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: 5.509 IF 5.509
  • IF 5-year value: 5.689 IF 5-year 5.689
  • CiteScore value: 5.44 CiteScore 5.44
  • SNIP value: 1.519 SNIP 1.519
  • SJR value: 3.032 SJR 3.032
  • IPP value: 5.37 IPP 5.37
  • h5-index value: 86 h5-index 86
  • Scimago H index value: 161 Scimago H index 161
Discussion papers | Copyright
https://doi.org/10.5194/acp-2017-616
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 30 Aug 2017

Research article | 30 Aug 2017

Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal Atmospheric Chemistry and Physics (ACP) and is expected to appear here in due course.

Investigating the Impacts of Saharan Dust on Tropical Deep Convection Using Spectral Bin Microphysics

Matthew Gibbons1, Qilong Min1, and Jiwen Fan2 Matthew Gibbons et al.
  • 1Atmospheric Science Research Center, State University of New York, Albany NY 12203, USA
  • 2Earth Systems Analysis & Modeling, Pacific Northwest National Laboratory

Abstract. To better understand the impacts of dust aerosols on deep convective cloud (DCC) systems reported by previous observational studies, a case study in the tropical eastern Atlantic was investigated using the Weather Research and Forecasting (WRF) model coupled with a Spectral Bin Microphysics (SBM) model. A detailed set of ice nucleation parameterizations linking ice formation with aerosol particles have been implemented in the SBM. Increasing IN concentration in the dust cases results in the formation of more numerous small ice particles in the heterogeneous nucleation regime (between −5°C and −38°C) compared to the background (Clean) case. Convective updrafts are invigorated by increased latent heat release due to depositional growth and riming of these more numerous particles, which results in increased overshooting and higher convective core top heights. Competition between the more numerous particles for available water vapour during diffusional growth and available smaller crystals/drops during collection reduces particle growth rates and shifts precipitation formation to higher altitudes in the heterogeneous nucleation regime. Homogeneous ice formation is reduced in the dust cases as IN concentration is increased, due to more liquid drops converting to ice by freezing or riming before reaching −38°C and reduced peak supersaturation values from increased diffusional growth. Local IN activation in the stratiform regime contributes to increased cloudiness in the heterogeneous nucleation regime. A greater number of large snow particles form in the dust cases, which are transported from the core into the stratiform regime and sediment out quickly. Together with reduced homogeneous ice formation, fewer particles form within and/or are transported into the anvil regime. This shifts the stratiform/anvil cloud occurrence frequency to warmer temperatures and reduces anvil cloud extents. Total surface precipitation accumulation is reduced proportionally as IN concentration is increased, due to less efficient graupel formation reducing convective rain rates. Stratiform precipitation accumulation is increased due to greater snow formation and growth, but does not counteract the reduced convective accumulation. Riming efficiency in the dust cases is reduced due to smaller cloud ice crystals, resulting in smaller graupel sizes overall. Ice particle aggregation occurs earlier in the simulation and over a wider temperature range in the dust cases, which increases snow formation in the heterogeneous nucleation regime. Radar reflectivity values are increased in the dust cases at temperatures below 0°C in both the convective and stratiform regimes due to more large snow particles. More numerous small ice/graupel particles that form in the heterogeneous nucleation regime in the dust cases melt and reduce reflectivity values in the convective core near the surface, consistent with case study observations.

Download & links
Matthew Gibbons et al.
Interactive discussion
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement
Interactive discussion
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement
Matthew Gibbons et al.
Matthew Gibbons et al.
Viewed
Total article views: 388 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
260 117 11 388 7 11
  • HTML: 260
  • PDF: 117
  • XML: 11
  • Total: 388
  • BibTeX: 7
  • EndNote: 11
Views and downloads (calculated since 30 Aug 2017)
Cumulative views and downloads (calculated since 30 Aug 2017)
Viewed (geographical distribution)
Total article views: 386 (including HTML, PDF, and XML) Thereof 382 with geography defined and 4 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Cited
Saved
No saved metrics found.
Discussed
No discussed metrics found.
Latest update: 17 Jul 2018
Publications Copernicus
Download
Short summary
The effects of dust aerosols on ice formation within a tropical Atlantic thunderstorm system was investigated using a 3D weather model and compared with observations. Updated ice formation mechanisms directly connect available dust particles with ice particle formation.

The resulting clouds were lower and narrower and produced less rain at the surface compared to cleaner conditions, due to ice formation occurring at warmer temperatures. These results agree well with observed changes.
The effects of dust aerosols on ice formation within a tropical Atlantic thunderstorm system was...
Citation
Share