(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 52, No. 2, pp. 105-118, 2005
A typical life cycle of an extratropical cyclone has been described by a classical cyclone model developed by the Bergen school. Recently, a new cyclone model was proposed by Shapiro and co-researchers based on special observation campaigns conducted off the east coast of the U. S. In this work, we analyze extratropical cyclones developed around Japan during the period from February 7, 2000 to March 10, 2000, focusing on their frontogenetical aspects. It is found that one of the 8 cyclones observed during the period exhibited characteristics typical for the Shapiro-type cyclone development including a frontal fracture, a bent-back warm front, frontal T-bone and warm-core seclusion. The particular cyclone had no occluded front that characterizes the classical cyclone model. The temperature gradient across the warm front of this cyclone was intensified throughout the life cycle, while the cold front was simply advected eastward. The rear side of the bent-back warm front was maintained and extended backward by the advection of the intensified temperature gradient by an easterly wind along the warm front. The large-scale background flow for this cyclone development was characterized by a weak meridional shear of westerly wind, in accordance with a condition for the Shapiro-type cyclone development as pointed out by previous studies.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 52, No. 2, pp. 119-128, 2005
In this study we clarified the temperature variation in Seoul, Korea and discussed the city representative air temperature. We used data of 24 AWS in Seoul, which are located above building roofs. The temperature distribution in Seoul is divided into two parts;warm core at the center of city and cool area to the north of the city center. The temperature difference between them is comparable to the heat island intensity of Seoul. The standard deviation of temperature in Seoul could reach several tens percents of the heat island intensity. The inner city temperature variation is not negligible in evaluating the heat island intensity.
The air temperature variance in the urban area depends on a day of the week. This analysis indicates the anthropogenic heat as a source of temperature variation. Temperature difference between Seo-Cho district, which is a typical office area, and residential Kang-nam district is 0.45C for weekday and 0.37C for holidays, those area four years average. The difference between Seo-Cho and Kang-nam is statistically significant where the significance level is 5%.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 52, No. 3, pp. 163-170, 2005
A snowband and a wind field around Kashiwazaki were observed by single-Doppler radar when a wind disaster occurred. The snowband developed from west-southwest to east-northeast just before the disastrous gust occurred. The echo top of the snowband was more than 5000 meters. A deep strong-wind zone extended from 500 meters to 4000 meters above sea level on the south side of the snowband. A shear line with a vorticity on the order of 10-3 s-1 formed where the snowband bordered the strong-wind zone, and the whole structure slowly propagated southward. A mesoscale vortex with a diameter of 5 km formed on the shear line. The vorticity in the mesoscale vortex was on the order of 10-2 s-1. The evidence strongly suggests that the disastrous gust was a tornado which formed as the updraft of the snowband caused the concentration of the vorticity of the mesoscale vortex on the shear line.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 52, No. 4, pp. 235-239, 2005
Long-term changes in diurnal variation patterns of thunder frequency were analyzed using visual observation data (present weather) for 42 years (1961-2002) in Japan. The thunder frequency has increased throughout a day in winter and spring, while that in summer has a decreasing trend, which is largest at 15 JST with a value of -10% per decade. The 15 JST frequency relative to the daily mean has also decreased at a rate of about -0.08 per decade in summer and for the annual mean. As a result the afternoon peak of thunder frequency has weakened or delayed in the recent decade in comparison to the 1960's.