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# ATMOSPHERIC PROFILING OF WATER VAPOR AND LIQUID WATER WITH A K-BAND AUTOCORRELATION RADIOMETER

#### Abstract

An atmospheric water vapor and non-precipitating liquid water profiling system is presented. Included are a review and performance characterization of the hardware, a description with results of the calibration procedure, and experimental confirmation of the profiling system with coincident radiosonde balloon comparisons.^ The hardware consists of a K-Band (20.5-23.5 GHz) Autocorrelation Radiometer (CORRAD), designed, built, and operated by the Microwave Remote Sensing Laboratory at the University of Massachusetts at Amherst. CORRAD measures the autocorrelation of thermal noise at K-Band generated by water in the atmosphere. The sensor represents a novel approach to microwave remote sensing of the atmosphere with regard to pre-detection bandwidth (3 GHz) and number of equivalent frequency channels (31).^ The complete system calibration procedure is presented, including frequency resolution (100 MHz) and accuracy, front end system noise debiasing, and absolute gain calibration.^ An algorithm is developed to recover the atmospheric profiles of water vapor and liquid water from the measured autocorrelation samples. The algorithm uses a constrained minimum squared error estimation procedure on a first order perturbation of the full equation of radiative transfer in the atmosphere. Water vapor lapse rates are estimated with better than $\pm$150 m accuracy. Profile results are in excellent agreement with simultaneous radiosonde balloon soundings by the National Weather Service.^ A complete system signal-to-noise analysis is performed, from the statistics of the raw data to the uncertainties in the estimated profile. Profile relative uncertainties are 5-10% in the lower troposphere with a 1.0 K standard deviation in the antenna temperature spectrum measurements. ^

#### Subject Area

Engineering, Electronics and Electrical|Remote Sensing

#### Recommended Citation

CHRISTOPHER STEPHAN RUF, "ATMOSPHERIC PROFILING OF WATER VAPOR AND LIQUID WATER WITH A K-BAND AUTOCORRELATION RADIOMETER" (January 1, 1987). Doctoral Dissertations Available from Proquest. Paper AAI8727101.
http://scholarworks.umass.edu/dissertations/AAI8727101

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