Elsevier

Aeolian Research

Volume 13, June 2014, Pages 51-57
Aeolian Research

Synoptic-scale dust transport events in the southern Himalaya

https://doi.org/10.1016/j.aeolia.2014.03.008Get rights and content
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Highlights

  • Identified 275 days affected by synoptic-scale dust transport at NCO-P.

  • Thar desert is the predominant source of mineral dust reaching NCO-P.

  • Large enhancements in coarse aerosol number concentration (average: +689%).

  • Large enhancements in coarse aerosol mass concentration (average: +1086%).

  • Higher SSA values during synoptic-scale dust transport, ranging from 0.87 to 0.90.

Abstract

The variability of long-range dust transport events observed in the southern Himalaya and its relation with source areas have been studied thanks to five years’ continuous measurements which were carried out at the “Nepal Climate Observatory-Pyramid” (NCO-P, 27°57′N, 86°48′E), the highest Northern Hemisphere GAW-WMO global station sited at 5079 m a.s.l. in the high Khumbu valley (Nepal) on the southern Himalaya. During the period March 2006–February 2011, the analyses of the aerosol particle concentrations and LAGRANTO three-dimensional backward trajectories indicated the occurrence of 275 days affected by synoptic-scale dust transport, which account for 22.2% of the investigated period. The frequency of dust transport days (DTDs) showed a clear seasonal cycle, with the highest seasonal value observed during pre-monsoon season (33.5% of the pre-monsoon’s days are DTDs).

Large enhancements in coarse aerosol number concentration N1–10 (average: +689%) and mass PM1–10 (average: +1086%) were observed during the dust transport events as compared to the days without dust (dust-free days, DFDs). In addition, the single scattering albedo (SSA) also showed higher values, ranging from 0.87 to 0.90, during DTDs with respect to DFDs (0.80–0.87).

The predominant source of mineral dust reaching the measurement site was identified in the arid regions of the north-western Indian subcontinent (Thar desert), which accounted for 41.6% of the trajectories points associated with DTDs. Seasonal analysis also indicated that the winter season was significantly influenced by far western desert regions, such as North Africa and the Arabic Peninsula.

Keywords

Mineral dust
Synoptic scale transport
Himalaya
Atmospheric brown clouds
Aerosol number size distribution
Single scattering albedo

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