In:
Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 20, No. 3 ( 2020-02-07), p. 1591-1605
Abstract:
Abstract. The realistic representation of aerosol–cloud interactions is of primary
importance for accurate climate model projections. The investigation of these interactions in strongly contrasting clean and polluted atmospheric conditions
in the Amazon region has been one of the motivations for several field
campaigns, including the airborne “Aerosol, Cloud, Precipitation, and Radiation Interactions and Dynamics of Convective Cloud Systems–Cloud Processes of the Main Precipitation Systems in Brazil: A Contribution to Cloud Resolving Modeling and to the GPM (Global Precipitation Measurement) (ACRIDICON-CHUVA)” campaign based in Manaus, Brazil, in September 2014.
In this work we combine in situ and remotely sensed aerosol, cloud, and
atmospheric radiation data collected during ACRIDICON-CHUVA with regional,
online-coupled chemistry-transport simulations to evaluate the model's ability
to represent the indirect effects of biomass burning aerosol on cloud
microphysical and optical properties (droplet number concentration and effective radius). We found agreement between the modeled and observed median cloud droplet number
concentration (CDNC) for low values of CDNC, i.e., low levels of pollution. In
general, a linear relationship between modeled and observed CDNC with a slope
of 0.3 was found, which implies a systematic underestimation of modeled CDNC
when compared to measurements. Variability in cloud condensation nuclei (CCN)
number concentrations was also underestimated, and cloud droplet effective radii
(reff) were overestimated by the model. Modeled effective radius
profiles began to saturate around 500 CCN cm−3 at cloud base,
indicating an upper limit for the model sensitivity well below CCN
concentrations reached during the burning season in the Amazon Basin. Additional
CCN emitted from local fires did not cause a notable change in modeled cloud
droplet effective radii. Finally, we also evaluate a parameterization of CDNC at
cloud base using more readily available cloud microphysical properties, showing
that we are able to derive CDNC at cloud base from cloud-side remote-sensing
observations.
Type of Medium:
Online Resource
ISSN:
1680-7324
DOI:
10.5194/acp-20-1591-2020
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2020
detail.hit.zdb_id:
2092549-9
detail.hit.zdb_id:
2069847-1
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