First question: are the units shown here on the left-hand (vertical, Y axis) as “PA” in Pascals?
Second question: I notice sometimes among mostly slow changes, there are more rapid changes, for example here it appears to go from -2 PA to +2 PA in the course of about 2.5 seconds, while the remainder of the time the rate of change is significantly less than that. Is this something related to how a gust of wind behaves around obstacles? Also, what in general causes a relatively isolated gust of wind when the background is fairly calm?
Hello jbeale,
Yes, the HDF infrasound sensor units on the DataView Y axis can be changed between Pa (Pascals) or the standard counts. The default is what you have highlighted, Pascals.
Regarding the second question, yes, it could be. I frequently see sharp, rapid changes during windstorms here where I live, particularly associated with the stronger gusts.
Indeed, near obstacles (buildings, trees, terrain, and more), airflow becomes turbulent. Eddies and brief flow separations can produce a quick pressure drop followed by a rebound as they move past.
Generally speaking, atmospheric turbulence is intermittent by nature, as accumulated energy isn’t released smoothly and the overall energy balance can “break” in bursts, so isolated “gust-like” events can appear even when the background looks quiet.
Furthermore, in both urban and non-urban environments, thermal effects also play a role. Small temperature differences (sun-warmed surfaces, rising air pockets) can generate short-lived pressure signals without any obvious wind increase.
It’s honestly a fascinating field. Always wished I had more time to dedicate to it.