Observations and Modeling of Orographic Cumulus Development Using Digital Imaging and Data Cataloguing

Arizona State University, Scottsdale AZ

Investigators

Abstract

This project will focus on the development of orographic cumulus, and in particular, the transition from shallow to deep convection and the accompanying modification of the thermodynamic profile. The formation of orographic cumulus over in the desert southwest offers an ideal test environment to explore these issues. The convection develops over the tops of the mountains in generally clear air, so the initial location is well defined. One can sample the pre-cloud environment and characterize modifications due to the convection. The surface forcing (latent and sensible heat) is sufficiently strong so that even in marginally unstable conditions, modification of the vertical profile may result in eventual deep convection. These factors result in a wide variety of time scales associated with onset of the initial, shallow convection, transition from shallow to deep convection and recovery time between deep convective events. This project will rely on refinement of existing image analysis techniques and data cataloguing tools developed at Arizona State University to automatically identify cloud boundaries and track volumetric changes over time. This project approaches the problem by using pixel segmentation based on hue to transform, segment, and model the cloud volume using triangular mesh, iteratively identifying and automatically morphing the underlying 3D model to represent volumetric changes over time, and using iterative feedback to refine the process. Intellectual Merit: The goal is to extend understanding of fundamental aspects of cumulus development. In particular, the Principal Investigators will focus on the behavior of individual turrets, plumes and thermals in the context of similarity theory, classical conceptual models and those emerging from high resolution numerical simulations. They will examine the mechanics of cumulus entrainment/detrainment, timing of the transition from shallow to deep convection and interaction of cumulus with the environment under varying shear, stability and moisture profiles. By extracting quantitative information from the images automatically, they will be able to process large numbers of cases and extend and generalize the results of previous work on this subject. Broader Impact: The collected information will be of use to operational forecasters in the desert southwest, and to those in southern Arizona in particular. The evolution of the convective boundary layer over the elevated terrain is largely unexplored. A compilation of convective development under different environmental conditions will allow forecasters to relate conditions in the valley to those in the regions where storms are triggered. The data collected during this project will be useful in designing and tuning cloud parameterizations for numerical weather prediction, meso- and cloud resolving process model studies and large-scale, general circulation and climate models. Finally, the tools and techniques to be developed should be generalizable to other dynamic volume characterization and tracking problems.