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Title: Investigating the impacts of Saharan dust on tropical deep convection using spectral bin microphysics

Journal Article · · Atmospheric Chemistry and Physics (Online)
; ;

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 has been implemented in the SBM. Increasing ice nuclei (IN) concentration in the dust cases results in the formation of more numerous small ice particles in the heterogeneous nucleation regime (between −5 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 vapor during diffusional growth and available smaller crystals and/or drops during collection reduces particle growth rates and shifts precipitation formation to higher altitudes 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, the stratiform and/or anvil cloud occurrence shifts frequency to warmer temperatures and reduces anvil cloud extents. Total surface precipitation accumulation is reduced proportionally as IN concentration is increased; though the stratiform precipitation accumulation is increased due to greater snow formation and growth, it does not counteract the reduced convective accumulation due to less efficient graupel formation. 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, and reduced in the convective core near the surface due to melt of small ice or graupel particles, consistent with case study observations.

Research Organization:
Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
Sponsoring Organization:
Office of Science (SC), Biological and Environmental Research (BER). Earth and Environmental Systems Science Division; National Science Foundation (NSF); National Oceanic and Atmospheric Administration (NOAA), Washington, DC (United States)
Grant/Contract Number:
FG02-03ER63531; AC0676RLO1830; AGS-1138495; PIRE-1545917; AC0576RLO1830; NA17AE1625; NA17AE1623
OSTI ID:
1466060
Alternate ID(s):
OSTI ID: 1468614
Report Number(s):
PNNL-SA-134455
Journal Information:
Atmospheric Chemistry and Physics (Online), Journal Name: Atmospheric Chemistry and Physics (Online) Vol. 18 Journal Issue: 16; ISSN 1680-7324
Publisher:
Copernicus Publications, EGUCopyright Statement
Country of Publication:
Germany
Language:
English
Citation Metrics:
Cited by: 15 works
Citation information provided by
Web of Science

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