In the atmosphere, microphysics - the small-scale processes affecting cloud and precipitation particles such as their growth by condensation, evaporation, and melting - is a critical part of Earth’s weather and climate. Because it is impossible to simulate every cloud particle individually owing to their sheer number within even a small cloud, atmospheric models have to represent particle populations statistically using microphysics parameterization schemes. However, there are critical gaps in knowledge of the microphysical processes that act on particles, especially for atmospheric ice particles because of their wide variety and intricacy of their shapes. The difficulty of representing cloud and precipitation particle populations and fundamental knowledge gaps in microphysical processes both introduce important uncertainties into models that translate into uncertainty in weather forecasts and climate simulations. I will discuss several specific challenges related to these problems. To improve how cloud and precipitation particle populations are represented within microphysics schemes, a “particle-based” approach is advocated that addresses several limitations of traditional approaches and has recently gained traction as a tool for cloud modelling. Advances in observations, including laboratory studies, are argued to be essential for addressing critical gaps in knowledge of microphysical processes. I will also advocate using statistical modelling tools to improve how these observations are used to constrain microphysics schemes. Finally, a hierarchical approach will be outlined that combines the various pieces discussed in this talk, providing a possible blueprint for accelerating progress in how microphysics is represented in models.
Speaker Biography: Dr. Hugh Morrison studies cloud physics and dynamics, especially using numerical models. He grew up in Minnesota and got his B.S. at the University of Minnesota in 1997. He moved to Boulder, Colorado and received his M.S. in 2000 and Ph.D. in 2003 at the University of Colorado in Atmospheric Science. He then went to the National Center for Atmospheric Research (NCAR) as a post-doc in the Advanced Study Program. Hugh became a staff scientist at NCAR in 2008 and is currently a senior scientist in the Mesoscale and Microscale Meteorology Laboratory at NCAR. He is on sabbatical at UNSW until May 2020.