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EvapoTranspiration (ET)
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E v a p o Tr a n s p i r a t i o n ( E T )
Note: Requires optional solar radiation sensor (#6450, included on Vantage Pro Plus
weather stations).
EvapoTranspiration (ET) is a measurement of the amount of water vapor returned
to the air in a given area. It combines the amount of water vapor returned through
evaporation (from wet vegetation surfaces and the stoma of leaves) with the
amount of water vapor returned through transpiration (exhaling of moisture
through plant skin) to arrive at a total. Effectively, ETo is the opposite of rainfall,
and it is expressed in the same units of measure (Inches, millimeters).
The Weather Envoy uses air temperature, relative humidity, average wind speed,
and solar radiation data to estimate ET. (ET is calculated once an hour on the
hour.)
Please note that calculating ET requires the optional solar radiation sensor.
L e a f We t n e s s
Note: Leaf Wetness is only available with the wireless Weather Envoy using the optional
Leaf and Soil Moisture/Temperature station (#6343) with a Leaf Wetness sensor
(#6420).
Leaf wetness provides an indication of whether the surface of foliage in the area
of the sensor is wet or dry by indicating how wet the surface of the sensor is. The
leaf wetness reading ranges from 0 (dry) to 15.
S o i l M o i s t u r e
Note: Soil Moisture is only available with the wireless Weather Envoy using the optional
Leaf and Soil Moisture/Temperature station (#6343) with a Soil Moisture sensor
(#6440).
Soil Moisture, as the name suggests, is a measure of the moisture content of the
soil. Soil moisture is measured on a scale of 0 to 200 centibars, and can help choose
times to water crops. The soil moisture sensor measures the vacuum created in the
soil by the lack of moisture. A high soil moisture reading indicates dryer soil; a
lower soil moisture reading means wetter soil.
Ti m e
The Weather Envoy has a clock and a calendar for tracking time and date. The
calendar automatically adjusts during leap years and daylight savings, providing
you have entered the correct year, lattitude and longitude, and daylight savings
settings in the Setup Mode.
