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Effects of Local Meteorology and Emissions on Winter PM2.5 Variability in the Northern Hemisphere
AuthorGamalathge, Thishan D. K.
AdvisorGreen, Mark C.
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Aerosols are a component of air pollutants which leads to both health and atmospheric concerns. Thus, scientific findings would help minimizing the associated problems. We worked with PM2.5, which are particles less than 2.5 micrometers of diameter. We used a concept called Heat Deficit (HD) to represent the atmospheric stability. To represent the Northern Hemisphere, we selected three cities; Fairbanks in Alaska, Milan in Italy, and Beijing in China. We were concerned about the winter season, so we considered five winters for each valley starting November 1st of the previous year till the end of February of next year. We used University of Wyoming’s sounding data to calculate HD and did the analysis for each winter and all five winters combined. Just by looking at the scatter plots or time series of average daily PM2.5 against average daily HD at 925 mb, it was not possible to clearly distinguish patterns between the cities. However, the equation corresponds to a linear fit that provided valuable insights. Case with all winters combined were quite similar to each winter separately. We looked at how the PM2.5 level in Fresno varies with meteorology and emissions in four sites; Garland, Clovis, Fancher Creek, and Trimmer. The unavailability of radiosonde data in SJV led us to use temperature difference as a surrogate for HD. Results revealed different periods for increasing and decreasing trends of PM2.5 for Garland and Clovis despite those two sites are quite closely located. PM2.5 level at Garland against temperature gradients with other sites showed a reasonable relationship except for Clovis. Searching for how the PM2.5 level varies with different types of pollutant emissions over the 17 years showed the reasons for non-smooth pattern of PM2.5 variation.