Saturday, October 22, 2016

Inversion Season Is upon Us

A quick look at yesterday afternoon's sounding shows that inversion season is indeed upon us.  The afternoon boundary in which surface heating drives turbulence and mixing, extended to only 850 mb, just a couple hundred meters or so above the valley floor.  This mixed layer was capped by a series of stable layers and inversions, effectively putting a cap or lid on the valley atmosphere.  In other words, what you emit is what you breath.  

Source: SPC
Welcome to late October.  We are now moving into the time of year during which surface heating is often not enough to mix out the valley atmosphere.  In other words, its inversion season.  However, don't blame the inversion for our air pollution problems.  In fact, meteorologists like myself hate it when people say "the pollution is bad because of the inversion."  Nope.  The pollution is bad because of emissions.  We have met the enemy and it is us.  

A shallow layer of pollution could be spied in all directions while on my bike ride this morning.  

And, in case you were wondering, PM2.5 concentrations at Hawthorne Elementary have been running in what I'll call the "Low Moderate" category at around 20 ug/m3.  

Source: DAQ
With southwesterly flow on tap for the next couple of days, this should be a brief-lived, moderate episode without major concerns.  It is, however, a stress test for the coming winter.  

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