NOAA ship Discoverer Ancillary Data Reduced and Compiled by NOAA-PMEL Version 2, 29 April 1996 Jim Johnson and Tim Bates Data File 95ATM30.CSV contains the following parameters: DOY Latitude Longitude Air T RH True WS True WD Rel WS Rel WD Barometric Pressure Rainfall Solar Radiation UFCN (>3nm) Radon DOY: The data are compiled in 30 minute averages from 15 minutes before to 15 minutes after the half hour. The time is given as decimal day of year (DOY) such that DOY 32.5 is 12 noon GMT on February 1. Ship position: The ships position was recorded on the PMEL data logger from the PMEL Trimbal GPS unit. The latitude and longitude are each even 30 minute points with no averaging. For those times when there were no data at the 30 minute point, a point was taken from the Discoverer's SCS data system file. Units are decimal degrees north for latitude and decimal degrees east for longitude (200 degrees east = 160 degrees west). Atmospheric Temperature and Humidity: Air temperature (degrees C) and relative humidity (%) were recorded with the ship's RM Young sensor, the PMEL RM Young sensor, and the PMEL Qualimetrics sensor. The ship's sensors were mounted on the flying bridge railing next to the stack. The PMEL sensors were mounted on top of aerovan forward of the bridge. Both the ship's RM Young sensors and the PMEL RM Young sensors were calibrated before the cruise at the PMEL TAU calibration facility. The data reported in the ACE-1 data set are from the ship's RM Young sensors. Linear regressions of PMEL sensors versus the ship's gave: Temperature Ship's RM Young vs. PMEL RM Young: y = 0.95x + 0.011 r^2 = 0.99 Ship's RM Young vs. Qual: y = 1.0x + 0.51 r^2 = 0.99 Relative humidity Ship's RM Young vs. PMEL RM Young: y = 1.2x-16.03 r^2 = 0.97 Ship's RM Young vs. Qual: y = 0.75x + 10.6 r^2 = 0.95 Wind: Wind speed and direction were measured with the PMEL Qualimetrics anemometer and the Ship's RM Young anemometer. The PMEL anemometer was mounted above the top of the rain/seaspray shelter at the top of aerosol/gas sampling mast. The location of the PMEL anemometer was chosen primarily to select the times when the sampling mast was in the 'clean' sector, not being influenced by ship pollution. The ship's RM Young anemometer was located on the starboard side of the ship's mast, 33 meters above the water. The PMEL anemometer and ship anemometer were calibrated in the PMEL wind tunnel in July and October 1995, respectively. The data from the PMEL anemometer were recorded on the PMEL data logger as one minute averages. The data from the ship's RM Young anemometer were recorded on the ship's SCS data system as one minute averages. The final 30 min average data are reported in 4 columns: Rel WS, Rel WD, True WS, True WD Relative wind speed (Rel WS) is the 30 minute average of the wind speed (in m/s) relative to the ship. The relative wind direction (Rel WD) is the 30 minute average of the wind direction relative to the bow of the ship (0 degrees, wind is dead ahead; +90, wind is from the starboard beam ; -90, wind is from the port beam). Because the relative wind information is used primarily to determine local ship pollution episodes for air sampling, the PMEL anemometer was used exclusively for the reported relative wind. True wind speed (True WS) is the 30 minute average of the true wind speed in m/s. True wind direction (True WD) is the 30 minute average wind direction in compass degrees. The PMEL anemometer was located closer to the superstructure of the ship and the wind that it measured was more distorted than that measured by the ship's RM Young anemometer. Thus, the RM Young anemometer was used to derive the true wind speed and direction. During the few times when the SCS system was not working, the PMEL wind data were used. The ship's gyro compass input was used to correct the relative wind to true wind. The wind vector was separated into North and East components and the ship's velocity vector components (as determined from the GPS record) were subtracted to find the true North and true East components of the wind. These components and the resulting (computed) speed and direction at one minute intervals were plotted. A few outliners were eliminated and the resulting data were reduced into 30 minute averages. The averaged North and East components were then used to calculate the 30 minute average wind speed and direction. Barometric Pressure: Barometric pressure was measured with the PMEL Qualimetrics sensor. The data were corrected using a linear regression with the ship's barometer and averaged into 30 minute values. The data are reported in millibars. Rainfall: Rainfall was measured with a Scientific Technology Inc. ORG-100 Optical Precipitation Intensity Sensor. The instrument was mounted on the railing of Aero van and was used along with wind direction, wind speed and CN to control the aerosol chemistry pumps. The dynamic range of the sensor is 0.5 to 1600 mm/h. Spikes in the signal are often associated with sea spray. The 30 minute averaged data include all data points. The data are reported in units of mm/hr. (Note: since the data are 30 minute averages, summing all 48 points for one day and dividing by two will give total precipitation in mm for that day.) Solar Radiation (Insolation): 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. Both instruments were calibrated by The Eppley Laboratory on October 11, 1994. There were times when the sampling mast shaded the sensor. Most of these times occurred for about a 30 minute period in the afternoon. (When the ship was traveling South, the mast was West of the sensor). There were also times when the ship's mast shaded the sensor. Both of these shading events can be clearly seen in the sky camera pictures. These "bad" data due to shading have not been edited out of the 30 minute data record. The data reported in the 95atm30.csv file in watts per square meter are 30 minute averages of the Epply 8-48 (SN 12946). Any 30 minute period without valid data is marked with a -99. Total Particle Number (UFCN): The total number of particles with diameters > 3nm were measured with a TSI 3025 UFCN at the base of the aerosol sampling mast. Missing and polluted data values have been replaced by -99. A one-minute data file with all values has also been included in the ACE-1 data archive as a record of ship pollution events. Units are particles per cubic centimeter. Radon: Radon was measured with a dual-flow-loop two-filter radon detector constructed at PMEL by Stewart Whittlestone (ANSTO). The system was calibrated with a dry radon source (Pylon Electronics Corp. Canada - 2737 mBq/min) and intercalibrated in Hobart at the beginning of the experiment (Nov.) with the source used by Stewart Whittlestone. The radon data set includes all data points with the exception of the instrument calibration periods in Seattle and Hobart. The data are reported in units of mBq per cubic meter. A background value of 20 counts was used in the data reduction. This value was based on the lowest 2.5 hr running mean values obtained during the transit cruise. These low values occurred at approximately 10 degrees south. The final values are based on the following equation: concentration in mBq/m3 = (counts - 20) * 3.75 mBq/m3/count Occasionally the 30 minute data were less than the background value of 20. In these cases a radon concentration of zero was entered in the 30 minute data. Also given in this file is the 2.5 hour running mean concentration which is perhaps a better estimate of the real concentration.