(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 49, No. 1, pp. 47-56, 2002
Antomobile observations of air temperature were conducted in order to investigate nocturnal temperature distribution and its causal factors in Nankoku City, Kochi Prefecture. The results obtained in this study are as follows:
(1) From December to early April, an island-shaped warm area was observed in the vicinity of the business district. After the middle of April, no isotherms surrounding the city area were found, although the city area was warmer than the suburbs.
(2) The intensity of the heat island was highest in winter, with maximum temperature difference of 4.0ˇî.
(3) According to observations on a steep slope which is about 6km east of the city area, an inversion layer often appeared between 25m and 200m above the sea level. The intensity of the inversion was highest in winter, with maximum temperature gradient of 3.5ˇî/100m. In summer, no inversion was observed.
(4) A principal component analysis on the temperature distribution shows that the first component accounts for 63.1% of the total variation. This component is related to some urban factors such as the densities of buildings and population. The second principal component, which accounts for 14.2% of the temperature distribution variation, is related to the inversion intensity in winter.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 49, No. 1, pp. 57-66, 2002
The superior mirage is observed during the months from April to June at ten and several times per every year in east coast of Toyama Bay. Until now, as the reason of occurrence of this mirage, it is well known the air cooled by cold thaw water from Mt. Tateyama forms into the warm upper layer and cool lower one. However, we find the surface temperature of sea water during the month of May show a tendency to be warm different from near sea. From the observed perpendicular temperature distribution of air in the day of occurrence of mirage, we consider the former well-known theory is not sufficient because the superior mirage is a phenomenon caused by which the warm air insert into upper layer in the sea. By comparing these results with the calculation of the temperature distribution of air and the weather data, we think the superior mirage depends on the topographical character in Toyama Bay, and the sea wind brings warm air to the sea by warming up in land when it passes through a projecting land, then the mirage occurs.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 49, No. 5, pp. 395-405, 2002
Analysis was made on local wind fields preceding the occurrence of short-time heavy rainfall in Tokyo, with attention to their relationship to the behavior of radar echoes. Data for seven years were used to select 16 cases in which temperature reached 30ˇî and precipitation of 20 mm/h or more was observed in the afternoon in the Tokyo ward area. It was found that 12 among the 16 cases were characterized by the ˇČE-S type" pattern, in which easterly winds blowing from the east coast of the Kanto plain and southerly winds from the southwestern coast were converging in the vicinity of Tokyo. A detailed analysis for the Tokyo area revealed the presence of one or a few convergence zones having a scale of 10-20 km, corresponding to the subsequent development of radar echoes. The E-S type wind pattern can be formed on sunny days also, if the synoptic-scale pressure gradient is favorable for the onset of easterly sea breeze, but days with heavy rainfall tended to be characterized by higher humidity in the lower and middle troposphere, with larger values of the K-index and precipitable water vapor than sunny days without rainfall.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 49, No. 6, pp. 457-464, 2002
The relationship between the acidification of rain/ fog and the droplet size of fog was investigated. Samples of rain and fog water were collected in the Akita Hachimantai mountain range from June to August 1997. The ionic components were analyzed by ion chromatography and the insoluble substances were analyzed by PIXE analysis. Combining 72 h back trajectory analysis and chemical analysis, the effect of the course of transportation of the air mass on the chemical composition of the samples was also studied.
When the air mass was transported from northern China to the Hachimantai range, the fog and rain water contained soil dust particles from China and the acidity of the fog water was higher than that in other cases. The slope of log-log plots of the ion concentration versus the droplet size of fog was found to be minus three, and this can be explained on the basis of a simple droplet growth model involving a diffusion process.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 49, No. 6, pp. 473-476, 2002
Long-term trends of relative humidity and vapor pressure in the central part of Tokyo were evaluated from forty years' data, which were stratified with daily maximum temperature. It was found that the changing rates of relative humidity and vapor pressure for days with maximum temperature of 33-36ˇî showed a positive anomaly of a few percent and 0.5-1 hPa per 40 years, respectively, in comparison to those for days with lower temperature. This fact suggests the effect of water vapor emission from cooling towers on urban humidity.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 49, No. 7, pp. 541-553, 2002
Automobile traverses were done seventy-four times to gather data on air temperature distributions in Matsumoto City, Nagano, to study the causes of the nocturnal heat island phenomenon. The relationship between wind speed and the supremum heat island intensity when other factors ideally foster development of heat island is discussed separately for fine and cloudy days. The supremum heat island intensity ΔTu-r(sup) of cloudy days becomes smaller when the wind is stronger, while that of fine days does not follow the same rule: ΔTu-r(sup) is largest for 2-3 m/s wind. This dependence of the temperature difference on wind cannot be explained by canyon radiative geometry. A possible explanation leads that the mixing of the urban atmosphere plays a significant role in the nocturnal heat island formation on fine days by preventing the development of strong surface inversion.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 49, No. 9, pp. 763-772, 2002
The heat probe method in which a line heat source in an infinite media is heated at a constant rate of heat and temporal variation of temperature at a certain point is recorded has frequently been used to measure heat conductivity. In the present paper, the profile of soil heat conductivity is estimated by an instrument that uses this principle. It is found that soil heat conductivity should be estimated when the variation of heat supply from the line heat source as well as the soil temperature variation due to the change of the outside condition is small. Soil heat conductivity depends on both moisture and temperature of the soil: It becomes large as soil water content and/or temperature increases.
Though the present sensor can in principle estimate thermal diffusivity at the same time, its estimated error is found to be ten times larger than that of the heat conductivity. Accordingly, thermal diffusivity is often estimated from the vertical profiles of amplitude and phase of the soil temperature. Since this method assumes a sinusoidal variation of the temperature, however, it is recommended to solve the heat conduction equation directly and compare the results with the observation in order to obtain more accurate estimate of the thermal diffusivity.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 49, No. 11, pp. 887-899, 2002
In order to obtain validation data for a model system describing the relationship between urban energy system and thermal environment, meteorological properties were measured on the roof of buildings in the central areas of Tokyo. From a series of measurement in the skyscrapers quarter and its neighborhood, typical contrast was found in air temperature variations in the building canopy layer and above a bare soil corner of a garden. From another series of measurement performed in the old city for more than one year, four major factors of heat budget were evaluated for the roof surface of a building of 24 stories --- net short-wave and long-wave radiations, total turbulent sensible and latent heat fluxes, and heat conduction through the wall. Comparison of these factors on four cloudless days selected from different seasons, when the latent heat flux could be neglected, indicated that the heat transfer from the surface to the ambient air was rather larger in April than in August. General coincidence was found between the sensible heat flux (H) evaluated for the surface as the residual term and that measured by the eddy correlation method at the 2.5 m height, while the condition of wind measurement was unsatisfactory because of the rooftop structures. The heat transfer coefficient, defined as the ratio of upward H under unstable condition and the temperature difference between the surface and the air, could be represented as a linear function of the mean wind speed.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 49, No. 11, pp. 901-911, 2002
Temperature data at 74 points around Hakuba village, Nagano prefecture, Japan, which is surrounded by paddy fields were collected by automobile travelling method. The heat island intensity is estimated by the difference between the average temperature of the warmest three points in urban areas and that of coldest three points in rural areas. The hourly temperature differences between Hakuba AMeDAS, a representation of an urban site, and a temporary meteorological station in the central part of paddy field are also calculated using one year of data. The principal results of the present paper are as follows: Heat island intensity and its variance in snow season are larger than those in other seasons. The nighttime (2000 LST) temperature difference in January, March, April and September is larger than that in other months and the daytime temperature difference in July and August is larger than that in other months. Diurnal variation of temperature difference in snow season is similar to that in other seasons. The temperature difference is small after sunrise, but starts to increase from 2-3 hours after sunrise until sunset. The peak of the temperature difference occurs at 1300 and 1400 LST in irrigation season. The temperature difference attains at its maximum between 1900 and 2200 LST but not before sunrise.
(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)
TENKI, Vol. 49, No. 12, pp. 955-968, 2002
This is an expansion of a lecture delivered in accepting the 2002 Medal of the Meteorological Society of Japan. Behavior of ocean-atmosphere interaction differs where sea surface temperature (SST) is greater or less than a certain criteria (~27oC). Over warm ocean surface, atmospheric deep convection reacts to changes in SST, leading to tropospheric-wide response. Over cold ocean surface, by contrast, the direct effect of SST anomalies is trapped in the planetary boundary layer and the response further above is poorly understood. Modes of warm ocean-atmosphere interactions include the Bjerknes and wind-evaporation-SST (WES) feedback, which give rise to El Nino/Southern Oscillation (ENSO) and is key to the northward departure of the Pacific and Atlantic intertropical convergence zone (ITCZ) from the geographic equator, respectively. A comparative discussion of climate variability in the three tropical oceans is given in light of these air-sea feedbacks. Finally, the potential of satellite observations for describing and understanding cold ocean-atmosphere interaction is demonstrated with examples. Modulation of storm track by SST gradient is proposed as a possible mechanism for extratropical SST to influence the free troposphere.