#ACCESSION NUMBER: 0099078 #CONTRIBUTOR: Fernando Santiago-Mandujano Contact Information: Work: 808 956 7000 mandujan@soest.hawaii.edu #CONTRIBUTOR INSTITUTION: University of Hawaii Dept. of Oceanography 1000 Pope Road Honolulu, HI 96822 #ORIGINATOR: Dr. Roger Lukas Contact Information: Work: 808 956 4101 Fax: +1 808 956 9222 rlukas@hawaii.edu #ORIGINATOR INSTITUTION: University of Hawaii Dept. of Oceanography 1000 Pope Road Honolulu, HI 96822 #TITLE: Ocean currents and water temperatures measured by moored ADCPs from the WHOI Hawaii Ocean Timeseries Site (WHOTS) program in the North Pacific from 2004 to 2011 #PROJECT: The Woods Hole Oceanographic Institution (WHOI) Hawaii Ocean Timeseries (HOT) Site (WHOTS) Data available free of charge. User assumes all risk for use of data. User must display CITATION in any publication or product using data. CITATION: "These data were collected and made freely available by Woods Hole Oceanographic Institution (WHOI) Hawaii Ocean Timeseries (HOT) Site (WHOTS), supported by the National Oceanic and Atmospheric Administration (NOAA) through the Cooperative Institute for Climate and Ocean Research (CICOR) under Grant No. NA17RJ1223 to the Woods Hole Oceanographic Institution, and via a subcontract from the UH NSF project OCE03-27513." #ABSTRACT: The Woods Hole Oceanographic Institution (WHOI) Hawaii Ocean Timeseries (HOT) Site (WHOTS) is a coordinated part of HOT, and consists of a mooring that has been providing measurements of high-quality air-sea fluxes and the associated upper ocean response at Station ALOHA, about 100 km north of Oahu, Hawaii since August 2004. WHOTS is funded by NOAA and NSF and it is led by the WHOI Upper Ocean Processes Group. The WHOTS mooring is located at station ALOHA (a 6 nautical mile radius circle centered at 22 45'N, 158 W) in the central subtropical gyre of the North Pacific. The mooring has been in place for one-year periods since 2004 at a location that has been alternating between the eastern and southern edges of ALOHA. This NODC accession contains raw and quality controlled east, north, and upward current components, water temperatures, and ancillary diagnostic parameters for the first 7 WHOTS deployments (2004-2011) as measured by moored, upward-configured Acoustic Doppler Current Profilers (ADCP) of frequencies 300, 600, and 1200 kHz. The 300 kHz ADCP was deployed at 125 m depth while the 600 and 1200 kHz instruments were mounted at 48 m depth. The greater the frequency of the ADCP ping, the higher the resolution within a given bin, the shorter the bin length, and the smaller vertical range. Temporally, final data are 10-minute ensembles, except deployment 4 for the 600 kHz with 15-minute ensembles. The data are provided within NetCDF files (OceanSITES time-series Conventions 1.2). NODC accession 0090188 holds temperature and conductivity (salinity) data collected using SeaBird SBE-16 SeaCAT and SBE-37 MicroCAT instruments for the first 7 WHOTS deployments (2004-2011). NODC accession 0098789 has the Next Generation Vector Averaging Current Meter (NGVM) measurements at 10 and 30 m depths for the first 7 WHOTS deployments (2004-2011). #PURPOSE: In 2003, Robert Weller (Woods Hole Oceanographic Institution [WHOI]), Albert Plueddemann (WHOI) and Roger Lukas (University of Hawaii [UH]) proposed to establish a long-term surface mooring at the Hawaii Ocean Time-series (HOT) Station ALOHA (22 45N, 158W) to provide sustained, high-quality air-sea fluxes and the associated upper ocean response as a coordinated part of the HOT program, and as an element in the National Oceanic and Atmospheric Administration’s (NOAA) array of global ocean reference stations. With support from the NOAA and the National Science Foundation (NSF), the WHOI HOT Site (WHOTS) surface mooring has been maintained at Station ALOHA since August 2004. The objective of this project is to provide long-term, high-quality air-sea fluxes as a coordinated part of the HOT program and contribute to the goals of observing heat, fresh water and chemical fluxes at a site representative of the oligotrophic North Pacific Ocean. The approach is to maintain a surface mooring outfitted for meteorological and oceanographic measurements at a site near Station ALOHA by successive mooring turnarounds. These observations will be used to investigate air sea interaction processes related to climate variability. #LOCATION EXTREMES: SOUTHERNMOST LATITUDE: 22.670167 SOUTHERNMOST LATITUDE HEMISPHERE: N NORTHERNMOST LATITUDE: 22.766667 NORTHERNMOST LATITUDE HEMISPHERE: N WESTERNMOST LONGITUDE: 157.95 WESTERNMOST LONGITUDE HEMISPHERE: W EASTERNMOST LONGITUDE: 157.89833 EASTERNMOST LONGITUDE HEMISPHERE: W #LOCATION KEYWORDS: North Pacific Ocean, Hawaii, Station ALOHA #SAMPLING STATIONS: The WHOTS mooring is located at station ALOHA (a 6 nautical mile radius circle centered at 22 45'N, 158 W) in the central subtropical gyre of the North Pacific. The mooring has been in place for one-year periods since 2004 at a location that has been alternating between the eastern and southern edges of ALOHA (22 46.00'N, 157 53.90'W (Station 50), and 22 40.21'N, 157 57.00'W (Station 52) respectively). #BEGIN AND END DATES: 14 August 2004 - 18 April 2011 #SAMPLING PERIODS: Deploy- Deployment-Recovery Station Coordinates ment Date Date Number Number ------- ---------------------------- --- ---------------------- WHOTS-1 12 August, 2004-25 July, 2005 50 22 46.00'N 157 53.90'W WHOTS-2 28 July, 2005-26 June, 2006 50 22 46.00'N 157 53.91'W WHOTS-3 26 June, 2006-28 June, 2007 50 22 45.99'N 157 53.99'W WHOTS-4 25 June, 2007-6 June, 2008 52 22 40.21'N 157 57.00'W WHOTS-5 5 June, 2008-16 July, 2009 50 22 46.01'N 157 53.83'W WHOTS-6 10 July, 2009-3 August, 2010 52 22 39.91'N 157 56.66'W WHOTS-7 27 July, 2010-11 July, 2011 50 22 39.91'N 157 56.66'W Specifics for ADCP time series Columns 1: WHnn, where nn is WHOTS deployment number 2: Frequency of ADCP (kHz) 3: date of start 4: time of start (GMT) 5: date of end 6: time of end (GMT) 1 2 3 4 5 6 wh01adcp_300 2004-08-14 00:00:00Z 2005-07-25 17:10:00Z wh02_adcp_300 2005-07-28 09:40:00Z 2006-06-24 18:20:00Z wh03_adcp_300 2006-06-28 00:00:00Z 2007-06-28 09:49:60Z wh04_adcp_300 2007-06-26 12:00:00Z 2008-06-06 16:50:00Z wh04_adcp_600 2007-06-26 12:00:00Z 2008-06-06 16:45:00Z wh05_adcp_1200 2008-06-05 11:30:00Z 2009-07-15 16:33:60Z wh06_adcp_300 2009-07-11 09:20:00Z 2010-08-02 17:00:00Z wh06_adcp_600 2009-07-11 09:20:01Z 2010-08-02 17:00:01Z wh07_adcp_300 2010-07-29 11:10:00Z 2011-04-18 01:39:60Z wh07_adcp_600 2010-07-29 11:10:00Z 2011-04-18 01:39:60Z #PARAMETERS: primary oceanographic parameters: Current velocities, raw and quality controlled (Eastward, Northward and Upward) sea water temperature current east component current north component current upward component ancillary diagnostic ADCP parameters: Quality control tests ADCP beams Percent Good Fields velocity quality control tests tilt_angle_from_vertical error velocity raw beam correlation raw percent good echo_amplitude #METHODOLOGY: A Teledyne/RD Instruments 300, 600 and 1200 kHz broadband Workhorse Sentinel ADCPs were deployed in the upward looking configuration at 125 m (300 kHz) and 48 m (600 and 1200 kHz) depths below the ocean surface. Some WHOTS deployments had more than one ADCP. The instrument was installed in an aluminum frame along with an external battery module to provide sufficient power for the intended period of deployment. The four ADCP beams were angled at 20 degrees from the vertical line of the instrument. The 300 kHz ADCP was set to profile across 30 range cells of 4 m with the first bin centered 6.2 m from the transducer and a maximum range of the instrument just short of 125 m. The 600 kHz ADCP has 25 range cells with 2 m depth bins while the 1200 kHz has 17 cells with 1 m bins. The greater the frequency of the ADCP ping, the higher the resolution within a given bin, the shorter the bin length, and the smaller vertical range. Temporally, final data are 10-minute ensembles, except deployment 4 for the 600 kHz ADCP with 15-minute ensembles. Quality control led to a system of flags for the final data. Quality control of the data involved the thorough examination of the velocity, attitude and diagnostic fields to determine the basis of the flagging scheme. The first bin (closest to the transducer) is sometimes corrupted due to what is known as ringing. A period of time is needed for the sound energy produced during a transmit pulse at the transducer to dissipate before the ADCP is able to receive the returned echoes. This gap is known as the blanking interval and if it is too short, signal returns can be contaminated from the lingering noise from the transducer. The default value for the blanking interval is 1.76 m. Each deployment was examined for too short of a blanking interval. For an upward looking ADCP within range of the sea surface with a beam angle of 20 degrees, the upper 6 per cent of the depth range is contaminated with sidelobe interference. This is a result of stronger signal reflection from the sea surface (than from scatterers) overwhelming the sidelobe suppression of the transducer. Data are flagged empirically using echo intensity (a measure of the strength of the return signal) from each beam to determine when the signal is contaminated with reflection from the sea surface. In practice, the majority of the data within the upper 4 bins (~14 per cent of the vertical range) were flagged. The use of four beams to resolve currents into their component velocities provides us with a second estimate of the vertical velocity. The difference between these two vertical velocities is defined as the error velocity and is useful for/in assessing data quality. Error velocities with an absolute magnitude greater than 0.15 m/s were flagged and removed. An indication of data quality for each ensemble is given by the PERCENT GOOD data fields. The use of the percent good fields is determined by the coordinate transformation mode used during the data collection. With profiles transformed into earth coordinates, the percent good fields show the percentage of data that was made using 4 and 3 beam solutions in each depth cell within an ensemble, and the percentage that was rejected as a result of failing one of the criteria set during the instrument setup. Data were flagged when data in each depth cell within an ensemble made from 3 or 4 beam solutions was 20 per cent or less. Data were rejected using correlation magnitude, which is the pulse-to-pulse correlation in a ping for each depth cell. If any one beam had a correlation magnitude of 20 counts or less that data point was flagged. Originally, it was thought that the maximum vertical velocities experienced at the WHOTS site would be due to displacements as a result of the M2 tide. The maximum displacement would be 23 m which would give rise to vertical velocity of 0.03 cm/s. However based on histograms of raw data and partially cleaned data from the ADCP, this estimate seems of an order of magnitude too small. At present we are unsure as to the cause of these higher than anticipated velocities but based on the histograms of the partially cleaned observed data, depth cells with an absolute value of vertical velocity greater than 0.3 m/s were flagged. A median filter was used in the removal of data spikes from data that had passed through the flagging process documented above. A vertical mean of both the east and west velocity components was taken across depth cells 2 to 20, as data across this range are generally considered to be of high quality and somewhat unaffected by the lack of scatterers and other factors that are responsible for the degradation of data quality in depth cells closer to the surface. After examining a number of different schemes, a 7-point median filter was applied to this vertical mean and points that were greater than a threshold value of 0.1 m/s were flagged. The ADCP thermistor is mounted on the transducer and measures in-situ sea water temperature using International Temperature Scale of 1990. Cross- comparisons with other temperature data were used as a check. Instrument configurations, and additional notes on post-deployment calibration, processing and quality-control details are given in a technical data report (Santiago-Mandujano et. al, 2008). #INSTRUMENT TYPES: Teledyne/RD Instruments Workhorse 300, 600 and 1200 kHz ADCPs #REFERENCES Fernando Santiago-Mandujano, Paul Lethaby, Roger Lukas, Jefrey Snyder Robert Weller, Albert Plueddemann, Jeffrey Lord, Sean Whelan, Paul Bouchard, and Nan Galbraith, Hydrographic Observations at the Woods Hole Oceanographic Institution (WHOI) Hawaii Ocean Timeseries (HOT) Site (WHOTS): 2004 - 2006, Data Report No. 1. School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, 2008. pp 229. http://www.soest.hawaii.edu/whots/docs/Whots_data_report_1.pdf #SUBMITTING MEDIUM: FTP #FILE FORMATS: Directories and files: /data root data directory /0-data Files as received by NODC from the originator File Naming Convention and Format Filename: WHnn_adcp_.nc where nn: WHOTS deployment number : ADCP transmission ping frequency in kHz (300, 600 or 1200) .nc: denotes NetCDF file note: wh01adcp_300.nc does not have the first underscore in the filename Format: Netcdf_version = 4.0.1 , NetCDF Conventions: OceanSITES 1.2 Naming_authority: OceanSITES Content: data file for specific deployment and ADCP Current quality control flags: The CUR_QC three-dimensional matrix contains quality control tests for data in each bin and each ensemble for 12 different criteria. Criteria 1 through 6 are applied independently, and 7 through 12 are applied in order. Values are 1 if the criteria applies to the data point and thus it is considered suspect, and 0 if it does not apply. Data points for which at least one of the quality criteria apply are -999 in the UCUR and VCUR variables. This CUR_QC matrix can be used to generate a different data product (u,v,w) by neglecting any of the quality control tests to make a mask matrix to transform the raw data. In addition, the user may establish other criteria for quality control based on tilt, echo intensity, etc. The quality control criteria in the CUR_QC matrix are the following: 1:bin 1 is bad due to ringing, the echo was contaminated by residual energy from the transmission pulse. 2:sidelobe interference due to a stronger signal reflection from the sea surface than from scatterers, 3:error velocity assessment, velocity is bad if the error velocity is greater than 0.15 m/s in magnitude (error velocity is the scaled difference between vertical velocity estimates from the two Janus pairs of beams). 4:percent good, the data are bad if the percentage of data within an ensemble using 3 and 4 beam solutions is 20% or less. 5:correlation magnitude, the data are bad if the pulse-to-pulse correlation in a ping for each depth cell is 20 counts or less. 6:vertical velocity, data are bad when the absolute vertical velocity is greater than 0.3 m/s. 7:flag_edgers, identifies suspect data in the upper bins, the median velocity of the upper bins (i.e. bins 18-30 for 300 kHz instruments) is used to calculate a 5 point running median in time (ignoring gaps), velocities differing by more than 0.48 m/s from this median are flagged bad. 8:low-pass filter residuals to flag vertical stripes (mostly observed in the 300 kHz instruments), residuals of a 5 pole low pass Butterworth filter with a cutoff frequency of 1/4 cycle/hour in the vertical greater than 4 standard deviations from the mean (for each bin) are flagged bad. 9:median filter residuals to flag vertical stripes, the vertical velocity median is used to calculate a 7 point running median in time, residuals from this median differing by more than 4 standard deviations from the mean are flagged bad. 10:horizontal residuals to flag horizontal stripes (applies only to 600 and 1200 kHz instruments), residuals of a horizontal velocity median from the 7 horizontally closest bins are used to calculate an 11 point running median in time, residuals from this median are used to identify horizontal stripes with cutoffs determined by looking at the root mean square of bin to bin velocity differences. 11:outliers routine, for each point residuals from a 5 point horizontal median (temporal median difference) and 4 point vertical median (spatial median difference) are compared against the standard deviation of these residuals, points are flagged bad when both temporal and spatial median differences exceed 4 times the standard deviation or when either one of them exceeds the standard deviation by 6 times. 12:visually detected outliers, time series of both bins and vertical profiles are visually examined for any additional suspicious points. /1-data Files created by NODC Filename: same as /0-data as above except nc replaced by txt Format: ASCII text Content: these text files contain metadata associated with each NetCDF file created using NetCDF function ncdump. #DATASET SIZE: 734,660 mbytes #NUMBER OF DATA UNITS: 7 unique mooring deployments #MISCELLANEOUS: NODC accession 0090188 holds temperature and conductivity (salinity) data collected using SeaBird SBE-16 SeaCAT and SBE-37 MicroCAT instruments for the first 7 WHOTS deployments (2004-2011). NODC accession 0098789 has the Next Generation Vector Averaging Current Meter (NGVM) measurements at 10 and 30 m depths for the first 7 WHOTS deployments (2004-2011).