[A-AS23_28PM2] Hyper-dense observation network to elucidate micro-scale atmosphreric phenomena

[AAS23-P01_PG] A study on an atmospheric propagation delay estimation method using a fixed radio source

3-min talk in an oral session

*Shigeru INAKA¹, Jun-ichi FURUMOTO¹, Hiromu SEKO², Toshitaka TSUDA¹, Hiroyuki HASHIGUCHI¹, Masahito ISHIHARA³ (1.Research Institute of Sustainable Humanosphere, Kyoto University, 2.Meteorological Research Institute, 3.Education unit for Adaptation to Extreme Weather Conditons and Resilient Society, Kyoto University)

Keywords:Wind Profiling Radar, estimation of horizontal humidity distribution, non-hydrostatic forecast model, software radio, side-lobe, propagation delay

This study aims to develop a new method to observe water vapor horizontal distribution using a side-lobe emission of the 1.3 GHz-band wind profiling radar (WPR). The phase delay of the received side-lobe emission is mainly due to the refractive index fluctuation along the propagation path. In the atmospheric boundary layer, the temporal and spatial non-uniformity of water vapor determines the refractive index fluctuation. Main scope of the study is to extract humidity information from the atmospheric phase delay of side-lobe emission from a WPR. Horizontal humidity distribution can be derived by the data assimilation into numerical prediction model.The receiver system and data analysis algorithm were developed. A software radio, USRP N200 with an RX daughter board was employed to detect side-lobe emission received by an antenna. A Rubidium frequency standard and a 1 pps signal source of GPS receiver were used for accurate estimation of phase delay variation. The frequency stability of a crystal oscillator, which is generally employed for a reference frequency source of WPR, is insufficient for the accurate estimation. We proposed a new method to compensate the frequency uncertainty of WPR by using data of the additional receiver nearby the WPR site.IQ data detected by USRP B210 which is controled by GNURadio, an open source software. By using GNURadio the system will be low cost.The program written in IDL language extracts the temporal variation of the phase delay from the received IQ signal. In order to achieve good performance even in low SNR conditions, we developed an algorithm using STFT (Short-term Fourier transformation) aiming to remove noise in undesired frequency range. The developed system is promising to derive humidity information from side-lobe emission from various WPRs such as the operational WPR network in Japan (WINDAS (WInd profiler Network and Data Acquisition System)).