Description of data

FILE START TIME (UTC) = MMDDHHMMSS = 1031161438
FILE START TIME (UTC)= 1223025143
PI NAME = MCMURRY
FACILITY = C130
DATA VERSION = 1

P. H. McMurry, University of Minnesota, 125 Mechanical Engineering, 111
Church St. S. E., Minneapolis, MN, 55455.

Measurements are of total concentration = number/cm^3 larger than 3 nm
measured with the University of Minnesota UCNC and ultrafine particle
concentration = nominal number/cm^3 between 3 and 4nm measured with the
pulse height analysis method.  For a detailed explanation of ultrafine
concentration see; Weber et al. J. Atms. Sci. v52, 2242, 1995; Saros et at.
Aerosol Sci. Tech., v25, 200, 1996.  The data reported are at ambient
temperature and pressure.

Missing value indicator = -9.99

Periods of droplet shatter in the community aerosol inlet resulted in
measurements that are not representative of ambient particle
concentrations.  Periods of good data and periods when shatter was
suspected are identified with the flag, "SHATTER FLAG". SHATTER FLAG=1 are
episodes of no cloud droplet shatter; SHATTER FLAG = 0 are episodes of
likely cloud droplet shatter (i.e., measured concentrations are likely a
sampling artifact).

Sample air was extracted from the community aerosol inlet.  The sample air
was not altered.  The sampling interval was nominally 60s.  Live time
sampling and dilution of sample aerosol when necessary eliminated particle
coincidence errors.  The detection efficiency of the UCNC was calibrated at
the UW/PMEL ACE1 CNC workshop in Seattle, WA, August 1995.  The results
will be included in the NCAR, ACE1 data set.

Sampling losses have not been accounted for.  We estimate that for 3nm
particles diffusion losses in the community aerosol inlet are on the order
of 50% and in our sampling train less than 10% (ignoring bends).  Larger
particles will have lower diffusion losses.

Uncertainty in the reported concentrations (N) is due to counting (C),
sampling time (T) and sample flow rate (Q) uncertainties , where;
(dN/N)^2=(dC/C)^2+(dQ/Q)^2+(dT/T)^2; C=(NQT), T=60s, Q=0.39cm3/s;
(dC/C)=(NQT)^-0.5 (i.e., Poisson statistics), (dT/T) is small, (dQ/Q) is
estimated to be 5%.




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Rodney J. Weber                        Phone:     (516) 344-6198
Environmental Chemistry Division       Fax:       (516) 344-2887
Brookhaven National Laboratory         Secretary: (516) 344-3275
Bldg. 426 (51 Bell Ave.) PO Box 5000
Upton NY 11973-5000                    Internet:  rweber@bnl.gov


Secretary: Maggie Marsch or Pat Kriss  Internet:  mmarsch@bnlux1.bnl.gov
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