Absorbing aerosol influence on temperature maxima: An observation based study over India

Abstract

Increasing trends in summer-time temperature maxima (Tmax) over India, show consequent in creases in the intensity and frequency of heat wave events in recent years. Heat waves have been largely attributed to large-scale meteorological blocking, characterized by subsidence, clear skies and low soil moisture, in observational studies, or green house gas enhancements in model studies. While radiative effects of absorbing aerosols are acknowledged, the association of absorbing aerosols with temperature maxima has not been investigated comprehensively. In the current study, statistical tools (such as correlation and Granger causality) were applied to long term (1979–2013) satellite and ground based observations to evaluate in fuence of absorbing aerosols on Tmax in north-west India (Tmax-NW). Regional absorb ing aerosol index (AAI) in the north-west (AAI-NW) and central-India (AAI-CI) showed co-variability with Tmax-NW, implying connections to both lo cal and non-local absorbing aerosols. The effects persisted on seasonal and heat wave event scales, be coming stronger on heat wave days with presence of enhanced AAI loadings. Causal effects of AAI-NW and AAI-CI were identifed on Tmax-NW with a lag of 1–11 days, across multiple years, thereby establishing the infuence of absorbing aerosols on heat wave events. The absence of confounding effects of surface pres sure on these links suggests that, even during heat wave events linked to atmospheric blocking, absorbing aerosols can further enhance temperature maxima and related heatwave intensity.