Geology Reference
In-Depth Information
(0,0) coordinate). Comparisons between the different equations were made in
hourly and daily time steps. Comparisons on hourly and daily steps were demon-
strated using the suggested equations and these values were accumulated for esti-
mating longer time steps (monthly and yearly). Summed hourly values of ET
0
were
used for daily estimation.
7.4.2.1 Hourly ET
0
Comparison
This section describes the regressive comparison between hourly ET
0
values cal-
culated using the FAO56-PM equation and those calculated by the hourly ASCE-
PM, CIMIS-PM, and
equations for 5 years in the Brue
catchment. Plots of the hourly reference evapotranspiration, FAO56-PM versus
ASCE-PM, FAO56-PM versus CIMIS-PM, FAO56-PM versus FAO56 PM ET
0
for
the 1995
“
Copais Approach
”
1999 record are shown in Figs.
7.6
,
7.7
,
7.8
and
7.9
, respectively. The
comparison results based on various performance statistics between ET
0
estimates
for individual years for the different methods are shown in Table
7.3
.
The lower SEE value implies the better performance of an empirical equation.
From Table
7.3
, the calculated average SEE values for hourly time steps are
0.00244, 0.01724, and 0.01268 mm h
−
1
for the ASCE-PM, CIMIS-PM and Copais
Approach methods, respectively. From these SEE values, we can infer that ASCE-
PM has shown the best performance, since it has the lowest SEE value, followed by
Copais and CIMIS-PM, respectively.
-
Fig. 7.6 Hourly reference evapotranspiration comparison between the FAO56 Penman equation
(FAO56-PM ET
0
) and the standardized ASCE Penman
Monteith equation (ASCE-PM ET
0
) for
-
