Proposal of a new equation to estimate globe temperature in an urban park environment

Globe temperature is one element of the heat stress index, the Wet Bulb Globe Temperature, which is used to evaluate how radiation adds to thermal discomfort in the workplace. As the measurement of globe temperature is not standardized, empirical equations were introduced to estimate the globe temperature from weather factors, including air temperature, solar radiation and wind speed. As it was not known whether these equations were applicable in an urban park environment with vegetation, we observed the globe temperature using a set of instruments in three parks. The observation along with the heat balance analysis of the globe revealed that the globe temperature depended curvilinearly on solar radiation and that wind speed influenced this dependence. We compared two previously proposed empirical equations to the observed globe temperature and found both equations had systematic estimation errors. Although the errors were reduced by fitting the equations to the observed data and reevaluating their numerical constants, the equations still had shortcomings, as one did not consider wind speed and the other included a discontinuity. We therefore derived a new equation based on the heat balance equations of the globe with its numerical constants experimentally determined. This equation was able to predict the curvilinear dependence of the globe temperature on global solar radiation without any discontinuity, and it also showed the globe temperature response to wind speed

Climatology of Precipitation during the Passage of the Double Cyclone

The double-cyclone type is considered to be one of the most important pressure patterns around Japan as it is known to cause severe weather such as heavy rain and strong winds in various parts of the country. In this study, double cyclones are classified into the following three types\u27 Heishin type; Nihonkai-L main type! and Nangan-L main type. They are examined in a climatologic context to assess the regional charac teristics of precipitation amount and intensity, and snowfall after the passage of double cyclone. Furthermore, precipitation characteristics of each type of double cyclone, the Nihonkai and Nangan lows are examined. Precipitation from the NihonkaHow main type tends to be weak, although the precipitation caused by the double cyclone is strong along the southern coast and the Hokuriku region of Japan. For the Heishin type, precipitation is observed at nearly 90% of observation points in the whole country. The ratio of observation points with precipitation is greater in eastern Japan for the NihonkaHow main type. Compared to the Nihonkai low and the Nangan low, the double cyclone tends to cause snowfall more frequently in the whole country. The mean total snowfall amount is the greatest for the Nihonkai-low main type among the threetypes of double cyclone. The Heishin type and the Nihonkai-low main type have a tendency to cause snow storms in the Tohoku region and in Hokkaido. The Nangan-low main type may cause relatively calm snowfall nationwide and even bring snowfall to the southern part of Kanto. Heavy precipitation events tend to occur when the southern low moves nearer to the Japanese islands for all of the three types of double cyclone. Moreover, the southern cyclone tends to be stronger than the northern cyclone

Analyses of Southerly Winds along the Kitakami Basin when the Yamase Prevails

The Yamase is a cold, humid, northeasterly wind blowing toward the coast on the Pacific side of the Tohoku region of Japan during summer. However, the Yamase blows in a southerly direction in the Kitakami Basin. Inthis study, analyses of data and numerical experiments using the Weather Research and Forecasting(WRF) model were conducted to determine the reason for this southerly direction. The results of numerical experiments indicated that the Yamase is southerly in the Kitakami Basin where theactual topography is reduced to 90% of the average terrain height. Meanwhile, it is easterly in areas of the Kitakami Basin when the topography is reduced to 80% of the average terrain height. The results of numerical experiments were consistent with those of mechanical analyses using the Foude number and Rossby number. Analyses of the Yamase in the Kitakami Basin therefore suggest that its characteristics are influenced by topographic obstacles and gravitational flow

Case Study of Local Heavy Rainfall, Focusing on GPS Precipitable Water Vapor : Rainfall Event Observed in Tokyo on July 4, 2000

The present study examined the essential features of local heavy rainfalls observed in Tokyo on July 4, 2000. The following results were obtained: 1) The atmosphere was unstable while the Japanese islands were covered by the Pacific high. 2) The easterly surface winds converged with southerly winds (E-S-type wind system) in the central part of the urban area several hours before the precipitation occurred. 3) The cold air outflow associated with the precipitation system flowed into the convergence zone formed by the E-S wind system. Examining the spatial distribution of and temporal change in the precipitable water vapor (PWV) on theKanto plain shows that the PWV tends to increase before rainfall occurs both over the mountains and on the plain. However, it does not appear that the PWV increased in Tokyo due to the urban heat island circulation. Therefore, the urban heat island did not produce heavy rainfall by inducing a strong upwind and drawing in water vapor in this case

Ice thikness measurement on glaciers in Suntar Khayata, Eastern Siberia (A preliminary result)

第3回極域科学シンポジウム/特別セッション「これからの北極研究」11月28日（水） 国立極地研究所 2階大会議

Effect of Mountain Convexity on the Locally Strong “Karakkaze” Wind

This study numerically examined how the locally strong “Karakkaze” wind in the Kanto Plain of Japan is affected by terrain shape, particularly by a convex feature in the mountain range. Our method involved running idealized numerical simulations using the Weather Research and Forecast model with a horizontal grid spacing of 3 km. The results revealed that a strong­wind region formed in the lee area of the convex feature, hereafter the semi­basin, and leeward of the semi­basin. In contrast, weak­wind areas formed adjacent to the strong­wind region. These results were consistent with the basic features of the observed surface wind pattern of the Karakkaze during the winter monsoon. However, such a flow pattern did not appear in the numerical simulation with a mountain range that lacked a convex feature. Sensitivity experiments were also conducted to evaluate the detailed effects of a mountain range with convex­ity. Sensitivity experiments with different convex shapes revealed that strong winds appeared within and leeward of the semi­basin when the aspect ratio of convexity (ratio of the wave amplitude to the wavelength of the con­vexity) exceeded about 0.5. Sensitivity experiments on terrain shape suggested that saddles in the mountain range were not essential to the formation of the Karakkaze, but they could affect its strength. Sensitivity experiments on the mountain Froude number, Frm, showed that locally strong winds within and leeward of the semi­basin appeared only when the Frm was in the range 0.42 – 1.04. Sensitivity experiments with surface heat fluxes (SHFs) showed that the basic structure of the strong­wind region in the leeward plain of the convex feature did not de­pend strongly on SHFs. However, the addition of SHFs reduced the surface wind speed, but increased the size of the strong­wind region

Assessing the Sustainability of Ski Fields in Southern Japan under Global Warming

This is the first study in assessing the impact of climate change on Japanese ski fields with ensemble dynamical downscaling simulations. We target three ski fields in Ehime Prefecture, a southern border area for skiing in Japan. Our field survey revealed that a field located above 1200 m altitudes currently operates on natural snow supply, but those located at lower altitudes depend solely or partially on artificial snow supply. Fields are currently open for 82∼105 days. We analyzed ensemble high-resolution (5 km) dynamical downscaling simulations for future ski season durations with natural and artificial snow supplies. The future projection results for the end of the twenty-first century suggested that there would be virtually no natural snow accumulation in the study area for skiing. With artificial snow supply, a field located above 1200 m would be able to retain more than two months of ski season duration. Fields located at lower altitudes would only be able to open for 37∼43 days even with artificial snow supply. While the above projections suggest a severe outlook for the targeted ski fields, it is important to note that there is a strong demand from local skiers at beginner/intermediate levels for these ski fields. Thus, as long as these demands remain in the future, and if a business model to maximize profit during short opening periods is established, it may be possible to offset profit loss due to climate change