PISTON 2018, Philippine Sea r1 = version 1 Preliminary dataset for meteorology, near-surface seawater, air-sea fluxes, and ship navigation NOAA Physical Sciences Laboratory (PSL) Please acknowledge: NOAA PSL: Chris Fairall, Elizabeth Thompson, Sergio Pezoa NOAA PSL / CU CIRES: Ludovic Bariteau, Byron Blomquist Oregon State University: Simon de Szoeke Dataset is subject to change as updates, corrections, and more data become available Please contact the following group if errors are found or if changes/additional variables are requested. Elizabeth Thompson NOAA PSL, elizabeth.thompson@noaa.gov Ludovic Bariteau NOAA PS / CU CIRESL, ludovic.bariteau@noaa.gov Chris Fairall NOAA PSL, chris.fairall@noaa.gov 10-min met and flux results from processing in Spring 2019 Fluxes are positive when heating the ocean, negative when heating the atmosphere. The only positive fluxes are: lw_dn, sw_dn, and sometimes hs when the air-sea temperature gradient change sign from normal tropical conditions. hnet = sw_dn + sw_up + lw_dn + lw_up + hs_b + hl_b + hr_b hnet>0 is heating ocean % heights of sensors as measured in May 2018, Kaohsiung, Taiwan, during installation zu = 16.59; % NOAA bow mast sonic anemometer sensor height (m) ... for wind zt = 15.34; % NOAA bow mast aspirated air T sensor height (m) zq = 15.34; % NOAA bow mast aspirated air rh sensor height (m) zp = 10; % NOAA midship rail dynamic air P sensor height (m) zWXT = 12; % NOAA second weather station height on stern A-frame (m) zsnk = 0.05; % NOAA sea snake depth below water (m)'); zu_ship = 18; % ship wind sensor height (m) zt_ship = 15; % ship temperature sensor height (m) zq_ship = 15; % ship humidity sensor height (m) ztsg_ship = 4; % depth of ship SBE 21 intake for TSG according to SAMOS (m) Wind directions are in meteorological convention: direction from. Wind speed and direction come from the NOAA sonic anemometer on the bow mast. Flow distortion corrections were applied to cross and streamwise winds based on calculations derived from a sister ship, the Ronald H Brown. The wind speed was corrected for flow blockage when wind was from the stern. For this, the ship propellor vanes on top of the bridge were used after height adjustment to that of the NOAA sonic measurement. Only 8% of data for leg 2 were affected, about 30% on leg3. For reference, U_flag is 1 when the data were corrected. Tair is taken from the NOAA aspirated Vaisala air temperature sensor on the bow mast. This was least affected by solar heating. The air temperature was however corrected for ship deck heating effects due to poor relative wind direction (from the stern, over the ship). A correction was computed based on a period when Tsnk-Tair was relatively constant. For reference, Ta_flag is 1 when the data were corrected. Because of issues with NOAA humidity sensor during leg 2 (salty probe), we reconstructed the humidity signal from the ship humidity instrument (also at the bow mast). The ship T/RH sensor is greatly affected by solar heating since it is not sufficiently aspirated, but the quantity qa is less sensitive to solar heating as long as the Tair and rh are measured simultaneously. Thus we first corrected q_air from the ship sensor to correct for offsets with the NOAA sensor for leg 3. We then reconstructed rh from the corrected ship qa, the aspirated and corrected NOAA Tair, and the paired ship measurements. This removed the effects of solar heating on the humidity measurement. Tsnk is measured by the sea snake at 5 cm, 0.05 m, depth. SST is estimated after correction for cool skin and this accounts for the difference between Tsnk and SST. SSQ is calculated from the adjusted SST value. The sea snake appeared well calibrated compared to the ship's TSG and the OSU otter, all of which were agreed within 0.002 deg C at night when the ocean was well mixed. RMSE = 0.32 deg C. Therefore, no further bias correction appears necessary for the ship TSG T or the sea snake, and therefore SST computed from SST (Tsnk - cool_skin). Tskin was provided by the ROSR, an infrared radiometer. Contact: Michael Reynolds, RMR Co. The data included here were reprocessed by Mike April 2020. Tskin is slightly different than SST by 0.1 deg C. We are still investigating the origin of this offset. An update might be provided in the future. The ship's TSG salinity appears to have an offset compared to the OSU otter that drifts with time. It's not clear which sensor is drifting, so no correction to the TSG data has been made. It is also not possible to correct the TSG for the entire time periods because the Otter data were not continuous, and were only first available toward the end of Leg 2 out of 3. The TSG S and Otter S disagree by up to +/- 0.03 (TSG is saltier at beginning, but fresher by end). prate represents a mean rainrate computed as the average of several rain gauges, the NOAA and OSU optical rain gauge, the APL-UW disdrometer, and the ship's bucket rain gauge. Each sensor was QC'd for noise spikes and other contamination. The ship bucket rain gauge was corrected for under sampling associated with the horizontal relative wind. A mean rain rate time series was computed and a gain corrected for each gauge was determined. A new mean was computed and provided here by averaging the gain-corrected time series for all gauges. sw_dn and lw_dn are provided by NOAA's radiometer and represent an average of two collocated pyranometers and pyrgeometers respectively. Some values of sw_dn are provided by the ship radiometer for periods of shadowing on the NOAA instruments. A solar offset correction at night was also applied on sw_dn. sw_up is taken from a commonly used parameterization for surface albedo of the ocean (Payne, 1972). lw_up was derived from the SST measurements and lw_dn, using the COARE 3.6 algorithm. The bulk fluxes of stress (momentum), sensible heat, latent heat, and sensible heat due to rain were provided by the COARE 3.6 algorithm. The COARE 3.6 algorithm was also used to compute the 10-m values of wind speed, temperature, and humidity. SOG and COG were taken from the ship GPS compass. These were used to compute the wind speed relative to earth. cdir is oceanographic convention: direction toward. Surface currents are measured by the ship's ADCP and have been QCed compared to a side mounted ADCP operated by OSU. These were used to compute the wind speed relative to water. The wind speed relative to water are used to compute the fluxes. The significant wave height Hs and phase speed Cp come primarily from the NOAA Reigel 1-D laser altimeter. Some values were corrected with the WAMOS system and the WaveWatchIII model hindcasts. NOTICE TO USERS The data is intended for use by PISTON investigators. Although the data has been through some quality control, it should be considered as preliminary data and users should expect revisions. Revisions will be posted on this site and changes to the data will be documented in the readme files. Questions about the data and its use in publications should be addressed to: Chris Fairall NOAA PSL, chris.fairall@noaa.gov Ludovic Bariteau NOAA PSL, ludovic.bariteau@noaa.gov Elizabeth Thompson NOAA PSL, elizabeth.thompson@noaa.gov