Heat Index; Pyranometer; Relative Humidity; Sea Level Pressure - Columbia Weather Systems Weather Display User Manual

54 Weather Display
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Heat Index

The heat index or apparent temperature is a measure of discomfort due to
the combination of heat and high humidity. It was developed in 1979 and is
based on studies of evaporative skin cooling for combinations of
temperature and humidity.

Pyranometer

It measures the combined intensity of incoming direct solar radiation and
diffused sky radiation. The Pyranometer consists of a radiation-sensing
element, which is mounted so that it views the entire sky.

Relative Humidity

Popularly called humidity. The ratio of the actual vapor pressure of the air
to the saturation vapor pressure.

Sea Level Pressure

The atmospheric pressure at mean sea level, either directly measured or,
most commonly, empirically determined from the observed station
pressure.
In regions where the earth's surface pressure is above sea level, it is
standard observational practice to reduce the observed surface pressure
to the value that would exist at a point at sea level directly below.

Solar Radiation

The total electromagnetic radiation emitted by the sun. 99% of the sun's
energy output falls within the wavelength interval from 0.15 microns to 4.0
microns, with peak intensity near 0.47 microns. About one-half of the total
energy in the solar beam is contained within the visible spectrum from 0.4
to 0.7 microns, and most of the other half lies near infrared, a small
additional portion lying in the ultraviolet.

Wind Chill

That part of the total cooling of a body caused by air motion.
Columbia Weather Systems, Inc.