Davis Instruments Vantage VUE Console Manual

Also see for Vantage VUE: User manual Quick reference guide Installation manual

Contents

Davis Instruments Vantage VUE Console Manual Manual pdf 49 page image

45Wind ChillWind ChillWind chill takes into account how the speed of the wind affects our perception of theair temperature. Our bodies warm the surrounding air molecules by transferring heatfrom the skin. If there is no air movement, this insulating layer of warm air moleculesstays next to the body and offers some protection from cooler air molecules.However, wind sweeps away that warm air surrounding the body. The faster thewind blows, the faster heat is carried away and the colder you feel. Wind has awarming effect at higher temperatures.Note: There is no windchill when the air temperature is at or above 93° F (-34° C).Heat IndexHeat index uses temperature and the relative humidity to determine how hot the airactually “feels.” When humidity is low, the apparent temperature will be lower thanthe 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 apparenttemperature “feels” higher than the actual air temperature, because perspirationevaporates more slowly.Note: Heat index and air temperature are equal at or below 0° F (-18° C).Dew PointDew 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. Thedew 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 whenthe air begins to turn colder, fog is likely during the night. Dew point is also a goodindicator of the air’s actual water vapor content, unlike relative humidity, which takesthe air’s temperature into account. High dew point indicates high water vaporcontent; low dew point indicates low water vapor content. In addition a high dewpoint indicates a better chance of rain, severe thunderstorms, and tornados.You can also use dew point to predict the minimum overnight temperature. Providedno new fronts are expected overnight and the afternoon relative humidity is greaterthan 50%, the afternoon’s dew point gives you an idea of what minimum temperatureto expect overnight. The higher the humidity is, the more accurate the dew pointprediction.Note: Dew point is equal to the air temperature when the humidity is 100%.RainVantage Vue incorporates a tipping spoon rain collector in the ISS that measures 0.01''or 0.2 mm for each tip of the spoon. Your station logs rain data in the same units it ismeasured in and converts the logged totals into the selected display units (inches ormillimeters) at the time it is displayed. Converting at display time reduces possiblecompounded rounding errors over time.Four separate variables track rain totals: “rain rate,” “daily rain,” “monthly rain,” and“yearly rain.” Rain rate calculations are based on the interval of time between eachspoon tip, which is each 0.01'' or 0.2 mm rainfall increment.