Time Variability of Chemical Species in Mt. Lemmon Aerosol using Principal Component Analysis Anna...
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Time Variability of Chemical Species in Mt. Lemmon
Aerosol using Principal Component Analysis
Anna WonaschützATMO 529 Class ProjectDec. 3rd, 2007
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
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
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
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)
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
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
Data Preparation
units:
mg/m3 (aerosol), ppbv (gases) standardize
gaps:
gap in one chemical species – eliminate those months for all other species
53 % variance explained
15.5 % variance explained
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