Development of a scheme for parameterizing the effects of cloud condensation nuclei on stratocumulus cloud albedo
- Colorado State Univ., Fort Collins, CO (United States)
The goal of this research is to develop a scheme for parameterizing the effects of varying concentrations of cloud condensation nuclei (CCN) on stratocumulus cloud albedo for use in global climate models. The challenges in achieving this goal are: CCNs are not a horizontally and vertically uniform species, but vary depending upon differential horizontal advection of differing CCN sources and upon local conditions (e.g., CCN formation by gas-to-particle conversion and cloud removal). CCNs are probably as variable as water vapor. The peak supersaturations that determine the activation of CCN and resultant aerosol and cloud droplet distributions are a function of cloud updraft and downdrafts on scales of a few hundred meters with magnitudes of a few meters per second. These scales cannot be represented properly either with large-scale grid-resolvable ascent rates of the order of 0.01 m/s or by eddy diffusion models. Cloud albedo is a strong function of the cloud macrostructure (holes, hills, troughs in cloud structure) and of the liquid water paths and aerosol/hydrometeor spectra. The aerosol/hydrometeor spectra, in turn, are not only a function of nucleation of cloud droplets at cloud base on resident CCN in the atmospheric boundary layer (ABL), but also the entrainment of CCN from above the capping inversion and the formation of drizzle. (Entrainment is one of the most difficult processes to model in the cloud-topped boundary layer [CTBL]). Drizzle formation is a complicated function of the CCN spectra, especially giant and ultra-giant aerosol, cloud liquid water contents, mixing processes, and the time scales of cloud drafts which are determined by the strengths and depths of cloud drafts.
- Research Organization:
- USDOE Office of Energy Research, Washington, DC (United States). Environmental Sciences Div.
- OSTI ID:
- 83164
- Report Number(s):
- CONF-940277-; ON: DE95009951; CNN: Contract NIGEC-91-S01; TRN: 95:003626-0023
- Resource Relation:
- Conference: Atmospheric radiation measurement science team meeting, Charleston, SC (United States), 28 Feb - 3 Mar 1994; Other Information: PBD: Apr 1995; Related Information: Is Part Of Proceedings of the Fourth Atmospheric Radiation Measurement (ARM) Science Team Meeting; PB: 373 p.
- Country of Publication:
- United States
- Language:
- English
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