Glossary

A

Air Temperature
(AT)

Measurement of the heat content of the air.

  • CF Standard Name: air_temperature

  • Units: °C (the CF standard calls for units of °K).

  • Epic Code: 21

B

Beam Correlation

ADCP variable. Correlation is a measure of the pulse-to-pulse correlation in a ping for each depth cell, indicating the validity or confidence in the data. Low values will increase noise level or increase variability in velocity data and reduce the measurement accuracy.

  • CF Standard Name:

  • Units: none

  • Epic Code (beams 1, 2, 3, 4): 1285, 1286, 1287, 1288

Bloom Trend

Numeric code stating whether or not a bloom is occuring. Produced daily. Currently allowed values are

CodeMeaning
0No Trend
1Biomass decreasing
2Biomass variable
3Biomass increasing
4Possible advection event
5Probable advection event
6Possible bloom
7Probable bloom

Breakout ID

First numeric value in a line in the Campbell input file.

C

Chlorophyll

The instruments that monitor Chlorophyll fluorescence emit specific wavelengths of light into a water column causing phytoplankton to fluoresce. The fluorescence is an important estimate of phytoplankton biomass and measurements can also be scaled to monitor chlorophyll concentration. This measurement is relevant to issues of aquaculture, eutrophication (over abundance of nutrients), primary production, fisheries, and ecosystem health.

  • CF Standard Name:

  • Units: micrograms/liter

  • Epic Code: 933

Current Direction
(CDIR)

Measured in oceanographic conventions (direction into which the water flows, measured from true north).

  • CF Standard Name: direction_of_sea_water_velocity

  • Units: angular_degrees (CF:degree)

  • Epic Code: 310

Current Speed
(CSPD)

Magnitude of current velocity.

  • CF Standard Name: sea_water_speed

  • Units: cm/s (CF:m/s)

  • Epic Code: 300

Current Velocity - East Component
(u)

Description needed.

  • CF Standard Name: eastward_seawater_velocity

  • Units: cm/s (CF:m/s)

  • Epic Code: 1205

Current Velocity - North Component
(v)

Description needed.

  • CF Standard Name: northward_seawater_velocity

  • Units: cm/s (CF:m/s)

  • Epic Code: 1206

D

Depth of PAR Downwelling Light Level
(ParLightLevel)

Depth where only a specific percentage of the total photosynthetically available radiation can penetrate.

  • CF Standard Name:

  • Units: meters

  • Epic Code:

Diffuse Attenuation Coefficient
(Kd)

The diffuse attenuation coefficient, averaged over the depth range from just below the sea surface (z = 0-) to depth z in meters, is required to calculate the attenuation of downwelling spectral irradiance.

  • CF Standard Name:

  • Units: m-1

  • Epic Code:

Diffuse Attenuation Coefficient of PAR
(Kd(PAR,))

The diffuse attenuation coefficient, averaged over the depth range from just below the sea surface (z = 0-) to depth z in meters, is required to calculate the attenuation of downwelling photosynthetically available radiation.

  • CF Standard Name:

  • Units: none

  • Epic Code:

Dissolved Oxygen
(DO)

Dissolved oxygen refers to the volume of oxygen that is contained in water. Oxygen enters the water by photosynthesis of aquatic biota and by the transfer of oxygen across the air-water interface. The amount of oxygen that can be held by the water depends on the water temperature, salinity, and pressure. Gas solubility increases with decreasing temperature (colder water holds more oxygen). Gas solubility increases with decreasing salinity (freshwater holds more oxygen than does saltwater). Both the partial pressure and the degree of saturation of oxygen will change with altitude . Finally, gas solubility decreases as pressure decreases. Thus, the amount of oxygen absorbed in water decreases as altitude increases because of the decrease in relative pressure (Smith, 1990).

Once absorbed, oxygen is either incorporated throughout the water body via internal currents or is lost from the system. Flowing water is more likely to have high dissolved oxygen levels than is stagnant water because of the water movement at the air-water interface. In flowing water, oxygen-rich water at the surface is constantly being replaced by water containing less oxygen as a result of turbulence, creating a greater potential for exchange of oxygen across the air-water interface. Because stagnant water undergoes less internal mixing, the upper layer of oxygen-rich water tends to stay at the surface, resulting in lower dissolved oxygen levels throughout the water column. Oxygen losses readily occur when water temperatures rise, when plants and animals respire, and when microbes aerobically decompose organic matter.

  • CF Standard Name: none

  • Units: ml/l

  • Epic Code: 60

Downwelling Irradiance
(Ed)

Ed is the measured downwelling irradiance at wavelength lambda and depth z.

  • CF Standard Name:

  • Units: microwatts/cm^2/nm

Downwelling Irradiance of PAR
(EdPAR)
 

The Photosynthetically Active Radiation (PAR) measure of radiant power is important in evaluating the effect of light on plant growth. In 1972 it was shown by K. McCree (Agric. Meteorol., 10:443, 1972) that the photosynthetic response correlates better with the number of photons that with energy. This is expected because photosynthesis is a photochemical conversion where each molecule is activated by the absorption of one photon in the primary photochemical process.

PAR is defined in terms of photon (quantum) flux, specifically, the number of moles of photons in the radiant energy between 400 nm and 700nm. One mole of photons is 6.0222e+23 photons (6.0222e+23 is Avagadro's Number). The Photosynthetic Photon Flux Density (PPFD), i.e., the photon irradiance, is expressed in moles per square meter and per second (formerly, Einsteins per square meter and per second).

 
--OSRAM SYLVANIA, a division of OSRAM GmbH 

For the complete document, see [ Sylvania ].

  • CF Standard Name:

  • Units: micromoles/meter^2/second

Dominant Wave Period
(DWP)

Dominant period is the period with maximum energy and is always either the swell period or the wind-wave period.

  • CF Standard Name: period

  • Units: seconds

  • Epic Code: 4063

E

Error Velocity
()

Estimate of ADCP Velocity Errors.

  • CF Standard Name: none

  • Units: cm/s

  • Epic Code: 1201

Echo Intensity
()

An indicator of the intensity of the backscatterered acoustic signal, for each ADCP beam, in counts, where each count is about 0.45 dB.

  • CF Standard Name: none

  • Units: none

  • Epic Code (four beams): 1221, 1222, 1223, 1224

O

Oxygen Saturation
(OXSAT)

The volume of oxygen gas (STP) absorbed from humidity-saturated air at a total pressure of one atmosphere, per unit volume of the liquid at the temperature of measurement.

  • CF Standard Name: none

  • Units: ml/l

  • Epic Code: 64

P

Percent Good

The percent-good data field is a data-quality indicator that reports the percentage (0-100) of good data collected for each depth cell of the velocity profile.

  • CF Standard Name: none

  • Units: %

  • Epic Codes (four beams): 1270, 1271, 1272, 1273

Percent Oxygen Saturation

Ratio of Dissolved Oxygen to Oxygen Saturation.

  • CF Standard Name: none

  • Units: percent

  • Epic Code: 62

Percent Sun

Description needed.

S

Salinity
(S)

The Practical Salinity Scale defines salinity in terms of the conductivity ratio of a sample to that of a solution of 32.4356 g of KCl at 15°C in a 1 kg solution. A sample of seawater at 15°C with a conductivity equal to this KCl solution has a salinity of exactly 35 practical salinity units (psu). A typical measurement far out in the ocean might be around 34.7, but near shore measurements might be expected to be 31-32 due to fresh water discharge.

  • CF Standard Name: sea_water_salinity

  • Units: PSU (practical salinity units)

  • Epic Code: 41

Sigma T

Sigma T is basically the density of seawater. The density of seawater at atmospheric pressure usually varies between 1025 and 1028 kilograms per cubic meter, and since the variability is so small, oceanographers typically subtract of 1000 to get a value between 25 and 28.

  • CF Standard Name: sea_water_density

  • Units: kg/m3

  • Epic Code: 70

Significant Wave Height
(HMO)

The average height of the highest third of the waves.

  • CF Standard Name: sea_height_of_wind_and_swell_waves

  • Units: meters

  • Epic Code: 4061

Solar Zenith Angle
(SZA)

The angle between the local zenith and the line of sight to the sun.

  • CF Standard Name: none

  • Units: radians

  • Epic Code:

Sun Icon

Description needed.

T

Temperature
(T)

Measurement of the heat content of the water. This is slightly different from sea surface temperature (SST) as measured by such satellites as AVHRR or MODIS. SST is a valid measurement for the upper skin of the ocean surface, typically the top 1 millimeter or less. The buoy water temperatures typically come in at a variety of depths.

  • CF Standard Name: sea_water_temperature

  • Units: celsius (the CF standard calls for units of K).

  • Epic Code: 20

Transmissivity

The total transmitted light to incident light.

  • CF Standard Name:

  • Units: percent

  • Epic Code:

U

Upwelling Irradiance
(Lu)

Upwelling irradiance beneath the sea surface.

  • CF Standard Name:

  • Units: microwatts/cm2/nm/steradian

  • Epic Code:

V

Vertical Velocity
(up)

Upward component of current velocity.

  • CF Standard Name: upward_seawater_velocity

  • Units: cm/s (CF:m/s)

  • Epic Code: 1204

Visibility
(VIS)

The purpose of the visibility observation is to identify reduced visibility events. For readings that come in at 3000 meters, it is implied that the visibility is 3000 meters or greater.

An observational value for visibility is based upon a "homogeneous" air mass and not specific to any given direction. For example, if a cloud bank pops in front of the sensor on an otherwise clear-as-can-be day, the visibility might be reported as 3000m because the local air mass in general is still clear, but the visibility in the direction of said cloud bank might not be 3000 meters.

Remember, visibility is not reported in a directional sense here!

  • CF Standard Name: visibility_in_air

  • Units: meters

  • Epic Code: none

W

Wind Direction
(WDIR)

Follows meteorological conventions (direction from which the wind blows, measured from true north). See wind_speed.

  • CF Standard Name: wind_from_direction

  • Units: angular degrees

  • Epic Code: 410

Wind Gust
(WG)

Maximum measured wind speed over the observation interval.

  • CF Standard Name:

  • Units: m/s

  • Epic Code: 402

Wind Speed
(WSPD)

One would think that this is just how fast the wind is moving past the anemometer, but no. Quoting NDBC,

 

Two wind averaging methods are used to calculate average wind speed and direction.

  1. The first wind averaging technique applies to those measurements reported by all DACT, VEEP, and ARES payloads. The average wind speed is the simple scalar average of the wind speed observations. A "unit-vector" average is used to calculate the average wind direction. In this technique, unity serves as the length of the vector, and the wind direction observations serve as the orientation of the vector. The u and v components are then calculated for each observation. Next, the average u and v components are computed and the average wind direction is derived from "arctan(u/v)." Note that this technique will produce greater wind speeds than if a true vector average was used.

  2. The second method, used to calculate average speed and direction reported by NDBC's older GSBP payloads, is a true vector average. In this scheme, the magnitude of the vector is represented by the wind speed observation and the direction observations are used for the orientation. The vectors are then broken down into their u and v components. All u and v components are then averaged separately. The resulting average speed and direction are calculated from the Pythagorean Theorem and "arctan(u/v)," respectively.

 
--NDBC 

Both methods are employed, and in fact both variables are archived in the sensor-raw NetCDF files, but only wind_speed_sc (scalar average) is reported as "wind speed" and wind_direction_uv (unit vector method) as "wind direction".

  • CF Standard Name: wind_speed

  • Units: m/s

  • Epic Code: 401