Question on Indirect Meteorological Influences on CMAQ Simulated PM2.5

CMAQ
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Dear Teachers,

I’m currently working with WRF-CMAQ and have a question regarding the influence of meteorological variables on CMAQ-simulated PM₂.₅ concentrations.

From what I understand, several direct meteorological fields processed via MCIP—such as those in METCRO2D—can impact CMAQ outputs. However, I’m curious whether some indirect or derived meteorological indicators, such as the strength of the temperature inversion (as observed in reality), could also play a role.

Specifically, I found a significant correlation between PM₂.₅ concentrations and the temperature difference between the surface and the 850 hPa level—a metric I computed myself rather than one directly output by MCIP. I’m wondering if such a relationship is physically meaningful and whether this kind of derived variable could reasonably explain variations in PM₂.₅ levels.

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Yes, an inversion will trap PM near the surface and limit transport. There are many indirect pathways that allow meteorology to affect surface concentrations. Here is a paper from EPA that looks at some correlations you may be interested in:

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Thank you for your kind reply!

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