About Us

My Equipment

Davis Vantage Pro Plus

  

Davis VPP in field

  

   Rain Guage

 

 Wind Sock

  

     Discone Antenna

 

     

North-West

North

North-East

West

 

East

South-West

South

South-East


TEMPERATURE

Vantage Pro Plus uses the Integrated Sensor Suite's (ISS) temperature sensor to measure the outside air temperature.  A second temperature sensor in the console measures the inside air temperature.

APPARENT TEMPERATURE MEASURES

The Vantage Pro Plus Weather Station at Gorge Creek Orchards calculates apparent temperature readings; wind chill and heat index:

WIND CHILL

Wind Chill takes into account how the speed of the wind affects our perception of the air temperature.  Our bodies warm the surrounding air molecules by transferring heat form the skin.  If there's no air movement, this insulating layer of warm air molecules stays next to the body and offers some protection from cooler air molecules.  However, wind sweeps that comfy warm air surrounding the body away.  The faster the wind blows, the faster the heat is carried away and the colder you feel.   At above 30C wind movement has no effect on apparent temperature, so wind chill is the same as the outside temperature.

 

HEAT INDEX

The Heat Index uses the temperature and the relative humidity to determine how hot the air actually "feels".  When humidity is low, the apparent temperature will be lower than the air temperature, since perspiration evaporates rapidly to cool the body.   However, when the humidity is high (ie. the air is saturated with water vapour) the apparent temperature "feels" higher than the actual air temperature, because perspiration evaporates more slowly.

 

HUMIDITY

Humidity itself simply refers to the amount of water vapour in the air.  However, the amount of water vapour that the air can contain varies with the air temperature and pressure.  Relative humidity takes into account these factors and offers a humidity reading which reflects the amount of water vapour in the air as a percentage of the amount the air is capable of holding.   Relative Humidity, therefore, is not actually a measure of the amount of water vapour in the air, but a ratio of the air's water vapour content to it's capacity.  Vantage Pro Plus calculates and displays this relative humidity.

It is important to realise that relative humidity changes with temperature, pressure and water vapour content.  For example, a parcel of air with a capacity for 10g of water vapour which contains 4g of water vapour, the relative humidity would be 40%.  Adding 2g more water vapour (for a total of 6g) would change the humidity to 60%.  If that same parcel of air is warmed so that it has a capacity for 20g of water vapour, the relative humidity drops to 30% even though the water vapour content does not change.

 

DEW POINT

Dew Point is the temperature to which air must be cooled for saturation (100% relative humidity) to occur, providing there is no change in water content.  The Dew Point is an important measurement used to predict the formation of dew, frost and fog.  If Dew Point and temperature are close together in the late afternoon when the air begins to turn colder, fog is likely during the night.  Dew Point is also a good indicator of the air's actual water vapour content, unlike relative humidity, which takes the air's temperature into account.   High Dew Point indicates high vapour content; low Dew Point indicates low vapour content.  In addition, a high Dew Point indicates a better chance of rain and severe thunderstorms.

You can even use Dew Point to predict minimum overnight temperature.  Provided no new fronts are expected overnight and the afternoon relative humidity >50%, the afternoon's Dew Point gives you an idea of what minimum temperature to expect overnight, since the air is not likely to get colder than the Dew Point anytime during the night.

 

RAINFALL

Vantage Pro Plus provides four separate registers for tracking rainfall totals: "rain storm", "daily rain", "monthly rain" and "yearly rain".  The Vantage Pro Plus also calculates the rate of rainfall by measuring the interval of time between each 0.254mm rainfall increment.

 

BAROMETRIC PRESSURE

The weight of air that makes up our atmosphere exerts a pressure on the surface of the earth.  This pressure is known as atmospheric pressure.  Generally, the more air above an area, the higher the atmospheric pressure.  This in turn means that atmospheric pressure changes with altitude.  For example, atmospheric pressure is greater at sea level than it is on a mountain top.  To compensate for this difference and facilitate comparison between locations with different altitudes, atmospheric pressure is generally adjusted to the equivalent sea level pressure.  This adjusted pressure is known as Barometric Pressure.

In reality, the Vantage Pro Plus Weather Station measures atmospheric pressure, but this is converted to barometric pressure because the altitude of the Gorge Creek Orchards Weather Centre (540m) has been entered into the station.  This essentially means that the Vantage Pro Plus has stored the necessary 'offset' value to consistently translate atmospheric pressure into barometric pressure.

Barometric Pressure also changes with local weather conditions, making barometric pressure an extremely important and useful weather forecasting tool.  High-pressure zones are generally associated with fair weather while low-pressure zones are generally associated with poor weather.

For forecasting purposes, however, the absolute barometric pressure value is generally less important than the change in barometric pressure.  In general, rising pressure indicates improving weather conditions while falling pressure indicates deteriorating weather conditions.


A Stevenson Screen is a white boxed shelter that contains temperature and relative humidity equipment. It shields the instruments from sunshine and precipitations and has louvered sides to permit the free movement of air. The shelter is placed over grass, mounted 1 meter above the ground and as far from buildings as circumstances permit.

Climate refers to the average weather conditions at a specific place over a lengthy period of time (more than 30 years). The climate of a region plays a role in determining what agricultural crops can be grown in that region. The World Meteorological Organization, an agency of the United Nations, is responsible for the international exchange of weather data. It certifies that the data observation procedures do not vary among the over 130-nation participants.

Temperature refers to how hot or cold the atmosphere is as measured by a thermometer (in Celsius (C) or Fahrenheit (F), or Kelvin (K) ). A traditional thermometer consists of mercury, red spirit or green spirit in a glass tube and operates on the principle that the liquid expands more that the glass does when heated. Digital electronic devices can also be used were the unit can record the max and min temperature reached and some units can store a series of data (a data logger) and others transmit an electronic signal measuring temperature back to a second temperature display on a PC or a base. These new probes can also be used to measure soil temperature.

Atmospheric Pressure - the weight of the atmosphere overhead (the force exerted on a unit area, such as a square centimeter, by the mass of the atmosphere as gravity pulls it to earth) - expressed in millibars of inches of mercury. Commonly measured with a mercury barometer, a glass tube in which the height of a column of mercury fluctuates as the weight of the atmosphere changes. Changes in atmospheric pressure signal shifts in the weather and can be measured with a simple dial barometer.

Humidity refers to the amount of water vapour the air contains. (Expressed as relative humidity, or the amount of water vapour air contains expressed as a percentage of the maximum amount it can hold at the same temperature). Cool air holds less water than warm air.

Measuring Humidity; A Psychrometer is an instrument used to measure relative humidity. It traditionally consists of two thermometers, one covered with a wet cloth. Evaporation cools this thermometer below the actual air temperature, recorded on the dry thermometer. Evaporation and cooling depends on how dry the air is at a given temperature. A table can be used to determine the relative humidity from the amount of cooling. Digital electronic instruments (hygrometers) can be used for quick readings and more upmarket units offer data logging. Some instruments offer a simple dial readying of Relative Humidity, while these offer the least accuracy they can be used as a good indication.

Growing Degree Day (or Heat Units) - a measure of the departure of the mean daily temperature above or below a given standard. Information can be used to optimize timing of planting, fertilizing, pesticide application and harvesting.

Growing Season - the period of the year when crops and other plants grow successfully. Calculated by the average number of days between the last heavy frost in spring and the first severe frost in autumn. The length of the growing season varies from place to place and partially determines what crops can be grown in an area.

Precipitation is a term that covers all of the forms in which water falls to earth from the atmosphere. Main types: rain, snow, sleet and hail. Precipitation is life-sustaining - its amount and distribution a regions receives plays a major role in determining what can survive there and what plants can be grown.

A tipping bucket is an instrument used to measure precipitation. It contains a dual-chamber mini-collection bucket located beneath a collection funnel. When precipitation fills one side of the bucket, gravity empties it and sends a signal to the data logger. Some tipping buckets are equipped with internal heaters to melt snow and frozen rain.

Simple rain gauges. Basically, any measuring glass left outside can serve as a rain gauge. However, since most rain showers are usually quite windy, you'll want to fasten your rain gauge somewhere so that it doesn't blow over. Locate a good place for your gauge. There should be nothing overhead, like trees, electric wires, or the edge of a roof. These obstructions can direct rainwater into or away from your gauge, creating a false reading. The edge of a fence, away from the building, is often a good place for your gauge. Tip: A ring of slated metal around the perimeter of the rain gauge provides a wind shield to decrease splash and wind-induced errors. Once you have found the spot, attach a holding rack. Then, slip your measuring glass into position. Wait for rain, then record your measurement, and empty the glass.

Rain refers to liquid precipitation that falls from clouds as drop 0.5 millimeters in diameter or larger. Drizzle consists of drops smaller than 0.5mm.

Hail originates when colliding drops of water freeze together in the cold upper regions of a thunderstorm. Hail can cause considerable damage to agricultural regions, depending on the size and intensity of the hail storm. At 12:15, May 30, 1985 45 cm of hail fell in the Leamington area causing damage to plants and greenhouses.

Drought refers to a prolonged period of greatly reduced precipitation. Droughts can last a few weeks (in which case they are called dry spells) or months, or even years.

Frost refers to the white coating of ice crystals you often see on or near the ground after a cold night. Frost occurs through a process called sublimation where a gas, such as water vapour, becomes a solid, or when a solid becomes a gas without first becoming a liquid. (i.e. a leaf losses heat during the night. If the leaf's temperature falls below 0 C, water vapour in the surrounding air will freeze on it. Fruit growers are concerned about "killing frosts". (Temperatures that are far enough below freezing to harm cold-sensitive plants such as peach trees

Wind is the movement of air. It arises because of differences in temperature and atmospheric pressure between nearby regions of the earth. Winds tend to blow from areas of high pressure to areas of low pressure. It is one of the weather's most changeable forces. It can change form a light breeze to a fierce storm within a short time. Wind has been carefully measured for centuries


Reference and Specifications - Weather Stations

What is a MED?

Minimum Erythemal Dose (MED) is the amount of sunlight exposure necessary to induce a barely perceptible redness of the skin within 24 hours after sun exposure. In other words, exposure to 1 MED results in a reddening of the skin. You can determine the number of minutes of sun exposure it takes to burn by dividing 60 by the MEDs per hour. We use the term "skin factor" to describe how different skin types burn at different rates.

What is "skin factor"?

MED stands for Minimum Erythemal Dose, which is defined as the amount sunlight exposure necessary to induce a barely perceptible redness of the skin within 24 hours after sun exposure. As different skin types burn at different rates, MED's may be scaled to take into account skin type. The lower the skin factor, the longer it takes the skin to burn.

How do you know what your skin factor is?

You can find your skin type from the following table:

I - Always burns easily, never tans - 1.2 to 1.4

II - Always burns easily, tans minimally - 0.9 to 1.1

III - Burns moderately, tans gradually & uniformly - 0.7 or 0.8

IV - Burns minimally, always tans well - 0.5 or 0.6

V - Rarely burns, tans profusely - 0.4 or 0.5

VI - Never burns, deeply pigmented - 0.3 or 0.4

Warning: Be aware that skin types relate only to the sun burning effects of UV. Other UV-related health problems such as cataracts and immune system suppression do not relate to skin type.

What is UV radiation and what does the UV index mean?

Energy from the sun reaches the Earth as visible, infrared, and ultraviolet (UV) rays. Exposure to UV rays can cause numerous health problems, such as sunburn, skin cancer and other skin damage, cataracts, and can suppress the immune system. The Health EnviroMonitor can help analyze the changing levels of UV radiation and can serve to warn of situations where exposure is particularly unacceptable. The UV Index assigns a number between 1 and 16 for the current UV intensity. The lower number the lower the danger of sunburn. Here are exposure categories according to index values:

Index Values

Exposure Category

0 - 2 -- Minimal
3 - 4 -- Low
5 - 6 -- Moderate
7 - 9 -- High
10 + -- Very High
 

What is a cooling/heating degree day?

Cooling degree-days is a unit of measure for calculating the effect of temperature on the consumption of energy (e.g. electricity) to cool a location. Temperature plays an important part in the consumption of energy to cool a house or other structure. Heating Degree-days is a unit of measure for calculating the effect of temperature on the consumption of energy (e.g. heating oil) to heat a location, essentially the opposite of Cooling Degree-days.

What is temperature/humidity index?

Temperature-Humidity Index (THI) commonly called heat stress, uses temperature and relative humidity to determine how hot the air temperature actually "feels". When humidity is high the apparent temperature is higher than the air temperature.

What is meant by wind run?

Wind run is a measure of the amount of wind which passes a given point during the measurement period.

What is ET and what readings are used to calculate ET?

Evapotranspiration ( ETo ) is a measure of the amount of water vapor that returns to the air in a given area. It combines the amount of water vapor returned through evaporation (water leaving the earth) with the amount of water vapor returned through transpiration (water leaving plants) to arrive at a total for the area.

What is a growing degree day and how is it calculated?

Growing degree-days is a measure for calculating the effect of temperature on the development of plants and pests. The GroWeather uses the temperature reading in conjunction with the base and upper thresholds that you set to calculate degree-days.

How does barometric pressure differ from atmospheric pressure?

Atmospheric pressure is the total pressure exerted on an object taking into account the effects of altitude. Barometric pressure is a pressure that does not take into account the effects of altitude, only those of the current weather system. It's as if it were atmospheric pressure at sea level.

Heat Index Table (degrees C)

Environmental temperature (C) v Relative Humidity (%)

 

26

28

30

32

34

36

38

40

42

44

0%

25

27

28

30

32

33

35

36

37

38

10%

25

27

28

30

32

33

35

37

39

41

20%

24

27

28

30

32

34

37

39

42

46

30%

26

27

29

31

33

36

39

43

47

52

40%

26

28

30

32

35

39

43

48

54

60

50%

27

28

31

34

38

43

49

55

62

 

60%

27

29

33

37

42

48

55

62

 

 

70%

27

31

35

40

47

54

63

 

 

 

80%

28

32

38

44

52

61

 

 

 

 

90%

28

34

41

49

58

 

 

 

 

 

100%

28

36

44

56

 

 

 

 

 

 

  Beaufort Scale - Wind Speed & Observed Effects
Force Knots Mph Kph Sea Term Sea Conditions On-land Appearance
0 <1 <1 <1 Calm sea like a mirror smoke rises vertically
1 1-3 1-3 1-6 Light air ripples with appearance of scales: no foam crests smoke drifts and leaves rustle
2 4-6 4-7 7-11 Light breeze small wavelets: crests of glassy appearance, not breaking wind felt on face
3 7-10 8-12 12-19 Gentle breeze large wavelets: crests begin to break: scattered whitecaps flags extended, leaves move
4 11-16 13-18 20-30 Moderate breeze small waves, becoming longer: numerous whitecaps dust and small branches move
5 17-21 19-24 31-39 Fresh breeze moderate waves, taking longer form: many whitecaps: some spray small trees begin to sway
6 22-27 25-31 40-50 Strong breeze larger waves forming: whitecaps everywhere: some spray large branches move, wires whistle
7 28-33 32-38 51-61 Near gale sea heaps: white foam from breaking waves begins to be blown in streaks trees in motion, resistance felt when walking
8 34-40 39-46 62-74 Gale moderately high waves of greater length: edges of crests begin to break into spindrift: foam is blown in well-marked streaks walking impeded
9 41-47 47-54 75-87 Strong gale high waves: sea begins to roll: dense streaks of foam: spray may reduce visibility structural damage may occur
10 48-55 55-63 88-102 Storm very high waves with overhanging crests: sea takes white appearance as foam is blown in very dense streaks: rolling is heavy and visibility is reduced trees uprooted, structural damage likely
11 56-63 64-72 103-117 Violent Storm Exceptionally high waves: sea covered with white foam patches: visibility still more reduced damage to structures wide spread
12 >63 >72 >117 Hurricane air filled with foam: sea completely white with driving spray: visibility greatly reduced severe structural damage to buildings, wide spread devastation, flooding

Apparent Temperatures

The Vantage Pro calculates three apparent temperature readings: Wind chill, Heat Index, and the Temperature/Humidity/Sun/Wind (THSW) Index. Apparent temperatures use additional weather data to calculate what a human body perceives the temperature to be in those conditions.

Wind Chill

Wind Chill takes into account how the speed of the wind affects our perception of the air temperature. Our bodies warm the surrounding air molecules by transferring heat from the skin. If there’s no air movement, this insulating layer of warm air molecules stays next to the body and offers some protection from cooler air molecules. However, wind sweeps that comfy warm air surrounding the body away. The faster the wind blows, the faster heat is carried away and the colder you feel.

Heat Index

The Heat Index uses temperature and the relative humidity to determine how hot the air actually “feels.” When humidity is low, the apparent temperature will be lower than the air temperature, since perspiration evaporates rapidly to cool the body. However, when humidity is high (i.e., the air is more saturated with water vapor) the apparent temperature “feels” higher than the actual air temperature, because perspiration evaporates more slowly.

Note: Vantage Pro measures Heat Index only when the air temperature is above 57° F (14° C) because it’s insignificant at lower temperatures. (Below 57°, Heat Index = the air temperature.) The Heat Index is not calculated above 135° F (52° C).

Temperature/Humidity/Sun/Wind (THSW) Index

The THSW Index uses humidity and temperature like the Heat Index, but also includes the heating effects of sunshine and the cooling effects of wind (like Wind chill) to calculate an apparent temperature of what it “feels” like out in the sun.

Humidity

Humidity itself simply refers to the amount of water vapor in the air. However, the amount of water vapor that the air can contain varies with air temperature and pressure. Relative humidity takes into account these factors and offers a humidity reading which reflects the amount of water vapor in the air as a percentage of the amount the air is capable of holding. Relative humidity, therefore, is not actually a measure of the amount of water vapor in the air, but a ratio of the air’s water vapor content to its capacity. When we use the term humidity in the manual and on the screen, we mean relative humidity.

It is important to realize that relative humidity changes with temperature, pressure, and water vapor content. A parcel of air with a capacity for 10 g of water vapor which contains 4 g of water vapor, the relative humidity would be 40%. Adding 2 g more water vapor (for a total of 6 g) would change the humidity to 60%. If that same parcel of air is then warmed so that it has a capacity for 20 g of water vapor, the relative humidity drops to 30% even though water vapor content does not change.

Relative humidity is an important factor in determining the amount of evaporation from plants and wet surfaces since warm air with low humidity has a large capacity to absorb extra water vapor.

Dew Point

Dew point is the temperature to which air must be cooled for saturation (100% relative humidity) to occur, providing there is no change in water vapor content. The dew point is an important measurement used to predict the formation of dew, frost, and fog. If dew point and temperature are close together in the late afternoon when the air begins to turn colder, fog is likely during the night. Dew point is also a good indicator of the air’s actual water vapor content, unlike relative humidity, which takes the air’s temperature into account. High dew point indicates high water vapor content; low dew point indicates low water vapor content. In addition a high dew point indicates a better chance of rain and severe thunderstorms. You can also use dew point to predict the minimum overnight temperature. Provided no new fronts are expected overnight and the afternoon Relative Humidity ≥ 50%, the afternoon’s dew point gives you an idea of what minimum temperature to expect overnight, since the air cannot get colder than the dew point anytime.

Rain

The Vantage Pro incorporates a tipping-bucket rain collector in the ISS that measures 0.01” for each tip of the bucket. The station logs rain data in inch units. Four separate variables track rain totals: “rain storm”, “daily rain”, “monthly rain”, and “yearly rain”. Rain rate calculations are based on the interval of time between each bucket tip, which is each 0.01” rainfall increment.

Barometric Pressure

The weight of the air that makes up our atmosphere exerts a pressure on the surface of the earth. This pressure is known as atmospheric pressure. Generally, the more air above an area, the higher the atmospheric pressure, this, in turn, means that atmospheric pressure changes with altitude. For example, atmospheric pressure is greater at sea-level than on a mountaintop. To compensate for this difference and facilitate comparison between locations with different altitudes, atmospheric pressure is generally adjusted to the equivalent sea-level pressure. This adjusted pressure is known as barometric pressure. In reality, the Vantage Pro measures atmospheric pressure. When you enter your location’s altitude in Setup Mode, the Vantage Pro stores the necessary offset value to consistently translate atmospheric pressure into barometric pressure.

Barometric pressure also changes with local weather conditions, making barometric pressure an extremely important and useful weather forecasting tool. High pressure zones are generally associated with fair weather while low pressure zones are generally associated with poor weather. For forecasting purposes, however, the absolute barometric pressure value is generally less important than the change in barometric pressure. In general, rising pressure indicates improving weather conditions while falling pressure indicates deteriorating weather conditions.

Solar Radiation

What we call “current solar radiation” is technically known as Global Solar Radiation, a measure of the intensity of the sun’s radiation reaching a horizontal surface. This irradiance includes both the direct component from the sun and the reflected component from the rest of the sky. The solar radiation reading gives a measure of the amount of solar radiation hitting the solar radiation sensor at any given time, expressed in Watts /sq. meter (W/m2).

UV (Ultra Violet) Radiation

Energy from the sun reaches the earth as visible, infrared, and ultraviolet (UV) rays. Exposure to UV rays can cause numerous health problems, such as sunburn, skin cancer, skin aging, and cataracts, and can suppress the immune system. The Vantage Pro can help analyze the changing levels of UV radiation and can advise of situations where exposure is particularly unacceptable. The Vantage Pro displays UV readings in two scales: MEDs and UV Index.

CAUTION: The station’s UV readings do not take into account UV reflected off snow, sand, or water, which can significantly increase your exposure. Nor do your UV readings take into account the dangers of prolonged UV exposure. The readings do not suggest that any amount of exposure is safe or healthful. Do not use the Vantage Pro to determine the amount of UV radiation to which you expose yourself. Scientific evidence suggests that UV exposure should be avoided and that even low UV doses can be harmful.

UV MEDs

MED stands for Minimum Erythemal Dose, defined as the amount of sunlight exposure necessary to induce a barely perceptible redness of the skin within 24 hours after sun exposure. In other words, exposure to 1 MED will result in a reddening of the skin. Because different skin types burn at different rates, 1 MED for persons with very dark skin is different from 1 MED for persons with very light skin.

Both the U.S. Environmental Protection Agency (EPA) and Environment Canada have developed skin type categories correlating characteristics of skin with rates of sunburn. See Table A-1 “EPA Skin Phototypes” and Table A-2 “Environment Canada Skin Types and Reaction to the Sun” for a description of skin types.

EPA Skin Phototypes

Skin Phototype

Skin color

Tanning & Sunburn history

1 - Never tans, always burns

Pale or milky white; alabaster

Develops red sunburn; painful swelling, skin peels

2 - Sometimes tans, usually burns

Very light brown; sometimes freckles

Usually burns, pinkish or red coloring appears; can gradually develop light brown tan

3 - Usually tans, sometimes burns

Light tan; brown, or olive; distinctly pigmented

Rarely burns; shows moderately rapid tanning response

4 - Always tans; rarely burns

Brown, dark brown, or black

Rarely burns; shows very rapid tanning re-sponse

Table A-1

 

Environment Canada Skin Types and Reaction to the Sun1

Skin Type

Skin Color

History of Tanning & Sunburning

I

White

Always burns easily, never tans

II

White

Always burns easily, tans minimally

III

Light Brown

Burns moderately, tans gradually

IV

Moderate Brown

Burns minimally, tans well

V

Dark Brown

Burns rarely, tans profusely

VI

Black

Never burns, deep pigmentation

Table A-2

 1Developed by T. B. Fitzpatrick of the Harvard Medical School



  UV Dose (MEDs)

UV Dose and Sunburn - Use this plot to estimate the MED dose leading to sunburn. A person with Type II (Environment Canada) skin type might choose 0.75 MED as the maximum for the day; in contrast, a person with Type V (Environment Canada) Skin Type might consider 2.5 MEDs a reasonable dose for the day. NOTE: the Vantage Pro assumes a Fitzpatrick (Environment Canada) Skin Type of II.

UV Index

Vantage Pro can also display UV Index, an intensity measurement first defined by Environment Canada and since been adopted by the World Meteorological Organization. UV Index assigns a number between 0 and 16 to the current UV intensity. The US EPA categorizes the Index values as shown in Table A-3 “UV Index.” The lower the number, the lower the danger of sunburn. The Index value published by the U.S. National Weather Service is a forecast of the next day’s noontime UV intensity. The Index values displayed by the Vantage Pro are real-time measurements.

UV Index

Index Values

Exposure Category

0 - 2

Minimal

3 - 4

Low

5 - 6

Moderate

7 - 9

High

10+

Very High

Table A-3

Evapotranspiration (ET)

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, ET is the opposite of rainfall, and it is expressed in the same units of measure (Inches, millimeters).

The Vantage Pro uses air temperature, relative humidity, average wind speed, and solar radiation data to estimate ET, which is calculated once an hour on the hour.

 


Please send us your comments