Evidence of alliesthesia during a neighborhood thermal walk in a hot and dry city.

Designing cities for thermal comfort is an important priority in a warming and urbanizing world. As temperatures in cities continue to break extreme heat records, it is necessary to develop and test new approaches capable of tracking human thermal sensations influenced by microclimate conditions, complex urban geometries, and individual characteristics in dynamic settings. Thermal walks are a promising novel research method to address this gap. During a thermal walk in Phoenix, Arizona, USA, we examined relationships between the built environment, microclimate, and subjective thermal judgments across a downtown city neighborhood slated for redevelopment. Subjects equipped with GPS devices participated in a 1-hour walk on a hot sunny day and recorded their experience in a field guide. Microclimate measurements were simultaneously collected using the mobile human-biometeorological instrument platform MaRTy. Results revealed significant differences in physiologically equivalent temperature (PET) and modified physiologically equivalent temperature (mPET) and between street segments with more than 18 °C (25 °C mPET) between the maximum and minimum values. Wider range of mPET values reflected the inclusion of individual level data into the model. Streets with higher sky view factor (SVF) and east-west orientation showed a higher PET and mPET overall. Furthermore, we showed evidence of thermal alliesthesia, the pleasure resulting from slight changes in microclimate conditions. Participants' sense of pleasure was related to the mean PET of the segment they just walked, with linear regression explaining over 60% of the variability. We also showed that estimated percent shade was significantly correlated with SVF, PET, mPET, and pleasure, indicating that participants could sense minor changes in microclimate and perceived shade as pleasant. Although generalization of results is limited by a low sample size, findings of this study improve the understanding of dynamic thermal comfort in complex urban environments and highlight the value of thermal walks as a robust research method.

Correction to: The influence of surface type on the absorbed radiation by a human under hot, dry conditions.

The original article contains mistakes in Eqs. 12 and 13.

The influence of surface type on the absorbed radiation by a human under hot, dry conditions.

Given the predominant use of heat-retaining materials in urban areas, numerous studies have addressed the urban heat island mitigation potential of various "cool" options, such as vegetation and high-albedo surfaces. The influence of altered radiational properties of such surfaces affects not only the air temperature within a microclimate, but more importantly the interactions of long- and short-wave radiation fluxes with the human body. Minimal studies have assessed how cool surfaces affect thermal comfort via changes in absorbed radiation by a human (R abs) using real-world, rather than modeled, urban field data. The purpose of the current study is to assess the changes in the absorbed radiation by a human-a critical component of human energy budget models-based on surface type on hot summer days (air temperatures > 38.5∘C). Field tests were conducted using a high-end microclimate station under predominantly clear sky conditions over ten surfaces with higher sky view factors in Lubbock, Texas. Three methods were used to measure and estimate R abs: a cylindrical radiation thermometer (CRT), a net radiometer, and a theoretical estimation model. Results over dry surfaces suggest that the use of high-albedo surfaces to reduce overall urban heat gain may not improve acute human thermal comfort in clear conditions due to increased reflected radiation. Further, the use of low-cost instrumentation, such as the CRT, shows potential in quantifying radiative heat loads within urban areas at temporal scales of 5-10 min or greater, yet further research is needed. Fine-scale radiative information in urban areas can aid in the decision-making process for urban heat mitigation using non-vegetated urban surfaces, with surface type choice is dependent on the need for short-term thermal comfort, or reducing cumulative heat gain to the urban fabric.

Association of weather and air pollution interactions on daily mortality in 12 Canadian cities.

It has been well established that both meteorological attributes and air pollution concentrations affect human health outcomes. We examined all cause nonaccident mortality relationships for 28 years (1981-2008) in relation to air pollution and synoptic weather type (encompassing air mass) data in 12 Canadian cities. This study first determines the likelihood of summertime extreme air pollution events within weather types using spatial synoptic classification. Second, it examines the modifying effect of weather types on the relative risk of mortality (RR) due to daily concentrations of air pollution (nitrogen dioxide, ozone, sulfur dioxide, and particulate matter <2.5 µm). We assess both single- and two-pollutant interactions to determine dependent and independent pollutant effects using the relatively new time series technique of distributed lag nonlinear modeling (DLNM). Results display dry tropical (DT) and moist tropical plus (MT+) weathers to result in a fourfold and twofold increased likelihood, respectively, of an extreme pollution event (top 5 % of pollution concentrations throughout the 28 years) occurring. We also demonstrate statistically significant effects of single-pollutant exposure on mortality (p < 0.05) to be dependent on summer weather type, where stronger results occur in dry moderate (fair weather) and DT or MT+ weather types. The overall average single-effect RR increases due to pollutant exposure within DT and MT+ weather types are 14.9 and 11.9 %, respectively. Adjusted exposures (two-way pollutant effect estimates) generally results in decreased RR estimates, indicating that the pollutants are not independent. Adjusting for ozone significantly lowers 67 % of the single-pollutant RR estimates and reduces model variability, which demonstrates that ozone significantly controls a portion of the mortality signal from the model. Our findings demonstrate the mortality risks of air pollution exposure to differ by weather type, with increased accuracy obtained when accounting for interactive effects through adjustment for dependent pollutants using a DLNM.

The SSC: a decade of climate-health research and future directions.

This year marks the tenth anniversary of the development of the revised Spatial Synoptic Classification, the "SSC", by Scott Sheridan. This daily weather-type classification scheme has become one of the key analytical tools implemented in a diverse range of climatological investigations, including analysis of air quality variability, human health, vegetation growth, precipitation and snowfall trends, and broader analyses of historical and future climatic variability and trends. The continued and expanding use of the SSC motivates a review and comparison of the system's research and geographic foci to date, with the goal of identifying promising areas for future efforts, particularly within the context of human health and climate change. This review also assesses how the SSC has complemented and compares with other current environmental epidemiological studies in weather and health.

Changing air mass frequencies in Canada: potential links and implications for human health.

Many individual variables have been studied to understand climate change, yet an overall weather situation involves the consideration of many meteorological variables simultaneously at various times diurnally, seasonally, and yearly. The current study identifies a full weather situation as an air mass type using synoptic scale classification, in 30 population centres throughout Canada. Investigative analysis of long-term air mass frequency trends was completed, drawing comparisons between seasons and climate zones. We find that the changing air mass trends are highly dependent on the season and climate zone being studied, with an overall increase of moderate ('warm') air masses and decrease of polar ('cold') air masses. In the summertime, general increased moisture content is present throughout Canada, consistent with the warming air masses. The moist tropical air mass, containing the most hot and humid air, is found to increase in a statistically significant fashion in the summertime in 46% of the areas studied, which encompass six of Canada's ten largest population centres. This emphasises the need for heat adaptation and acclimatisation for a large proportion of the Canadian population. In addition, strong and significant decreases of transition/frontal passage days were found throughout Canada. This result is one of the most remarkable transition frequency results published to date due to its consistency in identifying declining trends, coinciding with research completed in the United States (US). We discuss relative results and implications to similar US air mass trend analyses, and draw upon research studies involving large-scale upper-level air flow and vortex connections to air mass changes, to small-scale meteorological and air pollution interactions. Further research is warranted to better understand such connections, and how these air masses relate to the overall and city-specific health of Canadians.

Improved predictive ability of climate-human-behaviour interactions with modifications to the COMFA outdoor energy budget model.

The purpose of this paper is to implement current and novel research techniques in human energy budget estimations to give more accurate and efficient application of models by a variety of users. Using the COMFA model, the conditioning level of an individual is incorporated into overall energy budget predictions, giving more realistic estimations of the metabolism experienced at various fitness levels. Through the use of VO(2) reserve estimates, errors are found when an elite athlete is modelled as an unconditioned or a conditioned individual, giving budgets underpredicted significantly by -173 and -123 W m(-2), respectively. Such underprediction can result in critical errors regarding heat stress, particularly in highly motivated individuals; thus this revision is critical for athletic individuals. A further improvement in the COMFA model involves improved adaptation of clothing insulation (I (cl)), as well clothing non-uniformity, with changing air temperature (T (a)) and metabolic activity (M (act)). Equivalent T (a) values (for I (cl) estimation) are calculated in order to lower the I (cl) value with increasing M (act) at equal T (a). Furthermore, threshold T (a) values are calculated to predict the point at which an individual will change from a uniform I (cl) to a segmented I (cl) (full ensemble to shorts and a T-shirt). Lastly, improved relative velocity (v (r)) estimates were found with a refined equation accounting for the degree angle of wind to body movement. Differences between the original and improved v (r) equations increased with higher wind and activity speeds, and as the wind to body angle moved away from 90°. Under moderate microclimate conditions, and wind from behind a person, the convective heat loss and skin temperature estimates were 47 W m(-2) and 1.7°C higher when using the improved v (r) equation. These model revisions improve the applicability and usability of the COMFA energy budget model for subjects performing physical activity in outdoor environments. Application is possible for other similar energy budget models, and within various urban and rural environments.