My major research interests are in cloud and aerosol physics. Here you can view a description of recent research projects. At the end, I've included highlights of older studies.

Although I retired in 2003, I have emeritus status at UIUC and I am currently involved in two NSF funded projects: 

Field Studies of Raindrop Axis Ratio Distributions a Video Disdrometer & Dual-Polarized Radar.  I am working with Prof. Bringi (CSU EE Dept) to develop models for interpreting how raindrop shapes are affected by collisions. Data are being obtained in Colorado, Okinawa and Indonesia.

Aircraft Studies of Charge-Enhanced Contact Ice Nucleation.  I am working with Harry Ochs to investigate ice formation in clouds during the Fall 2007 Ice in Cloud Experiment. We are using a sensitive electrometer system onboard the NCAR C-130 to help evaluate whether charge-enhanced contact ice nucleation is responsible for initial ice formation.

Contact Ken Beard | Past Research | Recent Publications and Theses

New modes of ice initiation include freezing of supercooled drizzle drops by collision with giant ice nuclei and freezing of supercooled cloud drops by capture of evaporation ice nuclei enhanced by electric charge.

Diagram of experiment to test the effectiveness of evaporation ice nuclei. Cloud drops are nebulized from cloud water, rain water or sea water and then charged and evaporated. The charged drop residues are drawn into the mixing chamber containing supercooled cloud drops formed on cloud condensation nuclei.

Organic material from the sea surface is being tested as a possible source of ice nuclei in maritime clouds.

Ken and volunteer (J Redden) about to obtain sea water samples courtesy of the U. S. Coast Guard, Westport, Washington.

Cloud drop charges in stratocumulus clouds were found to have over 100 electron units of positive charge at cloud top with comparable negative charge within convective elements. Measurements were made over Lake Michigan from the NCAR Electra in the Lake-ICE field campaign during winter 1997-98.

Plot of measured cloud water content (CWC), cloud drop concentration (N), and electrometer current (Ecur). as well as derived mean drop size (<d>) and mean drop charge (<q>). Scientists participating in the drop charge measurements included Ken Beard, Harry Ochs (ISWS) and Cynthia Twohy (NCAR).

In the upper chamber high-voltage electrodes deflect most drops, leaving a widely space pair that falls and collides in front of the cameras. An image is recorded of the drop trajectories and also the collision outcome just after collision. In this side view the second computer-controlled drop generator is behind the one shown. A second set of lights and another camera at 90û is used so that the true separation of a drop pair just before collision can be calculated.

Water is forced through the generator assembly and exits through an orifice as a liquid jet. Vibrations of the transducer produce capillary waves, causing the jet to separate into uniform drops. A pulse on the charging electrode is used to discharge a drop so that it can be separated from the drop stream. Collisions are produced between dissimilar size drops using two drop generators inclined toward each other at about 1/2 degree.

The observed interaction between small precipitation drops includes miss (M) and collision followed by bounce (B), coalescence (C), and temporary coalescence (T), also producing satellite drops, for example, one (T1) or two (T2).

Simplified collision outcomes for expts. of Czys for drop radii of R = 0.34 and r = 0.19 mm, arranged by expt. number with increasing relative charge, showing regions of coalescence, bounce and temporary coalescence in 25 equal cross sections by impact-angle range.

The growth of precipitation drops is limited by drop collisions that bounce apart. This reduced "coalescence efficiency" is shown below, as derived from our experiments.

Contours of the percentage of colliding drops that coalescence for sizes from 100 to 1000 micrometers (i.e., 0.1 to 1.0 mm), based on our data for freely-falling drops. The contoured formula was derived from the tendency of drops to bounce apart during the deformation phase of inelastic collisions. The data points and numbers are the measured coalescence efficiency for uncharged drops from five separate experiments.