Urban Influences on Clouds, Precipitation and Lightning

Colorado State University, Fort Collins CO

Investigators

Abstract

Under this award, the Principal Investigator will continue research on the influence of the urban environment on clouds and precipitation. Under prior NSF support, which was focused on dynamical influences, results of sensitivity experiments have shown that the urban heat island is a factor in inducing deep, moist convection downwind of a major urban area. Surface convergence driven by the urban heat island is enhanced on the leeward side of the city. The nonlinear interaction between urban momentum drag and the urban heat island causes convection downwind of the urban area with a concomitant increase in precipitation. Topography is also shown to impact storm development. Under the current award, the Principal Investigator will undertake the following activities: -Modeling the effects of enhanced cloud condensation nuclei and giant cloud condensation nuclei concentrations on convection. -Idealized modeling and a case study of impacts of an urban area on mesoscale convective systems. -Participation in the Houston Environmental Aerosol Thunderstorm Project (HEAT). HEAT is in the planning stages and is a multi-investigator program designed to investigate the influence of the urban environment on weather. The Principal Investigator's modeling work will be helpful in the planning of this project. -Modeling urban impacts on convection and cloud structures favorable for lightning. This research will contribute to fundamental understanding of the influence of major urban centers on convective storms, lightning, and precipitation. The broader impacts of this research will be on urban land-use planning. The educational benefit is that results of this work will be immediately incorporated in the course content of first year and advanced courses in cloud physics and cloud dynamics, as well as in the textbook "Human Impacts on Weather and Climate" co-authored by the Principal Investigator.