Tuesday, 29 August 2023
Boundary Waters (Hyatt Regency Minneapolis)
In Japan, the operational frequencies of C- and X-bands are used for nationwide weather radar observations. The Japan Meteorological Agency (JMA) operates a network of single- or dual polarization C-band radars. Whereas, the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) has deployed and been operating single- or dual-polarization X- and C-band radars, referred to as the XRAIN, since 2010. In addition to the government-based operational radars, the private sector has been approved to operate X-band radars under a radio-frequency allocation in Japan. Weathernews Inc. (WNI) has been operating an adaptively located single-polarization X-band weather radar network in Japan since 2010, now with up to eighty radars, referred to as the "EAGLE Radar", developed in collaboration with the University of Oklahoma (OU).
Every winter several graupel fallout events occur with varying intensities along the coastline of the Sea of Japan, which can cause numerous traffic accidents. Considering the size of graupel particles, with diameters of approximately 2 - 5 mm in Japan, X-band radars have more sensitivity to detect such particles compared to C-band radars. Strong graupel events often occur in one of the cities in the Niigata prefecture, Jyoetsu, located out of the range of the MLIT dual-polarization X-band radars. To mitigate this, WNI and OU have been collaborating on the development of algorithms for the detection of graupel in the Niigata prefecture using the JMA C-band and WNI X-band radars, where both are single polarization. By deriving a dual-frequency ratio using C- and X-band radars, we can obtain a noticeable signature for graupel particles of approximately 5 mm in size, which likely corresponds to the existence of graupel. In this presentation, we will discuss the potential of exploiting radar observations from two frequencies for detecting graupel aloft using their ratio of radar reflectivities.
Keywords: dual-frequency ratio, graupel
Every winter several graupel fallout events occur with varying intensities along the coastline of the Sea of Japan, which can cause numerous traffic accidents. Considering the size of graupel particles, with diameters of approximately 2 - 5 mm in Japan, X-band radars have more sensitivity to detect such particles compared to C-band radars. Strong graupel events often occur in one of the cities in the Niigata prefecture, Jyoetsu, located out of the range of the MLIT dual-polarization X-band radars. To mitigate this, WNI and OU have been collaborating on the development of algorithms for the detection of graupel in the Niigata prefecture using the JMA C-band and WNI X-band radars, where both are single polarization. By deriving a dual-frequency ratio using C- and X-band radars, we can obtain a noticeable signature for graupel particles of approximately 5 mm in size, which likely corresponds to the existence of graupel. In this presentation, we will discuss the potential of exploiting radar observations from two frequencies for detecting graupel aloft using their ratio of radar reflectivities.
Keywords: dual-frequency ratio, graupel
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