Wecoma Quality Control Report Christopher Harvey Tropical Ocean Global Atmosphere (TOGA) Coupled Ocean Atmosphere Response Experiment (COARE) Surface Meteorological Data Processing Center Center for Ocean Atmospheric Prediction Studies The Florida State University August 1, 1995 Report COAREMET 95-10 Version 1.0 Introduction: The data referenced in this report were collected from the research vessel, Wecoma (call sign WSD7079), MIDAS Meteorological System (data acquired from Oregon State University College of Oceanography and Atmospheric Sciences) for TOGA COARE during the Intensive Observing Period (IOP). The data underwent postcalibration and correction before arriving at F.S.U. and information on these corrections are found in the appendix. All data were converted to a standard format and were then preprocessed using an automated data quality checking program. The data were then visually inspected by a data quality analyst who reviewed, modified, and added appropriate quality control (QC) flags to the data. This report summarizes the flags for the Wecoma data sets, including both flags added by the preprocessor and the analyst. Statistical Information: The data from the Wecoma during the IOP were expected to include averaged observations every thirty minutes, with each timestamp being the beginning time of the thirty minute averaging period, from three cruises. Table 1 provides a listing of the start and end dates of the MIDAS Meteorological System during each cruise. Time (TIME), latitude (LAT), longitude (LON), wind direction (DIR), wind speed (SPD), atmospheric pressure (P), relative humidity (RH), temperature (T), and two sea surface temperatures (TS and TS2) were quality controlled. A total of 34,510 values were reviewed and checked and no flags were added resulting in 0% of the data being flagged. Radiation data was included in the original data set, but this data is being quality controlled at The Pennsylvania State University Radiation Data Center. Table 1: Start and End Dates of the MIDAS Meteorological System Cruise Start End Date Total Number Leg Date of Days 1 11/11/92 12/03/92 23 2 12/17/92 01/12/93 27 3 01/24/93 02/14/93 22 Summary: As the statistical information indicates, the data from the Wecoma were in extremely good condition. No problems occurred and the analyst does not foresee any problems in using the data. Appendix: WECOMA COARE 30 MINUTE METEOROLOGICAL DATA (4/12/95) Principal investigator: Dr. Clayton A. Paulson, Oregon State University These data are, with the exception of sea surface temperature, 30 minute averages of the 1 minute data recorded on the Wecoma "Midas" system. The Midas system consists of three instrument towers, one each on the bow, port, and starboard side. The 30 minute means are a single time series combined from the best data from each of the three towers. Criterion for choosing the best tower data for a given time included the consistency of the calibration, how well the data compares with data from other locations on the Wecoma and other neighboring platforms, and how well exposed the instrument is at any given time. During computation of the 30 min. means, any mean value which was an average of less than 15 1-minute samples (means) was discarded, and the resulting gap was filled with a linear interpolation if it was less than a few hours long. Gaps that were more than a few hours long were filled with other data as indicated below. The following lists the location of the instruments and describes problems encountered in the analysis of the data: RELATIVE HUMIDITY Instrument: Vaisala humidity sensor probe mounted midship on the starboard side, 8 m above the water line. Corrections to data: The starboard Vaisala humidity was not turned on until day 325. Days 322.6458 to 325.1667 were filled with humidity from the port Rotronics sensor. Days 318.1458 to 322.6250 were filled with humidity measurements from the hourly Met Log data which was interpolated to 30 min. values. Notes: There were five humidity sensors mounted on the Wecoma: two Vaisalas, two Rotronics, and a General Eastern Dew Point Hygrometer. Careful comparison and post-cruise calibrations were performed. The Vaisala and Rotronics sensors mounted on the bow worked intermittently due to sea spray and other problems. The post-cruise calibration of the Rotronics on the port side was questionable. Data from the GE Dewpointer may still be incorporated, but was noisy and contained large gaps. AIR TEMPERATURE Instrument: Shielded thermistor mounted on a mast at the bow of the ship, 1 m towards the port side, 8 m above the water line. Corrections to data: The instrument was not turned on until day 322. Days 318.1458 to 322.6250 were filled with air temperature measurements from the hourly Met Log data which was interpolated to 30 min. values. There were gaps in the data from the bow during leg 2 due to spray/waves in heavy seas. These gaps were filled with data from the midship port sensor after correcting the port temperature data for the mean offset between the bow and midship port sensor for times when both were working. Notes: Two air temperature sensors were mounted on a mast at the bow of the ship, (1 m on either side of the ship's center line). There were also air temperature sensors located midship on either side of the ship. All sensors were about 8 m above the water line. The bow sensors agreed fairly well with each other, and the midship sensors also agreed with each other. The temperature measured by the bow sensors was on average 0.6 to 0.7 degrees less than measured by the midship sensors. This is expected because of the better exposure of the bow sensors. The bow sensors are not affected as much by the heating of the ship. Of the two bow sensors, a post cal was only possible for the port sensor. ATMOSPHERIC PRESSURE Instrument: Digital barometer mounted in dry lab with intake under the overhang on the main deck, 3.5 m above the water line Corrections to the data: none SEA SURFACE TEMPERATURE (20 cm depth) Instrument: Bucket thermometer. Readings were taken manually every hour by the watch standers on the Wecoma, usually at the fantail rail, midship, beneath the starboard met set. On occasion, readings were obtained on the port side as conditions required. Notes: The hourly readings were linearly interpolated to 30 minute values in order to use them in flux calculations with the 30 minute Midas means SEA SURFACE TEMPERATURE (2 m depth) Instrument: Seabird sensor mounted on a frame attached to the bow of the Wecoma, 2 m beneath the surface of the water. Corrections to the data: A few large spikes in the one minute data were eliminated Notes: Temperature was recorded at 8 Hz. 1 min. averages were computed and 30 min. averages were computed from the 1 min. aves. WINDS Instrument: Two R.M. Young Propeller anemometers mounted one on each side of the Wecoma's main mast, 20.8 m above the water line. Corrections to the data: There were as yet unexplained problems with the factory calibration of the anemometers. The starboard wind speeds were generally higher than the port by 0.5 to 1.0 m/s. Differences in wind direction between the two sensors, however, were small. Pre-cruise factory calibrations were different than post-cruise calibrations, but the pre- and post- cruise calibrations were similar for both sensors. Wind speeds were studied for wind directions which were +/- 5 degrees of head on in order to minimize effects of interference by the ship's superstructure. From scatter plots, the average offset was determined to be 0.83 m/s. This offset was subtracted from the starboard wind speeds before 30 minute means were computed. The post-cruise calibration was applied. Notes: The final wind time series includes data from both the port and starboard wind sensors. The best-exposed anemometer was selected for each 1-min. interval before 30-min. means were computed. Questions regarding this data should be addressed to: Lynn deWitt College of Oceanographic and Atmospheric Sciences Oregon State University Oceanography Admin. Bldg. 104 Corvallis, OR 97331-5503 e-mail: lynnd@oce.orst.edu