Kinetic limitations on cloud droplet formation and impact on cloud albedo

By A. Nenes, Steven Ghan, Hayder Abdul-Razzak, P. Chuang, John H. Seinfeld. 2001

215 citations recorded by the source corpus.

Under certain conditions mass transfer limitations on the growth of cloud condensation nuclei (CCN) may have a significant impact on the number of droplets that can form in a cloud. The assumption that particles remain in equilibrium until activated may therefore not always be appropriate for aerosol populations existing in the atmosphere. This work identifies three mechanisms that lead to kinetic limitations, the effect of which on activated cloud droplet number and cloud albedo is assessed using a one-dimensional cloud parcel model with detailed microphysics for a variety of aerosol size distributions and updraft velocities. In assessing the effect of kinetic limitations, we have assumed as cloud droplets not only those that are strictly activated (as dictated by classical Köhler theory), but also unactivated drops large enough to have an impact on cloud optical properties. Aerosol number concentration is found to be the key parameter that controls the significance of kinetic effects. Simulations indicate that the equilibrium assumption leads to an overprediction of droplet number by less than 10% for marine aerosol; this overprediction can exceed 40% for urban type aerosol. Overall, the effect of kinetic limitations on cloud albedo can be considered important when equilibrium activation theory consistently overpredicts droplet number by more than 10%. The maximum change in cloud albedo as a result of kinetic limitations is less than 0.005 for cases such as marine aerosol; however albedo differences can exceed 0.1 under more polluted conditions. Kinetic limitations are thus not expected to be climatically significant on a global scale, but can regionally have a large impact on cloud albedo.

Subfields: Atmospheric Science, Global and Planetary Change

View Paper: https://www.semanticscholar.org/paper/dac0fd36a3b98226391a296e4cef6673075f9e87

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Citations in the corpus

Aerosol Mixing State: Measurements, Modeling, and Impacts (2019, background): “Neglecting kinetic effects (Nenes et al., 2001), the CCN concentration is then the number concentration of particles for whom the environmental supersaturation is higher than their critical supersaturation.”
A Continuous-Flow Streamwise Thermal-Gradient CCN Chamber for Atmospheric Measurements (2005, methodology): “A thorough review and assessment of the performance of various CCN instruments is presented by Nenes et al. (2001a).”
Parameterization of cloud droplet formation in global climate models (2003, background): “[15] Equation (7) represents the CCN spectrum of the aerosol; once the maximum parcel supersaturation, smax, is known, the number of CCN that will activate into drops, Nd, is given by Nd ¼ Fs smaxð Þ: ð8Þ”
Influence of dust composition on cloud droplet formation (2006, background): “However, we initially equilibrate aerosol at an RH of 97% rather than 100% (Ghan et al., 1998) to account for kinetic limitations near the cloud base (Nenes et al., 2001; Phinney et al., 2003).”
A New Double-Moment Microphysics Parameterization for Application in Cloud and Climate Models. Part I: Description (2005, methodology): “Additional work will focus on improving these parameterizations by incorporating laboratory measurements and detailed numerical simulations (e.g., Nenes et al. 2001).”
Continued development of a cloud droplet formation parameterization for global climate models (2005, methodology): “The chemical complexity and heterogeneity of global aerosol can have an important effect on activation and must be included in aerosol-cloud interaction studies (e.g., Nenes et al., 2001; Rissman et al., 2002; Lance et al., 2004).”
Aerosol- and updraft-limited regimes of cloud droplet formation: influence of particle number, size and hygroscopicity on the activation of cloud condensation nuclei (CCN) (2009, background): “In most earlier studies of cloud droplet formation, the number concentration of aerosol particles did not exceed 10 4 cm−3 (e.g. Hjelmfelt et al., 1978; Hegg, 1999; Nenes et al., 2001; Feingold, 2003; Lance et al., 2004; Lohmann et al., 2004; Ervens et al., 2005; Segal and Khain, 2006; Kivekas et al”
On the effect of dust particles on global cloud condensation nuclei and cloud droplet number (2011, background): “Giant nuclei following FHH theory do not grow significantly after activation and therefore are kinetically limited by the inertial mechanism [Nenes et al., 2001]; indeed, Dc/Ddry < 2 for most atmospherically relevant combinations of AFHH and BFHH [Kumar et al., 2009b], where Dc is the critical wet…”