Atmospheric Radiation Measurement Climate Research Facility US Department of Energy

ndrop > Droplet number concentrationVAP Type(s) > Baseline

Cloud droplet number concentration is an important factor in understanding aerosol-cloud interactions. As aerosol concentration increases, it is expected that droplet number concentration (Nd) will increase and droplet size will decrease, for a given liquid water path. This will greatly affect cloud albedo as smaller droplets reflect more shortwave radiation; however, the magnitude and variability of these processes under different environmental conditions is still uncertain. McComiskey et al. (2009) have implemented a method, based on Boers and Mitchell (1994), for calculating Nd from ground-based remote-sensing measurements of optical depth and liquid water path.

They show that the magnitude of the aerosol-cloud interactions (ACI) varies with a range of factors, including the relative value of the cloud liquid water path (LWP), the aerosol size distribution, and the cloud updraft velocity. Estimates of Nd under a range of cloud types and conditions and at a variety of sites are needed to further quantify the impacts of aerosol-cloud interactions. In order to provide data sets for studying aerosol-cloud interactions, the McComiskey et al. (2009) method was implemented as the Droplet Number Concentration (NDROP) value-added product (VAP).


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McComiskey A, G Feingold, AS Frisch, DD Turner, MA Miller, JC Chiu, Q Min, and JA Ogren. 2009. "An assessment of aerosol‐cloud interactions in marine stratus clouds based on surface remote sensing." Journal of Geophysical Research – Atmospheres, 114(D9), D09203, 10.1029/2008jd011006.

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Damao Zhang
Pacific Northwest National Laboratory

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