RADIO PHYSICS AND RADIO ASTRONOMY

Subject and Purpose. The methods for precipitation remote sensing continue to be developed. One of the trends has been assessing amounts of precipitations to determine whether to issue alerts for large-scale floods and landslides or to make decisions regarding the agricultural land irrigation. The present work focuses on the inverse problem of dual-frequency sensing and its solution through Tikhonov regularization. The goal is to improve the algorithm for solving the inverse problem and retrieve a non-uniform rainfall intensity profile. The retrieval results are enhanced by taking into account the impacts of the signal attenuation and errors in the received power measurements.

Methods and Methodology. The retrieval of a non-uniform spatial profile of rain intensity is carried out by the numerical simulation using the integral scattering equation solution via Tikhonov regularization and employing dual-frequency sensing data.

Results. The numerical simulations of a non-uniform spatial profile of the rain intensity in the range 0…30 mm/h have been performed at the operating wavelengths 8.2 mm and 3.2 cm and for various errors of the received power measurement and complete attenuation of the signals. It has been observed that the signal attenuation at the shorter (8.2 mm) operating wavelength has a significant effect on the retrieved intensity of rains heavier than 5 mm/h and more distant than 1 km. For the longer (3.2 cm) operating wavelength, the signal attenuation can be neglected when the maximum intensity in the profile is under 30 mm/h and the distance is less than 20 km. The retrieval error of a non-uniform rain intensity profile is shown to be no worse than 40% for the intensities in the profile above 3 mm/h and measurement errors of ±20%.

Conclusions. The analysis of the results has shown that the proposed dual-frequency approach to solving the integral scattering equation makes it possible to retrieve a non-uniform rain intensity profile with a maximum error no worse than 40% for rain intensities above 3 mm/h and with the proviso that the error of the received power measurement and complete attenuation of signals at the shorter (8.2 mm) operating wavelength is no worth than ±20%.

Keywords: inverse problem, rain intensity, non-uniform profile, signal attenuation

Manuscript submitted  16.11.2023

Radio phys. radio astron. 2024, 29(3): 214-221

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