著者
Toshinori AOYAGI Nobuyuki KAYABA Naoko SEINO
出版者
(公社)日本気象学会
雑誌
気象集誌. 第2輯 (ISSN:00261165)
巻号頁・発行日
vol.90B, pp.11-31, 2012 (Released:2012-06-09)
参考文献数
32
被引用文献数
10 14 4

We investigated a warming trend in the Kanto-Koshin area during a 30-year period (1976-2006). The warming trends at AMeDAS stations were estimated to average a little less than 1.3°C/30 years in both summer and winter. These warming trends were considered to include the trends of large-scale and local-scale warming effects. Because a regional climate model with 20-km resolution without any urban parameterization could not well express the observed warming trends and their daily variations, we investigated whether a mesoscale atmospheric model with an urban canopy scheme could express them.To make the simulations realistic, we used 3 sets of real data: National Land Numerical Information datasets for the estimation of the land use area fractions, anthropogenic heat datasets varying in space and time, and GIS datasets of building shapes in the Tokyo Metropolis for the setting of building aspect ratios. The time integrations over 2 months were executed for both summer and winter. A certain level of correlation was found between the simulated temperature rises and the observed warming trends at the AMeDAS stations. The daily variation of the temperature rises in urban grids was higher at night than in the daytime, and its range was larger in winter than in summer. Such tendencies were consistent with the observational results.From factor analyses, we figured out the classic and some unexpected features of urban warming, as follows: (1) Land use distribution change (mainly caused by the decrease of vegetation cover) had the largest daytime warming effect, and the effect was larger in summer than in winter; (2) anthropogenic heat had a warming effect with 2 small peaks owing to the daily variation of the released heat and the timing of stable atmospheric layer formation; and (3) increased building height was the largest factor contributing to the temperature rises, with a single peak in early morning.
著者
Nobuyuki Kayaba Takashi Yamada Syugo Hayashi Kazutoshi Onogi Shinya Kobayashi Koichi Yoshimoto Kenji Kamiguchi Kazuya Yamashita
出版者
(公社)日本気象学会
雑誌
SOLA (ISSN:13496476)
巻号頁・発行日
vol.12, pp.1-5, 2016 (Released:2016-01-20)
参考文献数
8
被引用文献数
11

The Japan Meteorological Agency (JMA) completed its second global atmospheric reanalysis, the Japanese 55-year Reanalysis (JRA-55). However, the horizontal spatial resolution of JRA-55, TL319 (about 55 km), is insufficient for representing the hilly topography of the Japanese islands. Therefore, to reproduce extreme events caused by the hilly topography and their long-term climatological change in Japan, JMA has conducted a dynamical regional downscaling, called DSJRA-55, based on JMA's operational mesoscale model, which has a horizontal resolution of 5 km. DSJRA-55 receives its initial field and boundary conditions from the JRA-55 reanalysis. DSJRA-55 is historically the first products in the world that covers very long term for 55 years with very high resolution in 5 km. Furthermore, DSJRA-55 does not perform data assimilation; instead, initial field and boundary conditions are given at frequent intervals to the downscaled model and short-range forecasts are performed. Then, successive forecasts are connected continuously to create the DSJRA-55 product. In early evaluation results, DSJRA-55 was able to reproduce observed temperature and precipitation during 1958-2012. Although it showed a systematic temperature bias in some regions and seasons and it underestimated the frequencies of heavy-rain days and heavy-rain hours, DSJRA-55 reproduced the overall distribution of orographic precipitation well. DSJRA-55 is therefore expected to be useful for analyzing past extreme events and for statistical studies of long-term climate.