Spatial Assessments of Mesoscale Pressure Perturbations using Gridded Analyses and Observations from Earthscope's USArray Network

Mesoscale pressure perturbations originate from a variety of atmospheric processes (e.g., convective systems, gravity waves, frontal passages, etc.). This study uses a variational approach to combine numerical grids of surface pressure (at high spatial resolution) with observations (at high temporal resolution) to produce analysis grids that can be temporally filtered to isolate mesoscale perturbation features in space and time. The surface pressure observations utilized arise from a unique field campaign focused on seismic research. The Earthscope US Transportable Array (USArray) in-situ seismic network provides surface pressure observations at sampling frequencies of 1 and 40 Hz. Stations with pressure sensors were initially deployed in a pseudo-grid format across the central United States in 2010, reported for 1-2 years, and then were redeployed on the eastern edge of the network. At present, the array is finishing deployment along the east coast of the United States, with a subset of stations remaining in place for the next several years while the main array is deployed in Alaska.

The spring and summer seasons of 2011 are chosen for further analysis based on plentiful mesoscale pressure perturbations over the Central Plains where the array was located at that time. Background grids are generated from the first guess and analysis surface pressure grids of the hourly Real Time Mesoscale Analysis (RTMA). Utilizing the USArray observations and a modified University of Utah Two-Dimensional Variational Analysis (UU2DVAR) algorithm, analysis grids at five-minute intervals are produced. Analysis grids are filtered to identify prominent perturbation features over the geographical region assessed. Examples of high-impact mesoscale phenomena that traversed the USArray are provided.