Aerosol activation in updrafts

Markus Petters

University of Wyoming

Understanding cloud albedo is important for understanding the global heat budget. Processes affecting low cloud (stratus and stratocumulus) albedo are tightly linked to cloud microphysical processes. Twomey speculated that increases in the concentration of particles suspended in the atmosphere (aerosols) may prompt changes in climate. The process he was referring to involves particles that act as nuclei for condensation, the cloud condensation nuclei (CCN), and data which showed that their concentration is larger in airmasses contaminated by anthropogenic pollution. One factor that has motivated this work is the recognition that increases in CCN can lead to increases in cloud albedo, decreased solar radiation absorbed within the earth/atmosphere system, and cooling which counteracts warming of the climate system due to greenhouse gases.

Cloud droplet number concentration (CDNC) is a first order predictor of cloud albedo. The objective of the presented research is to predict cloud droplet number concentration (CDNC) based upon aircraft observations of CCN and updraft below cloud, and compare it to measurements of CDNC taken in cloud.