Terms & Definitions
 

Term

Definition

Temp Out The external temperature at the main reporting station. Station is equipped with a fan aspiration unit to draw air past the sensor for more accurate readings.
Hi Temp The highest temperature recorded in a 24-hour period from midnight to midnight (local time).
Low Temp The lowest temperature recorded in a 24-hour period from midnight to midnight (local time).
Outside Humidity The humidity of the outside air at the main reporting station
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.
Wind Speed The speed of the wind measured 30 feet above the lake level measured in MPH. Maximum wind speed that the station can record at this location is 150 MPH.
Wind Direction The direction of the compass that the wind is blowing from.
High Speed The highest wind speed recorded in a 24-hour period from midnight to midnight (local time).
Wind Chill Wind chill (often popularly called the wind chill factor) is the felt air temperature on exposed skin due to wind. It measures the effect of wind on the perceived air temperature.
Heat Index The heat index is an index that combines air temperature and relative humidity in an attempt to determine the human-perceived equivalent temperature — how hot it feels, termed the felt air temperature.
THW Index The THW Index uses humidity, temperature and wind to calculate an apparent temperature that incorporates the cooling effects of wind on our perception of temperature.
THSW Index The THWS Index uses humidity, temperature, the cooling effects of wind and the heating effects of direct solar radiation to calculate an apparent temperature.
Barometer The atmospheric air pressure (barometer) reading at the main reporting station expressed in millibars (mb).
Rain The amount of measured precipitation at the main station in a 24-hour period from midnight to midnight (local time). The station is equipped with a rain gauge heater that will melt and measure snow at a rate of 1/4 inch of liquid precipitation per hour. Higher snowfall rates may overwhelm the melting system and delay reporting.
Rain Rate The rate of precipitation that is falling measured in inches per hour. During winter conditions when the precipitation is in the form of snow, this measurement may not be accurate based on the time it takes for the heater to melt the snowfall into the receiver cone.
Solar Radiation 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 per square meter (W/m2). The value logged by WeatherLink is the average solar radiation measured over the archive interval (1 minute).
Solar Energy The amount of accumulated solar radiation energy over a period of time is measured in Langleys. 1 Langley = 11.622 Watt-hours per square meter = 3.687 BTUs per square foot = 41.84 kilojoules per square meter
Hi Solar Rad The highest solar radiation value recorded in a 24-hour period from midnight to midnight (local time) at the main station.
UV Index The UV (Ultra-violet (radiation)) Index measures the intensity of UV. UV Index uses a scale of 0 to 16 to rate the current intensity of UV. The UV value logged by WeatherLink is the average UV measured during the archive interval (1 min).
UV Dose UV Dose and Sunburn - Use this plot to estimate the MED (minimal erythema dose) 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. The station settings are for a person with Skin Type III and a skin factor of 0.75.
High UV The highest UV Index recorded in a 24-hour period from midnight to midnight (local time).
Heating Degree Days One heating degree-day is the amount of heat required to keep a structure at 65ºF when the outside temperature remains one degree below the 65ºF threshold for 24 hours. One heating degree-day is also the amount of heat required to keep that structure at 65ºF when the temperature remains 24ºF below that 65º threshold for 1 hour.
Cooling Degree Days One cooling degree-day is the amount of cooling required to keep a structure at 65ºF when the outside temperature remains one degree above the 65ºF threshold for 24 hours. One cooling degree-day is also the amount of cooling required to keep that structure at 65ºF when the temperature remains 24ºF above that 65º threshold for 1 hour.
In EMC Moisture content in wood affects both the size and strength of lumber. If you know the EMC ((Wood) Equilibrium Moisture Content) of the storage or manufacturing area (which is derived using temperature and humidity readings), you can also determine the moisture content of the wood stored there. Data set should be disregarded in most cases.
In Air Density Air Density (the weight of 1 cubic foot or 1 cubic meter of air) is a valuable tool for racing enthusiasts, because it helps determine the optimal jetting under current weather conditions. The formula used to calculate air density in the WeatherLink Software requires measures of absolute pressure (barometric pressure uncorrected for altitude), relative humidity, and temperature. Air Density (in Kg/m3) = 1.2929 X 273.13 X ( AP - ( SVP x RH )) ( T + 273.13) 760 Where: T = Temperature in Celsius AP = Absolute Pressure (mm of Hg) SVP = Saturation Vapor Pressure of air over water at temp T RH = Relative Humidity (decimal)
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).)

Term

Definition

Temp Out
The external temperature at the main reporting station. Station is equipped with a fan aspiration unit to draw air past the sensor for more accurate readings.
Hi Temp
The highest temperature recorded in a 24-hour period from midnight to midnight (local time).
Low Temp
The lowest temperature recorded in a 24-hour period from midnight to midnight (local time).
Outside Humidity
The humidity of the outside air at the main reporting station
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.
Wind Speed
The speed of the wind measured 30 feet above the lake level measured in MPH. Maximum wind speed that the station can record at this location is 150 MPH.
Wind Direction
The direction of the compass that the wind is blowing from.
High Speed
The highest wind speed recorded in a 24-hour period from midnight to midnight (local time).
Wind Chill
Wind chill (often popularly called the wind chill factor) is the felt air temperature on exposed skin due to wind. It measures the effect of wind on the perceived air temperature.
Heat Index
The heat index is an index that combines air temperature and relative humidity in an attempt to determine the human-perceived equivalent temperature — how hot it feels, termed the felt air temperature.
THW Index
The THW Index uses humidity, temperature and wind to calculate an apparent temperature that incorporates the cooling effects of wind on our perception of temperature.
THSW Index
The THWS Index uses humidity, temperature, the cooling effects of wind and the heating effects of direct solar radiation to calculate an apparent temperature.
Barometer
The atmospheric air pressure (barometer) reading at the main reporting station expressed in millibars (mb).
Rain
The amount of measured precipitation at the main station in a 24-hour period from midnight to midnight (local time). The station is equipped with a rain gauge heater that will melt and measure snow at a rate of 1/4 inch of liquid precipitation per hour. Higher snowfall rates may overwhelm the melting system and delay reporting.
Rain Rate
The rate of precipitation that is falling measured in inches per hour. During winter conditions when the precipitation is in the form of snow, this measurement may not be accurate based on the time it takes for the heater to melt the snowfall into the receiver cone.
Solar Radiation
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 per square meter (W/m2). The value logged by WeatherLink is the average solar radiation measured over the archive interval (1 minute).
Solar Energy
The amount of accumulated solar radiation energy over a period of time is measured in Langleys. 1 Langley = 11.622 Watt-hours per square meter = 3.687 BTUs per square foot = 41.84 kilojoules per square meter
Hi Solar Rad
The highest solar radiation value recorded in a 24-hour period from midnight to midnight (local time) at the main station.
UV Index
The UV (Ultra-violet (radiation)) Index measures the intensity of UV. UV Index uses a scale of 0 to 16 to rate the current intensity of UV. The UV value logged by WeatherLink is the average UV measured during the archive interval (1 min).
UV Dose
UV Dose and Sunburn - Use this plot to estimate the MED (minimal erythema dose) 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. The station settings are for a person with Skin Type III and a skin factor of 0.75.
High UV
The highest UV Index recorded in a 24-hour period from midnight to midnight (local time).
Heating Degree Days
One heating degree-day is the amount of heat required to keep a structure at 65ºF when the outside temperature remains one degree below the 65ºF threshold for 24 hours. One heating degree-day is also the amount of heat required to keep that structure at 65ºF when the temperature remains 24ºF below that 65º threshold for 1 hour.
Cooling Degree Days
One cooling degree-day is the amount of cooling required to keep a structure at 65ºF when the outside temperature remains one degree above the 65ºF threshold for 24 hours. One cooling degree-day is also the amount of cooling required to keep that structure at 65ºF when the temperature remains 24ºF above that 65º threshold for 1 hour.
In EMC
Moisture content in wood affects both the size and strength of lumber. If you know the EMC ((Wood) Equilibrium Moisture Content) of the storage or manufacturing area (which is derived using temperature and humidity readings), you can also determine the moisture content of the wood stored there. Data set should be disregarded in most cases.
In Air Density

Air Density (the weight of 1 cubic foot or 1 cubic meter of air) is a valuable tool for racing enthusiasts, because it helps determine the optimal jetting under current weather conditions. The formula used to calculate air density in the WeatherLink Software requires measures of absolute pressure (barometric pressure uncorrected for altitude), relative humidity, and temperature.

Air Density (in Kg/m3) = 1.2929 X 273.13 X ( AP - ( SVP x RH ))
( T + 273.13) 760
Where:
T = Temperature in Celsius
AP = Absolute Pressure (mm of Hg)
SVP = Saturation Vapor Pressure of air over water at temp T (see Table 1 below)
RH = Relative Humidity (decimal)

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).