Accession Number : AD0420921

Title :   RELATIVE HUMIDITY ERRORS RESULTING FROM AMBIGUOUS DEW-POINT HYGROMETER READINGS,

Corporate Author : AIR WEATHER SERVICE SCOTT AFB ILL

Personal Author(s) : Appleman,H. S.

Report Date : SEP 1963

Pagination or Media Count : 7

Abstract : The instruments currently used in weather stations for measuring humidity work very well at high temperature, but become increasingly inaccurate at temperatures below freezing because of the small amount of water vapor in the air. Consideration is being given to using a dewpoint hygrometer, an instrument which is able to deect small quantities of moisture with great accuracy. Unfortunately, over a considerable temperature range below 32 F the instrument may record either the dew point or the frost point of the air. This study was carried out to determine whether this ambiguity would lead to significant errors in the computed relative humidity. It was found that the effect was large enough to adversely affect the accuracy of current techniques for forecasting clouds, fog, contrails, and other moisture-dependent phenomena. Suggestions are given for designing the instrument to eliminate the problem. (Author)

Descriptors :   (*HUMIDITY, ERRORS), (*HYGROMETERS, RELIABILITY), DEW POINT, METEOROLOGICAL INSTRUMENTS, FREEZING, TEMPERATURE, WEATHER, MEASUREMENT, TABLES(DATA)

Distribution Statement : APPROVED FOR PUBLIC RELEASE