Akira Hoyano

Climatological uses of plants for solar control and the effects on the thermal environment of a building

Abstract The following climatological uses of plants were chosen to study how they control solar radiation, reduce the cooling load and improve the indoor and outdoor thermal environment: (a) a pergola composed of a horizontal wisteria sunscreen; (b) a vine sunscreen designed for a south-west veranda; (c) an ivy sunscreen covering a west wall; (d) a row of evergreens placed next to a west wall; (e) rooftop turf planted on layers of loam and perlite. An outline of each experiment and the remarkable results for solar control are presented.

Development of a method to predict the heat island potential using remote sensing and GIS data

Abstract Most studies directed to urban climate simulation have been carried out under the assumption that an urban canopy layer is a sublayer comprised of various roughnesses, and as a consequence, difficulties have arisen in obtaining a suitable heat balance for such a layer. This paper, therefore, focuses on investigating the surface temperature distributions of all urban surfaces via a new index based on sensible heat flux, named the heat island potential (HIP), which can be employed in urban development planning to evaluate the urban thermal environment. Simulation results following the use of HIP are verified by side-looking airborne multi-spectral scanner (MSS) and geographic information system (GIS) data; thereby enabling elucidation of these thermal effects on the atmosphere. In addition, a heat balance algorithm is developed which simulates urban surfaces such that construction of urban thermal images is possible.

Analysis of the sensible heat flux from the exterior surface of buildings using time sequential thermography

In this study, the distribution of surface temperature on the surface of two buildings having different characteristics was measured using a thermal infrared camera. Measurements were made in the summer, the period in Japan during which heat flux from buildings is of major interest, and again in the winter for comparison purposes. The heat characteristics of each building were obtained throughout the day by time-sequential thermography (TST), and the surface temperature of each physical element was classified according to temperature, shape, material and position. When the temperature of a surface could not be determined by an infrared camera mounted on the top of a building or a pole, temperature measurements were made using a hand-held IR camera. In addition, the sensible heat flux from each surface was calculated using TST and the surface area of each element as calculated from blueprints of the buildings.

A SOLAR COOLING PROJECT FOR HOT AND HUMID CLIMATES

This paper presents a solar house built in a southern city of China where the summer is long, hot and humid. The house was designed appropriately for the climate and was constructed with local building materials where possible. A multifunctional solar system was used and a method for indoor ventilation was proposed. The design included double walls and a triple roof in order to remove heat by ventilation of the building envelope. The external walls were clad with unglazed bricks to allow evaporative cooling. The house has been monitored since completion and more than one year of data is available. Analysis of the monitored data shows that the solar techniques proposed in this design are effective in a hot and humid climate. Effective ventilation strategies for the improvement of thermal comfort are also discussed.

Net primary production in Southeast Asia following a large reduction in photosynthetically active radiation owing to smoke

[1] In Southeast Asia, large forest fires occur during El Nino years, and smoke from these forest fires reduces the amount of photosynthetically active radiation (PAR). This study evaluated the reduction in net primary production (NPP), associated with the large reduction in PAR in this region, resulting from smoke. NPP was estimated from a slightly modified light-use-efficiency model using satellite-derived PAR. The results suggest that the reduction in NPP was large when heavy smoke occurred. On the islands of Kalimantan and Sumatra, the estimated reduction in NPP owing to smoke in 1997 was 0.12 (PgC/yr), which is approximately 3.5% of the total NPP in Southeast Asia (20N–10S, 90E–130E) and 6.8% of the total NPP in Kalimantan and Sumatra. This reduction in NPP influences the interannual variation in NPP on Kalimantan and Sumatra. Our results show the importance of including the effect of PAR reduction owing to smoke when assessing NPP in Southeast Asia. Citation: Kobayashi, H., T. Matsunaga, and A. Hoyano (2005), Net primary production in Southeast Asia following a large reduction in photosynthetically active radiation owing to smoke, Geophys. Res. Lett., 32, L02403, doi:10.1029/ 2004GL021704.

Estimating ice breakup dates on Eurasian lakes using water temperature trends and threshold surface temperatures derived from MODIS data

Ice breakup dates on lakes have a confirmed relationship with the local climates and are useful as a quantitative indicator of climate change, especially in the middle‐high latitudes. Many lakes on the Eurasian continent freeze over in winter, but data on their ice breakup dates are incomplete. In this study, we attempt to infer ice breakup dates for 18 lakes on the Eurasian continent using the proposed method based on long‐term surface temperature (water temperature trend) and threshold surface temperature. The threshold surface temperature was estimated using reflectance data from the near infrared band together with surface temperature data derived from MODIS. After obtaining the estimated ice breakup dates, we compared them with observed results in order to evaluate our proposed method for ice breakup date estimation. According to this comparison, the estimation error of the ice breakup dates was less than three days. In the last stage of this study, we estimated the ice breakup dates at the centres of 18 Eurasian lakes from 2001 to 2003. The mean ice breakup dates on these lakes in 2002 were two weeks earlier than in 2003 and one week earlier than in 2001.

Passive ventilation system that incorporates a pitched roof constructed of breathing walls for use in a passive solar house

Abstract This paper describes a natural ventilation system that incorporates a pitched roof constructed of Breathing Walls for use in a passive solar house. The Breathing Wall is expected to solve the inherent contradiction that exists for a building that is open to the outside air, in which a balance in the indoor air/moisture conditions is maintained, but energy efficiency is low. In other words, the use of Breathing Walls can provide a healthy and comfortable environment at higher energy efficiency in a passive solar house. In the present study, we experimentally evaluate the effects of roof pitch on the heat recovery capability and the occurrence of internal condensation within the Breathing Wall, using a simulation of the ventilation rate of a natural ventilation system. The effective opening area per unit area required to provide sufficient air change capability, i.e., 0.5 ACH, even for zero wind velocity, was determined to be 10 and 5 cm2/m2 for pitches of 26.5° (Pitch 1) and 45° (Pitch 2), respectively. Furthermore, at the maximum predicted wind velocity of 10 m/s for Pitch 1/2, even though the outdoor air temperature is 5°C, the temperature of the indoor-most air reaches 13.2/12.5°C, corresponding to a heat flux of ≈128/158 W/m2. No internal condensation occurs, even at the maximum pressure differential, which corresponds to a wind velocity of 10 m/s across the wall of the Pitch 1/2 model, when a Breathing Wall having an opening area per unit area of 11.3 cm2/m2 was installed in the ventilation system.

Monitoring of coral reefs on Ishigaki Island in Japan using multitemporal remote sensing data

In recent years environmental problems in the coral reefs attract both scientific and social attentions. However, most coral reefs have few maps showing the reef topography and the distributions of various benthic habitats in the reef. Satellite remote sensing can be used for coral reef mapping because satellites can observe the reefs scattered in tropical oceans in a short time repeatedly. Simple comparison between satellite images acquired on two different days is, however, strongly affected by the changes of the tidal level. Applying conventional classification algorithms to such satellite images often results in misclassification. We developed Bottom Index (BI) algorithm to minimize the water depth effect on satellite data. BI is a modified reflectance ratio between two bands in satellite data and corresponds to the proportion of benthic community cover in a pixel. In this study we applied this algorithm to Landsat TM data acquired during 1984 - 1996 on Ishigaki coral reefs, Japan, and evaluated its accuracy. We also developed the method for the separation of sand and coral/ algae/seagrass habitat using BI. We also found that the extinction coefficient ratio between two TM bands that is necessary for BI algorithm was basically constant there. And temporal variations of the sea floor cover type in Ishigaki during 1984 - 1996 were indicated by BI maps. Sea truth survey was conducted in August 2000 to validate the BI maps.

Application of a new spherical thermography technique to monitoring of outdoor long-wave radiant fields

This paper describes the evaluation of the long wave radiant field using the spherical thermography technique we developed in previous studies. Four urban street spaces were chosen for comparison based mainly on differences in the above-ground conditions. Evaluations were conducted during good weather on summer days. The measurement results indicate that the long wave radiant field is directly influenced by the design characteristics of the urban space. The present study confirmed the usefulness of spherical thermography for evaluating the long wave radiant field.

The Effects of Windbreak Forests on the Summer Thermal Environment in a Residence

Abstract As urbanization progresses, the outdoor thermal environment is deteriorating due to the decrease of vegetation and increase of constructed surfaces. Environmental problems such as the heat island phenomenon occur not only in large cities but also in mid-sized and small cites. Increasing tree or vegetation plantings is one of the most effective strategies to mitigate environmental problems and create a comfortable living environment. In this study, the microclimatic effect of a windbreak forest surrounding a residence was analyzed based on field measurements and numerical simulation results. Spherical thermographs of surface temperature distribution observed in an actual residence were used to identify the thermal effect of the windbreak forest and surface materials. A coupled numerical simulation method of computational fluid dynamics (CFD) and outdoor thermal simulation was used to evaluate the microclimate and thermal comfort in outdoor living spaces. The proposed simulation method was validated by comparing the simulated results with the measurement data. In addition, the residence was modeled using the coupled simulation program to quantify the microclimate and outdoor thermal comfort. Simulation results show that this simulation method is capable of predicting the solar shading effect and wind speed reduction due to trees as well as thermal improvement from decreased ambient air temperature and surface temperature.