Project/Cruise: NEAQS 2004

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Ship's Position (Latitude and Longitude)
In the one minute files the position is treated somewhat differently then all the other data.  The position given is the ship's position at the start of the one minute 'averaging' period.  (All other data are a true average).  The PMEL GPS was the primary source, the ship's p-code GPS was used when there were missing data in the PMEL DL record.  The P-Code and PMEL GPS data were compared for the over 50,000 minutes of  concurrent data, and the difference between the two was never more that 100 meters (about one ship length).

Ship's Speed, Course and Gyro:
The ship's GPS speed in knots (Speed Over Ground) and  GPS Course in compass degrees (Course Over Ground) are the one minute averages from the GPS (ship P-code GPS as the primary source, the PMEL GPS as the secondary source.  To make the one minute averages the 2-second recorded motion vector was separated into east and north components that were averaged into one minute bins.  The one minute components were then combined into the ship Velocity Vector.  The GyroCompass in compass degrees is the one minute average heading.  The 2-second data was separated into an east and north component before averaging and then recombining.  NOTE:  The GPS-Course is the direction the ship is moving.  The GyroCompass is direction the ships bow is pointing.  When the ship is moving at 6 or more knots they generally are almost the same.  Due to water currents, at slow speeds there can be quite a difference between the two.  When the ship is stationary, the two are totally unrelated.


Atmospheric Temperature:
One minute averages in degrees C. There were three possible sources, the 2 PMEL rotronics sensors (T1 and T2) and the ship's SCS IMET sensor.  The ship's IMET sensor was located on the IMET mast at the bow of the ship, the PMEL sensors were located at the top of the Aero-phys van.  In plotting the raw data it was found that T1 and the SCS IMET sensor both generally agreed within a fraction of a degree C.  T2 was generally about one degree warmer than T1 or SCS IMET.  The IMET sensor being located at the bow had less warming from the daytime heating of the ship deck, (and the data record did show that IMET was cooler than T1 during the afternoon, when deck heating was a max).    Therefore, the SCS IMET sensor was used as the primary source and for the few times that data were missing from SCS, the PMEL-T1 sensor was used.


Relative humidity:
One minute averages in units of %.  The RH sensors were problematic.  The two PMEL rotronics sensors (RH1, and RH2) agreed very well for the first 48 hours of the cruise, and then output from RH1 jumped to 120% RH, and stayed over 100% for much of the time.  The output from the SCS RH sensor appeared 'stuck' and flat-lined at about 96% for much of the time.  Because only the PMEL RH2 sensor appeared to give 'reasonable' data, RH2 was used as the data source for all of the NEAQS2004 record. 


Barometric Pressure:
One minute averages in units of mb.  There were two sources of raw data, the PMEL (Qualimetrics sensor) and the SCS digital (Vaisala) sensor.  There was one other data source, the Weather Service certified aneroid barometer, but this 'bridge barometer' cannot be electronically recorded.  The PMEL and the SCS barometer data tracked each other very well but the PMEL barometer had a 'drift' in that the two agreed very well at the start of the cruise, but by the start of leg 2 they differed by 8 mb.  In seven readings over the course of the cruise the SCS barometer agreed within 1 mb of the 'bridge barometer'.   Therefore the SCS barometer data was used for this record.  For the few hours at the start of leg 1 when there was no SCS data, the PMEL barometer was used as they both agreed very well at this time.  For the period at the end of leg 1 and the start of leg 2 when the SCS system was off, a calibration factor of 8.29 mb was added to the PMEL barometer signal and used for this record.


Insolation:
One minute averages in units of watts per square meter. Total solar radiation was measured with an Epply Black and White Pyranometer (horizontal surface receiver -180, model 8-48, serial number 12946) and an Epply precision pyranometer (horizontal surface receiver -180, twin hemispheres, model PSP, serial number 133035F3) that were mounted on the top of AERO van. Both instruments were calibrated by The Epply Laboratory on October 11, 1994. There were times when the sampling mast shaded one or both sensors. There were also times when the ship's mast/bridge shaded the sensors. The shaded data have not been edited out of the 1 minute data record. The data reported here are from the model 8-48, serial number 12946 radiometer and are in watts per square meter and are the average value over the 1 minute sampling period.


Relative Wind
The primary source for the relative wind data was the PMEL "Skyvane" anemometer that was located at the top of the aerosol sampling mast. For periods of missing data from the PMEL data source the ships IMET SCS wind sensor was used.  We assume that the relative wind information is primarily used to determine periods of ship contamination, thus we are using the anemometer that is closest to the sample inlet. This anemometer also was used as an input to the algorithm that turned off the sample pumps during periods of ship contamination.)

The one minute average relative wind speed and direction data were separated into orthogonal components of "keel" and "beam". These components were averaged into 1 minute averages, and then recombined to relative wind vectors. Wind speed is reported meters per second and wind direction is in degrees with -90 being wind approaching the ship on the port beam, 0 degrees being wind approaching the ship directly on the bow, and +90 degrees being wind approaching the ship on the starboard beam.


Wind Components/ True Wind Speed/ True Wind Direction:
True wind speed and direction were calculated from measurements obtained with the Ships IMET wind sensor. This sensor was mounted 14 meters above the sea surface on the ship's meteorological sampling mast at the bow and should be less affected by bending of streamlines as the air moves over the ship. (The PMEL “Skyvane” was on the top of the Aero-Van and in the ‘perturbed airflow’.)  The true North and East components of the wind vector from the 2 second SCS data were calculated and then averaged into 1 minute intervals in m/s. The true wind vector was calculated from these components and is given as wind speed in m/s and wind direction in compass degrees.  The WindU and WindV are the east and north components of the wind vector (in m/s).


Rainfall Rate:
The rainfall rate was measured with a Scientific Technology Inc. ORG-100 Optical Precipitation Intensity Sensor. The instrument was mounted on the railing of Aero van. The dynamic range of the sensor is 0.5 to 1600 mm/h. Spikes in the signal may be associated with sea spray and/or fog. The data are reported in units of mm/hr.


PMEL/UW CN and UFCN measurements:

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 less than 60% and partially 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 twenty one 1.6 cm diameter tubes was used to supply ambient air to TSI 3010 and TSI 3025A particle counters. A separate 1/4" line was used to supply air from the top of the mast directly to a TSI 3760 particle counter. The 3760, 3010 and 3025 measure all particles larger than roughly 13, 12 and 3 nm respectively. The counts from the three detectors are referred to here as CN>13 (TSI3760), CN>12 (TSI3010), and CN>3 (TSI3025). The total particle counts from each instrument were recorded each minute. The data were filtered to eliminate periods of calibration and instrument malfunction and periods of ship contamination (based on relative wind and high CN counts). The value of -999 was assigned to any one minute period without data.


SO2 Measurements aboard Ronald H. Brown during NEAQS/ITCT/ICARTT 2004

 Inlet and Instrument :
Air was pulled from 18 m above sea level down the 20 cm ID powder-coated aluminum aerosol sampling mast (6 m) at approximately 1 m3min-1. At the base of the sampling mast a 0.5 Lmin-1 flow was pulled through a 0.32 cm ID, 1m long Teflon tube, a Millipore Fluoropore filter (1.0-um pore size) housed in a Teflon filter holder, a Perma Pure Inc. Nafion Drier (MD-070, stainless steel, 61 cm long) and then through 2 m of Telfon tubing to the Thermo Environmental Instruments Model 43C Trace Level Pulsed Fluorescence Analyzer. The initial 1 m of tubing, filter and drier we located in the humidity controlled (60%) chamber at the base of the mast. Dry zero air (scrubbed with a charcoal trap) was run through the outside of the Nafion Drier at 1 Lmin-1. The analyzer was run with two channels (0-10 ppb full scale and 0-100 ppb full scale) and a 20 sec averaging time. Data were recorded every minute.
Standardization:
Zero air was introduced into the sample line upstream of the Fluoropore filter for 10 minutes every 6 hours to establish a zero baseline. An SO2 standard was generated with a permeation tube held at 40C. The flow over the permeation tube, diluted to 6.2 ppb, was introduced into the sample line upstream of the Fluoropore filter for 10 minutes every 24 hours. The limit of detection for the 1 min data, defined as 2 times the standard deviation of the signal during the zero periods, was 100 ppt. Uncertainties in the concentrations based on the permeation tube weight and dilution flows are <5%.



Ozone:

In one minute averages in units of ppb. Air was sampled from 18 m above sea level down the 20 cm ID powder-coated aluminum aerosol sampling mast (6 m) at approximately 1 m3min-1. At the base of the sampling mast a 1 Lmin-1 flow was pulled through a 0.32 cm ID, 2m long Teflon tube into a TECO 49 ozone analyzer and a Dasibi 1008 AH ozone analyzer.  The TECO instrument has been calibrated to a NIST traceable analyzer at NOAA-CMDL.  At the end of leg one the TECO 49 instrument developed a leak and failed.  It was fixed several days into leg 2.  For the first 10 days of leg one the Dasibi instrument was ‘calibrated’ to the TECO instrument.  The correction factor was then applied to the entire Dasibi record.  Data from the two instruments were then averaged together (except for the days that only the Dasibi was running)..  A small portion of the data have been deleted (consisting mostly of times that the inlet air was passed through a zero filter - usually when the relative wind was well behind the beam of the ship).  



Sea Surface Temperature and Salinity:

Sea Surface Temperature (SST) in degrees C  and Salinity in PSU were measured with the Ship's Thermosalinograph. The intake depth was at 5.6 meters.



Seawater DMS

Seawater enters the ship at the bow, 5.6 m below the ship waterline, and is pumped to the ship laboratory at approximately 30 lpm (water residence time within the ship is < 5 min).  Every 30 minutes a 5 ml water sample is valved from the ship water line directly into a Teflon gas stripper.  The sample is purged with hydrogen at 80 ml/min for 5 min. DMS and other sulfur gases in the hydrogen purge gas are collected on a Tenax filled trap, held at -5 deg C.  During the sample trapping period, 6.2 pmoles of methylethyl sulfide (MES) are valved into the hydrogen stream as an internal standard.  At the end of the sampling/purge period the trap is rapidly heated to +120 deg C and the sulfur gases are desorbed from the trap, separated on a DB-1 megabore fused silica column held at 70 deg C, and quantified with a sulfur chemiluminesence detector.  Between each water sample the system analyzes either a DMS standard or a system blank.  The system is calibrated using gravimetrically calibrated DMS and MES permeation tubes.  The precision of the analysis has been shown to be ± 2% based on replicate analysis of a single water sample at 3.6 nM DMS. The automated DMS system is described in greater detail in Bates et.al., (J. Geophys. Res., 103, 16369-16383, 1998; Tellus, 52B, 258-272, 2000).  The major improvements since these papers are a new automation-data system and a more reliable cold trap consisting of a electically heated stainless steel tube embeded in an aluminum block that is cooled to -5 deg C with a thermoelectric cooling chip. 


Radon:
The PMEL radon instrument is a "dual flow loop, two filtered radon detector". The general features of the instrument are described in Whittlestone and Zahorowski, Baseline radon detectors for shipboard use: Development and deployment in the First Aerosol Characterization Experiment (ACE1), J. Geophys. Res., 103, 16,743-16,751, 1998. The instrument response is due to radon gas, not radon daughters (all of the existing radon daughters are filtered out before entering the decay/counting tank). The instrument registers the total number of decay counts per 30 minute interval on a filter arising from the decay of radon in the tank. The time given in the data file is the time of the start of the counting interval. As the volume of the decay/counting tank was 905 l and the sample flow rate into and out of the tank was typically 70 l/min, the response time of the radon instrument was about 13 minutes. The radon detector was standardized in Portsmouth at the beginning of the cruise using radon emitted from a known source.



Aerosol Organic and Elemental Carbon

Information about the OCEC sampling and data is available in a separate PDF document.



Aerosol Chemistry data -- NOAA PMEL PILS Chemistry Data

Contact person:  Trish Quinn, Patricia.K.Quinn@noaa.gov

See Weber etal. (2001) and Orsini et al. (2003) for a description of the PILS (Particle-Into-Liquid-Sampler). The 15 lpm version was used in this experiment.  The common aerosol inlet (heated to maintain the sample air at 55 +/- 5% RH) was used to deliver aerosol to the PILS. A Berner-type impactor with a 50% aerodynamic cutoff diameter of 1.1 um was upstream of the PILS and sampled air at 55% RH.  In order to maintain a 1.1 um cut off diameter, the impactor must have 30 slpm of flow at all times.  The PILS itself runs at 15 slpm with the flow controlled by a critical orifice.  To maintain 30 slpm through the impactor, a make up flow through a bypass line was added of 15 slpm.  Two denuders were located in series after the impactor. These were 1) a URG denuder coated with sodium carbonate for the removal of gas phase acids, and  2) a URG denuder coated with citric acid to remove gas phase bases.  Liquid sample flow from the PILS went simultaneously to a cation IC and an anion IC (Metrohm compact 761 ICs).

Cation analysis: a Metrohm Peak C2-100 column for Na, NH4, K, Mg, Ca. Eluent was 2.5 mM HNO3, 10% ACN, and 1.5 mM dipicolinic acid with no suppression. Flow rate was 1.1 ml/min. Anion analysis: a Methrohm Peak ASupp5-100 for Cl, NO3, SO4.

Anion eluent is 5 mM Na2CO3/2 mM NaHCO3 with Methrohm's packed bed suppressor. Flow rate is 1.25 ml/min.  Samples were collected and analyzed every 5 min.

Ion concentrations are reported in ug/m3 at STP. PILS concentrations were compared to the submicron stages of a 2 and 7 stage impactor (Impactors 1 and 9, respectively). PILS concentrations were corrected based on the slope of the  Impactor vs. the PILS for NH4+ and SO4=. The average of the slopes for impactor 1 and 9 was used. The NH4+ slope was applied to all cations and the SO4= slope was applied to all anions. Hence, cation concentrations were divided by 0.785 for leg 1 and 0.855 for leg 2. Anion concentrations were divided by 0.785 for leg 1 and 0.685 for leg 2. The reduced collection efficiency for the PILS appears to be due to incomplete filling of the sample loops.  (This conclusion is based on a series of tests conducted post-cruise in the van park).

Weber, R.J., D. Orsini, Y. Daun, Y.-N. Lee, P.J. Klotz, and F. Brechtel, A particle-into-liquid collector for rapid measurement of aerosol bulk  chemical composition, Aerosol. Sci. Technol., 35, 718-727, 2001.

Orisini, D.A. et al., Atmos. Environ., 37, 1243 - 1259, 2003.



Aerosol Mass Spectrometer, AMS

Chemically classified and size-resolved mass loadings of sub-micron aerosol were measured using an Aerosol Mass Spectrometer (AMS) developed at Aerodyne Research, Inc., (Billerica, Massachusetts, USA) [Jayne et al, 2000; Allan et al., 2003]. The AMS measured both the mass concentrations of chemical species and the vacuum aerodynamic size (Dva) of the particles.  The vaporized species analyzed by the AMS are referred to as non-refractory (NR), and are defined as all chemical components that vaporize (<5 s) at the vaporizer temperature of ~550°C. This includes most organic carbon species and inorganic species such NH4NO3 and (NH4)xH2SO4 but does not include crustal oxides, elemental carbon, or sea salt.

Version 0 on the data server included hourly average data with a “best guess” collection efficiency.
Version 1 (29 March 2005) on the data server includes all data collected.  The data have been corrected for collection efficiency based on DMPS and PILS-IC data.

Jayne, J.T., D.C. Leard, X. Zhang, P. Davidovits, K.A. Smith, C.E. Kolb, and D.R. Worsnop, Development of an aerosol mass spectrometer for size and composition analysis of submicron particles, Aersol Sci. Technol., 33, 49-70, 2000.

Allan, J.D., J.L. Jimenez, P.I. Williams, M.R. Alfarra, K.N. Bower, J.T. Jayne, H. Coe, and D.R. Worsnop, Quantitative sampling using an Aerodyne aerosol mass spectrometer. Part 1: Techniques of data interpretation and error analysis, J. Geophys. Res., 108(D3), 4090, doi:10.1029/2002JD002358, 2003.



Ronald H. Brown ship Aerosol in-situ scattering and absorption during NEAQS 2004

Berko Sierau* (bsierau@atmos.washington.edu  ph: 206-543-6674)
David S. Covert (dcovert@u.washington.edu  ph: 206-685 7461)
Dept. of Atmospheric Science
University of Washington
Box 351640
Seattle, WA  98195 USA
fax: 206-543-0308
* contact for questions about the data

Patricia Quinn (patricia.k.quinn@noaa.gov)
NOAA Pacific Marine Environmental Laboratory
7600 Sand Point Way NE
Seattle, WA, USA

INSTRUMENT DESCRIPTION:

A suite of instruments was used to measure light scattering and absorption.  Two TSI, Inc. integrating nephelometers (Model 3563) measured integrated total scatter  and hemispheric backscatter at 450, 550, and 700nm wavelengths (Anderson et al, 1996; Anderson and Ogren, 1998).  One nephelometer ("SupermicronScattering/Neph10") always measured aerosols of aerodynamic diameter D<10micron; the second nephelometer("SubmicronScattering/Neph1") measured only aerosol of aerodynamic diameter D<1micron. Both nephs measured at approximately 60% RH. The 10 and 1micron cut-off was accomplished by using standard berner impactors. One Radiance Research Particle Soot Absorption Photometer ('SubmicronAbsorption/PSAP1') was used to measure light absorption by aerosols at 467, 530, and 660nm (Bond et al., 1999; Virkkula et al.,2005) under'dry' (<25% RH) conditions.

Additionally, a 'dry' system measured total scatter ('OECneph', extinction ('OEC'), and absorption ('PSAP2') at RH<25%. The system includes a TSI, Inc. integrating nephelometer measuring scattering only at 550nm, a three-wavelength (467, 530, 660nm) optical extinction cell (Virkkula, 2005), and a three-wavelength Radiance Research Particle Soot Absorption Photometer (again 467, 530, and 660nm). A Condensation Particle Counter (TSI, Inc. 3010) measured total particle counts, as sampled from the nephelometers, for quality-control only.  

 DATA COLLECTION AND PROCESSING

Data of the 'wet' system were collected at between 1 and 5 sec resolution, depending on the instrument (1 sec for PSAP, 5 sec for Neph). However, while reported at 1-5 Hz, light absorption and scattering measurements represent 60-second averages which is also the time resolution the data will be provided. Data from each instrument are corrected and adjusted as described below, allowing for derivation of extensive parameters (light scattering and absorption) and intensive parameters (single scatter albedo, Angstrom exponent). For the 60-second data files light scattering values are smoothed over a window 40-seconds wide before calculating the Angstrom exponents.  Similarly, light absorption is instrument-internally smoothed over a window 10-seconds wide. The smoothed neph data are used *only* to calculate the intensive parameters; in all cases, the reported extensive parameter light scattering is un-smoothed. The Angstrom exponent is smoothed over a 40-seconds window before averaging.  Data of the 'dry' system were also collected between 1 and 5 sec resolution but are reported at a 1080 sec resolution. This is due to the determination of the light extinction which is based on a 1080 sec average time.

For all parameters, the bad value code is "NaN" (-999 in the .acf files). If no data was acquired by the data acquisition system, time lacks exist in the data files.  Intensive parameters are set to NaN when the extensive properties used in their calculation fell below the measurement noise threshold (v2 noise thresholds are based on former campaigns). Both extensive and intensive properties are set to NaN during certain events, such as during filter changes, instrument calibration, obvious instrument failure etc. Negative values of absorption might occur during periods of absorption signals near or in the
range of the instrument noise, and are partly shifted into the negative range due to  scattering correction.

STP values to be adjusted to are p_STP=1013.2 hPa, T_STP=273.2 K.


DERIVATI ON OF MEAN VALUES:

Data from the TSI integrating nephelometers Neph10 and Neph1, and OECneph are processed as  follows:
    1) Span gas (air and CO2) calibrations were made before the field
campaign. However, due to problems of the Neph1 calibration shutter during
the cruise several additional calibrations had to be made during the cruise
to determine TSI nephelometer gain and offset calibration coefficients. This
calibration correction was applied for the Neph1 scattering data in the data
processing code.
    2) The TSI nephelometers measure integrated light scattering into 7-170
degrees.  To derive total scatter (0-180degrees) and hemispheric backscatter
(90-180degrees) angular truncation correction factors were applied as
recommended by Anderson and Ogren (1998).
    3) Total and hemispheric backscatter were adjusted to STP.
    

Data from the Radiance Research Particle Soot Absorption Photometers, PSAPs 1 and 2,
are processed as follows:
    1) Reported values of light absorption are corrected for spot size, flow  rate, artifact response to scattering, and error in the manufacturer's  calibration, all given by Bond et al. (1999). Except the spot size, all corrections were made after data collection, i.e. they are not integrated into the PSAP firmware. However, the PSAP's were flow-calibrated prior to the campaign, and a flow correction was applied based on routine flow checks during the cruise.
    2) Light absorption is adjusted to STP

    
DATA FORMAT

All varibles are in STP.

REFERENCES

Anderson, T.L., D.S. Covert, S.F. Marshall, M. L. Laucks, R.J. Charlson, A.P. Waggoner, J.A. Ogren, R. Caldow, R. Holm, F. Quant, G. Sem, A. Wiedensohler, N.A. Ahlquist, and T.S. Bates, "Performance characteristics of a high-sensitivity, three-wavelength, total scatter/backscatter nephelometer", J. Atmos. Oceanic Technol., 13, 967-986, 1996.

Anderson, T.L., and J.A. Ogren, "Determining aerosol radiatve properties using the TSI 3563 integrating nephelometer", Aerosol Sci. Technol., 29, 57-69, 1998.

Bond, T.C., T.L. Anderson, and D. Campbell, "Calibration and intercomparison of filter-based measurements of visible light absorption by aerosols", Aerosol Sci. and Tech., 30, 582-600, 1999.

A. Virkkula, N. C. Ahquist, D. S. Covert, P. J. Sheridan, W. P. Arnott, J. A Ogren,  "A three-wavelength optical extinction cell for measuring aerosol light extinction and its application to determining absorption coefficient", Aero. Sci. and Tech., 39, 52-67, 2005

A. Virkkula, N. C. Ahquist, D. S. Covert, W. P. Arnott, P. J. Sheridan, P. K. Quinn, D. J. Coffman,"Modification, calibration and a field test of an instrument for measuring light absorption by particles", Aero. Sci. and Tech., 39, 68-83, 2005

PMEL Aerosol Optical Depth Data
Contact person:  Trish Quinn, patricia.k.quinn@noaa.gov

Three 5-channel handheld Microtops sunphotometer (Solar Light Co.) were used. Two units (SN 4080 and 3803) have wavelengths of 380, 440, 500, 675, and 870 nm). The third unit (SN 5355) has wavelengths of 340, 380, 500, 675, and 870 nm).  The full angular field of view for the Microtops is 2.5 deg.  The instruments have built in pressure and temperature sensors and were operated with a GPS connection to obtain position and time of the measurements. Raw signal voltages were converted to aerosol optical depths by correcting for Rayleigh scattering [Penndorf, 1957], ozone optical depth, and an air mass that accounts for the Earth's curvature [Kasten and Young, 1989]. Ozone column amounts used to calculate the ozone optical depth were obtained from TOMS data as a daily average throughout the cruise for the latitude and longitude of Boston. Units 4080 and 5355 were calibrated at MLO in June, 2004, one month prior to the start of the cruise. Unit 3803 was calibrated at the factory in January, 2004. Calibrations were done using a Langley plot approach [Shaw, 1983]. Measurements on the ship followed the protocol of Knobelspiesse et al. [2003]. The scan length was set to 20 so that 20 measurements are obtained during each "shot". The largest voltage of the 20 measurements is recorded which corresponds to the lowest AOD. This approach helps to eliminate erroneous measurements that result from pointing errors on a moving ship. After the experiment, a post processing algorithm was applied. This algoritm calculates a coefficient of variation for each measurement equal to the sample standard deviation divided by the sample mean. If the CoV > than 0.05, the highest AOD is removed and CoV is recalculated. This procedure is repeated until all points "pass". All units were compared at each common wavlength. For 380 nm, the slope was 0.98 and r^2 was 0.99. For 500 nm, the slope was 0.98 and r^2 was 0.98. For 675 nm, the slope was 0.95 to 0.98 and the r^2 was 0.96. For 870, the slope was 0.92 and the r^2 was 0.90. For 440 nm the slope was 0.99 and r^2 was 0.99. The uncertainty of the Microtops is esimated to be +/- 0.015 AOD.

Kasten, F. and A. T. Young, Revised optical air mass tables and approximation formula, Applied Optics, 28, 4735 - 4738, 1989.

Knobelspiesse, K.D. et al., Sun-pointing-error correction for sea deployment of the Microptops II handheld sun photometer, J. Atmos. Ocean. Tech., 20, 767, 2003.

Penndorf, R. , Tables of refractive index for standard air and the Rayleigh scattering coefficient for the spectral region between 0.2 and 20 um and their application to atmospheric optics, J. Opt. Soc. America, 47, 176 - 182, 1957.

Shaw, G. E., Sun Photometry, Bull. Am. Met. Soc., 64, 4-9, 1983.




NOAA PMEL Chemistry Data - collected with 2 stage impactors

Contact persons: Trish Quinn, patricia.k.quinn@noaa.gov; Kristen Schulz, Kristen.schulz@noaa.gov

Two-stage multi-jet cascade impactors (Berner et al., 1979) sampling air at 55 ± 5% RH were used to determine the sub- and supermicron concentrations of Cl-, NO3-, SO4=, methanesulfonate (MSA-), Na+, NH4+, K+, Mg+2, and Ca+2. Sampling periods ranged from 4 to 6 hours. The RH of the sampled air stream was measured a few inches upstream from the impactor. The 50% aerodynamic cutoff diameters, D50,aero, were 1.1 and 10 um. Submicron refers to particles with Daero < 1.1 um at 55% RH and supermicron refers to particles with 1.1 um < Daero < 10 um at 55% RH.

The impaction stage at the inlet of the impactor was coated with silicone grease to prevent the bounce of larger particles onto the downstream stages. Tedlar films were used as the collection substrate in the impaction stage and a Millipore Fluoropore filter (1.0-um pore size) was used for the backup filter. Films were cleaned in an ultrasonic bath in 10% H2O2 for 30 min, rinsed in distilled, deionized water, and dried in an NH3- and SO2-free glove box. Filters and films were wetted with 1 mL of spectral grade methanol. An additional 5 mLs of distilled deionized water were added to the solution and the substrates were extracted by sonicating for 30 min. The extracts were analyzed by ion chromatography [Quinn et al., 1998]. All handling of the substrates was done in the glove box. Blank levels were determined by loading an impactor with substrates but not drawing any air through it.

Non-sea salt sulfate concentrations were calculated from Na+ concentrations and the ratio of sulfate to sodium in seawater. Concentrations are reported as ug/m3 at STP (25C and 1 atm).

Berner et al., Sci. Total Environ., 13, 245 - 261, 1979.
Quinn et al., J. Geophys. Res., 105, 6785 - 6805, 2000.


NOAA PMEL Gravimetrically-determined Mass - collected with 2 stage impactors

Contact person: Trish Quinn, patricia.k.quinn@noaa.gov

Two-stage multi-jet cascade impactors (Berner et al., 1979) sampling air at 55 5% RH were used to determine sub- and supermicron aerosol mass concentrations. The RH of the sampled air stream was measured a few inches upstream from the impactor. The 50% aerodynamic cutoff diameters, D50,aero, were 1.1 and 10 um. Submicron refers to particles with Daero < 1.1 um at 55% RH and supermicron refers to particles with 1.1 um < Daero < 10 um at 55% RH.

The impaction stage at the inlet of the impactor was coated with silicone grease to prevent the bounce of larger particles onto the downstream stages. Tedlar films were used as the collection substrate in the impaction stage and a Millipore Fluoropore filter (1.0-um pore size) was used for the backup filter. Films were cleaned in an ultrasonic bath in 10% H2O2 for 30 min, rinsed in distilled, deionized water, and dried in an NH3- and SO2-free glove box.

Films and filters were weighed at PMEL with a Cahn Model 29 and Mettler UMT2 microbalance, respectively. The balances are housed in a glove box kept at a humidity of 33 2%. The resulting mass concentrations from the gravimetric analysis include the water mass that is associated with the aerosol at 33% RH.

The glove box was continually purged with room air that had passed through a scrubber of activated charcoal, potassium carbonate, and citric acid to remove gas phase organics, acids, and ammonia. Static charging, which can result in balance instabilities, was minimized by coating the walls of the glove box with a static dissipative polymer (Tech Spray, Inc.), placing an anti-static mat on the glove box floor, using anti-static gloves while handling the substrates, and exposing the substrates to a 210Po source to dissipate any charge that had built up on the substrates. Before and after sample collection, substrates were stored double-bagged with the outer bag containing citric acid to prevent absorption of gas phase ammonia. More details of the weighing procedure can be found in Quinn and Coffman [1998].

Concentrations are reported as ug/m3 at STP (25C and 1 atm).

Berner et al., Sci. Total Environ., 13, 245 - 261, 1979.
Quinn et al., J. Geophys. Res., 105, 6785 - 6805, 2000.



U.S.Dept of Commerce / NOAA / OAR / PMEL / Atmospheric Chemistry