(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 60, No. 1, pp. 5-14, 2013
Campaign aerological observations of winter monsoon and Yamase (cool easterly observed in summer in the northeastern part of the Honshu island) were performed in Tsugaru Plain in the western part of Aomori Prefecture, Japan. We found that wind speed of winter monsoon was reduced over the southern part of Tsugaru Plain below 500 m AGL and that a very shallow (100 m) wet cold air appeared during a short period when the monsoon weakened. In Yamase observations, a thin strong wind layer concentrated around 200 m AGL in the northern part of Tsugaru Plain. Downscale experiments are performed using the nonhydrostatic meso-scale numerical prediction model of Japan Meteorological Agency (JMA) by changing horizontal resolution from 5 km to 1 km. Although vertical structure of winter monsoon and Yamase were simulated even in the 5 km run, that is a condition similar to operational prediction use of JMA, 1 km run showed fairly higher performance for simulating vertically confined thin phenomena, i.e., the shallow wet cold layer and the concentrated strong wind of Yamase. Observation and model simulation suggested that winter monsoon was weakened in the southern part of Tsugaru Plain by a shadow effect of upstream mountains and that the upper strong wind of Yamase was a down-slope wind caused by the Tsugaru mountain range in the upstream.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 60, No. 4, pp. 223-246, 2013
We report results from "Innovative Program of Climate Change Projection for the 21st Century" (KAKUSHIN program) by Ministry of Education, Culture, Sports, Science and Technology (MEXT), under which most part of the data from Japan have been obtained for submission to the Coupled Model Intercomparison Project Phase 5 (CMIP5), putting emphasis on CMIP5 simulations. CMIP5 experiments in the program have been conducted by Long-Term Global Change Projection Team (Team 1), Near-Term Climate Prediction Team (Team 2) and Extreme Event Projection Team (Team 3) focusing on a centennial (Team 1) and decadal (Team 2) timescale, and extreme events such as typhoon and downpour (Team 3). Team 1 obtained results such as improved reproducibility for past climate change during the 20th century and projection for future vegetation shift, Team 2 establishment of an initialization scheme for a climate change projection model and improved predictability of climate change on a multiple-year timescale, and Team 3 projection of typhoon intensity approaching to Japan and creation of a map of Japan for probabilistic precipitation change. Also, it is a great legacy of the program that a network between the two research communities of climate change projection and impact assessment has been established. These results will be succeeded to a new program by MEXT "Program for Risk Information on Climate Change", and it is hoped that they are further developed and utilized for developing climate mitigation and adaptation policies.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 60, No. 4, pp. 247-260, 2013
Simultaneous observations of cumulonimbi using the MTSAT-1R (rapid scan), the 95-GHz FM-CW cloud radar, the X-band radar, and photogrammetry were carried out during the summer of 2010 in the Kanto region, Japan to understand the convection initiation and the structure of heavy rainfall in the Tokyo metropolitan area.
The formation process of an isolated cumulonimbus which generated in the afternoon on a fine mid-summer day on 23 August 2010 was presented. An isolated cumulonimbus developed suddenly near the Chiba site after 13:30 JST on 23 August 2010. The first echo appeared at a height of 4 km AGL at 13:42 JST. After forty minutes from the cloud generation, the turrets developed vertically and an anvil formed at 14:42 JST. The lifetime of the cumulonimbus was approximately two hours.
The rapid scan data is useful for the observation of isolated cumulonimbi under the mid-summer days and the detection of cumulonimbus initiations. The features of the cumulonimbus analyzed by the rapid scan images are as follows:
1) At the formation stage of the cumulonimbus, cumulus and cumulonimbus are detected by the visible brightness data.
2) The temporal change of the visible brightness suggests the evolution of the cumulonimbus turrets.
3) The temporal and spatial structures of the anvil were presented.
It is shown that the generation, development and decaying of an isolated cumulonimbus on a fine mid-summer day can be recognized based on the MTSAT-1R rapid scan data.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 60, No. 5, pp. 371-381, 2013
Variations in heat mortality in Japan were examined in relation to summer temperature, using vital statistics data for 1909 to 2011. The number of deaths from excessive heat was around 200 to 300 each year until the middle of the 20th century, and then decreased until the 1980s, but abruptly increased in 1994 and has remained higher than ever. For the mortality rate, however, the recent increase has been limited to a level that is only as high as that in the middle 20th century, whereas statistics for each age group indicates a high rate of heat mortality for elderly people throughout the analysis period. These facts indicate that the rapid increase of deaths from excessive heat in recent years is largely attributable to the increase in the population of elderly people, although it is also likely to be caused by changes in post-mortem practice, in which more attention has been paid in recent years to heat disorder. On the other hand, there is a positive correlation of 0.7-0.8 between summer temperature (average for July and August) and heat mortality in each year, with a regression coefficient of 40-60% for a 1°C increment in temperature.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 60, No. 7, pp. 505-519, 2013
The present study analyzed the influence of the urban heat island (UHI) phenomenon in Tokyo on the nocturnal atmospheric pressure distribution and local wind system by using observed atmospheric pressure data in the central Tokyo and its surroundings. We used the atmospheric pressure data observed at the JMA observatories located in and around the central Tokyo, and that observed by METROS network which had been installed in the Tokyo wards area. The atmospheric pressure data of METROS included specific instrument errors. Moreover, the observational instruments had already been removed. Therefore we corrected the atmospheric pressure data by assuming hydrostatic equilibrium. We focused on the period from July to August 2004 which was a hot summer. The results of the present study can be summarized as follows:
1) The formation process of a remarkable low pressure area due to the development of the UHI in the central Tokyo was shown for the first time by using observed data. Moreover, it was shown that the high temperature and low pressure areas existed together, and that they moved together toward the central Tokyo as time passed.
2) In the middle of the night, it was shown that a local wind front advanced toward the central Tokyo from the inland side. The front arrived at the central Tokyo at about 0300 JST, and it advanced near the coast temporarily. However, it began to retreat at about 0600 JST, and as a result it did not head out to Tokyo Bay.
3) By analyzing the front stagnation using the atmospheric pressure distribution, it was revealed that the high temperature due to the UHI caused a maximum about 0.5 hPa low pressure in the central Tokyo compared with Tokyo Bay. It is found that the stagnation was caused by the southerly wind converging from the southern high pressure area to the central Tokyo, and the southerly general wind flowing on Tokyo. Similarly to the stagnation of the sea breeze front in the afternoon shown in the previous studies, the high temperature due to the UHI affected the front stagnation of the nocturnal local wind shown in the present study.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 60, No. 9, pp. 709-722, 2013
In January 12th, 2013 very rare mirages, which comprised of one inferior inverted mirage and several superior inverted and erect mirages, were observed in 10-20 km distance over frozen Huhren Lake in Nemuro province, Hokkaido. To reproduce this mirage, using very stable temperature profiles, ray tracing was performed and qualitatively successful results can be obtained. It is found that the minimum region of the radius of curvature causes totally internal reflection for rays emitted near the Earth's surface and these rays form mirages. When there is a maximum region below the minimum region, rays reflected in this maximum region travel to far distance and overlap with those reflected in the minimum region, resulting in multi-image mirage in a certain distance range. Inferior mirage with a single image is also reproduced through the totally internal reflection in a stable condition. The extremum altitude of the radius of curvature coincides with the inflection altitude of temperature, and the inflection altitude from convex downward to convex upward corresponds to the altitude of a maximum radius of curvature in a stable atmosphere. Conversely, the inflection altitude from convex upward to convex downward corresponds to the altitude of a minimum radius of curvature. Further, multi-image mirages include more information of atmospheric thermal condition than single-image mirages and thereby the possibility of retrieving temperature profile through solving the inverse problem is also discussed.