Instruction manual

4-1
SECTION 4. CALCULATING FLUXES USING SPLIT
SPLIT (PC208E software) can be used to apply the air density and oxygen corrections to the measured
surface fluxes. This section provides example SPLIT programs to make the necessary calculations on
the data produced by the sample datalogger program. All the calculations in ECRAW.PAR and
ECFLUX.PAR are explained in Sections 1 and Appendix A.
Two runs through SPLIT are required to combine the data and then apply the corrections. The first run
operates on the raw data produced by the datalogger. The parameter file ECRAW.PAR is used to make
the first run and produces the file called EC.PRN. The second run is made with the parameter file
ECFLUX.PAR. This parameter file corrects the air density and applies the necessary oxygen correction
to the data. The output file name is FLUX.PRN. To apply the oxygen correction (OCLE) to the latent
heat flux, subtract OCLE from LE (see Eq. 14 and 15). To apply the oxygen correction to the standard
deviation of water vapor, add OCSD to STDR.
4.1 FLUX CALCULATIONS
The surface flux data is combined with the
energy balance and meteorological data. The
SPLIT parameter file that does this is listed in
TABLE 4.2-1. The parameter file assumes that
the data files from the datalogger were saved
on disk under the name EC.DAT. An output
data file (EC.PRN) is created that will be used
to apply all the necessary corrections.
4.2 EXAMPLE SPLIT PROGRAMS
Table 4.2-2 lists the parameter file that is used
to apply the corrections. The equations that
ECFLUX.PAR uses are described in detail in
Section 1 and Appendix A. Appendix D
summarizes the variable names and definitions.
In some cases it may be necessary to apply an
additional correction to the latent heat flux
(Webb et al., 1980). The soil storage term and
the heat capacity of soil was found following
Hanks and Ashcroft, 1980. Soil water content
(W) is measured by the CS615. Bulk density
(BD) is unique for each site and must be
measured for the site. An estimate for
atmosphere pressure (P) must also be entered.
TABLE 4.2-1. Split Parameter File to Combine Raw Data
Param file is C:\ECRAW.PAR
Name(s) or input DATA FILE(s): EC.DAT, EC.DAT
Name of OUTPUT FILE to generate: EC.PRN
START reading in EC.DAT: 2:3
START reading in: 2:3
STOP reading in EC.DAT:
STOP reading in:
COPY from EC.DAT: 1[12] AND 3[30]
COPY from: 1[21] AND 3[30]
SELECT element #(s) in EC.DAT: 2..5,P = 85.,P,6..11,SQRT(12..15),16..18
SELECT element #(s) in: BD=1330.,W =18,LV=(2500.5-2.359*5),
TA=5+273.15,Q=(.622*6)/(P-(6*1.622)),
CP=(1.+(.87*Q))*1005.,RD=(P-6)*1000./
(287.04*TA),RV=6*1000./(461.5*TA),RA=RD+
RV,F=SPAAVG(7,8),S=11*.08*BD*(840.+
W*4190.)/1800.,TA,6,9,F,S,12..14,LV,CP,RA
HEADING for report: RAW EDDY COVARIANCE DATA
HEADINGS for EC.DAT, col # 1: DAY
column # 2: TIME
column # 3: -kw
column # 4: -xkw
column # 5: P
column # 6: rhoCp