HOPKINS GLOSSARY OF WEATHER TERMS D
- A thermal sensor (thermometer) with a sensing element that
bends or deforms by an amount which is a function of temperature.
An example of a deformation-type thermometer is the bimetallic
thermometer used in a thermograph.
dewpoint temperature (or dewpoint)
- Temperature to which an air parcel must be cooled at constant
pressure and constant water vapor content in order for saturation
of that air parcel with water vapor to occur with respect
to a liquid water surface. Dewpoint can be measured by a dewpoint
hygrometer or indirectly with a psychrometer. The units
for dewpoint are the same for air temperature. Compare with
- An instrument used for determining the dewpoint; a
type of hygrometer operating on the principle that air
in contact with a polished metallic surface is cooled to point
where a thin film is observed to form on the metal surface, where
upon the temperature of that surface is measured. This observed
temperature is essentially the same as the theoretical dewpoint
- A radar unit that, in the velocity mode, determines
the radial movement of airborne hydrometeor or aerosol targets
either to or from the unit; based upon the Doppler Effect
or Shift, where a slight change in the frequency (or phase) between
the broadcast and reflected microwave radiation signaloccurs
because the target is moving toward or away from the radar antenna.
Precipitation location and intensity are determined also by Doppler
radar when operated in a reflectivity mode.
- A modified radiosonde package that is dropped by parachute
from an aircraft to obtain temperature, pressure, and humidity
profiles of the atmosphere below flight level; often used by aircraft
weather reconnaissance of hurricanes.
- The temperature indicated by the dry-bulb thermometer of a
psychrometer; the dry-bulb temperature is identical with
the ambient air temperature. Contrast with wet-bulb temperature
- The thermal sensor in a psychrometer that is not moistened,
but kept dry. The dry-bulb thermometer indicates or records the
dry-bulb temperature. Contrast with wet-bulb thermometer.
Last update 6 June 1996
Edward J. Hopkins, Ph.D.
Department of Atmospheric and Oceanic Sciences
University of Wisconsin-Madison