Tenki, Vol. 45, No. 1
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 45, No. 1, pp. 7-18, 1998
Spatial Anomalies and Long-Term Changes of Precipitation in Tokyo
By
Fumiaki Fujibe
Meteorological Research Institute, Tsukuba 305-0052, Japan
Abstract
Spatial distribution of precipitation in and around Tokyo were studied in search for urban anomaly by using data from the AMeDAS raingauge network for 16 years (1979-1994). The anomalies at five stations in Tokyo were defined by the departure from a quadratic interpolation based on 21 stations outside the city. Also, the long-term precipitation changes were analyzed by using data prior to the deployment of AMeDAS raingauges. The findings are summarized as follows: (a) Stations in the central and inland area of Tokyo show a positive anomaly of precipitation, while those in the coastal area of the city show a negative anomaly. (b) The positive precipitation anomaly tends to be enhanced in the early afternoon of the warm season, reflecting the large anomaly in the frequency of heavy precipitation (>=5mm/hour). (c) The feature in (b) is most conspicuous at the station in the central area of the city, where the diurnal variation pattern may have changed during the 20th century toward a higher percentage of precipitation in the afternoon than in other time of the day. (d) The stations in the inland area of the city are characterized by positive anomalies in the frequency of precipitation in general (>=1mm/hour and >=1mm/day), as well as a long-term increasing trend in the number of precipitation days (>=1mm/day). Part of these anomalies and changes may be attributable to urban effects, although a conclusive judgment will call for further evidence.
TENKI, Vol. 45, No. 1, pp. 19-33, 1998
Analysis of Thunderstorms Occurred over Kanto Plain on 10 August 1995
By
Masanori Yoshizaki,
Meteorological Research Institute, Tsukuba, 305-0052, Japan
Naotaka Uekiyo,
Meteorological Satellite Center.
Hiromu Seko, Hajime Takayama, Ken-ichi Kusunoki
Meteorological Research Institute
and
Tsukuba Area Precipitation Studies group
Abstract
Thunderstorms occurred when a synoptic-scale cold front passed over Kanto Plain on 10 August 1995. By utilizing data of AMeDAS, surface meteorological records, upper sounding, and Doppler radar, storm A, which attacked Tsukuba, was studied from a standpoint of three horizontal scales; synoptic (1000km), Kanto (100km) and storm (10km) scales. Prior to its formation, three wind systems (very warm southerly wind systemT，warm northwesterly wind systemII，and cold northeasterly wind systemIII) and wind shear lines were seen over Kanto Plain. In each wind system, temperature and moisture were nearly uniform, like mini-airmass. Storm A formed where three shear lines intersected, and developed and matured in the wind systemIII. At the mature stage of storm A, intense storm-scale downdrafts and outflows near the surface were found, and arc-shaped clouds were generated by these outflows.
Formation of the wind systemIII was quantitatively examined. It is concluded that it is a gust wind produced mainly by evaporation of precipitation in other storms in the wind systemIII.
Tenki, Vol. 45, No. 2
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 45, No. 2, pp. 93-103, 1998
Squall Line Observed in the Kanto Plain on 16 August 1995
By
Hiromu Seko, Masanori Yoshizaki, Ken-ichi Kusunoki
Meteorological Research Institute, Tsukuba, 305-0052, Japan
and
Members of Tsukuba Area Precipitation Studies
Abstract
On 16 August 1995, a squall line (SL), in which
convective cells aligned from the southwest to the
northeast, was observed in the Kanto Plain, when a
synoptic-scale cold front passed. The structure of
the SL at the mature stage was analyzed by using data
from Doppler radar at Tsukuba and AMeDAS, and surface
data of Meteorological observatory of JMA and local
governments (Gunma, Saitama, Tochigi, Chiba and
Ibaraki Prefectures).
The heavy precipitation region was observed on
the front side of SL and the weak precipitation
region spread behind it. The surface wind field
shows divergence of the cold outflow in the
precipitation region and convergence with a warm air
inflow in front of this cold outflow. On the other
hand, at a height of 2-4km, the rearward system-
relative flow in the heavy precipitation region and
the dry air inflow from the rear side of the weak
precipitation region were observed. The surface
records of pressure show mesoscale fluctuations of
low pressure ahead of SL, high pressure in the heavy
precipitation region and low pressure at the back
edge of the weak rain.
Characteristic features of SL in this case were
similar to those of SLs observed in the tropics and
U.S. Midwest, although the horizontal scale of the
present case was small.
TENKI, Vol. 45, No. 2, pp. 119-126, 1998
The Relationship between the Wind Speed and/or Ground Inversion Strength over Rural Environs and Nighttime Urban Heat Island Intensity at Nagano City
By
Yasushi Sakakibara,
Shinshu University, Nagano 380-0871, Japan
Shinobu Tanaka
Nangu Junior High School
and
Yuka Itoh
Wakaho Junior High School
Abstract
To investigate the urban heat island intensity of Nagano city, Japan, the population of which is about 0.35 million, 43 measurements of the air temperature distribution in and around the urban area were made by the car traverse method from summer to early winter in 1995 and 1996. Other meteorological elements measured at public observatories were also used to analyze the data. The results are as follows:
(1) The maximum intensity was 4.9 C, which is 1.7 C larger than that expected from its statistical relation to population for cities in Japan but is rather smaller than that in North America and Western Europe (Park, 1987).
(2) The intensity scarcely varied with changes in wind speed.
(3) The intensity correlated closely with the square root of the gradient of potential temperature in the vertical over the surrounding rural area.
Tenki, Vol. 45
Tenki, Vol. 45, No. 5
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 45, No. 5, pp. 351-360, 1998
Acidification of Precipitation at Ryori, Japan for 1976-1994
By
Yuriko Ishikawa
Graduate School of Humanities and Sciences, Ochanomizu University, Tokyo, 112-0012, Japan
Takuya Ohno
College of Science and Technology, Nihon University
Junichi Ohyama, Kan Ogawa
Oceanographical Division Climate and Marine Department, Japan Meteorological Agency
and
Hiroshi Hara
Department of Community Environmental Siences, National Institute of Public Health
Abstract
The data set for a nineteen-year long measurement of precipitation chemistry at Ryori was discussed in terms of the annual trend of pH as well as hydrogen ion concentration. The volume-weighted annual mean pH declined evidently from pH 5.3 in 1976 to pH 4.8 in 1994 with some fluctuations, which means the hydrogen ion concentration had increased by a factor of 3.2 in the measurement period. The acidification was concluded to be due to an increase in sulfuric and nitric acid concentrations rather than decreasing concentrations of alkaline species. The annual mean pH in 1994 was compared with the nation-wide monitoring results of the year by Japan Environment Agency (JEA): (a) The pH at Ryori was the same as the JEA mean, pH 4.8, (b) Concentrations and deposition of non-seasalt sulfate, nitrate, and ammonium ions were at levels fairly lower than the JEA means, (c) Those of non-seasalt calcium ion were close to the JEA means.
TENKI, Vol. 45, No. 5, pp. 361-368, 1998
An Experiment on Acquisition of Meteorological Reports for Fog Events Using Internet
By
Akira Yamamoto
Meteorological Research Institute, Tsukuba, 305-0052, Japan
and
Tokio Kikuchi
Faculty of Science, Kochi University
Abstract
From general users of Internet, meteorological reports on fog events in Kanto district, Japan on 29-31 October 1996 were acquired. These events had several features that were suitable for acquisition of meteorological reports from the general public: 1) thwy were relatively uncommon, 2) their durations were quite long, 3) it was easily observed, and 4) the population density of the area was large and they occurred during the time of high human activity. Although no preparation was made in advance, we were able to obtain detailed reports of relatively good quality, which supplied additional data to the existing observational network. As Internet becomes more popularized among the general public, new types of meteorological information networks may evolve.
Tenki, Vol. 45
Tenki, Vol. 45, No. 7
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 45, No. 7, pp. 515-530, 1998
Vertical Structures of Land and Sea Breezes in the Nohbi Plain
during a Passage of an Anticyclone over the Central Japan
By
Hiroaki Mori,
Techno Chubu Co. Ltd.,Nagoya, 455-8512, Japan
Toshihiro Kitada
Toyohashi University of Technology
and
Kenji Iyoda
Japan Weather Association
Abstract
Characteristic diurnal variations of vertical structure of land and sea breezes in the Nohbi Plain were investigated using rawinsonde and pilot balloon soundings when a traveling anticyclone passed over the Central Japan on 21-23 April 1991．
The major findings are as follows : i) a "plain-plateau wind", the southeasterly toward the Suzuka Mountains nearby the Nohbi Plain, blows early at the altitudes of 700-1100m at 1000 LST prior to the beginning of the "Ise Bay sea breeze" over the Nohbi Plain ; ii) the sea breezes show their different vertical depths depending on the horizontal scale of topography, i.e., the depth of the smaller-scale "Ise Bay sea breeze" is at most 400m, while large-scale "Enshu-nada sea breeze", caused by the Pacific Ocean, reaches 700m high ; iii) the large-scale "plain-plateau wind", ranging from southerly to southwesterly induced by the "thermal low" formed over the high Japan Alps, continues from 1500 to 2300 LST
while clear large-scale return flow is found in the upper layers over Central Japan ; iv) the large-scale topographic features of the Japan Alps and the Pacific Ocean dominate local winds over the Nohbi Plain.
Tenki, Vol. 45
Tenki, Vol. 45, No. 8
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 45, No. 8, pp. 621-632, 1998
Relationship between Negative Temperature Anomaly in the Western Tropical Pacific and Typhoon Fern (T9626)
By
Takanori Mizuno,
Climate Prediction Division（present affiliation: Maritime Meteorological Division）, Japan Meteorological Agency, Tokyo 100-8122, Japan
Koichi Ishikawa
Oceanographical Division（present affiliation: Hakodate Marine Observatory）, Japan Meteorological Agency
and
Yasushi Takatsuki
Oceanographical Division, Japan Meteorological Agency
Abstract
R/V Ryofu Maru of Japan Meteorological Agency(JMA) performed oceanographic observations along the meridian of 137E in the western North Pacific from January 24 to February 1, 1997, and it was found that negative sea water temperature anomaly less than 2 to 6C near the thermocline from 14N to 8N. According to the sea water temperature obtained by Ocean Data Assimilation System(ODAS) of JMA, this negative temperature anomaly formed a circular region having a diameter of 700 to 800 km, which appeared in the third 10-day period of December 1996 and remained stationary until February 1997. The location of the negative temperature anomaly area corresponded to the area where typhoon Fern (T9626) formed and remained stationary. It is assumed that the cyclonic wind stress with the typhoon induced upwelling so that thermocline rose and the negative temperature anomaly appeared.
It was also found that sea surface temperature (SST) decreased by a maximum of over 1.5C along the path of the typhoon Fern. The negative SST anomaly caused by Fern continued until March 1997, while previous observations showed that SST which was decreased by a typhoon returned within 10 or 14 days.
TENKI, Vol. 45, No. 8, pp. 633-642, 1998
Estimation of Upper Wind in Typhoon Region from Single-Doppler Radar
By
Ryozo Tatehira,
Meteorological Business Support Center, Tokyo 101-0054, Japan
Hiromu Seko,
Forecast Research Department, Meteorological Research Institute
and
Tomohiro Suzuki
BA Security System Division, Matsushitadenko Co. Ltd.
Abstract
A technique is proposed by which wind vectors in a typhoon region are
estimated, from single-Doppler radar observations, with a spatial resolution
of ca.10km. In estimating wind vectors from single-Doppler data, it is
needed to assume such conditions on the wind field within the sampling volume as uniformity or linearity.
In the case of a typhoon, an assumption that the wind field is axisymmetrically cyclonic is roughly appropriate. Under this assumption, both tangential and
normal components of the typhoon wind are constant along a concentric circle
of the typhoon center. The inflow angle to the center are also constant. However, the assumption cannot represent changes of the inflow angle owing to
a fine structure of typhoon (e.g., spiral bands). So, a more realistic
assumption is newly introduced in the current study. The new assumption is
that the tangential and normal components are constant along the curve of
an unknown curvature rather than the concentric circle. In order to find
the unknown curvature, firstly we estimate the wind vectors from the
Doppler velocities by assigning various value to the unknown curvature,
then select the optimum value that gives the best estimate of the actual
wind field (Optimum Curvature Technique). The algorithm to select the
optimum value of curvature is developed with numerical simulations on a model
cyclone, where the inflow angle sinusoidally varies +-30 degree around the average inflow. The performance of the algorithm is that the mean absolute value of
the error vector is ca.8ms-1, about 20% of the average wind speed.
In applying this technique to actual typhoons, it is necessary to know
the accurate position of typhoon center. However, if inaccurate center
locations are given, the estimated wind fields show a distinct asymmetry
characterized by the true center position relative to the given inaccurate one. This asymmetry allows us to make subjective adjustment of the center location to minimize the error caused by the inaccurate position.
TENKI, Vol. 45, No. 8, pp. 643-653, 1998
An Increasing Trend of Extremely Hot Days in the Inland of the Kanto Plain and its Relation to Urban Effects
By
Fumiaki Fujibe
Meteorological Research Institute, Tsukuba 305-0052, Japan
Abstract
A climatological analysis was made on the increase of extremely hot days (maximum temperature >=36C) in the inland area of the Kanto plain with attention to its causal factors. The synoptic conditions on hot days were classified into W-, N- and C-types corresponding to westerly, northerly and near-calm geostrophic winds, respectively. For all these types, there is an increase in the number of days characterized by extremely warm airmass and sufficient sunshine (for which temperature at 850hPa was 21C or more, and duration of sunshine was 8 hours or more). This suggests a synoptic-scale contribution to the increase of extremely hot days. For the W- and the C-types, however, the daily maximum temperature in the inland area shows a remarkable rising trend relatively to the 850hPa temperature. This implies the contribution of urban effects to the increase of hot days.
TENKI, Vol. 45, No. 8, pp. 655-661, 1998
A Study on Lightning Activity of the Thunderstorms during 1996 Winter Season around Wakasa, Hokuriku District, Japan
By
Jongho Lee,
Faculty of Engineering, Osaka University, Osaka
565-0871, Japan
Wada Masakazu,
Faculty of Engineering, Osaka University(present affiliation: Toshiba Co.)
Zen-Ichiro Kawasaki,
Faculty of Engineering, Osaka University,
Kenji Matsuura,
Faculty of Engineering, Osaka University,
Makoto Takeuti
Kansai Electric Power Co., Inc.
and
Yasuo Sonoi
Kansai Electric Power Co., Inc.
Abstract
The authors observed winter lightning discharges over the Hokuriku coastal area by means of SAFIR, from 30 November 1996 to 28 February 1997.
The paper presents the map of the flash density and the statistics of the lightning discharges, in terms of cloud flash, ground flash of negative and positive polarity. The paper also discusses the lightning activity with the meteorological conditions.
It is noticed that the occurrence rate of the cloud discharges becomes highest when the winter type synoptical situation prevails and the occurrence rate of the ground flashes, especiall, that of positive polarity tends to be higher, when the altitude of the -10C temperature level is higher. It is also noticed that the occurrence rate of the cloud discharges tends to be higher, when the SSI (Showalter Stability Index) is relatively higher.
TENKI, Vol. 45, No. 9, pp. 707-715, 1998
Evidance for Urban Heat Island Phenomena in Soil Temperature Profiles in Tokyo
By
Yutaka Genchi
Department of Chemical System Engeneering, School of Engeneering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 118-8656, Japan
Takehiro Otani
Department of Chemical System Engeneering, School of Engeneering, University of Tokyo
Haruo Amano
Department of Chemical System Engeneering, School of Engeneering, University of Tokyo
Nobuaki Kosugi,
Faculty of Engineering, Kogakuin University
Yutaka Osa
Faculty of Engineering, Kogakuin University
Hidetoshi Nagamoto
Faculty of Engineering, Kogakuin University
and
Hiroshi Komiyama
Department of Chemical System Engeneering, School of Engeneering, University of Tokyo
Abstract
Underground temperatuer profiles from ground level to 4m below the surface
were measured for about 1 year at two locations in Tokyo, Japan. The first site
was Kyoka elementary school in Chuo-ku, a highly urbanized area. The second site
was Tanashi city, a rural area. A one-dimensional thermal diffusion simulation
was carried out for the underground temperature field in Kyoka, and the results
were in good agreement with the measurements. Daily averages of the ground surface
temperature and the air temperature directly above the surface showed a linear
correlation. Annual average temperatures at 4m below the surface were 18.9C in Kyoka
and 16.9C in Tanashi. The yearly fluctuations at both sites were small. In comparison
with the past underground temperature in Tokyo of 15.0C, the underground temperature
at Kyoka and Tanashi were 3.9C and 1.9C higher, respectively.
From these results, the underground temperature fields are shown to record air
temperature changes through fluctuations in the ground surface temperature,
which was highly correlated with air temperature. Thus we can consider the underground
temperature field to be a recorder of past changes in air temperature. Through
analysis with air temperature fields, underground temperature fields could be important
as both indices and evidance for urban heat island phenomena.
TENKI, Vol. 45, No. 10, pp. 781-791, 1998
Response of Temperature and Precipitation over Japan and the Japan Sea to Variability of Winter Monsoon
By
Shinji Matsumura
Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060-0810, Japan
and
Shang-Ping Xie
Graduate School of Environmental Earth Science, Hokkaido University
Abstract
Winter monsoon is an important cause of winter climate variability over the northeast Asia and northwestern Pacific. Cross-correlation and composite analyses based on a monsoon index (MOI) are conducted to investigate the climate response over the Sea and Islands of Japan.
In a strong monsoon year, both column integrated water vapor and precipitation decrease over the Japan Sea. The Japanese west coast north of 35N receives more precipitation/snow because of enhanced winds impinging on alongshore mountain ranges. Winter precipitation decreases in the rest of the country because the upper westerly jet shifts southward reducing the number of cyclones passing over Japan.
Increased winds and reduced humidity enhance both latent and sensible heat fluxes from the ocean. This enhanced heat loss leads to negative sea surface temperature (SST) anomalies in the southern Japan Sea where the mixed layer is shallow, whereas in the northern ocean where the deep water forms, SSTs are not significantly correlated with the MOI. Significant negative correlation of air temperature with the MOI is found throughout Japan. The MOI-associated temperature variance is minimum within the planetary boundary layer over northern Japan presumably due to the effect of SST variability over northern Japan Sea. Largest monsoon-induced cooling occurs around 500 hPh along the Japanese Islands, reducing the static stability of the lower atmosphere.
In addition to interannual (2-3 years) monsoon-induced variability, pronounced quasi-decadal temperature variations, well correlated with the North Atlantic Oscillation since late 1960s, are found over northern Japan.