This postdoctoral research award is for an idealized numerical modeling study of self-critical behavior in tropical clouds. Self-critical behavior in this context refers to the phenomena whereby clouds grow quickly into rainfall producers when their immediate surroundings reach a certain moisture level. It is established on a large scale that this occurs in order to prevent the atmosphere from being overly moistened. However, the research in this award is aimed at discovering what role self-criticality plays on an individual cloud level. A successful outcome from this award would be increased understanding of cloud processes in order to improve weather and climate models. The researcher also plans to teach and advise undergraduate students with the goal of influencing more of them to pursue science careers.
This study will be carried out using the Ocean-Land-Atmosphere Model (OLAM). The researcher will address two topics related to the growth of individual clouds, cloud microphysics and gravity waves. The first hypothesis of the work is that certain cloud microphysical processes become efficient around the critical moisture value. To test this hypothesis, the researcher will turn off the depositional process in the model, the process whereby water vapor is transferred to ice crystals. If the hypothesis is correct, the critical value should break down or shift. The second hypothesis is that as the rain rate from the cloud increases the amplitude of the created gravity waves will also increase. This would in turn create more clouds and rainfall and force the system back to a stable state. This hypothesis will be tested by running the model with a short time step and following the waves and how they interact with nearby clouds. This postdoctoral fellowship will be split between the University of Melbourne in Australia and University of Miami Rosenstiel School of Marine and Atmospheric Science. This award was supported with funding from the Office of International and Integrative Activities.
