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<p>The present study examines a low intensity dust transport episode observed over the central Himalayan region (Nainital) during 15th-20th May 2025 using an integrated framework comprising ground-based lidar observations, surface meteorological and PM<sub>2.5</sub> measurements, satellite datasets, and reanalysis products. Lidar measurements captured the diurnal evolution of the dust layer, showing enhanced aerosol backscatters largely confined to below ~ 1.0&#xa0;km, with episodic deepening of the mixed layer during daytime hours. MODIS true color imagery revealed the gradual eastward transport of mineral dust from the Thar Desert and adjoining arid regions of northwest India toward the Himalayan foothills. Although the episode was of low intensity, surface PM<sub>2.5</sub> concentrations increased by a factor of ~ 1.5–2 during peak days in comparison to pre-event conditions, while MODIS AOD showed moderate enhancement (~ 0.4–0.6). Near-surface wind speeds increased to ~ 3.0–3.5&#xa0;ms<sup>−1</sup>, accompanied by enhanced turbulent kinetic energy (~ 2.5–3.0 m<sup>2</sup>s<sup>−2</sup>), stronger negative momentum flux (-0.6 to -1.0&#xa0;Pa) and increased sensible heat flux (~ 350–400 Wm<sup>−2</sup>), indicating increased boundary-layer mixing during the dust period. Daytime (~ 25–26&#xa0;°C) and nighttime (~ 21–22&#xa0;°C) temperature slightly increased during the mild dust episode due to warm air advection and enhanced boundary layer mixing. Reanalysis and trajectory analyses corroborate the synoptic-scale transport pathways and accumulation of dust along the Himalayan foothills. The results demonstrate that even mild dust episodes can measurably perturb aerosol loading, boundary-layer dynamics, and radiative processes over mountainous terrain. These findings highlight the importance of documenting such events for improving regional air quality assessments and for better representing aerosol processes in atmospheric and climate models over the Himalayan region.</p>

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Variation of Atmospheric Properties over the Central Himalaya During a Low-Intensity Dust Episode: Insights from Lidar and Auxiliary Observations

  • 期刊论文

  • 发表日期：

    2026年5月25日

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  • Shishir Kumar Singh,
  • Narendra Singh,
  • Ashish Kumar,
  • Subhajit Debnath,
  • Mayank Kumar Chauhan,
  • Vikas Rawat,
  • Chandra Prakash,
  • Jayshreekar Pant,
  • B. Krishna Reddy

摘要

The present study examines a low intensity dust transport episode observed over the central Himalayan region (Nainital) during 15th-20th May 2025 using an integrated framework comprising ground-based lidar observations, surface meteorological and PM2.5 measurements, satellite datasets, and reanalysis products. Lidar measurements captured the diurnal evolution of the dust layer, showing enhanced aerosol backscatters largely confined to below ~ 1.0 km, with episodic deepening of the mixed layer during daytime hours. MODIS true color imagery revealed the gradual eastward transport of mineral dust from the Thar Desert and adjoining arid regions of northwest India toward the Himalayan foothills. Although the episode was of low intensity, surface PM2.5 concentrations increased by a factor of ~ 1.5–2 during peak days in comparison to pre-event conditions, while MODIS AOD showed moderate enhancement (~ 0.4–0.6). Near-surface wind speeds increased to ~ 3.0–3.5 ms−1, accompanied by enhanced turbulent kinetic energy (~ 2.5–3.0 m2s−2), stronger negative momentum flux (-0.6 to -1.0 Pa) and increased sensible heat flux (~ 350–400 Wm−2), indicating increased boundary-layer mixing during the dust period. Daytime (~ 25–26 °C) and nighttime (~ 21–22 °C) temperature slightly increased during the mild dust episode due to warm air advection and enhanced boundary layer mixing. Reanalysis and trajectory analyses corroborate the synoptic-scale transport pathways and accumulation of dust along the Himalayan foothills. The results demonstrate that even mild dust episodes can measurably perturb aerosol loading, boundary-layer dynamics, and radiative processes over mountainous terrain. These findings highlight the importance of documenting such events for improving regional air quality assessments and for better representing aerosol processes in atmospheric and climate models over the Himalayan region.