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In a recent work, I'm trying to figure out the pollution situation of my case area. Dealing with the online equipments, I have got the PM2.5 and PM10 concentration time series for a whole year.

I plot their diurnal variation divided by the season.

PM2.5

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PM10

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Although this is a simple data visualization, I think there are some valuable information in the figures. I have found several points that may be interesting, but I can't explain them well.

(1) The diurnal variations of PM2.5 in different seasons are more similar comparing with PM10.

(2) The peak hour in winter for both species are late for 1 hour comparing with other seasons in the daytime.

(3) The concentration levels of both species between daytime and nighttime for spring are more close than other seasons

PS: Some background of the case area

  1. It is located in northeastern China as a industrial city with lots of metal mining and operation factories.
  2. The coal combustion behavior is more usual in winter for the need of domestic heating.
  3. The city is influenced by the dust storms originated from Takla Makan Desert and Gobi Desert.
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    $\begingroup$ In winter the lower troposphere is more often stratified and traps aerosols in lower levels vice versa for summer. That explains why in winter air is more polluted than summer. Which is more dominant: industry or traffic pollution? Is there steel industry or similar that burns coal for heat? Is there a large suburban area around that burns wood in stoves? Some of these clarifications may help the speculation. Also any additional information is welcome. $\endgroup$ – Communisty Aug 10 '17 at 6:11
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    $\begingroup$ A guess on (3): higher wind speeds, particularly at night, cause the mixing to be more consistent throughout the entire day (including the night). I'm probably a little US biased in this thinking, as we have a very classic nocturnal jet, but would think similar features exist if quite a few other parts of the world. $\endgroup$ – JeopardyTempest Aug 10 '17 at 9:23
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    $\begingroup$ A guess on (1): PM2.5 is dominated by anthropogenic emissions. The diurnal cycle of these emissions is similar throughout the year (if it is normalized by the "amplitude"/"daily max emissions"). Therefore, the PM2.5 diurnal cycles are similar in different seasons. The PM10 concentrations are impacted by dust. I would guess that there were major dust storm/emission events in spring and minor ones in autumn. $\endgroup$ – daniel.neumann Aug 10 '17 at 12:44
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    $\begingroup$ A guess on (2): Do you have a one hour shift in time between winter and summer as we have in Europe? You probably measure in UTC (or whatever, but without 1-hour-shift) but, due to the time shift in the local time, the emission processes are shifted by one hour. $\endgroup$ – daniel.neumann Aug 10 '17 at 12:51
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    $\begingroup$ @JeopardyTempest : shouldn't the pattern in PM2.5 look similar if it was due to a noctural jet or other meteorological conditions? A guess on (3): maybe dust - as guessed for (1). $\endgroup$ – daniel.neumann Aug 10 '17 at 12:54

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