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