Pedestrian environment prediction with different types of on-shore building distribution

The aim of this work is to evaluate how the building distribution influences the cooling effect of water bodies. Different turbulence models, including the S-A, SKE, RNG, Realizable, Low-KE and RSM model, were evaluated, and the CFD results were compared with wind tunnel experiment. The effects of the water body were detected by analyzing the water vapor distribution around it. It is found that the RNG model is the most effective model in terms of accuracy and computational economy. Next, the RNG model was used to simulate four waterfront planning cases to predict the wind, thermal and moisture environment in urban areas around urban water bodies. The results indicate that the building distribution, especially the height of the frontal building, has a larger effect on the water vapor dispersion, and indicate that the column-type distribution has a better performance than the enclosed-type distribution.

Micro-site Conditions of Epiphytic Orchids in a Human Impact Gradient in Kathmandu Valley, Nepal

We studied distribution and site conditions of epiphytic orchids in a gradient of human interference in Kathmandu valley, central Nepal. The aim was to understand the recent distribution pattern of epiphytic orchids, with respect to (i) the micro-site conditions and (ii) the type and intensity of land use. The occurrence of epiphytic orchids was recorded for a grid with 1.5 km cell size. The cells represent different types and intensities of human impact. Site factors such as bark rugosity, bark pH, diameter at breast height (dbh; 1.3 m) of host trees, exposure to wind and sunlight intensity were recorded. With regard to the species richness and abundance of epiphytic orchids, we compared different human impact categories from very strong human impact (settlement area) to very low human impact (national park). Remote sensing was used for a supervised classification of land cover. Ficus religiosa turned out to be the most important host species for orchids in urban areas, while Schima wallichii and Alnus nepalensis significantly host orchids in the other categories. Both species richness and abundance of epiphytic orchids were significantly higher under very low human impact (forest in national park) and also some remaining patches of primary forest than the other regions. Micro-climate is crucial for orchid populations. Host bark pH, bark rugosity, sunlight intensity and host exposure were significantly different for all human impact categories in order to harbour epiphytic orchid species. Habitats with a mixture of mature trees are suitable and essential for the conservation of viable populations of epiphytic orchids in settled areas. The study reveals that to improve the population size of orchids it is essential for future urban forestry to: (i) Protect old trees as carriers of existing epiphytic orchid diversity, (ii) protect medium old trees to ensure that they may become old trees, (iii) plant new host trees for the future, (iv) plant in groups instead of single isolate trees. Trees should especially be planted in areas where orchids still exist to provide more trees for orchid population enlargement (e.g. along riparian system). Native species should be favoured; the pool of such native host species is wide.

Effects of Urban Morphology Changes on Ventilation： Studies in Wind Tunnel

This paper presents study of the effects of urban morphology changes on ventilation dynamics through a comparative study between blocks of Copacabana and Ipanema neighborhoods, located in Rio de Janciro City, Brazil. The study was developed with the aid of experimental simulations in a wind tunnel, taking into account the urban morphology and its relations to open spaces. A diagnosis was produced through the exam of the wind effects in relation to the volume of built and non-built spaces. The effects were classified as positive or negative, in relation to the tropical climate. At first, both blocks studied, one in Ipanema and one in Copacabana, were selected according to common characteristics, which establish a relation between the two regions, such as the distance to the beach and the presence of a public square. The results confirmed our expectations showing Ipanema as a more ventilated area.

Urban Heat Island and Land Use/Cover Dynamics Evaluation in Enugu Urban, Nigeria

This study specifically estimated the effect of land use/cover change (LULC) processes on land surface temperature (LST) in Enugu urban and its suburbs. With Landsat images and supervised classification technique, four LULC classes comprising built-up areas, vegetation, rock outcrop, bare ground/farmland areas were delineated. The LST was extracted from the thermal bands of the images. The rate of change in land cover classes between 2009 and 2018 showed that from 2009 to 2013, built-up areas increased from 31.65% to about 47.5%, while vegetation cover decreased from 18.43% to 11.23%. Also, the periods witnessed about 8.69 km2 of vegetation being converted to other land surfaces. The trend in the LST in Enugu urban showed the highest mean temperatures of 34.5°C in 2018 and 32.26°C in 2015. However, in 2013 there was a slight decrease in mean LST to 31.65°C which further decreased to 31.26°C in 2009. This change in temperature suggests that urbanisation could have significant effect on the micro-climate of Enugu city. Result also revealed weak relationships between LULC classes and the LST throughout the years. The results of the surface heat intensity for the urban and rural areas showed general increase over the years and this suggests that rural areas are also experiencing high temperature which could be due to the loss of vegetation, increase in artificial surfaces and urban encroachment. Findings from this study could be useful for effective urban land-use planning, policy development and management in Nigeria, and elsewhere.

Effect of the shelterbelt along the Tarim Desert Highway on air temperature and humidity

The temperature and humidity of the shelterbelt micro-climate on both horizontal and vertical scales in the extremely drought area were measured with multiple HOBO temperature and humidity automatic observation equipments in the hinterland of the Taklimakan Desert. The results show that the shelterbelt ecosystem of the desert highway plays typical micro-climate adjustment rolesin stabilizing surface air temperature and increasing air humidity, and so on. Solar radiation significantly affects both temperature and humidity of surface layers, and it has a positive correlation with the temperature but a negative correlation with the air humidity. When it is cloudy, the weather has a great impact on keeping temperature and humidity in the shelterbelt. The shelterbelt also significantly influences the environment, and the micro-climate in the belt has an obvious characteristic of cooling and humidification: compared with the original sand area, the temperature in the shelterbelt is always lower and the humidity is always higher. Moreover, the temperature range at the shelterbelt edge is greater than that in the sand area, but the humidity is always higher. Our conclusion is that the vertical-effect range of temperature of the shelterbelts is 4 -10 m, and the humidity range is 6 to 8 m; the horizontal-effect range of temperature is 16 m and the humidity range is about 24 m.

Assessment of terrace gardens as modifiers of building microclimate

Hard concrete roofs cause excessive heat gain impacting thermal comfort in buildings.Terrace gardens promoting greening at higher levels of built structures are seen as one of the key mitigating strategies for modifying building microclimate and improving urban health.We have undertaken a research project to quantitatively assess the value of a terrace garden in a residential scale.A garden patch of about 15 m 2 in area,a typical size available in most urban terraces is developed.Surface temperatures are measured over a period of 15 months between July 2018 to January 2020 using four thermocouple sensors,placed within and outside the garden bed,on and below the roof.We compare the thermal performance of the terrace garden across years,seasons,time of the day,presence or absence of garden bed and type and height of vegetation.The surface temperature data was found to correlate well with the ambient air temperature values.The results show that the terrace garden moderates and stabilises the ceiling temperatures and reduces it by about 2-3°C in winter months and 5-7°C in hot summers.The garden also provided nearly 400 g of fresh monthly vegetable harvest per m 2 of garden.Further,the cooling impact of the terrace garden with natural,tall,wild vegetation is higher as compared to planted vegetation.The study demonstrates a sustainable approach to terrace garden design at residential scale through quantified dual benefits of temperature control within buildings and urban farming.