Improving atmospheric path attenuation estimates for radio propagation applications by microwave radiometric profiling

Ground-based microwave radiometer (MWR) observations of downwelling brightness temperature (span classCombining double low line"inline-formula") are commonly used to estimate atmospheric attenuation at relative transparent channelsfor radio propagation and telecommunication purposes. The atmospheric attenuation is derived from span classCombining double low line"inline-formula"span by inverting the radiative transfer equation with a priori knowledge of the mean radiating temperature (<span classCombining double low line"inline-formula").span classCombining double low line"inline-formula"MR span is usually estimated by either time-variantsite climatology (e.g., monthly average computed from atmospheric thermodynamical profiles) or condition-variant estimation from surface meteorological sensors. However, informationon span classCombining double low line"inline-formula"MR span may also be extracted directly from MWRmeasurements at channels other than those used to estimate atmospheric attenuation. This paper proposesa novel approach to estimate span classCombining double low line"inline-formula"T MR/span in clear and cloudy sky from independent MWR profiler measurements. A linear regression algorithmis trained with a simulated dataset obtained by processing 1 year of radiosonde observations of atmospheric thermodynamic profiles. The algorithm is trained to estimate span classCombiningdouble lowline"inline-formula"T/iMR/span at K- and V-W-band frequencies (22-31 and 72-82 span classCombining double low line"inline-formula"GHz/span respectively) from independent MWR observations at the V band (54-58 span classCombining double low line"inline-formula"/span). The retrieval coefficients are then applied to a 1-year dataset of real V-band observations, and the estimated span classCombining double low line"inline-formula"MR /span at the K and V-Wband is compared with estimates from nearly colocated and simultaneous radiosondes. The proposed method provides span classCombining double low line"inline-formula"/i MR /span estimates inbetter agreement with radiosondes than a traditional method, with 32 %-38 % improvement depending on frequency. This maps into an expected improvementin atmospheric attenuation of 10 %-20 % for K-band channels and <span classCombining double low line"inline-formula"1/430</span % for V-W-band channels.