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ICEALOT Knorr
Aerosol Number size distribution
(Covert/Bates)
RV Knorr
Aerosol Number-Size Distributions, 20 nm to 10 µm diameter
Version 0
PI contact information:
Timothy S Bates
OCRD
NOAA/PMEL
7600 Sand Point Way NE
Seattle, WA 98115
USA
Phone: 206-526-6248
Fax: 206-526-6744
E-Mail Address: tim.bates@noaa.gov
Or
David S Covert
University of Washington
Department of Atmospheric Science
Box 354235
Seattle, WA 98195
USA
206-685 7461
E-Mail Address: dcovert@u.washington.edu
Or
Derek Coffman
NOAA/PMEL
7600 Sand Point Way NE
Seattle, WA 98115
USA
206-526-6574
206-526-6790
E-Mail Address: derek.coffman@noaa.gov
Short Description:
The data files contain particle number-size distribution measured
onboard the
RV Knorr during ICEALOT. These are measured by an integrated system of
Aitken-DMPS, Accumulation-DMPS and APS instrumentation and presented as
two
files, one from the APS and one from the dual DMPS. The two data files
represent DMPS scans and APS averages over 15 minute intervals defined
in the
data file. The measurement RH was 25% or less in the DMPSs and the APS.
Data were inverted, edited, and analyzed by the PIs at PMEL.
Keywords: number concentration, number-size distribution, ultrafine
differential mobility particle sizer, differential mobility particle
sizer,
aerodynamic particle sizer, UDMPS, DMPS, APS, relative humidity
Full Description of data set:
DOY:
DOY is decimal day of year such that DOY 1.5 is 12 noon UTC on 1
January. The
DOY values are the start time of the scan period.
Particle number-size distributions, [N(Dp)], aboard the RV Knorr:
Aerosol particles were sampled at 18 m above sea level through a heated
mast.
The mast extended 5 m above and forward of the aerosol measurement
container.
The inlet was a rotating cone-shaped nozzle that was automatically
positioned
into the relative wind. Air was pulled through this 5 cm diameter inlet
nozzle
at 1 m3 min-1 and down the 20 cm inner diameter mast. The lowest 1.5 m
of the
mast was heated to reduce the relative humidity (RH) to a value of not
more
than 25% and dry the aerosol. Twenty one 1.6 cm inner diameter
conductive tubes
extending into this heated zone were used to subsample the main air
flow for
the various aerosol instruments at flows of 30 l min-1.
One of the 21 1.6 cm diameter tubes was used to supply ambient air to a
short
differential mobility particle sizer (Aitken-DMPS) and a medium
differential
mobility particle sizer (Accumulation-DMPS). The two DMPSs were located
in a
temperature-controlled box at the base of the mast. The temperature was
controlled such that the RH of the sample stream was maintained at 25%
RH or
lower. The Aitken-DMPS was a
Mobility distributions were collected every 15-minutes from a mobility
scan
that started at even 15 minute intervals and lasted ca. 14.75 minutes.
The mobility distributions from the Aitken-DMPS, Accumulation-DMPS were
inverted to a number distribution by assuming a Fuchs-Boltzman charge
distribution resulted from the Kr85 charge neutralizer (Stratman, F.
and A.
Wiedensohler, 1997). The overlapping channels between the two
instruments were
eliminated in the inversion. The data were corrected for diffusional
losses and
size dependent counting efficiencies based on pre-ACE-2
intercalibration
exercises at IfT.
The same 1.6 cm diameter tube was used to supply ambient air to the APS
(TSI
3321) located in the lower temperature controlled box at the base of
the mast.
The temperature was controlled to maintain the RH of the aerosol sample
stream
at 25% or lower.
The APS data reported here are in 34 size bins with the nominal
manufacturers
aerodynamic diameters ranging from 0.96 to 10.37 µm. Data are
reported in
aerodynamic diameter (micrometers) in units of dN/dlogDp (cm-3) at an
RH of 25%
or lower.
All data were filtered to eliminate periods of calibration and
instrument
malfunction. The value of -999 is assigned to any period without data.
The v0 data are given in two file types: DMPS size distributions where
the
sizes are geometric diameters and APS size distributions where the
sizes are
aerodynamic diameters. Additionally, file are provided at two levels of
cleaning, “filtered” and “non-filtered”. The “non-filtered” data have
been
cleaned as stated above while the filtered data (denoted by the keyword
“filter” in the filename) contain distributions where the particle
concentrations were stable during the 15 minute scan. Distributions
where the
particle concentrations deviated by more than 20% of the mean value
over the
course of the scan were removed.
Format: comma-delimited ASCII. DOY (Julian Decimal Date) (UTC) followed
by the
dmps, aps size bins as described above. The first two rows of data
contain the
bin numbers and the midpoint diameters in micrometers of each bin,
respectively.
References:
Stratman, F. and A. Wiedensohler. A new data inversion algorithm for
DMPS
measurements. J. Aerosol Sci., 27, 339-340, 1997.
Data can be downloaded in a comma delimited format (.csv).
U.S.Dept of Commerce / NOAA / OAR / PMEL / Atmospheric Chemistry