Prof. William R. Cotton
Colorado State University
Abstract. My introduction to the study of aerosol impacts on convective clouds began in the late 1960’s when working on my PhD at first under the supervision of Dr. Larry Davis and later of Dr. Ron Lavoie at Penn State University. This was followed by my first post-PhD employment in 1970 in the NOAA Experimental Laboratory under Dr. Joanne Simpson where I worked on the Florida Area Cumulus Experiment(FACE). My research focused on modeling and observation of convective invigoration by AgI seeding of convective clouds. The idea was to enhance rainfall by convective invigoration rather than to seed clouds to enhance the cloud microphysical efficiency of clouds. In 1975 I joined the faculty in the Department of Atmospheric Science at Colorado State University(CSU), where I continued to do research on AgI seeding of convective clouds to enhance rainfall. But by the mid-1980’s funding in weather modification research had plummeted and my research focus changed to studies of mesoscale convective systems(MCSs), boundary layer stratocumulus, cirrus clouds, and other areas.
In 2002 I along with my CSU colleagues Sue van den Heever, Paul DeMott, Gustavo Carrio, and Toni Prenni participated in the NASA funded Cirrus Regional Study of Tropical Anvils and Cirrus Layer–Florida Area Cirrus Experiment (CRYSTAL–FACE). Subsequent to that field campaign we performed simulations of the effects of African dust on the intensity of the convective storms, cirrus anvil formation, and rainfall. That study catapulted me back to investigations of aerosol effects on convection storm intensity and rainfall for another 17 years. This included studies of hygroscopic aerosol impacts on urban convection over St. Louis, MO and Houston, TX, impacts on hail, on tornadoes, derecho-producing MCSs, and even tropical cyclones(TCs).
In this talk I will focus on what I have learned from those 50 years of research.