Connecting Vertical Velocity and Microphysics at the Subgrid Scale in General Circulation Models (GCMs)

University Of Wisconsin-Milwaukee, Milwaukee WI

Investigators

Abstract

This research addresses two atmospheric boundary layer parameterization problems in weather and climate models: coupling turbulence with cloud fields and the inclusion of subgrid variability. The focus of this research will be on marine stratocumulus clouds. The approach relies on probability density functions (PDFs) and "Latin hypercube sampling" to introduce stochastic randomness into the solutions to achieve the effects of subgrid variability in coarser parameterizations without the explicit complexity of so-called "super-parameterization" approaches (that explicitly represent the complexity but over a small subset of the region). This approach should make the methodology generally applicable to other microphysics codes and relatively easy to retrofit. These techniques will be implemented in one global circulation model (GCM) to test the scaling of locally accurate microphysics to large GCM grid boxes (tens to hundreds of kilometers on a side) via the PDF. The goal is to avoid microphysical tuning that depends on the grid box size. GCM integrations will be performed to test the impact of the new parameterizations. Intellectual Merit: The methodology, which has been implemented in single-column models with success will be extended to GCM parameterizations in a generalized fashion. The extension of the statistically-based approach to a GCM parameterization and its testing amounts to a culmination of past research in this area. The expected broader impacts of this research are the training of a graduate student, wide dissemination of research results on the web and in the academic literature, and improved simulation of weather and climate in not just the test GCM, but a wide range of atmospheric models.