Study of Human Thermal Comfort in Urban Environments: A Case Study in Santa Maria-RS, Brazil

This article aims to present the results of the theoretical and methodological procedures implementation that support, subsidize and standardize the human thermal comfort studies in external environmental conditions, from a case study in Santa Maria, RS, based on collection of raw data using a mobile weather station and the application of population perception questionnaire. To perform the proposed evaluation of human thermal comfort outdoors by the correlation between the climatological study of the area and the subjective variables of users, in order to established the level of thermal adaptation of the population, it was made using experimental inductive method, based on the survey of primary climatological data in the field and individual and subjective variables for a population adapted to the climatic conditions in which it is. The collection of climatological data was performed with a mobile station located in the city center, while the collection of sensory evaluation data of the population to conditions of comfort or discomfort was collected with questionnaires. It was used a Campbell CR-1000 weather station with a maximum height of 2.0 m, containing the following sensors: Rain gauge; Global Radiation Sensor; Temperature and Air humidity Sensor;  Speed and Wind Direction Sensor; Grey Globe Thermometer. Meteorological data were recorded every 10 (ten) minutes and data collection and interviews with the local population were made between 09:00h and 17:00h between  August 3rd to August 7th, 2015. Six people were interviewed every ten (10) minutes (according to the recording period of the meteorological data by the station), totaling 36 people interviewed every hour, 288 (two hundred and eighty-eight) people interviewed in the 8 (eight) hours of data collection for each day and 1440 (one thousand four hundred and forty) people interviewed at the end of the five (5) days of field work. Interviews were also limited with people aged between 20 and 60 years old, who did not appear overweight and / or underweight, with standard body covered area set between 0.5 and 1.0 clo (ISO 9920, 2007), with a physical activity pattern of 300W for each individual interviewed, since only moving people were interviewed (walking) (ISO 8996, 2004). As for the questionnaire, it was used the model established by ISO 10551 (1995). Meteorological data of EMA-Mobile were introduced in the platform of the Bioklima 2.6 model (Błażejczyk, 2010), along with the subjective data of the interviewed population, where different subjective answers from the questionnaire were given a numerical value according to ASHRAE / ANSI scale 55 (2004) ranges -3, -2, -1, 0, 1, 2 and 3 regarding the predictive responses: Very Cold -3; Cold -2; A Little Cold-1; Neither cold nor heat 0; A Little Hot 1; Hot 2; Very Hot 3. Next the model has presented results to indexes Effective Temperature (TE) from Houghten and Yagloglou (1923), Effective Temperature with Wind (TEv) from Suping et al. (1992), Equivalent Temperature (TEK) from Bedford (1951), Radiative-Effective Temperature (TRE) from Błażejczyk (2004), Wind chill Index (WCI) from Siple and Passel (1945), Humidex index (HU) from Masterton and Richardson (1979), Wet bulb globe temperature (WBGT) from Yaglou (1957) and Approximated heat stress index  (pHSI) from Belding and Hatch (1955). From the calculated indices, the correlation was obtained between these and wind chill responses from the population of Santa Maria, as well as the comparison between the classes of respective indices and the percentage of thermal sensation votes from the population to the ASHRAE scale / ANSI 55 (2004), identifying the indexes with the best correlation with the actual thermal sensation of the observed population. Finally, the comparison between rural and urban area effective temperature (ET) and effective temperature with wind (TEV) was made, to the rural area (weather station from Santa Maria, EMA-INMET / SM) and urban (mobile weather station, EMA-Mobile) from the municipality calculated from meteorological data collected in the field, from the meteorological station of Santa Maria and the  population thermal sensation vote. This review concluded that, given the data collected in the field and due to anomalous atmospheric situation observed during the field work in August 2015, there was a negative influence from the North Wind in the thermal sensation of most individuals interviewed. The evaluation showed discomfort during the days when temperatures exceeded 25 ° C and from the comparison between urban and rural atmosphere, it was observed that the sensations of thermal comfort and discomfort during the days of study were not limited only to the microclimate variables and they were strongly influenced by variables conditioned by atmospheric circulation associated with regional climate.