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Wondering what the massive, yet brief, spikes in Guangzhou are...the ceiling of the Hazardous category of the AQI is capped at 500. That would mean that readings like the 1/12/13 of 827 are quite literally 'off-the-chart.'

The safe bet would be some atmospheric event that concentrated existing pollution. Any new pollution generation event would be expected to have more impact on the baseline, right?

Did a bit more poking around. Could be a temperature inversion causing a spike (http://www.wrh.noaa.gov/slc/climate/TemperatureInversions.ph...). Would be heavily dependent on the location of the sensor and surrounding topography, which all fits. If I find time, I might overlay weather data and see what it looks like.

Possibly. They appear to be events that truly saturate the sensor, as all of the spikes have the exact same concentration and air quality index readings (995 and 827 respectively).

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