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Abstract <p>This study presents a comparative analysis of aerosol black carbon (BC) characteristics during 2015–2019 at two tropical locations in Southern India: Thumba (a coastal semi-urban site) and Ponmudi (a rural highland station) in the Western Ghats. These sites, separated by ~1 km in elevation and 35 km in distance, experience similar synoptic-scale air masses but different mesoscale meteorological conditions. The analysis revealed substantial heterogeneity with a higher annual mean BC at Thumba (2375±1492 ng m<sup>−3</sup>) than at Ponmudi (1143±794 ng m<sup>−3</sup>). Notwithstanding the observed similar annual pattern (though with varying BC amplitudes) at two sites, contrasting diurnal BC patterns highlighted the role of short-scale driver processes. Diurnally, BC displayed a ‘two-peaks and a midday-trough’ pattern at Thumba, driven by local atmospheric boundary layer dynamics and sea-land breeze interactions. Ponmudi exhibited a distinct ‘afternoon BC peak followed by a plateau’, which can be attributed to mesoscale transport dynamics, including convective uplift of aerosols and transport by sea-breeze from the coastal region towards the hills, and their further elevation by upslope winds to the hilltop. The WRF-Chem model simulations supported the above mechanism, highlighting the complex interactions of topography, local meteorology, transport pathways, and mesoscale processes in controlling BC variability in tropical environments.</p> Research highlights <p><UnorderedList Mark="Bullet"> <ItemContent> <p>Multi-year BC measurements from two nearby tropical locations with contrasting environments highlighted substantial heterogeneity.</p> </ItemContent> <ItemContent> <p>Similar annual patterns, but higher BC (38–85%) at the coastal semi-urban location compared to the highland site.</p> </ItemContent> <ItemContent> <p>BC variability indicated the control of varying synoptic and mesoscale processes.</p> </ItemContent> <ItemContent> <p>The interplay of ABL evolution and sea–land/valley–hill circulations drives contrasting diurnal patterns between the stations.</p> </ItemContent> <ItemContent> <p>Potential interaction of sea and valley breezes contributed to the daytime BC peak at Ponmudi.</p> </ItemContent> </UnorderedList></p>

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On the variability of black carbon over coastal and highland tropical environments in Southern India

  • 期刊论文

  • 发表日期：

    2026年5月4日

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  • Sobhan Kumar Kompalli,
  • Anas Ibnu Basheer,
  • Revathy S Ajayakumar,
  • Vijayakumar S Nair,
  • S Suresh Babu

摘要

Abstract

This study presents a comparative analysis of aerosol black carbon (BC) characteristics during 2015–2019 at two tropical locations in Southern India: Thumba (a coastal semi-urban site) and Ponmudi (a rural highland station) in the Western Ghats. These sites, separated by ~1 km in elevation and 35 km in distance, experience similar synoptic-scale air masses but different mesoscale meteorological conditions. The analysis revealed substantial heterogeneity with a higher annual mean BC at Thumba (2375±1492 ng m−3) than at Ponmudi (1143±794 ng m−3). Notwithstanding the observed similar annual pattern (though with varying BC amplitudes) at two sites, contrasting diurnal BC patterns highlighted the role of short-scale driver processes. Diurnally, BC displayed a ‘two-peaks and a midday-trough’ pattern at Thumba, driven by local atmospheric boundary layer dynamics and sea-land breeze interactions. Ponmudi exhibited a distinct ‘afternoon BC peak followed by a plateau’, which can be attributed to mesoscale transport dynamics, including convective uplift of aerosols and transport by sea-breeze from the coastal region towards the hills, and their further elevation by upslope winds to the hilltop. The WRF-Chem model simulations supported the above mechanism, highlighting the complex interactions of topography, local meteorology, transport pathways, and mesoscale processes in controlling BC variability in tropical environments.

Research highlights

Multi-year BC measurements from two nearby tropical locations with contrasting environments highlighted substantial heterogeneity.

Similar annual patterns, but higher BC (38–85%) at the coastal semi-urban location compared to the highland site.

BC variability indicated the control of varying synoptic and mesoscale processes.

The interplay of ABL evolution and sea–land/valley–hill circulations drives contrasting diurnal patterns between the stations.

Potential interaction of sea and valley breezes contributed to the daytime BC peak at Ponmudi.