Preferred Atmospheric Patterns for Vernal and Autumnal Nocturnal Bird Migrations using the Plymouth, New Hampshire NOAA-ERSL Snow-Level Radar

In recent years, migratory species of birds have been largely affected by changes in habitat due to climate change and urbanization of many rural areas. The use of radar in the study of bird migration is not a new concept, however the use of a vertically-oriented radar in identifying migratory patterns of birds has not yet been studied. The NOAA-ERSL Snow-Level Radar (SLR) at Plymouth State University, the only one on the east coast, has been collecting data since November 2014. This project uses this two-year dataset to study the relationship between the timing of bird migrations and synoptic-scale weather patterns in central New Hampshire during the Fall and Spring seasons of 2015 and 2016.

NCEP’s North American Regional Reanalysis 3-Hourly Composite dataset was used as well as NOAA-ERSL SLR imagery provided through Plymouth State University. We analyzed Sea-Level Pressure and 500 hPa geopotential heights to determine the preferred synoptic-scale weather systems across the United States for bird migrations as well as low-level winds up to 800 hPa where most migratory birds are observed flying in the SLR imagery.

We identified two main pulse events through the SLR imagery (8 in total) for each season over the two-year span. These events were chosen for their robust reflectivity as seen in the SLR imagery. Using the dates provided for each event, we examined the synoptic set-up over the United States, including the proximity of the center of circulations for both high- and low-pressure systems to Plymouth, NH, to determine the correlation between wind direction and strength and the intensity of SLR reflectivity data. In addition to peak migratory pulses, we identified the apparent start and end times for the migration period for these seasons using the SLR reflectivity imagery. The reflectivity for these early and late migration events were not as pronounced as those selected for the peak pulse events, however, through the understanding of atmospheric conditions at the times of these events important information about bird migration in central New Hampshire can be resolved.