Abstract
Abstract. Ground-based microwave radiometer (MWR) observations of downwelling brightness temperature (TB) are commonly used to estimate atmospheric attenuation at relative transparent channels for radio propagation and telecommunication purposes. The atmospheric attenuation is derived from TB by inverting the radiative transfer equation with a priori knowledge of the mean radiating temperature (TMR). TMR is usually estimated by either time-variant site climatology (e.g., monthly average computed from atmospheric thermodynamical profiles) or condition-variant estimation from surface meteorological sensors. However, information on TMR may also be extracted directly from MWR measurements at channels other than those used to estimate atmospheric attenuation. This paper proposes a novel approach to estimate TMR in clear and cloudy sky from independent MWR profiler measurements. A linear regression algorithm is trained with a simulated dataset obtained by processing 1 year of radiosonde observations of atmospheric thermodynamic profiles. The algorithm is trained to estimate TMR at K- and V–W-band frequencies (22–31 and 72–82 GHz, respectively) from independent MWR observations at the V band (54–58 GHz). The retrieval coefficients are then applied to a 1-year dataset of real V-band observations, and the estimated TMR at the K and V–W band is compared with estimates from nearly colocated and simultaneous radiosondes. The proposed method provides TMR estimates in better agreement with radiosondes than a traditional method, with 32 %–38 % improvement depending on frequency. This maps into an expected improvement in atmospheric attenuation of 10 %–20 % for K-band channels and ∼30 % for V–W-band channels.
Highlights
There is a continuous trend to use higher frequencies in the development of satellite communication (SatCom) as lower-frequency bands become saturated (e.g., Biscarini et al, 2017)
To the aim of reducing this uncertainty, in this work we propose an original approach increasing the accuracy of TMR estimates by exploiting independent microwave radiometer (MWR) profiler measurements
For the considered pointing angle (35◦ elevation), the cloud liquid water path estimated from radiosondes reaches 2.8 mm for the training set, while the liquid water path estimated from MWR observations within the validation set reaches 4.6 mm
Summary
There is a continuous trend to use higher frequencies in the development of satellite communication (SatCom) as lower-frequency bands become saturated (e.g., Biscarini et al, 2017). Europe’s current Earth observation programs with the Sentinel satellite constellation generate a daily data volume of terabytes, requiring new broadband links to access the data. In future interplanetary explorer missions, the need for high-throughput communications will become more pressing due to a wider range of observed parameters and teleoperated landers or rovers to avoid data loss due to limited onboard memory or data compression (Jebril et al, 2007; Acosta et al, 2012). A. Alyosef et al.: Improving atmospheric path attenuation estimates for radio propagation crease in data volume requires higher transmission capacities than those currently available. Moving beyond the X and Ku bands to less congested higher frequencies increases the available bandwidth, allowing smaller equipment that reduces the size of the satellite and launch vehicle (Cianca et al, 2011; Acosta et al, 2012; Emrick et al, 2014)
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