A lower adiabatic lapse rate named for higher values of this quantity occurs when an air front approaches mountains in orographic lifting. Field measurements of this quantity utilize (-5[1])a ratchet-like “sling” instrument (10[1])whose outputs are plotted nonlinearly against the mixing ratio. At different altitudes, radiosondes record temperature, pressure, and this quantity, which is (-5[1])inversely proportional to air density. Temperature equals the dew point when a form of this quantity reaches values of 100. (10[4])This quantity’s impact on apparent temperature is estimated by the heat index. For 10 points, hygrometers measure what percentage of (10[1])water vapor in the air? ■END■