Weather FAQs

Q: What is dew point?

A: The temperature at which water condenses given a constant temperature and pressure.

Q: What is the difference between relative humidity, absolute humidity, and specific humidity?

A: Relative humidity refers to the amount of water vapor in air divided by the amount of water vapor the air can hold.  Absolute humidity is the mass of water vapor in a particular volume of air.  Specific humidity is the mass of water vapor in a parcel of air divided by the total mass of the air in that parcel.

Q: If air feels humid and heavy, is it more or less dense than dry air?

A: In a break from common sense, humid air is less dense than dry air.  In a particular volume of air, higher humidity means more water vapor means less of the components that make up dry air.  Since water vapor is less dense than dry air, the density of parcel of air decreases as humidity increases.

Q: Can consoles for wireless weather stations be kept indoors even though the sensors are outdoors?

A: As a general rule, most wireless consoles can receive data through walls.  If a unit is behind steel or thick walls, a repeater may need to be installed in a window or wall to insure the signal is captured.

Q: How does a tipping bucket rain gauge measure rainfall?

A: Tipping bucket style rain gauges feature two individual cells calibrated to a known volume of water.  The cells balance on a fulcrum, and at the center of the fulcrum is a contact switch.  During a precipitation event a cell will fill with water and tip, emptying the water.  As the cell tips it causes a momentary contact closure that is recorded by the weather station or data logger to which it is attached.  The weather station or data logger calculates the amount of precipitation required to fill the cell and cause it to tip.

Q: Do Enviro-Safe thermometers contain mercury?

A: No, the liquid in Enviro-Safe thermometers is a mixture of citrus oil and non-toxic dye. 

Q: What is the difference between total immersion and partial immersion thermometers?