Daytime Heat Research Articles

Using Commercial Aircraft Meteorological Data to Assess the Heat Budget of the Convective Boundary Layer Over the Santiago Valley in Central Chile

The World Meteorological Organization Aircraft Meteorological Data Relay (AMDAR) programme refers to meteorological data gathered by commercial aircraft and made available to weather services. It has become a major source of upper-air observations whose assimilation into global models has greatly improved their performance. Near busy airports, AMDAR data generate semi-continuous vertical profiles of temperature and winds, which have been utilized to produce climatologies of atmospheric-boundary-layer (ABL) heights and general characterizations of specific cases. We analyze 2017–2019 AMDAR data for Santiago airport, located in the centre of a 40times 100 km^2 subtropical semi-arid valley in central Chile, at the foothills of the Andes. Profiles derived from AMDAR data are characterized and validated against occasional radiosondes launched in the valley and compared with routine operational radiosondes and with reanalysis data. The cold-season climatology of AMDAR temperatures reveals a deep nocturnal inversion reaching up to 700 m above ground level (a.g.l.) and daytime warming extending up to 1000 m a.g.l. Convective-boundary-layer (CBL) heights are estimated based on AMDAR profiles and the daytime heat budget of the CBL is assessed. The CBL warming variability is well explained by the surface sensible heat flux estimated with sonic anemometer measurements at one site, provided advection of the cool coastal ABL existing to the west is included. However, the CBL warming accounts for just half of the mean daytime warming of the lower troposphere, suggesting that rather intense climatological diurnal subsidence affects the dynamics of the daytime valley ABL. Possible sources of this subsidence are discussed.

Heat Waves and Emergency Department Visits Among the Homeless, San Diego, 2012-2019.

Objectives. To determine the effect of heat waves on emergency department (ED) visits for individuals experiencing homelessness and explore vulnerability factors. Methods. We used a unique highly detailed data set on sociodemographics of ED visits in San Diego, California, 2012 to 2019. We applied a time-stratified case-crossover design to study the association between various heat wave definitions and ED visits. We compared associations with a similar population not experiencing homelessness using coarsened exact matching. Results. Of the 24 688 individuals identified as experiencing homelessness who visited an ED, most were younger than 65 years (94%) and of non-Hispanic ethnicity (84%), and 14% indicated the need for a psychiatric consultation. Results indicated a positive association, with the strongest risk of ED visits during daytime (e.g., 99th percentile, 2 days) heat waves (odds ratio = 1.29; 95% confidence interval = 1.02, 1.64). Patients experiencing homelessness who were younger or elderly and who required a psychiatric consultation were particularly vulnerable to heat waves. Odds of ED visits were higher for individuals experiencing homelessness after matching to nonhomeless individuals based on age, gender, and race/ethnicity. Conclusions. It is important to prioritize individuals experiencing homelessness in heat action plans and consider vulnerability factors to reduce their burden. (Am J Public Health. 2022;112(1):98-106. https://doi.org/10.2105/AJPH.2021.306557).

Effect of Daytime Heating on Fruit Yield, Photosynthesis, Translocation and Distribution of <sup>13</sup>C-photoassimilates of Strawberry ‘Sagahonoka’ during Winter Season

Effect of Daytime Heating on Fruit Yield, Photosynthesis, Translocation and Distribution of <sup>13</sup>C-photoassimilates of Strawberry ‘Sagahonoka’ during Winter Season

Effects of Daytime Heating on Growth of Tomato and Heating Loads of Greenhouse under Low Light Conditions

Effects of Daytime Heating on Growth of Tomato and Heating Loads of Greenhouse under Low Light Conditions

Thermal design method of building wall considering solar energy utilization and thermal insulation

This study makes a breakthrough out of the original thermal design idea which is mainly aim to improve thermal insulation performance of building wall, putting forward thermal design method of building wall to consider solar energy utilization and insulation simultaneously. Firstly, a day is divided into daytime and nighttime, and the expressions of indoor heat gain through the wall during such two periods are derived respectively according to the harmonic response method. The weighted sum of daytime and nighttime heat gain, then, could be used as the evaluation index of wall thermal performance. Taking this index as objective function and wall thermal resistance as well as heat capacity per unit wall area having the corresponding thickness of the thermal resistance as variables, a method for determining the optimum wall thermal resistance and heat capacity is proposed. Finally, for the room without heating measures in Lhasa area, using the typical weather data in winter as input conditions, the optimal matching curve of wall thermal resistance and heat capacity taking into account both the effect of solar energy utilization and insulation is calculated, so are the optimal value of them under different indoor temperatures (0–12 °C, interval of 2 °C). The results show that, in Lhasa area, the south wall has great potential to improve indoor thermal environment by using solar energy. From the perspectives of wall’s “carrier” role of utilizable climatic resources, the higher thermal insulation performance doesn’t always bring better results.

The dynamics and temperature regime of the crater lakes in the Nevado de Toluca volcano, Mexico

Volcanic lakes are unique ecosystems with complex relationships between atmospheric variables and crater lake dynamics. In two adjacent tropical, high mountain lakes, spectral analysis of coupled in situ meteorological and hydrodynamic measurements revealed strong diurnal fluctuations in water temperature due to wind-forced internal gravity waves and free seiche oscillations. Although the amplitudes of these internal motions were small, they contribute to the transfer of momentum and mixing, with large potential impacts on lake productivity. During daytime heating, in both lakes, a thermocline formed in the near-surface layer (2−3 m depth) but eroded at night. The heat penetration into each lake within the crater differed significantly, even though they were ∼ 500 m apart, driven by differences in water transparency and algal growth. Analyses of coupling between local meteorology and lake hydrodynamics revealed complex forcing of small-scale patterns which are important to incorporate into future studies to understand how ecosystem productivity is modulated.

Anthropogenic emissions and urbanization increase risk of compound hot extremes in cities

Urban areas are experiencing strongly increasing hot temperature extremes. However, these urban heat events have seldom been the focus of traditional detection and attribution analysis designed for regional to global changes. Here we show that compound (day–night sustained) hot extremes are more dangerous than solely daytime or nighttime heat, especially to female and older urban residents. Urban compound hot extremes across eastern China have increased by 1.76 days per decade from 1961 to 2014 with fingerprints of urban expansion and anthropogenic emissions detected by a stepwise detection and attribution method. Their attributable fractions are estimated as 0.51 (urbanization), 1.63 (greenhouse gases) and −0.54 (other anthropogenic forcings) days per decade. Future emissions and urbanization would make these compound events two to five times more frequent (2090s versus 2010s), leading to a threefold-to-sixfold growth in urban population exposure. Our findings call for tailored adaptation planning against rapidly growing health threats from compound heat in cities.

Role of pavement radiative and thermal properties in reducing excess heat in cities

While pavements are currently a significant contributor to the urban heat island effect, modified pavements could play a role in cooling cities. Specifically, the radiative and thermal properties of pavements can be manipulated to alter the timing and magnitude of sensible heat storage and release into the urban airshed. The present study developed and applied a one-dimensional heat transfer model to Phoenix AZ as a case study to explore the potential for modified pavements in a hot desert climate. We explored solar reflective (0.35 albedo) and traditional (0.10 albedo) asphalt pavements. Pavement thermal conductivity and heat storage capacity values were varied across a reasonable range based on existing products. The results from this study show that daytime peak surface temperature of highly conductive (2.4 WK-1m−1) and thermally massive pavements (4.0 MJK-1m−3) is 17.5 °C cooler than less conductive (0.4 WK-1m−1) and thermally light (1.0 MJK-1m−3) pavements. However, at night, the more thermally massive and conductive pavements were as much as 10.8° C warmer than the less conductive and less massive counterpart. Therefore, when the focus is on reducing excess urban heat during the day, it is better to use pavement materials with higher conductivity and thermal storage. However, when the focus is on reducing the nocturnal heat island, it is wise to use lower conductivity and lower thermal storage pavements. Regardless of thermal properties, the use of reflective pavement surfaces will mitigate both the daytime and nocturnal urban heat island effect. We find up to a 10° C reduction in peak daytime surface temperature and a modest reduction of nocturnal temperatures (by up to 1.0° C) when pavement albedo is increased by 0.25. However, reflective pavements result in a higher influx of net radiation for pedestrians walking on these surfaces during the daytime. So, reflective pavement projects should be evaluated for potential adverse impacts on thermal comfort. Nevertheless, depending upon the time of day and the overall solar reflectivity of pedestrian clothing and skin, we argue that the benefits of reduced surface and air temperatures associated with highly reflective paving likely outweigh the adverse effects for pedestrians. However, for regions where daytime thermal comfort is of primary concern, pavements with higher thermal conductivity and thermal storage may perform better than reflective pavements.

Surface Urban Heat Island Assessment of a Cold Desert City: A Case Study over the Isfahan Metropolitan Area of Iran

This study investigates the diurnal, seasonal, monthly and temporal variation of land surface temperature (LST) and surface urban heat island intensity (SUHII) over the Isfahan metropolitan area, Iran, during 2003–2019 using MODIS data. It also examines the driving factors of SUHII like cropland, built-up areas (BI), the urban–rural difference in enhanced vegetation index (ΔEVI), evapotranspiration (ΔET), and white sky albedo (ΔWSA). The results reveal the presence of urban cool islands during the daytime and urban heat islands at night. The maximum SUHII was observed at 22:30 p.m., while the minimum was at 10:30 a.m. The summer months (June to September) show higher SUHII compared to the winter months (February to May). The daytime SUHII demonstrates a robust positive correlation with cropland and ΔWSA, and a negative correlation with ΔET, ΔEVI, and BI. The nighttime SUHII displays a negative correlation with ΔET and ΔEVI.

Urbanization Magnified Nighttime Heat Waves in China

AbstractNighttime heat waves have greater impacts on human society than daytime because nighttime heat waves deprive humans to recover from daytime heat and increase energy consumption for cooling. In this study, we found increased occurrence and severity of nighttime heat waves across China during 1980–2017 based on measurements from more than 2,000 meteorological stations. The nighttime heat waves have been longer lasting and occurred more often in spring and fall. Compared to rural areas, urban areas have shown enhanced frequency, intensity, and duration of nighttime heat waves. Urbanization accounted for nearly 50% of the extended duration and nearly 40% of the enhanced intensity and frequency of nighttime heat waves in urban areas relative to rural areas. Urban expansion, causing reduced evapotranspiration and weakened wind speed that normally cools the lower atmosphere by turbulent heat loss and cooled air advection, led to nighttime urban heat island, thus magnifying nighttime heat extremes.

More Persistent Summer Compound Hot Extremes Caused by Global Urbanization

AbstractWorldwide urbanization has resulted in more hot extremes in urban areas than surrounding rural areas. Most studies focused on the contribution of urbanization to daytime hot extremes (DayHot), while the contribution to compound hot extremes (CoHot) that considers the concurrence of both daytime and nighttime heat is less understood. Here, we quantify the urbanization contributions across the world by comparing the characteristics of hot extremes between urban and rural areas from 3,401 meteorological stations classified by 30‐m resolution impervious area data. We find more significant increases in frequency, duration, and intensity of CoHot over most urban stations, where urbanization contributes to 12.5%, 15.4%, and 16.7% of the increases, respectively. Urbanization also contributes to the increase in frequency of DayHot, but has weaker impacts on the duration and intensity of Dayhot. This study implies that urbanization effects on the characteristics of hot extremes might be underestimated if only considers DayHot.

Comparison of kilometre and sub‐kilometre scale simulations of a foehn wind event over the Larsen C Ice Shelf, Antarctic Peninsula using the Met Office Unified Model (MetUM)

AbstractA foehn event on 27 January 2011 over the Larsen C Ice Shelf (LCIS), Antarctic Peninsula and its interaction with an exisiting ground‐based cold‐air pool is simulated using the MetUM atmospheric model at kilometre and sub‐kilometre scale grid spacing. Atmospheric model simulations at kilometre grid scales are an important tool for understanding the detailed circulation and temperature structure over the LCIS, especially the occurrence of foehn‐induced surface melting, erosion of cold‐air pools, and low‐level wind jets (so‐called foehn jets). But whether there is an improvement/convergence in the model representation of these features at sub‐kilometre grid scales has yet to be established. The foehn event was simulated at grid spacings of 4, 1.5 and 0.5 km, with the results compared to automatic weather station and radiosonde measurements. The features commonly associated with foehn, such as a leeside hydraulic jump and enhanced leeside warming, were comparatively insensitive to resolution in the 4 to 0.5 km range, although the 0.5 km simulation shows a slightly sharper and larger hydraulic jump. By contrast, during the event the simulation of fine‐scale foehn jets above the cold‐air pool showed considerable dependence on grid spacing, although no evidence of convergence at higher resolution. During the foehn event, the MetUM model is characterised by a nocturnal cold bias of around 8 °C and an underestimate of the near‐surface stability of the cold‐air pool, neither of which improved with increased resolution. This finding identifies a key model limitation, at both kilometre and sub‐kilometre scales, to realistically capture the vertical mixing in the boundary layer and its impact on thermodynamics, through either daytime heating from below or the downward penetration of foehn jet winds from above. Detailed model‐resolved foehn jet dynamics thus plays a crucial role in controlling the near‐surface temperature structure over the LCIS, as well as sub‐grid turbulent mixing.

A Study on Heat Storage and Dissipation Efficiency at Permeable Road Pavements.

The main contributing factor of the urban heat island (UHI) effect is caused by daytime heating. Traditional pavements in cities aggravate the UHI effect due to their heat storage and volumetric heat capacity. In order to alleviate UHI, this study aims to understand the heating and dissipating process of different types of permeable road pavements. The Ke Da Road in Pingtung County of Taiwan has a permeable pavement materials experiment zone with two different section configurations which were named as section I and section II for semi-permeable pavement and fully permeable pavement, respectively. The temperature sensors were installed during construction at the depths of the surface course (0 cm and 5 cm), base course (30 cm and 55 cm) and subgrade (70 cm) to monitor the temperature variations in the permeable road pavements. Hourly temperature and weather station data in January and June 2017 were collected for analysis. Based on these collected data, heat storage and dissipation efficiencies with respect to depth have been modelled by using multi regression for the two studied pavement types. It is found that the fully permeable pavement has higher heat storage and heat dissipation efficiencies than semi-permeable pavement in winter and summer monitoring period. By observing the regressed model, it is found that the slope of the model lines are almost flat after the depth of 30 cm. Thus, from the view point of UHI, one can conclude that the reasonable design depth of permeable road pavement could be 30 cm.

Sahelian Heat Wave Characterization From Observational Data Sets

AbstractThis paper makes use of spaceborne observational data sets in order to characterize radiative processes involved in spring time heat waves in the Sahel. Spring corresponds to the hottest period of the year, with a high aerosol load, a gradual moistening, and the presence of clouds contributing to greenhouse effect. Heat waves are defined as synoptic events that have a large spatial extent and a duration longer than 3 days. Two types of heat waves are studied: daytime heat waves, detected with the daily maximum temperature and nighttime heat waves, detected with the daily minimum temperature. Daytime heat waves correspond to situations where cloud optical thickness is lower than the climatology and a large number of these situations are also associated with a lower aerosol load and a drier atmosphere. Nighttime heat waves correspond to a moister atmosphere compared to the climatology. In a large fraction of them, an increase in aerosol loading is also observed. This study, only based on observational data sets, highlights the subtle but different radiative balance at play in both types of events.

Analysis of the Urban Energy Balance in Bahía Blanca (Argentina)

The objective of this study is to define the effect of Bahía Blanca (Argentina) urban form and function on heat fluxes integrated in its energy balance at a local scale. The most frequent Local Climate Zones (LCZs) were identified in Bahía Blanca. Most of the LCZs are built types, corresponding to LCZ 1 and 2 in the microcenter, LCZ 3 in the macrocenter, and LCZ 6 and 9 in the city peri-urban area. The spatial distribution of Urban Energy Balance (UEB) was analyzed by calculating indices: the sensible heat index (χ), the evaporation index (γ), the storage index (Λ) and Bowen ratio (β). In the city central sectors there is a preponderance of sensible heat fluxes warming the atmosphere closest to the surface. Bahía Blanca estuary has the highest latent heat flux magnitudes, followed by coastal areas and islands associated. Peri-urban land surfaces and suburbs have greater magnitudes of latent heat flux since they are composed of a high percentage of permeable surfaces. A marked variability is observed in the daytime and nighttime QF anthropogenic heat fluxes, with maximums during the day. During the night, QF values decrease in magnitude throughout the urban area.

Mistletoes Facilitate a Desert Herbivore by Improving the Quality of Shade

In arid environments, shade provided by vegetation forms the crux of many facilitation pathways by providing other organisms with relief from high levels of solar radiation and extreme temperatures. Shade is an important determinant that structures arid ecosystem processes and functioning. While shade is considered an essential refuge for many organisms in arid environments, few studies have assessed how parasitic plants such as aerial mistletoes can influence the quality of shade provided by its host, and how this can subsequently influence species interactions. Here, we investigate how mistletoe influences the microclimate and daytime use of sub-canopy habitat by a large herbivore that seeks out shady micro-habitats to avoid daytime heat in Australia’s Strzelecki Desert. We experimentally removed the pale-leaved mistletoe (Amyema maidenii) from mulga trees (Acacia aneura) and monitored sub-canopy ambient temperatures and the daytime use of sub-canopy habitat by red kangaroos (Osphranter rufus). Results showed that average hourly temperature during the daytime and daily maximum temperature were cooler and that kangaroos were approximately three times more likely to shelter beneath trees where mistletoe was present (control) compared to where mistletoes had been removed (treatment). By showing that mistletoe can improve the quality of shade provided by their host trees, our study offers a novel insight into how mistletoes can facilitate the surrounding biota through modifying the abiotic environment beyond its physical structure. More broadly, the results of our study emphasise the prevalence of positive interactions within ecological communities and how they can occur in unexpected ways and indirectly between organisms that never come into direct contact.

Исследование временной изменчивости параметров вертикальной структуры вод в прибрежной зоне южного Крыма

The issues of the formation and temporal variability of the vertical structure of the Black Sea waters off the coast of the southern Crimea are considered. A large array of instrumental measurement data obtained in the second half of 2013 (June–December) during operational monitoring of the vertical temperature profile in the area of Stationary oceanographic platform of the Marine Hydrophysical Institute in the coastal zone near Cape Kikineiz is used. The measurements were carried out using a thermoline, which is a system of temperature sensors distributed in depth from the surface to the bottom. To study the vertical structure of the temperature field, a model of two-layer stratification is considered, when two quasi-homogeneous layers (the upper one is warmer and the lower one cold) are separated by a layer of large vertical temperature gradients—the thermocline. A number of parameters of the vertical structure of waters were calculated: the vertical temperature gradient, its maximum values and depth of occurrence, the temperature of the thermocline core (if it was recorded) and quasi-uniform layers, the temperature difference between these layers, and the thermocline thickness. The median estimates of the daily values of the listed parameters are analyzed. Specific cases of transformation of the vertical profile of water temperature during the upwelling and downwelling processes are considered. It is shown that the temporal variability of the parameters of the vertical structure is significant, especially in the summer hydrological season. The main contribution to the variability is caused by the seasonal course of the heat flow from the atmosphere through the sea surface and surge processes (upwelling and downwelling) in the summer period caused by abrupt changes in the alongshore wind component. In the autumn hydrological season, the thermocline is recorded sporadically with a slight gradient in the form of the lower boundary of the subsurface layer of daytime heating, or a thin bottom layer.

Summer thermal comfort in Russian big cities (1966-2015)

The main goal of the study is the assessment of modern bioclimatic conditions (1966-2015) for determining the level of comfort in large Russian cities based on the observations at the meteorological stations, including Physiological Equivalent Temperature (PET) for the main extent of thermal comfort. According to the distribution of thermal stress events (calculated for meteorological fix hours, 8 times per day) the authors created the comfort diagram for each city during daytime heat wave period and evaluated their comfort conditions. In the current research we are operating with WMO climatic data for eleven biggest cities of the Russian Federation: from the European part (Moscow, Saint-Petersburg, Ekaterinburg, Voronezh, Volgograd, Kazan, Nizhny Novgorod, Perm, Ufa) and from Siberia (Omsk and Krasnoyarsk). The most interesting result of the comparison of the long-period (50 years) urban trends (PET-index and Air Temperature) in different parts of Russia is its extraordinary cross-shaped form in Moscow (in other cities the trends lines are practically parallel to each other). It means that at the level of the average annual values, only in Moscow the PET index (and, hence, potentially the thermal stress) grows faster than the regional climate warms. In other cities this tendency is much weaker (N.Novgorod) or not significant. This interesting tendency is caused by both Moscow related urban planning dynamics in post-USSR period and by regional climate dynamics.

Thermodynamic Features and Design of Solar-Air Source Composite Heating System

Facing the huge energy consumption of buildings, it is highly practical to study every aspect of energy-saving technologies for heating and cooling devices. Solar thermal technology and air/water source heat pump are two popular energy-saving technologies, which could be combined into a composite heating system with good energy-saving effect and efficiency. This paper constructs a solar-air source composite heating system, analyzes its thermodynamic features, and builds up the corresponding thermodynamic model. In addition, the authors modeled the daytime and nighttime heat balances, as well as the monthly cumulative heat supply for the constructed system. Finally, a dual-tank composite heating system was designed with independent heat supply/storage. The proposed models and system were proved valid and scientific through experiments.

Reduced impacts of heat extremes from limiting global warming to under 1.5 °C or 2 °C over Mediterranean regions

Heat extremes have a serious impact on humans and on agriculture around the world. As one of the prominent climate change ‘hot spots,’ the Mediterranean area, especially the eastern portion, is expected to be more vulnerable to heat exposure than other regions due to its high population density and urbanization rate. The Paris Agreement includes the goal of ‘holding the increase in the global average temperature to well below 2 °C above preindustrial levels and pursuing efforts to limit the temperature increase to 1.5 °C above preindustrial levels’. It is interesting to study how heat extremes would change in the Mediterranean area in a +1.5 °C and +2 °C global warming world and how they would impact humans and agriculture. Based on high resolution climate scenario data from Coordinated Regional Downscaling Experiment Mediterranean, we calculate several heat extreme indices to study heat extreme changes in the future. We found that in most Mediterranean areas, both daytime and nighttime heat wave intensity and frequency will have a robust increase in the 21st century compared with that of the historical period, with the most prominent areas located in northwest Africa, the Iberian Peninsula, Italy and Middle East. Meanwhile, nighttime heat waves should be garnering more attention because more moderate and extreme events happen in nighttime than in daytime. If the global warming level is limited to 2 °C or even 1.5 °C, the percentage of population exposed to dangerous events (especially one-in-20 year events) and yield loss from maize harvested areas may be much less in the future than the percentage affected during 3 °C warming period. Moreover, limiting global warming to 1.5 °C instead of 2 °C would result in an additional 20%–25% reduction of exposure.