Tuesday, 29 August 2023
Boundary Waters (Hyatt Regency Minneapolis)
Handout (5.9 MB)
A microwave weather radar is used to observe a distribution of precipitation. However, non-precipitating clouds cannot be observed with the sensitivity of ordinary weather radars, because cloud droplets are much smaller than precipitation particles. Therefore, a cloud radar was developed with higher sensitivity using a shorter wavelength. National Research Institute for Earth Science and Disaster Resilience (NIED) developed a Ka-band cloud radar to observe cumulus cloud developing into cumulonimbus. To realize the detectability of such a cloud, 3 kW Extended Interaction Klystron (EIK) and pulse compression technology are used. NIED developed the detection system of developed cumuli which will generate rain by the Ka-band cloud radar network in Tokyo metropolitan area.
Recently, the EIK price is increasing and its delivery period is also getting longer. Solid State Power Amplifier (SPPA) may be an alternative device for EIK, but a transmit power of SPPA is smaller than that of EIK. Higher radio-frequency is needed to compensate the sensitivity of cloud radar. However, it is difficult to use higher frequency radar reflectivity, because such radio wave is easily attenuated by cloud and water vapor.
The current Ka-band cloud radar system uses radar reflectivity to detect the cloud, but the reflectivity is not well correlated with the cloud water content. The Dual-Wavelength Ratio (DWR) of the reflectivity is sometime used to estimate the difference of the attenuation between two frequencies, which is well correlated with the cloud water content. Ka- and W-bands are used for this purpose.
On the other hand, a remote sensing of water vapor is also a hot topic in recent meteorology, because the accurate water vapor information around the cumulus and cumulonimbus is necessary for forecasting of localized torrential rain. Various techniques (microwave radiometer, Raman lidar, GPS, and etc.) are examined to monitor the water vapor.
We propose a dual-frequency terahertz (95 GHz and 150 GHz) weather radar with SPPA to solve these problems. DWR of radar reflectivity is used to estimate the attenuation information by both cloud and water vapor. The cloud and water vapor effects in the DWR are separated by an artificial intelligence (AI) model, which learns the relationship between meteorological parameters and radar reflectivity simulated by meteorological model using the spectral-bin microphysics. The development of the proposed radar has just been started under the Beyond 5G R&D Promotion Project funded by National Institute of Information and Communications Technology (NICT), Japan.
Acknowledgements: The development of the dual-frequency terahertz radar is supported by the commissioned research (No. 06901) by National Institute of Information and Communications Technology (NICT), Japan.
Recently, the EIK price is increasing and its delivery period is also getting longer. Solid State Power Amplifier (SPPA) may be an alternative device for EIK, but a transmit power of SPPA is smaller than that of EIK. Higher radio-frequency is needed to compensate the sensitivity of cloud radar. However, it is difficult to use higher frequency radar reflectivity, because such radio wave is easily attenuated by cloud and water vapor.
The current Ka-band cloud radar system uses radar reflectivity to detect the cloud, but the reflectivity is not well correlated with the cloud water content. The Dual-Wavelength Ratio (DWR) of the reflectivity is sometime used to estimate the difference of the attenuation between two frequencies, which is well correlated with the cloud water content. Ka- and W-bands are used for this purpose.
On the other hand, a remote sensing of water vapor is also a hot topic in recent meteorology, because the accurate water vapor information around the cumulus and cumulonimbus is necessary for forecasting of localized torrential rain. Various techniques (microwave radiometer, Raman lidar, GPS, and etc.) are examined to monitor the water vapor.
We propose a dual-frequency terahertz (95 GHz and 150 GHz) weather radar with SPPA to solve these problems. DWR of radar reflectivity is used to estimate the attenuation information by both cloud and water vapor. The cloud and water vapor effects in the DWR are separated by an artificial intelligence (AI) model, which learns the relationship between meteorological parameters and radar reflectivity simulated by meteorological model using the spectral-bin microphysics. The development of the proposed radar has just been started under the Beyond 5G R&D Promotion Project funded by National Institute of Information and Communications Technology (NICT), Japan.
Acknowledgements: The development of the dual-frequency terahertz radar is supported by the commissioned research (No. 06901) by National Institute of Information and Communications Technology (NICT), Japan.
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