A wind blowing in a direction opposite to the heading of a moving object, thus opposing the object's intended progress; the opposite of a tailwind.

A instrument designed to study small fluctuations of some quantity. The microbarograph is an example of a recording pressure variometer.

Instrument used to measure the amount of water evaporated from the soil surface during a given time interval.

An instrument that shows changes in humidity.

Name sometimes given to a transmissometer.

An elongated area of relatively high pressure. Usually associated with and most clearly identified as an area of maximum anticyclonic curvature of the wind flow. The opposite of a trough.

Sustained winds greater than or equal to 40 mph or gust greater than or equal to 58 mph.

An absolute instrument developed by K. Angstrom for the measurement of direct solar radiation. The radiation receiver station consists of two identical manganin strips whose temperatures are measured by attached thermocouples. One of the strips is shaded, ...

A type of directional antenna used on some types of radar and radio equipment consisting of an array of elemental, single- wire dipole antennas and reflectors.

Downward scattered and reflected solar radiation, coming from the whole hemisphere with the exception of the solid angle of the sun's disc on a surface perpendicular to the axis of this cone.

The amount of sky covered or concealed by clouds or obscuring phenomena. It is reported in tenths, so that 0.0 indicates a clear sky and 1.0 (or 10/10) indicates a completely covered sky. The following classifications are used in aviation weather observat ...

An inert gas. An element found in the atmosphere to the extent of only 0.000114 percent by volume. Its molecular weight is 83.7.

A nephoscope in which the motion of the cloud is observed by its reflection in a mirror.

The rate of decrease of pressure per unit distance at a fixed time.

The direction from which the wind is blowing, measured in points of the compass or in azimuth degrees.

The minimum temperature shown by a minimum thermometer exposed in an open situation with its bulb at the level of the tops of the grass blades of short turf.

An instrument which indicates the presence of precipitation. The ombroscope consists of a heated, water-sensitive surface which indicates by mechanical or electrical techniques the occurrence of precipitation.

Apparatus using the combined simultaneous action of a bimetallic thermometer and a hair hygrometer to move a needle in front of a divided scale. fts construction permits dew point variations to be indicated approximately.

Federal Aviation Administration.

Pyrheliometer based on the comparison of the heating of two identical metal strips, one exposed to radiation, the other to a joule effect.