A wind profiler trajectory tool for air quality transport applications

Abstract

Horizontal transport is a key factor in air pollution meteorology. In several recent air quality field campaigns, networks of wind profiling Doppler radars have been deployed to help characterize this important phenomenon. This paper describes a Lagrangian particle trajectory tool developed to take advantage of the hourly wind observations provided by these special profiler networks. The tool uses only the observed wind profiles to calculate trajectory positions and does not involve any model physics or parameterizations. An interpolation scheme is used to determine the wind speed and direction at any given location and altitude along the trajectory. Only the horizontal winds measured by the profilers are included because the type of profiling radars used in this study are unable to resolve synoptic‐scale vertical motions. The trajectory tool is applied to a case study from the International Consortium for Research on Transport and Transformation air quality experiment conducted during the summer of 2004 (ICARTT‐04). During this international field study, air chemistry observations were collected at Chebogue Point, a coastal station in southwestern Nova Scotia, and factor analysis was used to identify time periods when air pollution from the United States arrived at the site. The profiler trajectories are compared to trajectories produced from numerical model initialization fields. The profiler‐based trajectories more accurately reflect changes in the synoptic weather pattern that occurred between operational upper air soundings, thereby providing a more accurate depiction of the horizontal transport responsible for air pollution arriving in Nova Scotia.

Quantifying sources of methane using light alkanes in the Los Angeles basin, California

“…This conclusion was based on measurements made at the Mount Wilson Observatory. A back‐trajectory [ White et al ., ; http://www.esrl.noaa.gov/psd/programs/2010/calnex/traj/] from MWO for 5 August 2009, the specific day that Townsend‐Small et al . [] used to determine the excess CH 4 stable isotopic ratio, shows the prevailing winds to MWO were from the southwest, or from downtown L.A. and the coast west of downtown L.A.…”

Airborne lidar measurements of ozone flux downwind of Houston and Dallas

“…This approach will yield unbiased results in most cases, except when the sampled plume is a conglomerate of the plume to be sampled and another pollution plume that originated from a source outside of the Houston or Dallas urban areas. If our data indicate that another plume may be interfering, we use wind profiler‐based trajectory analysis [ White et al , 2006] or, if available, collocated in situ chemistry data from another research aircraft to delineate the plume pieces and adjust the main plume's width and background sampling regions accordingly. Biases introduced in these “conglomerate plume” cases are difficult to estimate and depend on the particular circumstances.…”

Ozone differences between near‐coastal and offshore sites in New England: Role of meteorology

“…The back trajectories were computed from wind data from all profilers in the network using an inverse square distance weighted average. See White et al [2006] for more detail on the back trajectories.…”

“…For instance, through radar wind profiler measurements we evaluate measured mixing heights and infer mixing vigor, rather than using modeled mixing heights. Also, we will use the NOAA wind profiler trajectory tool [ White et al , 2006] to create surface trajectories and trajectories aloft to assess transport at more than one level. These back trajectories were based on measurements, rather than model output.…”