3-CHANNEL SOLAR RADIOMETER FOR THE DETERMINATION OF ATMOSPHERIC COLUMNAR WATER-VAPOR

The design of a three-channel solar radiometer used to determine total columnar atmospheric water-vapor amounts is presented. The main chann el is located in the 0.94-mum water-vapor band, and two other channels are located in adjacent nonabsorption regions of the solar spectrum a nd are used to remove scattering effects from the main channel. Water- vapor transmittance is determined by means of a modified Langley appro ach, and these transmittances are converted to columnar water vapor by means of a band model developed at the University of Arizona. Several cases are presented in which columnar water-vapor amounts are determi ned through the use of the instrument and method described here. These results are compared with sounding-balloon results. Tests of the meth od indicate that columnar water vapor may be retrieved with an uncerta inty of less than 10%.