A-E | F-J | K-O | P-T | U-Z

A-E

Barometric Pressure

Pressure is the measurement of a force (weight) on a per unit area. The barometer measures the force our atmosphere exerts on a per-unit area of surface, or the "weight of the air".

Dew Point

The dew point is the temperature the air must be cooled to for the air to become completely saturated. At that point the relative humidity is equal to 100%. The farther apart the air temperature is from the dew point, the drier the air and the lower the relative humidity. The closer the air is to the dew point, the damper or wetter the air, and the higher the relative humidity.

F-J

Heat Index

Heat index is the temperature your body feels when the air temperature is combined with the relative humidity. As humidity increases, the rate of evaporation decreases. Our bodies are cooled by the evaporation of our perspiration. Therefore, if evaporation is slowed, the cooling of our bodies is slowed and we feel warmer.

K-O

Light

The Automated Weather Source weather station includes a sensor called a photocell. This sensor responds and measures the amount of light that shines on it. The light that is being measured can be in just about any form; i.e., solar light (directly from the sun), moonlight or man-made light. The units for the measurement are percent (%) of full sunlight.

P-T

Relative Humidity

Relative humidity is a measure of the amount of moisture in the air. It is expressed in a percentage of how much moisture the air could possibly hold. The "wetter or damper" the air feels the higher the relative humidity. The drier the air feels the lower the relative humidity.

Temperature

Temperature is a measure of the heat content of a body (the atmosphere in the case of weather). The molecular motion of a substance creates energy, which can be measured in terms of the heat it generates. Air, water, and soil can all be measured for temperature.

U-Z

Wet Bulb Temperature

The air temperature drops after it rains. In the summertime a thunderstorm can break the oppressive heat of the day. As it precipitates, evaporation occurs and the air temperature drops. The wet bulb temperature is the temperature at which no more evaporation will occur, and thus no further decrease in the temperature. The air will continue to cool until the air can evaporate no more moisture. The temperature, when the cooling continues until the evaporation stops and the air becomes saturated, is the wet bulb temperature.

Wind Chill

The wind chill index is the temperature your body feels when the air temperature is combined with the wind speed. The higher the wind speed the faster exposed areas of your body lose heat and the cooler you feel.

Wind Speed / Direction

Wind speed is the measure motion of the air with respect to the surface of the earth covering a unit distance over a unit time. Wind direction is an indicator of the direction that the wind is coming from. For example, a northerly wind is coming from the north and blowing toward the south.