Mesoscale and Boundary-Layer Meteorology
Wave clouds, photo courtesy of NOAA.
The atmospheric boundary-layer is the layer of air directly influenced by the underlying surface and is up to two kilometers deep under convective conditions. Students in this field are investigating complex interactions between the air and the ground using observational, theoretical and numerical approaches. Mesoscale meteorology examines similar interactions but on a larger horizontal scale, and can also include modeling of cloud processes.
Select a faculty member's name below to visit their web page.
For further information, visit the Mesoscale Meteorology Group web site.
Professor Chen's research involves data assimilation and the study of idealized heavy orographic rainfall. A major forecasting problem is that there is not enough in-situ data over the oceans. One of the possibilities for improving model forecasting is to properly utilize remote sensing data to improve model initial conditions. In collaboration with Dr. Francois Vandenberghe at NCAR, Dr. Grant W. Petty at the University of Wisconsin, and Dr. James F. Bresch at NCAR, her group has applied SSM/I and QuikSCAT data to improve hurricane simulations. For heavy orographic rainfall, in collaboration with Dr. Y. L. Lin of North Carolina State University, she has studied the effects of the moist Froude number and the convective available potential energy on flow regimes associated with a conditionally unstable flow over a mesoscale mountain. In addition to these two directions, her research will also be extended to cumulus parameterization and the on-line tracer study in the near future.
Professor Faloona works to bridge the traditional fields of geophysical turbulence and chemistry with emphasis placed on an interdisciplinary understanding of the physical and chemical principles that control trace gas concentrations and their fluctuations in the atmosphere and ocean. The turbulent planetary boundary layers that lie adjacent to the interfaces of the earth, ocean, and sky play host to a great variety of exchange processes that are critical to understanding the climate system. Scientific investigation into such processes is undertaken by Professor Faloona's group on aircraft, ocean vessels, towers, and in the lab using a wide array of optical and mass spectrometric analytical techniques. The ultimate objective is to use the data to learn about both chemical reactions rates and the meteorological mixing processes, which strongly control the ability of compounds to react with one another. His group pursues research topics in atmospheric and oceanic photochemistry, boundary layer and mesoscale meteorology, and biogeochemical trace gas fluxes.
Professor Matthew Igel’s research focuses on examining physical processes related to clouds, especially tropical convective clouds, across a wide range of time and space scales. Clouds stand as one of the greatest remaining obstacles to our improved understanding of the atmosphere from both a theoretical and applied perspective. The complex interaction of many physical phenomena from microphysical processes related to individual cloud droplets, to dynamical movement of air within clouds including coherent and incoherent updrafts, downdrafts, and mixing, to organization of cloud systems influenced by processes such as surface and radiative fluxes, moisture feedbacks to dynamics, and downscale organizing influences from the large-scale are studied. How all these processes and interactions depend on climate state is a particular area of interest. He employs two complementary tools. Large-domain cloud models are used to examine physical processes and pathways within the convective atmosphere to better understand what causes extreme precipitation events and the relationship between far-field clouds and prolonged dry periods. Computer vision and machine learning techniques are applied to satellite data in order to infer bounds on mesoscale cloud dynamics from the real-world cloud population and to catalog cloud types.
Professor Largier's research, teaching and public service is motivated by contemporary environmental issues and centered on the role of transport in ocean, bay, nearshore and estuarine waters. His work has addressed transport of plankton, larvae, contaminants, pathogens, heat, salt, nutrients, dissolved oxygen, and sediment – and he places this work in the context of issues as diverse as marine reserves, fisheries, mariculture, beach pollution, wastewater discharge, wildlife health, desalination, river plumes, coastal power plants, kelp forests, wetlands, marine mining, coastal zone management and impacts of coastal development. At UCD he heads the 16-person Coastal Oceanography Group. Dr Largier is a leader in developing the field of “environmental oceanography” through linking traditional oceanographic study to critical environmental issues.
Professor Paw U studies the physical and biometeorological processes responsible for exchanges of momentum, heat, and gases such as water vapor between the lower atmosphere and vegetated surfaces. These processes are fundamental to understanding how forests, for example, absorb pollutant gases, how agricultural crops utilize water, and how plant communities exchange carbon dioxide with the atmosphere. The plant biometeorology research encompasses experimental observation in the field, numerical modeling, and theoretical analysis of turbulent mechanisms in and above plant communities. Experiments involve using fast response instruments to measure turbulence, such as sonic anemometers and infrared gas analyzers (IRGAs). Current projects include estimating turbulent parameters and dispersion coefficients for a California regional air quality study, and determining, by eddy-covariance and mean advection methods, and the carbon exchange between the atmosphere and a 500-year old, 65 m high forest at the Wind River Canopy Crane Research facility (WRCCRF). Our research group is measuring carbon dioxide fluxes, and is in collaboration with a group measuring biogenic hydrocarbon emissions from the forest canopy. Recent data indicated this old-growth forest is surprising active and is annually sequestering approximately 2 tons of carbon per hectare, similar to younger forests. Other areas of research focus on the observation and analysis of repeatable patterns in the turbulent wind fields. These characteristic motions, or coherent structures, appear to play an important role in the overall exchange process. Numerical modeling work involves two main topics, the first being state-of-the-art Large Eddy Simulation (LES) of turbulence within and above plan canopies, using the NCAR supercomputer system. The second topic is the numerical modeling of plant canopies using higher-order closure turbulence equations linked with radiation, energy budget, and plant physiology models. This set of models has been named the "Advanced Canopy-Atmosphere Simulation Algorithm" (ACASA). It has been connected to the regional scale model MM5 and can provide a regional scale understanding of ecosystem-atmosphere interactions of radiation, the energy balance, carbon, water, other gaseous and particulate emissions, transport, and deposition. In addition, Professor Paw U has studied the thermal budget of animals and humans in response to atmospheric variables.
Bruce White (Emeritus)
Professor White's research may be divided into two main areas of interest. The first involves fundamental investigation of the physics of turbulent boundary layers. The second area is more practical in nature and may be described as wind-engineering research. The turbulent boundary-layer structure research has been expanded to investigate the effect of adverse pressure gradients on flow structures including both fluid and thermal features. Direct turbulent Prandtl number measurements of adverse-pressure-gradient flows and third-order moments of velocity and temperature for adverse-pressure-gradient flow have been made in the Adverse Pressure Gradient Wind Tunnel Facility, which was designed by Professor White. In the wind-engineering research area, Professor White designed, oversaw construction of, and currently operates the four foot by six foot by 75 foot long UC Davis Atmospheric Boundary Layer Wind Tunnel Graduate Research Facility (ABLWT). Considerable research effort has been placed in the physical modeling of gas dispersion into the atmosphere. A flame-ion-detection system was designed and built and currently operates to model stack emissions and other dispersion processes into the atmosphere. This research led to engineering principles in the relatively new field of environmental laboratory modeling.
Professor White also has been involved in what might be termed Environmental Wind Engineering. This research includes three specific areas of interest: i) the study of large-scale environmental "problems" such as dust-emission suppression at Owens (dry) Lake; ii) Mars/Venus dust/sand storms; and, iii) the study of desert sand transport and dune physics through field testing, laboratory modeling and numerical-analytical analysis.
Two further projects are of interest to Professor White. One involves the physical modeling of radioactive gaseous releases from a stack located in the complex terrain of a mountainous region of California. The other project evaluates the prospect of forecasting wind energy for existing wind parks based on weather forecasts.