Regional variations in aerosol-temperature coupling over the Indo-Gangetic Plains and Central India: A vector autoregression analysis (2005–2023)

Abstract

This study investigates the complex interactions between aerosol absorption properties and maximum temperature during pre-monsoon seasons (2005–2023) across Indo-Gangetic Plains and Central India (21.5°–28.5° N, 69.5°–88.5° E). Utilising satellite-derived aerosol measurements from the Ozone Monitoring Instrument (OMI) and maximum surface temperature data from the India Meteorological Department (IMD), both spatial patterns and temporal evolution of aerosol-temperature coupling were analysed through correlation studies and vector autoregression (VAR) modelling. Our findings reveal distinct spatial gradients in aerosol distribution, with Aerosol Optical Depth (AOD) increasing west-to-east (0.35–0.93) and stronger absorption patterns in the eastern sector (Aerosol Absorption Optical Depth (AAOD): 0.037–0.092). Post-2018, the region experienced intensified Ultraviolet Aerosol Index (UVAI) and increased frequency of temperature extremes exceeding 40°C, with 2021 marking a peak of 162 high UVAI (>2) events. To investigate UVAI-temperature interactions, relative humidity and wind components were included in the VAR model with a consistent 2-day lag relationship. Our analysis revealed regionally distinct response patterns: the Primary Region (eastern Chhattisgarh-western Odisha) exhibits oscillatory temperature responses to UVAI shocks with multiple fluctuations persisting through day 10, with relative humidity functioning as a critical mediating factor and wind patterns establishing feedback mechanisms with aerosols. In contrast, the Secondary Region (eastern Uttar Pradesh) shows a smoother, monotonic temperature response with a more straightforward pathway from aerosol forcing to temperature response. Fire events are associated with only 6.1% of UVAI events (1.0–5.0), with declining fire association as UVAI intensity increases indicating substantial contributions from other sources, including industrial emissions and desert dust. These findings highlight the region-specific nature of aerosol-temperature coupling and its recent intensification, with important implications for understanding regional climate dynamics and air quality management strategies in South Asia.