A measurement of atmospheric conditions aloft, above the effective range of a surface weather observation. This is a general term, but is usually applied to those observations that are used in the analysis of upper-air charts (as opposed to measurements of upper-atmospheric quantities primarily for research). Among the elements evaluated are pressure, temperature, relative humidity (e.g., by radiosonde aircraft observations), and wind speed and direction (e.g., by rawinsonde, aircraft, or wind profiling radars). Also, some mountain stations are high enough and exposed enough so that their observations may be included in the upper-air network at their elevation. See Also meteorological rocket, radiosonde balloon.