhibiting ASC contain landmass with low heat inertia. Particularly, in contrast to the case of zonally symmetric Hadley cell, rotational flow, rather than the thermal-direct divergent flow, dominates the zonally asymmetric ASC in the tropics, although the divergent flow also contributes to the ASC over the zonal sectors associated with deep convection. We suggest that the interplay between tropical Rossby-type eddies with extratropical eddies and tropical circulation is essential to the zonally asymmetric ASC of tropical Hadley circulation.

physics.ao-ph↗