Objectively identified mesoscale surface air pressure waves in the context of winter storm environments and radar reflectivity features: a 3+ year analysis

Abstract. Atmospheric gravity waves (i.e., buoyancy waves) can occur within stable layers when vertical oscillations are triggered by localized heating, flow over terrain, or imbalances in upper level flow. Case studies of winter storms have associated gravity waves with heavier surface snowfall, but the representativeness of those findings for settings without orographic precipitation has not been previously addressed.

To detect gravity waves, we deployed networks of high precision pressure sensors from January 2020 to April 2023 in and around Toronto, ON, Canada, and New York, NY, USA, two regions without strong topographic forcing. Pressure wave events were identified when at least 4 sensors in a network detected propagating pressure waves with wave periods ≤ 67 min, wavelengths ≤ 170 km, and amplitudes ≥ 0.45 hPa. We detected 33 pressure wave events across 40 months of data, of which 23 were gravity waves and the rest were frontal passages, outflow boundary passages, or a wake low.

Reanalysis model output and operational weather observations provided environmental context for each gravity wave event. Consistent with previous work, most gravity wave events occurred with strong upper-level flow imbalance to the south or west of their location. Of the 79 winter storms with snow that occurred over our 40 months of observations, only 6 had detectable gravity waves. For New York City, the typical offshore cyclone low center track means the metro area is usually in a location where gravity waves are not expected to occur.