Campbell IRGASON User manual

Open-Path Eddy-Covariance
System Operator’s Manual
IRGASON, KH20, and FW05
Revision: 4/13
Copyright © 2004-2013
Campbell Scientific, Inc.

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Table of Contents
PDF viewers: These page numbers refer to the printed version of this document. Use the
PDF reader bookmarks tab for links to specific sections.
1. System Description ....................................................1
1.1 OPEC (CSAT3 Only)...........................................................................1
1.2 Basic OPEC..........................................................................................1
1.3 Extended OPEC ...................................................................................2
1.4 Additional Fast Response Sensors .......................................................2
2. Installation and Mounting ..........................................2
2.1 Fetch and Sensor Height ......................................................................4
2.2 Mounting..............................................................................................4
2.2.1 Measure Sonic Azimuth................................................................4
2.3 Wiring ..................................................................................................4
2.4 Power ...................................................................................................4
3. System Datalogger Program......................................5
3.1 Program Configuration.........................................................................6
3.1.1 Sonic Azimuth ..............................................................................6
3.1.2 Sensor Configuration ....................................................................8
3.2 Loading a Program to the Datalogger ..................................................9
3.2.1 Direct Connection via LoggerNet .................................................9
3.2.2 Remote via PC/CF Card................................................................9
3.3 System Operation...............................................................................10
3.3.1 Monitoring Data..........................................................................10
3.3.2 Status Table.................................................................................10
4. Data ............................................................................11
4.1 Data Retrieval ....................................................................................12
4.1.1 Direct Connection Data Retrieval via LoggerNet .......................13
4.1.2 File Management with Baler.......................................................15
4.1.3 Remote Data Retrieval via a PC/CF Card...................................17
4.1.4 File Management with CardConvert...........................................18
4.1.4.1 Collecting Data with One Card ........................................21
4.1.4.2 Collecting Data with Two Cards ......................................22
4.2 Data Processing..................................................................................24
4.2.1 Online Processing .......................................................................24
4.2.2 Off-line Processing with EdiRe ..................................................24
4.2.2.1 Creating Raw File Format and Processing Lists ..............25
4.2.2.2 Example EdiRe Raw File Format and Processing Lists ...27
5. Basic Eddy-Covariance Theory...............................31
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Table of Contents
Appendices
A. CSAT3 Orientation ..................................................A-1
A.1 Determining True North and Sensor Orientation ............................ A-1
A.2 Online Magnetic Declination Calculator ......................................... A-3
B. References...............................................................B-1
C. OPEC200 Open Path Eddy Covariance System
Quickstart Guide...................................................C-1
Figures
2-1. Open-Path Eddy-Covariance (IRGASON) System ............................. 3
3-1. IRGASON right hand coordinate system, horizontal wind vector
angle is 0 degrees............................................................................. 7
3-2. Compass coordinate system, compass wind direction is 140
degrees ............................................................................................. 8
4-1. LoggerNet station setup for the “flux” table...................................... 13
4-2. LoggerNet station setup for the “ts_data” table................................. 14
4-3. LoggerNet station data collection schedule....................................... 14
4-4. LoggerNet station status monitor ...................................................... 15
4-5. Baler station setup for the “flux” table .............................................. 16
4-6. Baler station setup for the “ts_data” table ......................................... 16
4-7. File format flow................................................................................. 18
4-8. Destination File Option screen .......................................................... 19
4-9. Fully configured CardConvert start up screen................................... 20
4-10. List of files created by CardConvert.................................................. 21
4-11. List of files created by CardConvert with duplicates ........................ 22
4-12. List of files where the duplicate files are renamed to *.bak .............. 22
4-13. List of files collected the first time using two cards .......................... 23
4-14. List of files collected the second time using two cards ..................... 23
4-15. Interpreter settings to read a Campbell Scientific TOB1 data file..... 26
4-16. Folder that contains the raw TOB1 time series data files .................. 26
4-17. Completed Interpreter screen............................................................. 27
4-18. Estimated sample frequency and correct sample frequency .............. 27
4-19. Default EdiRe processing list created by the Interpreter ................... 28
4-20. Output file location as part of the processing list .............................. 29
4-21. Output file location as part of the processing list .............................. 29
4-22. Processing Uzand CO2with 1 Chn Statistics instruction .................. 30
4-23. Computing CO2flux with 2 Chn Statistics and graphing Uz
statistic with Plot Value instruction ............................................... 30
5-1. Ideal vertical profiles of virtual potential temperature and specific
humidity depicting all the layers of the atmospheric boundary
layer ............................................................................................... 31
A-1. Magnetic declination for the conterminous United States (2004) ... A-1
A-2. A declination angle East of True North (positive) is subtracted
from 360 (0) degrees to find True North...................................... A-2
A-3. A declination angle West of True North (negative) is subtracted
from 0 (360) degrees to find True North...................................... A-2
A-4. Online magnetic declination calculator with inputs and output
for Longmont, CO........................................................................ A-3
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Table of Contents
Tables
2-1. Nominal Sensor Power Requirements..................................................5
2-2. Nominal Datalogger Power Requirements with the Display Off
and No RS-232 Communications .....................................................5
2-3. Nominal Datalogger Power Requirements with the Display and
Backlight On, and No RS-232 Communications..............................5
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Table of Contents
iv

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.
1

OPEC Open-Path Eddy-Covariance System
1.3 Extended OPEC
Energy balance sensors can be added to a basic OPEC system to also measure
the net radiation, soil heat flux, soil temperature, and soil water content. The
sensors required for these additional measurements are a NR-LITE, CNR2,
NR01 or CNR4 net radiometer; two or four HFP01 or HFP01-SC soil heat flux
plates, one or two TCAV averaging soil temperature probes, and one or two
CS616 or CS650 soil moisture reflectometers. The number of soil sensors will
vary with the site. A heterogeneous site will require more sensors to get
adequate spatial representation of the site. The datalogger can accommodate
the additional measurements with a multiplexer. Energy balance sensors no
longer carried by Campbell Scientific are also supported by the extended
OPEC datalogger program, including the Q7.1 and CNR1 net radiometers, and
HFT3 soil heat flux plates.
1.4 Additional Fast Response Sensors
If the application requires a direct measurement of sensible heat flux, a FW05
can be added to the system. In the absence of a FW05 or if the FW05 breaks,
the sensible heat flux can be found using the sonic temperature corrected for
humidity.
A KH20 Krypton hygrometer, instead of the IRGASON gas analyzer, can be
used to measure the latent heat flux. The KH20 can not be used to measure an
absolute concentration of water vapor, because of scaling on the source tube
windows caused by disassociation of atmospheric continuants by the ultra
violet photons (Campbell and Tanner, 1985 and Buck, 1976). A slow response
humidity sensor is used to measure the absolute humidity required to compute
the air density. Air density is needed to scale the covariances into sensible heat
flux and momentum flux. The rate of scaling on the KH20 windows is a
function of the atmospheric humidity. In high humidity environments, scaling
can occur within a few hours. That scaling attenuates the signal and can cause
shifts in the calibration. However, the scaling over a typical flux averaging
period is small. Thus, water vapor fluctuation measurements can still be made
with the hygrometer. The effects of the scaling can be easily reversed by
wiping the windows with a moist swab.
2. Installation and Mounting
When making eddy-covariance measurements near the surface (less than 3
meters), mount the datalogger enclosure between the legs of the CM106 tripod,
on a separate tripod, or user-supplied drive stake. Also, mount any sensor
electronics boxes as far from the fast response sensors as possible and always
use the tripod guy kit. This will minimize potential flow distortions and tower
sway caused by wind blowing against the fiberglass enclosure. See the tripod
manuals for detailed installation instructions.
FIGURE 2-1 depicts a typical Open-Path Eddy-Covariance station. Point the
Eddy-Covariance sensors into the prevailing wind to minimize the flow
distortion from the tower, mounting hardware, and other sensors.
2