Campbell Scientific Open Path Eddy Covariance (OPEC) - Manual (Page 9)

OPEC Open-Path Eddy-Covariance
System
This document will serve as a guide to properly install and operate a Campbell Scientific
Open-Path Eddy-Covariance System (OPEC). The OPEC is composed of various
products, e.g., dataloggers, fast response turbulence sensors, slow response meteorological
sensors, and software. These products are manufactured by Campbell Scientific and other
vendors. Manuals for each of these sensors shipped with the system. It is time well spent
reviewing these documents.
Before deploying the equipment in the field, Campbell Scientific Inc. recommends that it be
installed in the lab or outside near the office. Doing so will give the station operator an
opportunity practice installing the equipment, confirming that all the required parts are
available, and practice retrieving data from the system. It is much more convent and less
expensive to trouble shoot the station near the office.
The literature contains information that spans 50 years on Eddy-Covariance theory and
measurements. Section 5 briefly touches Eddy-Covariance theory. For more details on
Eddy-Covariance measurements and data analysis, see the literature.
1. System Description
The Campbell Scientific Open-Path Eddy-Covariance (OPEC) system
measures sonic sensible heat flux, momentum flux, and the flux of other scalars
between the atmosphere and earth’s surface. The system consists of a
datalogger, fast response three-dimensional sonic anemometer, and fast
response scalar sensors. Horizontal wind speed and direction are computed by
the datalogger from the three-dimensional measurements of wind made by the
sonic anemometer.
1.1 OPEC (CSAT3 Only)
The minimum components required to make eddy-covariance measurements
are a datalogger, a CSAT3 three-dimensional sonic anemometer, and a
temperature and humidity probe. This system configuration measures sonic
sensible heat flux, momentum flux, temperature, humidity, horizontal wind
speed, and wind direction. This system configuration is used to compute eddy
diffusivity required to compute fluxes of trace gases measured with a gradient
system (Warland, et al., 2001).
1.2 Basic OPEC
A more typical eddy-covariance system consists of a datalogger, an IRGASON
(integrated gas analyzer and sonic anemometer). With this configuration, the
system can measure carbon dioxide flux, latent heat flux, sonic sensible heat
flux, momentum flux, a sensible heat flux (using sonic temperature corrected
for humidity), temperature, humidity, horizontal wind speed, and wind
direction.
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