Daily solar measurements of atmospheric absorption and atmospheric emission were conducted simultaneously for a period of nine months during 1967 and 1968. Nighttime observavations of emission followed daytime observations of absorption and emission. The month of June 1968, provided a fortuitous opportunity to observe absorption during rain since 23 out of 30 days had light to heavy rainfall. The brightness temperature of clouds was measured by the multi‐frequency instrument during the observation period. The observational frequencies of 8, 15, 19, and 35 GHz were used to determine the frequency correlation between meteorological phenomena and the atmospheric parameters associated with the fine structure characteristics of absorption and emission.

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Measurement of the absolute temperature of microwave noise sources under field conditions is usually achieved at the expense of tedious rf attenuation measurements and the incorporation of cryogenic equipment in the measurement system. Measurement accuracy is determined by the precision to which the effects of passive rf attenuation are known. The technique described does not require this knowledge of the effects of rf attenuation on instrument calibration. The feasibility of this technique has been established by tests performed with a modified Dicke radiometer. The technique establishes the radiometer indicator output zero as a direct reading of absolute zero and provides calibration of the indicator scale directly in degrees Kelvin. Laboratory calibration of an appropriately modified radiometer and measurement of noise temperature near absolute zero are discussed.

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