Air quality forecasts and attainment projections rely upon semi-empirical parameterizations within numerical models for the description of dispersion, formation and fate of pollutants influenced by the spatial and temporal distribution of emissions in cities, the topography, and weather. The particulate matter (PM) mass and ozone (O3) measured at the ground level is a common way to evaluate air quality and validate models. Understanding how meteorological processes affect the spatial and temporal variability of aerosols and O3 within the lower atmosphere requires the need of vertically-resolved measurements to improve forecasting of air quality models, especially in the planetary boundary layer (PBL) where the resolution and precision of satellite retrievals are fundamentally limited.
Measurements of boundary layer and free tropospheric pollution have been historically difficult to obtain in regions within complex terrain and/or directly over bodies of water (e.g. the Chesapeake Bay watershed). This poses a continued challenge for air quality managers/forecasters and scientists that rely largely on forecasted or simulated concentrations of trace gases and aerosols near coastal waterways. Furthermore, in many operational, experimental, and research forecasts, surface level O3 is frequently simulated over bodies of water, including the Chesapeake Bay, in excess of the current 8-hour standard of 70 part per billion-by-volume (ppbv) set forth by the Environmental Protection Agency (EPA) via the National Ambient Air Quality Standards (NAAQS). However, there are sparse observations available to verify and comprehensively evaluate these simulated over-water reservoirs of pollutants.
To better sample coastal chemical gradients, the 2017 NASA Science Innovation Fund provided support for the Ozone Water-Land Environmental Transition Study (OWLETS). The OWLETS investigation was designed to utilize a combination of ground based lidar and UAV/drone platforms to more fully investigate transport and chemical gradients directly over water and over land within the Tidewater region of the lower Chesapeake Bay.
In the summer of 2018, the Maryland Department of the Environment sponsored OWLETS-2 with the goal of obtaining high-resolution aerosol, ozone, temperature and wind profiles to understand the effects of local source variability, PBL structure, and microphysical processes on the ability of a column measurement to be related to a surface concentration. The close proximity of urban centers to the Chesapeake Bay allows to study possible mechanisms that may control the planetary boundary layer under marine air incursion. Particle pollution and ozone lidar measurements combined with temperature and scanning Doppler wind lidar can verify how urban centers near coastal areas are often subject to poor air quality through either direct downwind transport of pollutants, in-situ production of O3, or a recirculation brought about by a bay breeze.
This work provides a comprehensive three-dimensional assessment of the air quality in Baltimore-Washington area that couples air quality surface measurements, lidar and satellite observations to better verify forecasts and provide analyses for future air quality simulations. This assessment will aid future policy decisions and strategies as key questions on the influence of gases and aerosols in air quality, atmospheric composition and climate are addressed. This campaign brought together scientists, faculty and students from UMBC, Howard University, Hampton University, City College of New York, University of Maryland, NOAA, and NASA.
Profiling and meteorological data collected by the UMBC Atmosheric Lidar Group can be found in the links below.