
Title:  METADATA FOR ADCP DATA SETS FROM FIXED VESSEL
	COLUMBIA RIVER LMER PROJECT

Contact: David Jay
	Center for Coastal and Land Margin Research
	Oregon Graduate Institute of Science and Technology
	PO Box 91000 
	Portland, OR  97291-1000
	USA
	email: djay@lternet.edu

Principle Investigators (Institution) and research area: 
	Antonio Baptista (Oregon Graduate Inst. of Science and Technology)	hydrodynamics;
	David Jay (Oregon Graduate Inst. of Science and Technology)		geophysics;

Data Description: The Acoustic Doppler Current Profiler (ADCP) acquires a fine-scale record of horizontal 
current flow through the water column.  Data document the temporal change in degree of riverine versus 
marine influence and, thus, are important in understanding the transport of material in estuarine turbidity 
maxima (ETM) over time.  These data are used to evaluate the hydrographic influences (e.g. tides, river 
flow) on the ETM and are used in conjunction with other data sets to model particle dynamics, biological 
production, and geochemical processing of organic material.

Spatial and Temporal Resolution:  Sampling took place during one 28-35 day cruise per year in each of 
1990, 1991, 1992, 1995, and 1996 from a fixed vessel. In 1997, there were 2 week cruises in May, July, and 
October. ADCP data was also taken from a roving vessel during these years.  For these data and metadata, 
please link to Oregon Graduate Institute data page.

Methodology:  A 1.2 mHz narrow-band ADCP was mounted on an anchored vessel during time series in 
1995 and 1996. Raw data were averaged 1 minute, and were then low-passed to 15 minute intervals.   In 
1997, data were averaged every 5 minutes and low-passed to 15 minute intervals. Vertical bin size of the 
narrow-band ADCP was 1 m, but since the ship moved vertically with the tide, these depths are NOT fixed 
relative to MLLW and may need to be adjusted vertically.  The first depth bin is usually around 6 m below 
the water surface.
	Ships position was determined using GPS or dGPS (after 1995).  Current direction was  resolved 
with a vessel gyrocompass.  The link to the vessel gyrocompass was not functional in 1995, however, and 
current speed was converted to velocity under the assumption that current was perfectly reversing and 
oriented in either the flood (ship's heading = 315) or ebb (ship's heading = 135) direction.  Although u and v 
velocity vectors are given for the 1995 data set, it is strongly recommended that one use total speed 
(sqrt(u^2 = v^2)) instead.

Variables:

Header line:
	Last two digits of year
	Month of year
	Day of month
	Hour (Pacific Standard Time) of measurement
	Minute of measurement
	Latitude (see note below)
	Longitude (see note below)
	Water column depth in m (see note below)
	Apparent bottom speed in east-west direction (mm / sec) 
	Apparent bottom speed in north-south direction (mm / sec)
	Ship's heading used in model (see below)
	Tidal height (always zero here since depths are relative to surface)
	Ebb/Flood tide (1995 data set)

Data lines:
	Depth (m) of profiled layer
	Current speed in the u (east-west) dimension (mm / sec)
	Current speed in the v (north-south) dimension (mm / sec)
	Current speed in the w (vertical) dimension (mm / sec)
	Error velocity estimate (mm / sec) (see below)

Notes and caveats on the data:
	*** positive values of the u velocity variable indicate flood tide due to the approximate e-w 
orientation of the estuary

	*** positive velocity values indicate east, north, and upward flowing currents
	
	*** depth is given from the transducers which are approximately 3 m below the water surface.

	*** error velocity is obtained from the ADCP as a measure of instrument error.  It represents the 
difference in the vertical velocity as estimated by the two pairs of opposite beams on the ADCP.

	*** velocity values of 19999.0 indicate non-applicable data bins (out of range)

	*** zero values for latitude and longitude may be present when readings were not taken or 
navigation was malfunctioning.  All coordinates should be identical for time series measurements since the 
boat only moved several  to tens of meters on its anchor line.

File format: comma-delineated ASCII with header line;
	maximum number of records = 32,000+;
	number of data columns = 14


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