Dynamax InteliMet Advantage 6, Руководство пользователя, Страница: 34 / 62

Intelimet Advantage 6
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irrigation is 333 kg or 86 gallons (per 10 m2), ie 266 kg / 80%. That would translate to an irrigation of
33.3 mm to replenish the water used over four days. Many variations on this theme can be formulated for
a specific application.
One caution should be stated. The ETp estimate is only a quantitative measure of the evaporative demand
of a well watered turf grass ¾ “ high, and is not intended to be an estimate of the actual water use by the
crop or the trees, even if they are well watered. Therefore, the two variables, ETp and stem or trunk flow
rate, are expressed as mm per hour and kg/plant/hour, respectively, even though the water use by
vegetation is often also expressed as mm per hour or per day. The relation between daily ETp and daily
transpiration is not even necessarily linear, as most Kc constants will assume. ETa – Actual
Evapotranspiration may not be constant over the entire range of weather conditions or the development
period of a crop.
4.2 ET Program Basics
This section covers the basics of Evapotranspiration algorithms and the ET algorithm implemented in
IMET_MP2_Main.CR2. ET program contains two constants that are always set for the installation site,
and two constants that could be modified for various situations. Only persons thoroughly familiar with
ETP modeling should modify parameters lev and zot. Normally, the last two constants are altered to
account for the barometric pressure and the height of the wind measurement. The present form of the
program is adapted to metric units. Each user needs to know the height of the weather station above
ground level.
zom = 2.0 wind speed height of measurement in meters, 2 m typical.
Only an advanced user with expertise and knowledge in the various ET models and roughness parameters
for various crops must attempt to change the following parameters.
zot = 0.0005 surface roughness parameter in m, for ¾ in. high turf grass
lev = 2.44 x 10
6
latent heat of vaporization – J/kg
has = 1004.0 Specific air heat capacity in J/KgC at 30
0
C
In this section we discuss definition of these parameters and their units followed by procedure to modify
these parameters in CR200 program to meet the geography of the location of weather station.