------------------------------------------------------------------------ Data Processing Notes Coastal Mixing and Optics Moored Array 05 May 2000, AJP ------------------------------------------------------------------------ General ------------------------------------------------------------------------ All surface mooring data from the Inshore site were blanked during a period that the mooring was off station (18 Sep 1996, 1849 to 26 Sep 1996, 1600 UTC). All surface mooring data from the Alongshore site were blanked during a period that the mooring was off station (09 Oct 1996, 0600 to 02 Nov 1996, 2118 UTC). Wind directions are in oceanographic convention (direction towards), opposite to the meteorological convention (direction from). An improved understanding of VMCM record timing resulted in changes to the processing scheme relative to previous experiments. First, it was determined that the counter for the first record written to tape is 2. The assigned record times relative to the reset time were adjusted to reflect this. Second, it was recognized that the appropriate sample times for temperature and velocity are different. Temperature is a point sample at the start of the interval, and is assigned the record start time Tn. Velocity is an average over the sample interval, and is assigned the time Tn + delta_T/2, where delta_T is the sample interval. Meteorology ------------------------------------------------------------------------ Wind Speed: VAWR 704 was used as the primary wind speed record, based on comparison with a sonic anemometer on the central discus buoy. Sonic anemometer wind speeds were used during two periods (09 Feb - 17 Apr 1997 and 7 May - 13 June 1997) when VAWR 704 wind speed was unavailable. Wind Direction: VAWR 704 was used as the primary wind direction record, based on comparison with several other wind measurements. The VAWR 704 compass failed on 12 May 1997 0330 UTC. After this, wind direction was from an anemometer mounted on a guard buoy. After this guard buoy was recovered on 10 June 1997, wind direction was from the nearest gridpoint of a regional weather prediction model. A magnetic variation (also referred to as magnetic declination) of -15.417 degrees was determined for the site based on the International Geomagnetic Reference Field (IGRF) model available from the National Geophysical Data Center. East and North wind components are rotated to account for this compass offset, but the actual compass values are not adjusted. Speed and direction are computed from the velocity components. Air Temperature: VAWR 704 was used as the primary air temperature record, based on a more complete record than VAWR 720 and better agreement with two other air temperature sensors. Sea Surface Temperature VAWR 704 was used as the primary air temperature record. A drift relative to surrounding temperature sensors (cumulative value 0.03 C) was detected starting on 27 Apr 1997, and was corrected by applying a polynomial fit. Barometric Pressure VAWR 704 was used as the primary barometric pressure record, based on a more complete record than VAWR 720. Relative Humidity VAWR 704 was used as the primary relative humidity record. The sensor failed on 8 May 1997. Relative humidity for the remainder of the deployment was from the nearest gridpoint of a regional weather prediction model. Longwave Radiation VAWR 704 was used as the primary longwave radiation record, based on a more complete record than VAWR 720. Shortwave Radiation VAWR 704 was used as the primary shortwave radiation record. A bias of -2.6 W/m^2 was applied to the record to account for the minimum observed night time bias. Precipitation BPRC 001 was used as the primary precipitation record due to a less noisy record than BPRC 002. The cumulative rainfall record was multiplied by a scaling factor so that the total rainfall equals the average of the two sensors. Temperature and Salinity ------------------------------------------------------------------------ Sampling: The nominal sampling interval for CMO was 7.5 min. However, all Tpods and MTR 3250 sampled at 30 min, Seacats 882, 883, 884 and 885 sampled at 15 min, and Tidegauges 45, 46 and 49 sampled at 5 min. These records were interpolated to 7.5 min. Seacats 1874, 1881 and 1882 sampled at 45 s prior to 30 Oct 1996 and 7.5 min afterwards. The 45 s data were subsampled at 7.5 min intervals. Performance: All Tpods stopped 10-15 days prior to recovery of the array due to limited internal storage. The Seacats using multiple sample rates (1874, 1881 and 1882) had short records due to battery power limitations. Seacats 71 and 1877 had short records. Tpods 4493 and 3274 had short records. Conductivity measurements from Seacat 927 were bad after 03 Sep 1996. Conductivity measurements from Seacat 1882 were truncated at 12 Nov 1996, 1540 due to excessive drift. VMCMs 24, 53, and 54 had an unusually large number of tape read errors and clock errors. VMCM 24 was omitted from the final data set. VMCM 54 had a short record. Calibration and Adjustments: In most cases temperature sensors were pre- and post- calibrated to within 0.02 C accuracy. A few instruments had temperature biases applied to improve agreement with surrounding measurements: MTR 3250, 0.04 C; Tidegauge 45, 0.013 C. Seacats were pre- and post- calibrated by the manufacturer. Many instruments had small conductivity drifts which were corrected with a linear trend to improve agreement with surrounding measurements. The cumulative drifts were: Seacat 68, 0.080; Seacat 70, 0.003 S/m; Seacat 71, 0.005 S/m Seacat 73, 0.015 S/m; Seacat 885, 0.007 S/m; Seacat 1873, 0.010 S/m; Seacat 1874, 0.004 S/m; Seacat 1875, 0.002 S/m. The Tidegauges and some Seacats had larger and/or more complex (non-linear) drifts which were corrected in an ad-hoc manner based on comparison with surrounding instruments: Seacat 72, 0.050 S/m; Seacat 144, 0.070 S/m; Seacat 882, 0.20 S/m; Seacat 883, 0.16 S/m; Seacat 1876, 0.023 S/m; Seacat 1878, 0.060 S/m; Seacat 1880, 0.030 S/m; Tidegauge 46, 0.35 S/m; Tidegauge 45, 0.26 S/m; Tidegauge 49, 0.30 S/m. Velocity ------------------------------------------------------------------------ Sampling: All VMCMs sampled at 7.5 min. Performance: VMCMs 24, 53, and 54 had an unusually large number of tape read errors and clock errors. VMCM 54 had a short record. VMCM 55 velocities were truncated at 12 Nov 1996 due to a compass failure. VMCMs 10 and 53 had rope in their rotors upon recovery. Based on visual inspection of rotor counts, the record for each instrument was truncated at the time the rotors stalled. Velocities from VMCMs 24 and 35 were omitted from the final data due data quality problems. Magnetic Variation: A magnetic variation (also referred to as magnetic declination) of -15.417 degrees was determined for the site based on the International Geomagnetic Reference Field (IGRF) model available from the National Geophysical Data Center. East and North velocity components are rotated to account for this compass offset, but the actual compass values are not adjusted. Speed and direction are computed from the velocity components.