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Toshinori Aoyagi and Naoko Seino

Abstract

A single-layered square prism urban canopy (SPUC) scheme for the Japan Meteorological Agency nonhydrostatic model (NHM) was developed. This scheme considers the urban canopy layer with square prism–shaped buildings. The basic concept of this scheme is similar to those of the conventional energy balance models for an urban canyon structure. The scheme presented here differs slightly from them in its representation of the bulk resistance circuit and some treatments of radiation processes, however, as well as by considering the water reservoir on building surfaces. A comparison between the SPUC scheme and the existing slab scheme of the NHM was made on summer days in the Tokyo metropolitan area. The SPUC run more accurately reproduced the expected behavior of the urban canopy effect than did the slab run. The effective albedo was smaller in the SPUC run than in the slab run (the upward shortwave radiation of the SPUC run was smaller than that of the slab run). The forecast heat fluxes in the SPUC run, however, showed worse performances. Adequate parameter settings (especially concerning latent heat fluxes) are needed in the SPUC run. The mean bias errors of the surface air temperature during nighttime were less negative and slightly improved in the SPUC run than in the slab run.

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Hiroaki Kawase, Yukiko Imada, Hiroshige Tsuguti, Toshiyuki Nakaegawa, Naoko Seino, Akihiko Murata, and Izuru Takayabu
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Tsuyoshi Nakatani, Ryohei Misumi, Yoshinori Shoji, Kazuo Saito, Hiromu Seko, Naoko Seino, Shin-ichi Suzuki, Yukari Shusse, Takeshi Maesaka, and Hirofumi Sugawara
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Ryohei Misumi, Yoshinori Shoji, Kazuo Saito, Hiromu Seko, Naoko Seino, Shin-ichi Suzuki, Yukari Shusse, Kohin Hirano, Stéphane Bélair, V. Chandrasekar, Dong-In Lee, Augusto Jose Pereira Filho, Tsuyoshi Nakatani, and Masayuki Maki

Abstract

The Tokyo Metropolitan Area Convection Study for Extreme Weather Resilient Cities (TOMACS) began as a Japanese domestic research project in 2010 and aimed to elucidate the mechanisms behind local high-impact weather (LHIW) in urban areas, to improve forecasting techniques for LHIW, and to provide high-resolution weather information to end-users (local governments, private companies, and the general public) through social experiments. Since 2013, the project has been expanded as an international Research and Development Project (RDP) of the World Weather Research Programme (WWRP) of the World Meteorological Organization (WMO). Through this project, the following results were obtained: 1) observation data for LHIW around Tokyo were recorded using a dense network of X-band radars, a C-band polarimetric radar, a Ku-band fast-scanning radar, coherent Doppler lidars, and the Global Navigation Satellite System; 2) quantitative precipitation estimation algorithms for X-band polarimetric radars have been developed as part of an international collaboration; 3) convection initiation by the interaction of sea breezes and urban impacts on the occurrence of heavy precipitation around Tokyo were elucidated by a dense observation network, high-resolution numerical simulations, and different urban surface models; 4) an “imminent” nowcast system based on the vertically integrated liquid water derived from the X-band polarimetric radar network has been developed; 5) assimilation methods for data from advanced observation instruments such as coherent Doppler lidars and polarimetric radars were developed; and 6) public use of high-resolution radar data were promoted through the social experiments.

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