Ship's Speed and Heading:
The ship's speed and heading are calculated from the ships position at even 30 minute intervals, as measured by the PMEL GPS.
Air temperature (degrees C) was measured with the PMEL RM Young sensor and the PMEL Qualimetrics sensor. The PMEL sensors were mounted on top of AeroVan, 6 m above sea level. The RM Young sensor was calibrated before the cruise at the PMEL Tropical Atmosphere Ocean (TOA) calibration facility. There are some minor differences between the two records that may be due to radiative heating of the sensor housings. The Qualimetrics sensor was aspirated by a fan drawing air into its housing, while the RM Young sensor relied on a white radiation shield to protect it from radiative heating. The data are the average value over the sampling period.
Relative humidity (%) was measured with the PMEL RM Young sensor. The Sensor was located on top of AeroVan in the white radiation shield along with the RM Young temperature sensor. The RM Young relative humidity sensor was calibrated before the cruise at the PMEL Tropical Atmosphere Ocean (TOA) calibration facility. The data are the average value over the sampling period.
Barometric pressure was measured with the PMEL Qualimetrics sensor mounted in aero van, 4.5 m above sea level. The sensor was calibrated during the ACE-1 project in 1995. The sensor was compared to the VODYANITSKIY ship barometer on several occasions during ACE-2 and always was found to agree to within one mb. The data are reported in millibars and are the average value over the sampling period.
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 AeroVan, 6 m above sea level. Both instruments were calibrated by The Epply Laboratory on October 11, 1994. There were times when the sampling mast shaded ether or both sensors. There were also times when the ship's mast/bridge shaded the sensors. These "bad" data due to shading have not been edited out of the 30 minute data record. The data are reported in watts per square meter and are the average value over the sampling period.
Wind Components/Wind Speed/Wind Direction:
Wind speed and direction were measured with the PMEL Qualimetrics anemometer mounted above the top of the rain/seaspray shelter at the top of the aerosol/gas sampling mast (10.5 meters above sea level). The location of the PMEL anemometer was chosen primarily to select the times when the sampling mast was in the 'clean' sector, i.e. not being influenced by ship pollution. The data from the PMEL anemometer were recorded on the PMEL data logger as one minute averages. The true North and East components of the wind vector were calculated by subtracting the ships velocity vector (as measured by the PMEL GPS and electronic compass) from the measured relative wind. The wind components were then averaged into 30 minute bins and are given as the N and E wind components, in m/s. The true wind vector was calculated from these components and is given as wind speed in m/s and compass direction. The 30 min average relative wind (speed and direction) was calculated by taking the 1 minute wind and separating the vector into the for-aft and beam components, averaging the two orthogonal components and the recombining the components into a 30 minute average vector. The relative wind vector is given in units of meters per second and in direction from the bow, with wind coming directly on the bow as 0, wind coming from the starboard beam as +90 and wind coming from the port beam as -90 degrees.
Two ozone uv analyzers were used, a Dasibi 1008 AH and a TECO 49. Both analyzers were calibrated to a NIST traceable analyzer at NOAA-CMDL prior to the project. One minute averages of the output of each analyzer were recorded on the PMEL data system and plots were made of the raw data. A small portion of the data was 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). After the raw data were cleaned, the calibration function from CMDL (offset and slope) was applied, and 30-minute averages were created. The 30-minute average from each instrument was then averaged together to create the final data file. 30-minute intervals that had no clean ozone data are tagged with a value -99. One minute ozone data for each instrument are available from Johnson@pmel.noaa.gov.
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 (ACE 1), J. Geophys. Res., 103, 16,743-16,751, 1998. The radon detector was calibrated several times during the cruise to radon emitted from a known source.
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.
During ACE-2 the radon instrument had major problems with RF interference. The instrument was located on the ship's flying bridge, less then 10 meters from a 1 kW, HF radio antenna that was used by the ship as its primary means of communication with its offices in Ukraine. During the radio broadcasts, the detector registered a high number of false counts, and during many broadcasts, the radon instrument computer/controller would also freeze. After a few days we worked around the RF interference by only allowing the ship to broadcast for a 30 minute period between 0800 and 0900 each day. The data from the radon instrument was "dumped" before the radio transmissions and the instrument was rebooted after the transmissions. It was not until day 180, (29 June) that the scheduling of the radio transmissions and the daily rebooting of the radon instrument was established. Before that time, much of the radon data was lost.
After plotting the data, it was apparent that there were periods of obvious data "dropout", i.e., during periods of "smooth" radon concentrations (in the 500 to 1000 mBq/m3 range, there were drops to near 0 that lasted for only one 30 minute interval. These were obviously from some unknown instrumental problem, and these data were edited out. This consisted of 28 data points over an 18 day period.
There were 3 calibrations (on days 170, 181 and day 205). Using the ACE-1 background count (counts arising from non-radon sources) of 13 per 30 min interval, and using the PMEL PYLON radon source strength of 2850 mBq/min, the calibration constants were 4.27, 5.24 and 5.49 mBq/m3/Count respectively (where Count is the number of counts in a 30 minute interval). As most of the reported measurements were between days 181 and 205 a mean of the day 181 and 205 calibrations of 5.37 mBq/m3/Count was used for the final data reduction. These numbers are higher than the pre-cruise values of 3.92 and 3.94. It appears that the Radon instrument had lost up to 40% of its sensitivity to radon during the ACE-2 project. This may have been due to the serious RF
CN and UFCN:
Aerosol particles were sampled at 10 m above sea level through a heated mast. The mast extended 6 m above the aerosol measurement container and was capped with a rotating cone-shaped inlet nozzle that was 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 diameter mast. The lower 1.5 m of the mast were heated to dry the aerosol to a relative humidity (RH) of 55%. Fifteen 1.9 cm diameter conductive tubes extending into this heated zone were used to isokinetically subsample the air stream for the various aerosol instruments at flows of 30 l min-1. Comparisons of the total particle count (Dp 3 nm) during intercomparisons with the NCAR C-130 and ground stations during ACE-1 agreed to within 20% suggesting minimal loss of particles in the inlet system (Weber et al., J. Geophys. Res., in press).
One of the 15 1.9 cm diameter tubes was used to supply ambient air to TSI 3010 (serial number 2086) and TSI 3025 (serial number 1041) particle counters. The 3010 and 3025 measure all particles larger than roughly 12 and 3 nm respectively. The counts from the two detectors are referred to here as CN and UFCN respectively. 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 data were also filtered of short duration (less than 15 minute) spikes of high CN concentrations presumably from passing ships. The filtered one minute data were averaged into 30 minute periods centered on the hour and half-hour.
Aerosol light absorption:
The aerosol light absorption at 550nm was measured with the PMEL PSAP (Radiance Research). The data were compiled as the 30-minute averages in units of Mm-1, inverse megameters (1 Mm-1 = 1E-6 m-1).
Aerosol light scattering:
Light Scattering by Aerosols was measured at three wavelengths (450,550,700nm) with the PMEL-TSI model 3563 nephelometer. The instrument was calibrated on the cruise using CO2. Two impactors were placed upstream of the nephelometer. One had a nominal size cut of 10 um and the other of 1 um. A valve was switched every 15- minutes by the data system so that either total aerosol or submicron aerosol (at 55%RH) light scattering was measured.
Aerosol light scattering data are given in units of Mm-1, inverse megameters (1Mm-1 = 1E-6 m-1).
Air and seawater were immediately analyzed aboard ship for DMS concentrations using the same automated collection/purge and trap system. Air samples were collected through a Teflon line which ran approximately 60 m from the top of the aerosol sampling mast (17 m above sea level, forward of the ship's bridge) to the analytical system. One hundred ml/min of the 4 L/min flow were pulled through a KI solution at the analytical system to eliminate oxidant interferences. The air sample volume ranged from 0.5 to 1.5 L depending on the DMS concentration. Seawater samples were collected from the ship's seawater pumping system at a depth of approximately 3 m. The seawater line ran to the analytical system where 5.1 ml of sample were valved into a Teflon gas stripper. The samples were purged with hydrogen at 80 ml/min for 5 min. Water vapor in either the air or purged seawater sample stream was removed by passing the flow through a -25C Teflon tube filled with silanized glass wool. DMS was then trapped in a -25C Teflon tube filled with Tenax. During the sample trapping period, 6.2 pmole of methylethyl sulfide were valved into the hydrogen stream as in internal standard. At the end of the sampling/purge period the coolant was pushed away from the trap and the trap was electrically heated. DMS was desorbed onto a DB-1 mega-bore fused silica column where the sulfur compounds were separated isothermally at 50C and quantified with a sulfur chemiluminesence detector. The detection limit during ACE-2 was approximately 0.8 pmole. The system was calibrated using gravimetrically calibrated permeation tubes. The precision of the analysis, based on both replicate analyses of a single water sample and replicate analyses of a standard introduced at the inlet of the air sample line, was typically +-8%. The performance of the system was monitored regularly by running blanks and standards through the entire system. Values reported here have been corrected for recovery losses. System blanks were below detection limit. Seawater concentrations are reported in units of nanoMolar, nM, air concentrations are reported in units of parts per trillion, ppt .
Sea Surface Temperature and Salinity:
A Seabird SBE-21 thermosalinograph (sn#=426, on loan from NOAA-PMC, Seattle WA) was used to make a continuous record of seawater temperature and salinity. The thermosalinograph was last calibrated by Seabird on 9/5/95. The thermosalinograph was located in the engine room on the port side and had a short, several meter tube feeding it sample water from ship's seachest. The inlet for the ship's seachest system was located amidships at a depth of about 3 meters.
The one minute data were cleaned of all obvious bad values and of a period on day on Day 193 when the sample water pump was off. The cleaned one minute data were averaged into 30 minute bins.
The TSG data were compared with the 4 meter depth temperature and salinity data from the Max Plank SeaBird CTD (calibrated by SeaBird on Feb. 26, 1997). The difference between the TSG and CTD data were plotted for the 87 casts conducted during ACE-2. On average the TSG temperature was 0.05 degrees warmer than the CTD temperature except for a 5 day period from day 194 through day 198 when the difference was about 0.10 degrees.
Using the data from days 171-193 and 199-203 the statistics of the difference between the TSG and the CTD are:
Thus it appears that the 'warming' of the sample water in the sample line plumbing was 0.05 degrees C. Also, for whatever reason, the reported TSG salinity was 0.068 PSU lower than that reported by the CTD.
Chlorophyll discrete samples:
Discrete chlorophyll samples were collected every four hours while underway. The continuously flowing seawater came through the ship’s seawater plumbing from an inlet located approximately 3 m below the surface on the port side midship. Samples were collected (530 ml), immediately filtered, put into 10 ml of 90% acetone, and frozen by ship personnel. The samples were analyzed within 3-4 days onboard ship using a Turner fluorometer. The fluorometer was calibrated after the cruise using algal chlorophyll ‘a’ from the Sigma Chemical Corp. The data are reported in units of micrograms per liter.
Submicron and supermicron aerosol ionic concentrations.
Two stage impactor data collected onboard the R/V VODYANITSKIY during ACE2, June-July 1997
Submicron and supermicron ionic concentrations.
Berner-type multi-jet cascade impactor used for sample collection. Ion chromatography used for sample analysis.
Details of the sampling and analysis methods can be found in Quinn et al., JGR, vol. 100, 6931, 1996.
All diameters are reported in terms of 50% aerodynamic cutoff diameters (D50,aero).
Sampling RH = 55 +/- 1.4%. Sampling temperature = 24 +/- 2.6degC.
|Stage number||Stage diameter||D50,aero (um)||dlogD (um)|
U.S.Dept of Commerce / NOAA / OAR / PMEL / Atmospheric Chemistry