Satellite-based radar wind sounder (RAWS) optimal frequency study

Modeling global atmospheric circulations and forecasting the weather would improve if worldwide information on winds aloft were available. Recognition of this led the authors to study a space-based instrument that could measure Doppler shifts from clouds and rain: the RAdar Wind Sounder (RAWS). Previous studies conducted at the University of Kansas show RAWS to be feasible (Moore, et al., 1992). This paper describes a new SNR sensitivity study conducted for the RAWS program. The authors first verified the Deirmendjian drop-size distribution model and then applied the radar range equation to obtain the SNR. The Deirmendjian distribution has the advantage of modeling many different cloud types with different altitudes. The authors computed the SNR versus cloud altitude at six frequencies to determine the optimal transmit frequency. The results show an improvement in performance with two transmit frequencies, a higher frequency (94 GHz) to obtain sensitivity for thinner clouds and a lower frequency (24 GHz) for better penetration in rain. The authors' previous studies used 10 and 35 GHz, which this study showed not to be optimum.<
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