Ship Ron Brown Meteorology Navigation and Surface State Parameters (Johnson)

Ship Ron Brown Meteorology Navigation and Surface State Parameters (Johnson)

Ship's Speed and Heading:
The ship's speed and heading were calculated from the ships position at even 30 minute intervals, as measured by the ship’s GPS. This is the average speed and direction between the reported 30 minutes locations.

Atmospheric Temperature:
Air temperature (degrees C) was measured with the ship's IMET RM Young sensor and recorded on the ship’s scientific computer system (SCS). The sensor was located on the ship's meteorological mast on the bow, 14 meters above the sea surface. This signal agreed well with the PMEL RM Young sensor, located 14 meters above the sea surface on top of the PMEL Aero Van, at night. However, during some daytimes with low relative wind speeds the PMEL sensor was warmer. We assume that this was a result of solar heating of the container deck. There were several occasions of a few hours where there were no available ship (SCS) data. During those times the PMEL RM Young sensor was used in this data record.

Relative humidity:
The relative humidity (%) reported here was measured with the ship's IMET sensor (SCS). The IMET RH was almost always within 3% of the two PMEL RM Young sensors except during the few above mentioned times when the PMEL temperatures were warmer due to solar heating. There were several occasions of a few hours when there were no available ship (SCS) data, during those times the PMEL RM Young sensor was used in this data record

Barometric Pressure:
Barometric pressure was measured with the ship's SCS electronic Vaisala sensor and the PMEL Qualimetrics model 7105-A sensor. There was also a handwritten record from the ship's bridge at 6-hour intervals that used the ship's aneroid barometer (calibrated to sea level by the NWS). When all three records were closely examined the PMEL sensor best followed the ship's aneroid barometer record, although it had a constant offset. Since there was no agreement between the three records, we assumed the recently calibrated aneroid barometer was the most accurate and used this record to calibrate the PMEL barometer. The data reported here are 30-minute averages of the 1-minute data from the PMEL barometer calibrated to sea level with the ship’s aneroid barometer.

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 30 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 30 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. 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.) There were three periods when the PMEL data system was down or the skyvane anemometer was broken. During these periods (DOY 81.2-81.4, 83.1-83.15, 90.16-91.1) the relative wind signal from the "mast" anemometer was used.

The one minute average relative wind speed and direction data were separated into orthogonal components of "keel" and "beam". These components were averaged into 30 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. The true North and East components of the wind vector were calculated and then averaged into 30 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. There were 4 periods when the IMET record was not available: a few hours at the beginning and end of the cruise, a large gap from DOY 80.4 to 91.2 when the IMET wind sensor was damaged and a short period at the start of DOY 95 when the SCS data system was down. During the period from DOY 80.4375 to 91.2500 the anemometer on the ship’s mast above the bridge (recorded on the SCS as "true mast winds") was used. The mast sensor is located higher than the IMET sensor and also is affected more by wind blowing over the ship. During periods of no IMET or mast winds (74.2917 to 75.7917, 95.0000 to 95.0208, and 109.6250 to 109.8750) the hourly hand written records from the ship's "Deck Weather Logs" were used.

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 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 may be 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.)

Data can be downloaded in ACF format by following the ASCII link, or in binary netCDF file format by following the netCDF link