Collaborative Research: SAVANT--Stable Atmospheric Variability ANd Transport

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Stable boundary layers (SBL) are still a relatively problematic component of atmospheric modeling, despite their frequent occurrence. While general agreement exists that Monin-Obukov similarity theory is not applicable in the SBL due to the non-homogeneous and non-stationary flow, no universal organizing theory for the SBL has been presented. This poses a problem when examining aerosol movement as a function of atmospheric dynamics. It is known that stable air stratification results in katabatic downslope winds, even in very shallow topographic airsheds. These downslope winds can converge with background flow, and it is hypothesized that this convergence provides a starting point for specific events, such as internal gravity waves (IGW). Even though the stable boundary layer is normally shallow, internal gravity waves can propagate at an angle from the horizontal plane, and modify local shear, thus generating periodic turbulent mixing in space. Few studies have examined this in low relief topographic areas. This project will conduct measurements to address these open issues. The major objective of the project is to quantify the effects of shallow cold air drainage on aerosol transport and dispersion. While the measurement campaign will result in a rich dataset, the research here will focus on answering the following questions:1.Under what mesoscale and microscale conditions (i.e. cloud cover, threshold wind speed, surface cover, stability regime, background flow, slope ratio and length, and gully volume) do converging flows exist?2.What is the spatial and temporal scale of turbulence forced oscillations and/or gravity waves generated by converging flows, and do these and do these oscillations/gravity waves follow the linear theory of IGW?3.How are aerosol dispersion and transport influenced by turbulence forced oscillations and/or gravity waves generated from a converging flow?The novel aspect of this work is the ability to identify turbulent events and features with aerosol lidars to add the missing spatial component to our current understanding.Intellectual Merit:The project will provide new knowledge on drainage and converging flows and their effects on aerosol transport in areas of low topographic variability. Especially of interest is how cloud cover, threshold wind speed, turbulence intermittency, topography, and stability regime affect the flows and aerosol transport. This project will fill the significant gaps in current model parameterizations of the flows and transport in SBL. It will provide new parameterizations and modifications to extend existing to the SBL theories. The project will also identify an empirical relationship between this resulting dispersion and the intensity of the convergence event.Broader Impacts:Scientific broader impacts will include a rich dataset as well as empirical relationships defining when and where convergence is likely to occur. These can be adapted in forecast models that are currently missing these relationships. The larger benefits to society are to a rich field data set to researchers interested in microscale meteorological impacts on agricultural crop security and those interested in predicting impacts of hazardous releases. In addition to this intrinsic benefit of scientific enquiry, the work will also seek to expand public knowledge in understanding the nature of scientific enquiry with a specific focus on instrumentation. The project will create a series of video modules for use in undergraduate classes and public education where traditional meteorology programs are not available.