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Air temperature in urban street canyons is increased due to the morphed urban geometry, increased surface area, decreased long wave radiation and evapo-transpiration, different thermo-physical properties of surface materials and anthropogenic heat which results in thermal discomfort. Outdoor thermal stress can be mitigated substantially by properly orienting the canyons. It is crucial for the urban planners and designers to orient street canyons optimally considering variable local climatic context. It is important especially for cities in warm humid climatic context as these cities receive higher insolation with higher relative humidity and low level macro wind flow. This paper examines influence of canyon orientation on outdoor thermal comfort and proposes the optimum canyon orientation for the Rajarhat Newtown, Kolkata – a city in warm humid climate zone. Different scenarios are generated with different orientations. Change in air temperature, wind speed, Mean Radiant Temperature (MRT) and Physiological Equivalent Temperature (PET) of different scenarios are compared to find out the optimum orientation by parametric simulation in ENVI_met. Analysing the simulation results it is observed that orientation angle between 30°–60° to north performs the best for the study area of the Rajarhat Newtown. The findings of this research will be helpful for the planners to orient the street canyons optimally for future development and extension of the Rajarhat Newtown, Kolkata.

This study investigates the impact of different orientations and canyon aspect ratios to improve street-level microclimate in a warm humid climate. It also contributes to the development of a methodology to develop design guidelines while planning urban neighborhoods. The study was carried out using ENVI_met version 4.0. Simulations were run for typical residential neighborhoods in the Rajarhat Newtown, Kolkata, India, characterized by a warm humid climate as per the National Building Code of India, for a typical summer day with a high level of discomfort. Different orientations and different canyon aspect ratios are simulated and compared to find the most suitable design alternative for the study area. The floor area ratio has been kept constant in order to keep the design alternative more realistic. Performance analysis of the design alternatives was carried out by comparing air temperature, wind speed, MRT and PET. It was found that an orientation angle between 30° and 60° with the wind direction and a Canyon Aspect Ratio of 2.5 can reduce the PET value by 5 to 9 °C throughout most of the study area during a mid-afternoon summer day. Improvement in the thermophysical assessment classes cannot be achieved for the adopted simulation date and time (May 31st, 14:00 h). [ABSTRACT FROM AUTHOR]

The thermal environment outdoors affects human comfort and health. Mental and physical performance is reduced at high levels of air temperature being a problem especially in tropical climates. This paper deals with human comfort in the warm-humid city of Guayaquil, Ecuador. The main aim was to examine the influence of urban micrometeorological conditions on people’s subjective thermal perception and to compare it with two thermal comfort indices: the physiologically equivalent temperature (PET) and the standard effective temperature (SET*). The outdoor thermal comfort was assessed through micrometeorological measurements of air temperature, humidity, mean radiant temperature and wind speed together with a questionnaire survey consisting of 544 interviews conducted in five public places of the city during both the dry and rainy seasons. The neutral and preferred values as well as the upper comfort limits of PET and SET* were determined. For both indices, the neutral values and upper thermal comfort limits were lower during the rainy season, whereas the preferred values were higher during the rainy season. Regardless of season, the neutral values of PET and SET* are above the theoretical neutral value of each index. The results show that local people accept thermal conditions which are above acceptable comfort limits in temperate climates and that the subjective thermal perception varies within a wide range. It is clear, however, that the majority of the people in Guayaquil experience the outdoor thermal environment during daytime as too warm, and therefore, it is important to promote an urban design which creates shade and ventilation. [ABSTRACT FROM AUTHOR]