Challenges in Applied Human Biometeorology

Facing the impacts of climate change and urbanization, adaptation and resilience to climate extremes have become important issues of global concern [...

Urban Climate and Air Pollution in Ouagadougou, Burkina Faso

ABSTRACT Africa has recently been singled out by UN Habitat as the fastest urbanizing continent in the world. The most extreme case was found in the Sahelian city of Ouagadougou, Burkina Faso, where the population is expected to almost double over the next ten years. It is well known that the rapid growth of an urban area is among the most important anthropogenic impacts on the environment, and that it has a profound impact on both the urban climate and air quality. Few studies have been focused on cities in the Sahel region, and the lack of information may consequently hinder adaptation to the extreme urbanization rates of these often heavily polluted cities. The main objective of this thesis was to study the nature of, and relationship between, urban climate and air pollution in Ouagadougou, Burkina Faso. Specific objectives were to; examine spatial variations in daily temperature and humidity patterns during early dry season with focus on effects of different land cover; to examine the influence of atmospheric stability on the intra-urban air temperature patterns, the urban wind field and on air pollution levels; and to examine spatial variations in air pollution levels. An additional objective was to document the status and potential development of synoptic meteorological stations in Burkina Faso. Empirical data used in analyses were collected during five field studies between 2003 and 2010. Meteorological and air pollution parameters were measured at fixed sites and through car traverses in areas of different land cover, activity, traffic density and road surface. The most distinct features in thermal patterns found in Ouagadougou were strong intra-urban nocturnal cool islands in vegetated areas, caused by evening evaporative cooling by the vegetation. Extremely stable nocturnal atmospheric conditions were observed during 80 % of days examined in early dry season, during which spatial patterns in temperature and humidity as well as in air pollution were most pronounced. An intra-urban thermal breeze generating almost opposite wind directions within the city was found during all extremely stable nights. Air pollution situation in Ouagadougou were characterized by; important spatial variations, high pollution levels in general, and extreme levels of coarse particles, commonly exceeding WHO air quality guidelines in all areas. Important sources were re-suspension of road dust, transported dust, traffic and biomass burning. Documentation of meteorological stations show that observations were made by well trained staff following a strict set of procedures. However, many risk factors potentially affecting data quality were found, such as many manual steps in data handling and limited funding for maintenance of the instrument park. In contrast to the many studies identifying urban built structure as most important land cover parameter for the nocturnal urban climate, vegetation was the dominating parameter in Ouagadougou. The strong influence of vegetation shown in this study should be carefully considered in all urban climate studies, especially in (semi) arid regions. In urban-rural comparisons, this is particularly important for the location of the rural area where vegetation often is dominant. The high frequency of extremely stable atmospheric conditions and the intra-urban thermal wind system show a very restricted ventilation of the urban air and limited dispersion of urban-derived pollutants. Large spatial differences in pollution levels found in the city are likely to create important differences in exposure situation within the population. When using data from synoptic meteorological stations in Burkina Faso, the many risk factors found should be considered. Findings presented in this thesis could used in order to increase comfort and health in urban planning, as well as in development of strategies for air pollution mitigation in this region, especially when considering the ongoing extremely rapid urban growth. The information of status and potential development of observational data may be valuable for more reliable predictions of future changes in climate in the region

Native influences on the construction of thermal sensation scales

Thermal scales assess thermal environments in terms of thermal sensation and comfort. The number of scale’s categories and their verbal realization/labels, especially when translated for local applications, are subjects of research. This study examined variations from the ISO 10551 thermal scale when translated into Greek language. We conducted an online survey asking participants to translate the English ISO 10551 scale, develop their own scales (five, seven and nine-point), report a wording for thermal comfort, and assign discrete values to scales’ categories proportional to their perceived distances. Overall, 357 participants enrolled in the survey while data from 321 questionnaires included in the analysis. The interpretations of ISO 10551 categories varied (6–18) although the majority consisted of the exact translation. The wordings of the formulated scales differed from ISO 10551 scale indicating a more intense expression mode. The labels overlapped in the extreme categories of the nine-point scale supporting the use of the seven-point scale. Most participants (~ 65%) reported thermal comfort equivalent to neutrality. About half of the participants reported equal distances between the categories of the scales. The results can be applied on thermal sensation studies having a possible impact on the use of outdoor spaces under various contexts, i.e., public health, urban design, and energy conservation