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Extreme heat is the deadliest meteorological hazard and is increasingly affecting the southeastern United States. Health effects of extreme heat are often not felt for hours or days after exposure and disproportionately affect vulnerable populations (e.g., youth, minorities). Personal heat exposure research has focused on occupational and everyday heat exposure among adults. To date, heat exposure in teenage populations has not been investigated. This population has unique heat exposure patterns that result from lifestyles that include outdoor jobs (e.g., lifeguard) and participation in outdoor sports. Better understanding of these exposure patterns is needed to reduce youth exposure and illnesses during heat events. Likewise, there have been no studies comparing paired indoor home conditions with individual exposure. Participants ( n  = 10) wore sensors to collect six days of personal heat exposure data (temperature and humidity) and placed sensors in and around their homes to collect ambient household data. When comparing individual exposure with ambient outdoor conditions and household conditions, this study revealed that: 1) teenagers are less exposed to dangerous heat (> 37.8 °C heat index) during the day; 2) teenagers are more exposed to dangerous heat (> 23.9 °C temperature) at night; 2) some teenagers are exposed to long periods of high heat at night, which is typically a time for heat recovery; and 3) household temperatures are typically not representative of heat exposure. To better understand teen exposure, we recommend future research focus on larger, representative sample sizes, collecting exposure data during the school year, and comparing exposure between heatwave and normal summer conditions.

Urban areas are typically warmer than nearby rural areas, especially during hot weather. This increases heat exposure, morbidity, and mortality rates of urban residents. Heat adaption methods can improve public safety during heat events, but the availability and usage of these resources vary based on socioeconomic and demographic characteristics, as well as personal perception of warmth. Heat events are often studied using city- and neighborhood-level meteorological and socioeconomic data, which do not reflect individual exposure or access to and use of heat adaption resources. We collected lifestyle surveys and individually experienced temperature and humidity data for 38 Knoxville, Tennessee, residents during a heatwave and a period of climatically normal summer conditions. Participants were less exposed to heat during the daytime than airport conditions suggest, indicating successful use of heat adaption methods, such as staying indoors. Some participants were warmer at night and during the non-heatwave period. Heat inequality is especially problematic at night, with older, less educated, and lower-income individuals being more exposed to heat. Even when exposed to dangerous heat levels, participants were less likely to take adaption actions to protect themselves from heat-health effects during the non-heatwave period and at night because they do not perceive themselves as being at risk or have the resources to do so. These findings signal the need for improved heat education, as future climate projections indicate an increase not only in heatwaves but also mean temperature and humidity during the warm season, and especially warmer temperatures at night.

Daily weather conditions for an entire city are usually represented by a single weather station, often located at a nearby airport. This resolution of atmospheric data fails to recognize the microscale climatic variability associated with land use decisions across and within urban neighborhoods. This study uses heat index, a measure of the combined effects of temperature and humidity, to assess the variability of heat exposure from ten weather stations across four urban neighborhoods and two control locations (downtown and in a nearby nature center) in Knoxville, Tennessee, USA. Results suggest that trees may negate a portion of excess urban heat, but are also associated with greater humidity. As a result, the heat index of locations with more trees is significantly higher than downtown and areas with fewer trees. Trees may also reduce heat stress by shading individuals from incoming radiation, though this is not considered in this study. Greater amounts of impervious surfaces correspond with reduced evapotranspiration and greater runoff, in terms of overall mass balance, leading to a higher temperature, but lower relative humidity. Heat index and relative humidity were found to significantly vary between locations with different tree cover and neighborhood characteristics for the full study time period as well as for the top 10% of heat index days. This work demonstrates the need for high-resolution climate data and the use of additional measures beyond temperature to understand urban neighborhood exposure to extreme heat, and expresses the importance of considering vulnerability differences among residents when analyzing neighborhood-scale impacts.

Heat is the deadliest meteorological hazard; however, those exposed to heat often do not feel they are in danger of heat-health effects and do not take precautions to avoid heat exposure. Socioeconomic factors, such as the high cost of running air conditioning, might prevent people from taking adaption measures. We assessed via a mixed-methods survey how residents of urban Knoxville, Tennessee, (n = 86) describe and interpret their personal vulnerability during hot weather. Thematic analyses reveal that many respondents describe uncomfortably hot weather based on its consequences, such as health effects and the need to change normal behavior, which misaligns with traditional heat-communication measures using specific weather conditions. Only 55% of those who perceived excessive heat as dangerous cited health as a cause for concern. Respondents who have experienced health issues during hot weather were more likely to perceive heat as dangerous and take actions to reduce heat exposure. Social cohesion was not a chief concern for our respondents, even though it has been connected to reducing time-delayed heat-health effects. Results support using thematic analyses, an underutilized tool in climatology research, to improve understanding of public perception of atmospheric hazards. We recommend a multi-faceted approach to addressing heat vulnerability.

Wearable sensors have been used to collect information on individual exposure to excessive heat and humidity. To date, no consistent diurnal classification method has been established, potentially resulting in missed opportunities to understand personal diurnal patterns in heat exposure. Using individually experienced temperatures (IET) and heat indices (IEHI) collected in the southeastern United States, this work aims to determine whether current methods of classifying IETs and IEHIs accurately characterize “day,” which is typically the warmest conditions, and “night,” which is typically the coolest conditions. IET and IEHI data from four locations were compared with the closest hourly weather station. Different day/night classifications were compared to determine efficacy. Results indicate that diurnal IET and IEHI ranges are higher than fixed-site ranges. Maximum IETs and IEHIs are warmer and occur later in the day than ambient conditions. Minimum IETs are lower and occur earlier in the day than at weather stations, which conflicts with previous assumptions that minimum temperatures occur at night. When compared to commonly used classification methods, a method of classifying day and night based on sunrise and sunset times best captured the occurrence of maximum IETs and IEHIs. Maximum IETs and IEHIs are often identified later in the evening, while minimum IETs and IEHIs occur throughout the day. These findings support future research focusing on nighttime heat exposure, which can exacerbate heat-related health issues, and diurnal patterns of personal exposure throughout the entire day as individual patterns do not necessarily follow the diurnal pattern seen in ambient conditions.

The eruption of Mt Mazama, c. 7630 yr BP, was the largest North American volcanic event during the Holocene. High-resolution pollen and charcoal analyses were used to examine the impact of Mt Mazama tephra on forest vegetation and possible synergistic interactions with fire activity in the Central Oregon Cascade Range. We selected four small watersheds on a longitudinal transect north of Mt Mazama and recovered lake sediment that spanned the period of tephra deposition. Our sediment records had between 14 and 50 cm of tephra deposited, and we analyzed the sediment at centimeter resolution before and after the deposition horizon in each sediment record. Our analysis shows that nonarboreal pollen percentages and accumulation rates were depressed after Mazama tephra deposition. Recovery to pre-tephra deposition rates occurred after approximately 50–100 years. Arboreal pollen percentage and accumulation rates were less severely impacted, suggesting that the Mazama tephra deposition disrupted understory communities more significantly than overstory species, and that forest communities returned to their pre-tephra-deposition conditions after approximately 50–100 years. Fire events in conjunction with the Mazama tephra occurred in two of the four sites, suggesting that tephra deposition did not create conditions that precipitated a fire event in a consistent way. This research reinforces the notion that disturbance events may have cumulative effects on forest vegetation, but that the impacts of disturbance events need to be felt by similar constituents of the forest ecosystem to be truly additive.

The storm system ushered in cold, dense air to the region, which interacted with the warm air, creating unstable atmospheric conditions. When this instability combines with significant wind shear – winds shifting in direction and speed at different heights in the atmosphere – it can create an ideal setup for strong rotating storms to occur. After severe storms and reports of tornadoes, the National Weather Service conducts in-person storm damage surveys to determine whether a tornado or straight-line winds created the reported damage and the degree of damage.

The storm system ushered in cold, dense air to the region, which interacted with the warm air, creating unstable atmospheric conditions. When this instability combines with significant wind shear – winds shifting in direction and speed at different heights in the atmosphere – it can create an ideal setup for strong rotating storms to occur. After severe storms and reports of tornadoes, the National Weather Service conducts in-person storm damage surveys to determine whether a tornado or straight-line winds created the reported damage and the degree of damage.