Climatic regionalization of Rio Grande do Sul (Brazil) based on zoning of the human thermal comfort

Thermal comfort is associated with the rhythm of heat and humidity exchanges between the human body and the environment. The human body reacts accordingly to temperature variations and attempts to self-regulate in order to maintain its internal temperature in balance, in order to adapt to the surrounding environment.

The reason for creating thermal comfort conditions resides therefore in the human need to feel thermally comfortable; furthermore, thermal comfort can be justified from the point of view of human performance as well as resistance to certain diseases and productivity of individuals.

So, thermal comfort can be viewed and analysed in two ways: from a personal standpoint and an environmental standpoint. From this, the objective of this research was to evaluate the thermal comfort conditions in the regional and sub-regional scales in the state of Rio Grande do Sul, Brazil, according to the mean monthly and seasonal air temperature, relative humidity and wind speed in order to establish a climatic regionalization zoning based on human thermal comfort.

Also, the thermal comfort conditions were established for rainy years, drier years and usual years. Weather systems prevalent in these years were also evaluated. A theoretical research on the topic was performed, and the climatic database of the National Institute of Meteorology (INMET) was used, digitalized using GIS (Geographic Information System).

The database for the research was built assigning Effective Temperature with Wind (ETW) indexes for autumn and winter, and the Resulting Temperature index (RT) for spring and summer seasons. The thermal sensation zones or categories were defined from the classes developed by Fanger (1972) and adapted to São Paulo, SP and by Maia and Gonçalves (2002). We used a total of 23 weather stations, distributed across different geomorphological compartments of the study area, into a series of 30 years with daily data.

In autumn, summer and spring, the determination of thermal sensation zones in the study area are influenced by geographic controls, such as altitude, continentality, distance from the ocean and latitude, while the winter station showed a stronger influence of regional atmospheric dynamics. Among the atmospheric systems defining the climatic zonation, we can highlight the Polar Atlantic Mass (PAM) and Atlantic Polar Front (APF) in spring, Old Polar Mass (OPM), Tropical Atlantic Mass (TAM) and Tropical Continental Mass (TCM) in summer, PAM and Stationary Front (SF) in autumn and PAM in winter.