Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

Journal metrics

  • IF value: 5.668 IF 5.668
  • IF 5-year value: 6.201 IF 5-year
    6.201
  • CiteScore value: 6.13 CiteScore
    6.13
  • SNIP value: 1.633 SNIP 1.633
  • IPP value: 5.91 IPP 5.91
  • SJR value: 2.938 SJR 2.938
  • Scimago H <br class='hide-on-tablet hide-on-mobile'>index value: 174 Scimago H
    index 174
  • h5-index value: 87 h5-index 87
Discussion papers
https://doi.org/10.5194/acp-2020-45
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/acp-2020-45
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 03 Feb 2020

Submitted as: research article | 03 Feb 2020

Review status
This preprint is currently under review for the journal ACP.

CCN characteristics during the Indian Summer Monsoon over a rain-shadow region

Venugopalan Nair Jayachandran, Mercy Varghese, Palani Murugavel, Kiran S. Todekar, Shivdas P. Bankar, Neelam Malap, Gurunule Dinesh, Pramod D. Safai, Jaya Rao, Mahen Konwar, Shivsai Dixit, and Thara V. Prabha Venugopalan Nair Jayachandran et al.
  • Indian Institute of Tropical Meteorology, Pune, India

Abstract. Continuous aerosol and Cloud Condensation Nuclei (CCN) measurements carried out at the ground observational facility situated in the rain-shadow region of the Indian sub-continent are illustrated. These observations were part of the Cloud-Aerosol Interaction Precipitation Enhancement EXperiment (CAIPEEX) during the Indian Summer Monsoon season (June to September) of 2018. Observations are classified as dry-continental (monsoon break) and wet-marine (monsoon active) according to air mass history. CCN concentrations measured for a range of supersaturations (0.2–1.2 %) are parameterized using Twomey's empirical relationship. CCN concentrations even at low (0.2 %) supersaturation (SS) were high (> 1,000 cm-3) during continental conditions associated with high black carbon (BC~2,000 ng m-3) and columnar aerosol loading. During the marine air mass conditions, CCN concentrations diminished to ~ 350 cm-3 at 0.3 % SS and low aerosol loading persisted (BC~900 ng m-3). High CCN activation fraction (AF) of ~ 0.55 (at 0.3 % SS) were observed before the monsoon rainfall, which reduced to ~ 0.15 during the monsoon and enhanced to ~ 0.32 after that. Mostly mono-modal aerosol number-size distribution (NSD) with a mean geometric mean diameter (GMD) of ~ 85 nm, with least (~ 9 %) contribution from nucleation mode (< 30 nm) particles persisted before monsoon, while multi-mode NSD with ~ 19 % of nucleation mode particles were found during the monsoon. Critical activation diameters (dcri) for 0.3 % SS were found to be about 72, 169, and 121 nm prior, during and, after the monsoon, respectively. The estimated dcri were inversely correlated to the AF, linearly up to 100 nm and non-linearly beyond that. The better association of CCN with aerosol absorption, and the concurrent accumulation mode particles during continental conditions, point to the possibility of aged (oxygenated) carbonaceous aerosols enhancing the CCN activity. The enhancement in CCN concentration and k-values during daytime along with the increase in absorption Angstrom exponent, indicate the freshly emitted local anthropogenic aerosols dominated by organics reducing the CCN AF during the monsoon. Best closure obtained using measured critical diameter, and ammonium sulfate composition during continental conditions emphasize the role of aged aerosols contributing to the accumulation mode, enhancing the CCN efficiency. But the over-estimation of CCN and less hygroscopicity of accumulation mode aerosols during the monsoon point to the significant role of size-dependent aerosol composition in CCN activity during the period.

Venugopalan Nair Jayachandran et al.

Interactive discussion

Status: open (until 30 Mar 2020)
Status: open (until 30 Mar 2020)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
[Subscribe to comment alert] Printer-friendly Version - Printer-friendly version Supplement - Supplement

Venugopalan Nair Jayachandran et al.

Venugopalan Nair Jayachandran et al.

Viewed

Total article views: 145 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
116 29 0 145 1 2
  • HTML: 116
  • PDF: 29
  • XML: 0
  • Total: 145
  • BibTeX: 1
  • EndNote: 2
Views and downloads (calculated since 03 Feb 2020)
Cumulative views and downloads (calculated since 03 Feb 2020)

Viewed (geographical distribution)

Total article views: 70 (including HTML, PDF, and XML) Thereof 69 with geography defined and 1 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 

Cited

Saved

No saved metrics found.

Discussed

No discussed metrics found.
Latest update: 18 Feb 2020
Publications Copernicus
Download
Short summary
Continuous aerosol and Cloud Condensation Nuclei measurements carried out at the ground observational facility of CAIPEEX campaign, situated in the rain-shadow region of the Indian sub-continent are illustrated. The variations in CCN characteristics within the monsoon period is investigated along with the aerosol physical and optical properties. The change in the dependency of CCN activity on aerosol size and composition due to the variations in air mass and meteorology is brought out.
Continuous aerosol and Cloud Condensation Nuclei measurements carried out at the ground...
Citation