A formula for luminance distribution on the clear cloudless sky and a formula for total horizontal illuminance from that sky are proposed based on a scattering theory. The light consists of the scattered light of the direct sunlight and that of the reflected light from the ground surface. And the main scattered light in the is the 1st-order scattered light of the direct sunlight, but its higher order scattered light than or equal to the 2nd-order and the scattered light of the reflected light from the ground surface are considerably included in the light and they have effect on the variation of light, respectively. In the proposed formulas, these effects are estimated from the result of a theoretical analysis. In the conventional formulas for the luminance distribution which are derived based on observation, however, these effects are not done because of difficulties of the estimation by means of measurements. Therefore the luminance distributions from the proposed formula approximate more closely to measured data under the than the conventional formulas. And the proposed formula for total horizontal illuminance from the is applicable not only to the but to the overcast sky because the scattering characteristics of the overcast sky is equivalent to those of the where aerosole is included quite densely.

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The spectral radiant flux distribution of light varies mainly from the following factors: aerosol density, solar altitude and angular distance from the sun, and reflected light from the ground surface. This paper investigates the relation between cause and effect of variation of light. The spectral radiant flux distributions of light are not measured but calculated theoretically. The following conclusions were obtained:
(1) The chromaticities of daylight in high latitudes are distributed up to the higher region of correlated color temperature (CCT) than in low latitudes and a number of chromaticities of daylight in low latitudes are distributed at the low region of CCT compared with in high latitudes.
(2) The chromaticities of north sky light in low latitudes are distributed with a slight shift into green side at high CCT and into purple side at low CCT compared with that of north sky light in high latitudes.
(3) The difference of the distributions of chromaticities of daylight falling on a horizontal surface of the ground between in high latitudes and in low latitudes is much smaller than that of the distributions of chromaticities of north sky light between in high latitudes and in low latituydes.

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This paper presents some formulae for the calculation of the luminance distribution of a and of the resultant horizontal illuminance. Both the luminance distribution of a and the resultant horizontal illuminance are mainly affected by the extraterrestrial sunlight illuminance, the altitude of the sun, and the transparency of the atmosphere. A formula for the luminance distribution of a has been derived through theoretical consideration upon these factors. The formula predicts the luminance in absolute values as proposed to the ClE formula for , which provides relative pattern of luminance distribution¹⁾. Obviously the horizontal illuminance from an unobstructed can be calculated from the luminance distribution of the sky by means of a fundamental formula for the calculation of illuminance. However, from a different point of view a relatively simple expression has been formulated for the calculation of the horizontal illuminance, by applying the factors which were used to develop the formula for the luminance distribution, but in a different way.

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The Mean Sky^{11)13)15∼18)} and the Average Sky^20∼22) have been proposed for new daylighting design methods which conform with the real sky conditions more closely than the conventional methods based upon the Uniform Sky^*01, the CIE Standard Overcast Sky¹⁾ and so on. In order to compose the mean Sky^*02) proposed by the authors at any geographical point in the world, the luminance distribution of all the sky conditions which really appear there are to be divided conveniently into three types, that is, the , the Intermediate Sky and the Overcast Sky, and their luminance distribution is to be defined respectively¹⁴⁾, and moreover, their relative frequency of occurrences within the total working hours is indispensably to be estimated. In this paper, the relation between the three Skies and the meteorological observation data recorded regularly in Japan is described, and a procedure is stated which has been developed in order to estimate the relative frequency of occurrences of the three Skies from the meteorological observation data, and finally, the yearly relative frequency of occurrences of the , the Intermediate Sky and the Overcost Sky relating to the usual working duration in Japan^*03 is assumed to be 5%, 70% and 25%, respectively, as the result of this research work.

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 This article reports on the impacts of Himawari-8

Radiance (CSR) data assimilation in the global and mesoscale numerical weather prediction (NWP) systems of the Japan Meteorological Agency (JMA). Adoption of the Advanced Himawari Imager (AHI) on board JMA's Himawari-8 and -9 satellites has enhanced observational capabilities in terms of spectral, horizontal, and temporal resolution. Improvements brought by the switchover from the Multi-functional Transport Satellite-2 (MTSAT-2) to the new-generation Himawari-8 satellite include an upgrade to the horizontal resolution of CSR data from 64 to 32 km and an increase in the number of available water vapor bands from one to three. CSR products are obtained every hour and distributed to the NWP community. The improved horizontal and spectral resolution of Himawari-8 CSR data provides new information on horizontal water vapor distribution and vertical profiles in data assimilation.

 In data assimilation experiments using JMA's global NWP system, the assimilation of Himawari-8's three water vapor bands significantly improved the tropospheric humidity field in analysis, especially in the lower troposphere, as compared to assimilation of the single MTSAT-2 water vapor channel. First-guess (FG) departure statistics for microwave humidity sounders indicated an improvement in the water vapor field, especially over Himawari-8 observation areas. Improved forecasting of tropospheric temperature, humidity, and wind fields for Himawari-8 observation areas was also seen.

 In data assimilation experiments using JMA's mesoscale NWP system, a disastrous heavy precipitation event that took place in Japan's Kanto-Tohoku region in 2015 was investigated. A single water vapor band of Himawari-8 CSR corresponding to MTSAT-2 was assimilated, resulting in enhanced contrast of the water vapor field between moist and dry areas, as well as a realistic representation of moist air flows from the ocean in analysis. The changes also improved mesoscale model heavy precipitation forecasts.

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Wrong:See PDF attached
Right:See PDF attached

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There are many uncertainties in the quantitative assessment of radiative effects due to atmospheric dust aerosol and the optical properties of dust particles contribute large to them. Numerical sensitivity experiments to evaluate the impacts of optical characteristics on the radiative forcing have been performed in this study. The experiments involve the effects of refractive indices, single scattering albedo, asymmetry factor and optical depth of the dust particles. An updated data set of refractive indices representing East Asian dust and the data set recommended by World Meteorology Organization (WMO) are used in our calculations for comparison. A k-distribution model for solar and thermal radiation transfer is employed in the calculation of radiative forcing. It is found that comparing with the WMO model, East Asian dust model has stronger scattering and weaker absorption at solar regime, which leads to higher negative forcing at the top of atmosphere (TOA) in this study. The more important is the signs of radiative forcing at TOA over certain regions could be reversed for the two dust models, which emphasizes the essentiality of accurate measurements of optical properties of dust aerosols for quantitatively estimating their radiative forcing.

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 The main objective of this study is to analyze downward shortwave radiation estimated from geostationary satellite by using an index called Rate (CSR) and apply it to see the impact of geographical and land use variation on clouds. Matsuyama, the target area in this study has mountains, plains and contrasting land uses of urban and rural areas. The following outcomes were obtained. CSR is likely to be lower in mountainous areas than in the plain areas. The temporal analysis shows that the CSR on the mountains decreases down to the midday and then increases accordingly with time compared to the plain areas. The comparison between urban and rural areas shows that formation and thickness of cloud in an urban area are higher than the rural area in the afternoon. The CRS index and the dataset has a high potential to understand the local cloud properties.

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 The classification of clouds and its spatial and temporal variation is important to understand the concept of local climate. Thus, this study was carried out to explore the potential for using the statistical analysis (standard deviation) of time series of one hour averaged pyranometer observation to determine the types of clouds in the Matsuyama plain. Instruments were installed at 6 observation points covering the entire study area. rate was considered as an index to identify the reduction in the solar radiation due to presence of cloud. The development of high raised cloud such as cirrostratus and cumulus were observed with small and large time standard deviation respectively and rate between 0.4 - 0.6. Also, the formation of cloud were observed to be high in the urban area and the inland area. This was further verified using the whole sky images taken by the camera installed at Ehime University. The results would be beneficial for the study of the rainfall pattern in different part of Matsuyama plain and to understand the effect of urbanization on the local climate.

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A formula for luminance distribution on the clear cloudless sky and a formula for total horizontal illuminance from that sky are proposed based on a scattering theory. The light consists of the scattered light of the direct sunlight and that of the reflected light from the ground surface. And the main scattered light in the is the lst-order scattered light of the direct sunlight, but its higher order scattered light than or equal to the 2nd-order and the scattered light of the reflected light from the ground surface are considerably included in the light and they have effect on the variation of light, respectively. In the proposed formulas, these effects are estimated from the result of a theoretical analysis. In the conventional formulas for the luminance distrinution which are derived based on observation, however, these effects are not done because of difficulties of the estimation by means of measurements. Therefore the luminance distributions from the proposed formula approximate more closely to measured data under the than the conventinal formulas. And the proposed formula for total horizontal illuminance from the is applicable not only to the but to the overcast sky because the scattering characteristics of cloud is equivalent to those tof the clear skywhere aerosole is included quite densely.

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This paper provides the first attempt to investigate the spatial variability of diurnal change patterns of land surface temperature (LST) in urban areas of Japan by applying principal component analysis on LST data retrieved from Himawari-8 geostationary satellite data. The Tokyo and Osaka metropolitan areas were the focus of the analysis, and the target days were days with zero cloud cover in summer and winter. The results of the analysis showed that diurnal cycles of LST are mainly formed by two temporal change patterns in both seasons. For the summer case, the first two principal components (PCs) represented the temporal change patterns related to the amplitude and phase, respectively. For the winter case, the first two PCs represented the temporal change patterns related to the amplitude and gradual change in LST throughout the day, respectively. Results suggest that these temporal change patterns in both seasons have spatial variability partially dictated by land use and wind speed/direction.

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In order to search for the end of energy spectrum of ultrahigh-energy cosmic rays (UHECR), the JEM-EUSO (Japanese Experimental Module - Extreme Universe Space Observatory) project is under preparation. In this project, atmospheric fluorescence light from the trajectory of the extensive air shower (EAS) produced by UHECR is planned to be measured by photosensors placed at the focal surface of a telescope (the fluorescence technique) on the International Space Station (ISS) and hence cloud information along the trajectory of the JEM-EUSO field of view is required. To select cloud-free pixels with about 1km spatial resolution, measurement of the brightness temperature in the infrared window region is under preparation. In this report we apply the MODIS (Moderate resolution Imaging Spectroradiometer)-type cloud mask algorithm to individual sky scenes and assign a confidence level of - between 1 and 0 to a pixel of about 1km×1km area above Fukui University of Technology (FUT), Fukui, Japan. By comparing the sky conditions observed by the infrared-thermograph (IRT) at FUT at the same time with a similar field of view, we examine to what fraction of cloud in 1km-spatial resolution, the - confidence level assigned using the MODIS-type cloud mask algorithm, is applicable.

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 A long-term (1948-2009) frontal data set was created with an objective method by using NCEP-NCAR (National Centers for Environmental Prediction-National Center for Atmospheric Research) reanalysis data. This method utilizes a gradient and a thermal front parameter (TFP) of a potential temperature and an equivalent potential temperature at 850 hPa (dθ, TFP(θ), and TFP(θe)). The TFP defined as the directional derivative of a gradient of a thermodynamic variable along its gradient is one of the measures of frontal intensity and is often used for objectively analyzing frontal positions on surface weather maps. On the basis of the frontal data set, the average seasonal behavior of the frontal zone around Japan, its influence on the weather in mid-summer, and the seasonal march of the frontal zone during El Niño/La Niña events were examined. The main results are summarized in the following points: 1) The frontal data set generated under the conditions of dθ > 0.04 K (100 km)⁻¹, TFP(θ) > 0.05 K (100 km)⁻², and TFP(θe) > 0.69 K (100 km)⁻² showed the strongest correlation to that compiled by counting the number of fronts on the surface weather maps around Japan. 2) Although the long-term frontal data set created in this study retained some differences in frequency, the seasonal march of the frontal zone was consistent with that created from fronts on the weather maps. 3) The relationship of interannual mid-summer variations (July 20-August 16) between the - ratio of Japan and the frontal zone and various mean characteristics of the Japanese climate during El Niño/La Niña events, most of which have been discussed in previous reports, were verified from the perspective of the variability in the frontal zone, which has not been clarified so far.
 These results of this work show that the frontal data set created herein has the advantage of being simple and objective and is useful for research on the detailed relationship in interannual variations between the regional climate around Japan and large-scale atmospheric conditions.

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Use of the Monte Carlo method to simulate sky luminance and daylight illuminance has led to the following findings.
(1) In the case of a sky with a uniform cloud cover, the sky luminance distribution approaches that in the CIE standard overcast sky as the optical thickness of the clouds grows larger. If the sky luminance (L_m) is given by the equation with luminance (L_c) and overcast sky luminance (L_o), that is, L_m=e^-AxτL_c+(1-e^-Axτ)L_o (where τ is the optical thickness of the clouds), coefficient A will have a value of 0.16-0.28 when the sun altitude is 30-60 degrees. On the other hand, if the daylight illuminance is given by equation S_r=S_o×e^-Bxτ, coefficient B will have a value of 0.012-0.027. The optical thickness of clouds in a heavily clouded sky is 52-82 when the sun altitude is 30-60 degrees.
(2) In the case of an intermediate sky with separate clouds, the sky luminance L_m is represented by equation L_m=(1-C/10)L_c+(C/10){e^-AxτL_c+(1-e^-Axτ)L_o}, where C is the total cloud amount. With an increase in the total cloud amount, the daylight illuminance averaged on the overall surface decreases, but this is not always so for the maximum and the minimum.

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In terms of designing daylighting of good quality, it is very important and necessary to predict and evaluate in advance the luminous environment in an interior space. Therefore, not only illuminance but also luminance distributions by daylight in an interior space should be predicted as precisely as possible. A new method of daylight calculation was developed. This method predicts luminous environment in an interior space of arbitrary shape lit by sunlight and skylight through the translucent or transparent openings. A new daylight source model under all-weather conditions is developed for the direct illuminance calculation. The luminous flux transfer method is adopted for the indirect or total illuminance calculation. In the luminance calculation, the sky luminance distribution seen through the transparent openings is predicted as well as the interior luminance distribution. The method was applied to a computer program of daylight and artificial light calculation on a membrane structure with open and closed translucent roofs under any condition of weather, location, date and hour. The program predicts the illuminance distribution in the interior space and the luminance distribution on the visual field watched at any view point. The luminance contrast of the fly ball is also predicted in the case of a baseball stadium.

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Suitable standard data on daylight and solar radiation are absolutely prepared and offered for the excellent energy saving interior environmental design. The first step of the modification of the data by real measurements into the useful standard data is to classify the sky, conditions when the data were gained. A proposal of a means is stated in this paper in order to divide the sky conditions into ordered categories. The sky conditions when the data were measured are arranged based upon the comparison with the sky, luminance distribution data obtained by sky scanning and the theoretical results on CIE(Commission Internationale de l'Eclairage) Standard Clear and Overcast Sky and Intermediate Sky by one of the authors. The sky conditions are finally classifred into Clear, Near Clear, Intermediate, Near Overcast and Overcast Sky. This Research work is deeply related to the IDMP(International Daylight Measurement Programme) promoted by CIE. Its result convinces authors of its great contributions to the progress IDMP and development of interior environmental design.

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日射や赤外放射等の輻射熱は舗装体の温度に大きく影響する因子である. 全天日射量を計測している気象観測点はあるが, 公開された大気放射の観測データはない. しかし, 大気放射量は, 舗装の温度解析では重要な環境因子であるので, 利用できる気象データから推測する必要がある. 大気放射量は, 緯度・経度だけでなく気候の影響も大きいことが知られており, 適切なモデルの選択が重要である. 本研究では, 鳩山舗装温度計測サイトで観測したデータを用いて従来の快晴時における大気放射モデルの適応性を検証している. 最後に露点温度と相対湿度を用いた大気放射モデルを提案している.

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In effective use of solar energy and the heating and cooling load calculation of buildings for energy conservation, the actual state meteorological data is indispensable. The sky radiance distribution has been expediently assumed to be uniform distribution in the heating and cooling load calculation of buildings because there was no suitable sky radiance distribution model. It is necessary to propose sky radiance distribution model, which can corresoond to all sky conditions from to overcast sky. A suitable index is necessary to presume sky radiance distribution because sky radiance distribution is not measured in ordinary weather observations. In this paper, normalized global irradiance and cloudless index are defined based on measured data as indices to classify sky radiance distributions. The relationship between both indices and sky radiance distributions was examined, and the validity as the indices for the presumption of sky radiance distributions was confirmed.

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The light is generated through the process that the direct sunlight is successively scattered by the air and aerosol in the turbid atmosphere and repeatedly reflected by the earth's surface.
The scattering-transmitting functions of the direct sunlight and the reflected light from the earth's surface were set up theoretically and the spectral power distributions of the light were estimeted.
It became clear how following factors effect the change of the light respectively.
(1) The scattering light by the air and that by the aerosol.
(2) The first scattering light and the higher order scattering light than the first.
(3) The reflected light from the earth's surface.

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