Measurement of Atmospheric Water Vapor by a Spectrophotometric Technique

Abstract

A spectroscopic technique was used to measure the total amount of water vapor between the point of observation and the sun. Measurements were taken continuously throughout the day, yielding a detailed picture of water vapor variations as a function of time. Results from 28 days of observation over a period of a year show a wide variety of situations ranging from days of relatively stable and constant precipitable water vapor W to days in which large changes occur, sometimes quite abruptly. The median value of the range of W within successive one-hour periods was found to be 0.05 in, with ten per cent of all ranges exceeding 0.12 in, the latter amounting to about fifteen per cent of the annual mean of W at the locality in question. It is concluded that significant W-fluctuations are commonly missed in routine radiosonde practice. Natural variations of Ware, on the average, somewhat greater than the instrumental errors of radiosondes. Crude estimates of moist 11 bubble11 diameters of 0.5 to 12 kilometers were obtained.