Program Sequence Of Measurement And Corrections - Campbell KH20 Product Manual

TABLE C-22. Data Fields in the Flux_Notes Output Table
Data Field Name
shfp_cal_fail_x_1_1
process_time
process_time_Max
buff_depth_Max
C.4.5 Program Sequence of Measurement and Corrections
Units
Result of TRUE indicates HFP01SC
returned an invalid number or the
none
calibrated sensitivity was not within
80%-105% of the original sensitivity
ms Average processing time for each scan
Ms Maximum processing time for a scan
Maximum number of records stored in
Number
the buffer
The following are the main correction procedures and algorithms implemented
in the program. The oxygen correction is unique to the KH20; see Appendix D,
Equations and Algorithms of Water Vapor Density and Water Flux in KH20
Eddy-Covariance Systems
the theory and implementation may be found in the appendices of the EasyFlux
DL CR6OP manual.
1. Despike and filter 10 Hz data using sonic and KH20 diagnostic codes.
2. Coordinate rotations with an option to use the double rotation method
(Tanner and Thurtell 1969), or planar fit method (Wilczak et al.
2001).
3. Lag CO and H O measurements against sonic wind measurements for
2 2
maximization of CO
Foken et al. 2012), with additional constraints to ensure lags are
physically possible.
4. Apply oxygen correction to covariances with water density from the
KH20. (See Appendix D, Equations and Algorithms of Water Vapor
Density and Water Flux in KH20 Eddy-Covariance Systems
5. Frequency corrections using commonly used cospectra (Moore 1986,
van Dijk 2002a, Moncrieff et al. 1997) and transfer functions of block
averaging (Kaimal et al. 1989), line/volume averaging (Moore 1986,
Moncrieff et al. 1997, Foken et al. 2012, van Dijk 2002a), time
constants (Montgomery 1947, Shapland et al. 2014, Geankoplis
1993), and sensor separation (Horst and Lenschow 2009, Foken et al.
2012).
6. A modified SND correction (Schotanus et al. 1983) to derive sensible
heat flux from sonic sensible heat flux following the implementation
as outlined in van Dijk 2002b. Additionally, fully corrected real
sensible heat flux computed from fine-wire thermometry may be
provided.
7. Correction for air density changes using WPL equations (Webb et al.
1980).
Appendix C. EasyFlux
Description
. For the other corrections, more details about
(p. D-1)
and H O fluxes (Horst and Lenschow 2009,
2 2
® DL CR6KH20
Data Field
Included
If HFP01SC
used
Always
Always
Always
.)
(p. D-1)
C-36