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Time Variability of Chemical Species in Mt. Lemmon
Aerosol using Principal Component Analysis
Anna WonaschützATMO 529 Class ProjectDec. 3rd, 2007
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Description of the Data (I)
Matichuk et al., 2006
mass concentration (monthly averages) of: 8 chemical species in aerosols 4 aerosol precursor gases PM2.0
time range: Sept. 1992 - Apr. 2003
location: Mt. Lemmon, AZ
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Location
Mt. Lemmon, elevation: 2791 m/9157 ft
winter (NDJF): summit in free troposphere (clean, continental air masses) summer(MJJA): summit in planetary boundary layer fall (SO) and spring (MA): boundary layer depth varies
Shaw, 2007, Philippin & Betterton, 1997
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Location
Mt. Lemmon, elevation: 2791 m/9157 ft
winter (NDJF): summit in free troposphere (clean, continental air masses) summer(MJJA): summit in planetary boundary layer fall (SO) and spring (MA): boundary layer depth varies
Shaw, 2007, Philippin & Betterton, 1997
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Description of the Data (II)
Aerosol (PM2.0):
sulfate (SO4
2-), nitrate (NO3
-), chloride (Cl-), sodium (Na+), ammonium (NH
4+), calcium (Ca2+),
elemental carbon (EC), organic carbon (OC)
precursor gases:
ammonia (NH3), nitric acid (HNO
3), sulfuric acid
(H2SO
4, proxy for SO
2), hydrochloric acid (HCl)
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Description of the Data (III)
Summary of results from Matichuk et al., 2006:
1. all species show a strong seasonal dependence
2. trends: - OC, Cl- and Na+: insignificant- NH
3, SO
42-, NH
4+, SO
2: negative
- all other species: positive
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Analysis Method
PCA using SVD:
U...principal components (derived variables)S...singular values (square root of eigenvalues)V...EOF's (eigenvectors of the correlation matrix)
1st PC: timeseries that represents most of the variability of the original dataset, i.e. the timeseries of the chemical species EOF's: contribution of the PC to each species
data = USV
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Data Preparation
units:
mg/m3 (aerosol), ppbv (gases) standardize
gaps:
gap in one chemical species – eliminate those months for all other species
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53 % variance explained
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15.5 % variance explained
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References
Matichuk R., Barbaris B., Betterton E., Hori M., Murao N., Ohta S., Ward D.: “A Decade of Aerosol and Gas Precursor Chemical Characterization at Mt. Lemmon, Arizona (1992 to 2002)”, Journal of the Meteorological Society of Japan, Vol. 84, No.4, 2006
Philippin S., Betterton E.A.: “Cloud Condensation Nuclei Concentrations in Southern Arizona: Instrumentation and Early Observations”, Atmospheric Research 43 (3), 1997
J.H. Seinfeld & S.N. Pandis: “Atmospheric Chemistry and Physics”, 2nd edition, 2006, John Wiley & Sons, Inc.
Shaw G.: “Aerosols at a mountaintop observatory in Arizona”, Journal of Geophysical Research, Vol. 112, 2007
D.S. Wilks: “Statistical Methods in the Atmospheric Sciences”, 2nd edition, 2006, Elsevier