Updraft velocity

During melting, the air curtain should efficiently direct fume towards the exhaust off-take without allowing recirculation within the enclosure. The air curtain design should therefore also consider the fume trajectory when a lower updraft velocity from melting is experienced. 

Similar to N50, we also show the number concentrations between 100 and 500 nm in diameter (Ni00), representing CCNs for lower updraft velocity clouds, and a rough estimate of the number concentration in accumulation mode as the Hoppel minimum between the Aitken and the accumulation modes is often around 100 nm of diameter. 

Key variables interstitial/activated fraction, CCN size/composition, cloud drop size/number/liquid water content (LWC), cloud optical depth (COD), and updraft velocity... 

Note that supersaturations depend both on the macroscale cloud dynamics represented by the cloud updraft velocities (larger updrafts result in higher supersaturations) and on the... 

TABLE 17.3 Updraft Velocities and Maximum Supersaturations for Clouds and Fogs... 

Cloud Type Updraft Velocity, ms-1 Maximum Supersaturation, % Reference... 

The CCN behavior of ambient particles can be measured by drawing an air sample into an instrument in which the particles are subjected to a known supersaturation, a so-called CCN counter (Nenes et al. 2001). If the size distribution and chemical composition of the ambient particles are simultaneously measured, then the measured CCN behavior can be compared to that predicted by Kohler theory on the basis of their size and composition. Such a comparison can be termed a CCN closure, that is, an assessment of the extent to which measured CCN activation can be predicted theoretically [see, for example, VanReken et al. (2003), Ghan et al. (2006), and Rissman et al. (2006)]. The next level of evaluation is an aerosol-cloud drop closure, in which a cloud parcel model, which predicts cloud drop concentration using observed ambient aerosol concentration, size distribution, cloud updraft velocity, and thermodynamic state, is evaluated against direct airborne measurements of cloud droplet number concentration as a function of altitude above cloud base. The predicted activation behavior can also be evaluated by independent measurements by a CCN instrument on board the aircraft. Such an aerosol-cloud drop closure was carried out by Conant et al. (2004) for warm cumulus clouds in Florida. 

The microphysics of the cloud will be represented in terms of the liquid water content, w, rainfall intensity po, updraft velocity w, cloud depth he, and cloud cross-sectional area A. 

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