Search Results
Abstract
The largest mass participation fun run in the world took place in Auckland, New Zealand where an estimated 80000 participants ran 10.4 km “Round the Bays” in the early fall of 1982. Even in the relatively mild climate of Auckland, heat stroke and other types of heat illness occur during this annual event. Techniques for thermal assessment of human bioclimate have not been applied to an exercising crowd although it is widely accepted that crowding will reduce the heat loss of individuals. To quantify the possible heat load brought about by running in a large crowd, those components of the microenvironment that affect radiant, evaporative and convective heat exchange were measured, both within the mass of runners and separately from it. These data were used as input for two detailed body-environment heat exchange models which show the effect of the runners themselves on the thermal environment. Since it is assumed that changes longwave radiation exchange and convective losses from the body are likely to be the major causes of differences between solo and group running, these avenues of heat exchange are carefully assessed . The results show that longwave radiative losses can be reduced substantially by running in a lame group compared to solo running, but the absolute size of the increase in net heat load on the individual is small. However, heat loss by convection for group runners is less than half that for sole runners. This may be the result of entertainment of air within an atmospheric envelope below head level in which wind speed and direction are the same as the runner's and direction. For the weather conditions prevailing at the time of the experiment, jogging in the main bunch of runners is estimated to cause, on occasions, more than three times the heat stress on the body compared to that experienced when running solo along the same route at the same time of day during identical weather conditions.
Abstract
The largest mass participation fun run in the world took place in Auckland, New Zealand where an estimated 80000 participants ran 10.4 km “Round the Bays” in the early fall of 1982. Even in the relatively mild climate of Auckland, heat stroke and other types of heat illness occur during this annual event. Techniques for thermal assessment of human bioclimate have not been applied to an exercising crowd although it is widely accepted that crowding will reduce the heat loss of individuals. To quantify the possible heat load brought about by running in a large crowd, those components of the microenvironment that affect radiant, evaporative and convective heat exchange were measured, both within the mass of runners and separately from it. These data were used as input for two detailed body-environment heat exchange models which show the effect of the runners themselves on the thermal environment. Since it is assumed that changes longwave radiation exchange and convective losses from the body are likely to be the major causes of differences between solo and group running, these avenues of heat exchange are carefully assessed . The results show that longwave radiative losses can be reduced substantially by running in a lame group compared to solo running, but the absolute size of the increase in net heat load on the individual is small. However, heat loss by convection for group runners is less than half that for sole runners. This may be the result of entertainment of air within an atmospheric envelope below head level in which wind speed and direction are the same as the runner's and direction. For the weather conditions prevailing at the time of the experiment, jogging in the main bunch of runners is estimated to cause, on occasions, more than three times the heat stress on the body compared to that experienced when running solo along the same route at the same time of day during identical weather conditions.
Abstract
Lagos, Nigeria, is rapidly urbanizing and is one of the fastest-growing cities in the world, with a population that is increasing at almost 500 000 people per year. Yet the impacts on Lagos’s local climate via its urban heat island (UHI) have not been well explored. Considering that the tropics already have year-round high temperatures and humidity, small changes are very likely to tip these regions over heat-health thresholds. Using a well-established model, but with an extended investigation of uncertainty, we explore the impact of Lagos’s recent urbanization on its UHI. Following a multiphysics evaluation, our simulations, against the background of an unusually warm period in February 2016 (during which temperatures regularly exceeded 36°C), show a 0.44°C ensemble-time-mean increase in nighttime UHI intensity between 1984 and 2016. The true scale of the impact is seen spatially as the area over which ensemble-time-mean UHIs exceed 1°C was found to increase steeply from 254 km2 in 1984 to 1572 km2 in 2016. The rate of warming within Lagos will undoubtedly have a high impact because of the size of the population (12+ million) already at risk from excess heat. Significant warming and modifications to atmospheric boundary layer heights are also found in rural areas downwind, directly caused by the city. However, there is limited long-term climate monitoring in Lagos or many similarly expanding cities, particularly in the tropics. As such, our modeling can only be an indication of this impact of urbanization, and we highlight the urgent need to deploy instrumentation.
Abstract
Lagos, Nigeria, is rapidly urbanizing and is one of the fastest-growing cities in the world, with a population that is increasing at almost 500 000 people per year. Yet the impacts on Lagos’s local climate via its urban heat island (UHI) have not been well explored. Considering that the tropics already have year-round high temperatures and humidity, small changes are very likely to tip these regions over heat-health thresholds. Using a well-established model, but with an extended investigation of uncertainty, we explore the impact of Lagos’s recent urbanization on its UHI. Following a multiphysics evaluation, our simulations, against the background of an unusually warm period in February 2016 (during which temperatures regularly exceeded 36°C), show a 0.44°C ensemble-time-mean increase in nighttime UHI intensity between 1984 and 2016. The true scale of the impact is seen spatially as the area over which ensemble-time-mean UHIs exceed 1°C was found to increase steeply from 254 km2 in 1984 to 1572 km2 in 2016. The rate of warming within Lagos will undoubtedly have a high impact because of the size of the population (12+ million) already at risk from excess heat. Significant warming and modifications to atmospheric boundary layer heights are also found in rural areas downwind, directly caused by the city. However, there is limited long-term climate monitoring in Lagos or many similarly expanding cities, particularly in the tropics. As such, our modeling can only be an indication of this impact of urbanization, and we highlight the urgent need to deploy instrumentation.
