2024年5-6月印度高温热浪特征及成因分析OA

During May and June 2024,India experienced a severe,widespread,and persistent heatwave event,with some regions enduring more than 50 consecutive days of extreme heat.The event resulted in at least 46 repor-ted fatalities in May alone and is considered the longest heatwave recorded to date.Understanding the characteris-tics and driving mechanisms of this extreme event is therefore critical for improving early warning systems and enhancing societal resilience for future heat extremes.This study provides a comprehensive analysis of the spatio-temporal characteristics of the May-June 2024 heatwave over India and investigates its underlying meteorological drivers.Heatwaves are identified using the excess heat factor(EHF)index,and their features are quantified using four indices:heatwave number,frequency,duration,and amplitude.To diagnose the causal mechanisms,a multi-parameter approach is employed,examining large-scale and regional atmospheric fields,including 500 hPa geopo-tential height,850 hPa wind patterns,zonal-and meridional-mean vertical circulation,surface radiation components(downward and upward shortwave radiation),surface energy fluxes(sensible and latent heat),and near-surface variables such as 2 m air temperature and relative humidity. The results reveal a strong coupling between large-scale atmospheric circulation anomalies and local land-at-mosphere processes.First,the subtropical high-pressure ridge,identified by the 588 dagpm contour,established over southern India unusually early in early May and subsequently expanded northward through late May and June.This anomalous persistence induced sustained subsidence,clear-sky conditions,and enhanced solar heating,contributing to the exceptional duration of the heatwave.Second,anomalous circulation patterns played a critical role:dry continental air intrusions from Central Asia increased heat stress over northern India in early May,while the convergence of warm,moist air from the Bay of Bengal and the Arabian Sea produced oppressive humid heat conditions western and southern regions by mid-May.In June,topographic modulation of pre-monsoon flow along the southern flank of the Qinghai-Xizang Plateau further shaped the heatwave evolution.Third,surface energy bal-ance analysis highlights key amplifying mechanisms.Over northern India,enhanced downward shortwave radiation combined with reduced upward shortwave radiation resulted in substantial net surface energy accumulation.Con-currently,suppressed latent heat flux and increased sensible heat flux limited evaporative cooling,directly elevating near-surface air temperatures.While low humidity in northern India intensified thermal aridity,higher hu-midity in southern regions amplified perceived heat stress despite slightly lower air temperatures. Overall,the extreme and prolonged heatwave during May-June 2024 resulted from the compound effects of 1)an anomalously strong and persistent subtropical high,2)circulation-driven transport of dry continental air and altered moisture pathways,3)suppression of monsoon onset under unfavorable multi-level wind anomalies,and 4)land-atmosphere feedbacks associated with surface energy partitioning and soil moisture deficits.This study ad-vances the understanding of heatwave dynamics in South Asia and underscores the need to integrate circulation a-nomalies,moisture transport,and surface processes in heatwave prediction and impact assessment frameworks.