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Passive evaporative cooling technology using the building envelope is a crucial measure to mitigate the urban heat island effect. This study aims to enhance the cooling efficiency of the surface of enclosure structures by utilizing volcanic ash, potassium–sodium stone powder, and silica-based mesoporous oxide (SMO) as primary materials. These components are incorporated into the ceramic brick production process to create innovative humidity-controlling ceramic bricks (HCCTs). This study extensively investigates the impact of SMO and the amount of applied glaze on the physical and mechanical characteristics of these HCCTs. Additionally, it examines the water absorption and evaporative cooling properties of the studied materials under optimal substitution conditions. Numerical calculations are used to determine the heat and moisture transfer properties of HCCTs. The results indicate that incorporating 2% SMO and applying 70 g/m2 of glaze results in a moisture absorption capacity of 385 g/m2 and a moisture discharge capacity of 370 g/m2. These conditions also yield a notable flexural strength of 15.2 MPa. Importantly, the HCCTs exhibit significantly enhanced capillary water absorption and water retention capabilities. Increased water absorption reduces surface temperature by 2–3 °C, maintaining the evaporative cooling effect for 20 to 30 h. It is also found that the temperature of HCCTs decreases linearly with increasing water content and porosity, while the temperature difference gradually decreases with thickness. Water migration in HCCTs with greater thickness is notably influenced by gravity, with water moving from top to bottom. Therefore, it is recommended that brick thickness does not exceed 15 mm. [ABSTRACT FROM AUTHOR]

An analysis of the crop microclimate is essential for assessing the climate's appropriateness for cultivation. Here, the Bowen ratio (BR) was used to characterize the energy balance in an irrigated wheat field in a hot, arid environment in Sudan. The hourly BR was calculated using micrometeorological data, including net radiation (Rn) and soil heat flux (G), observed in the 2021–2022 and 2022–2023 growing seasons (December–March) and used to compute hourly daytime latent heat (LE) and sensible heat (H) fluxes during the days before and after irrigation. In both seasons, the observed significant evaporative cooling effect of irrigation led to a daily maximum temperature difference of 2.5–5.7 °C between the wheat field and a nearby meteorological station in a non-vegetated desert area. The energy balance calculation results showed that LE was dominant over H and G. Because BR tended to be negative, H was negative; thus, LE was larger than Rn because of sensible heat advection from the surrounding area. Further, a decrease in G after irrigation indicated an alteration in the soil's thermal properties. These results provide insights into the micrometeorological response of irrigated wheat to a hot, arid environment and useful information for understanding soil–plant–atmosphere interactions in hot, dry environments. [ABSTRACT FROM AUTHOR]

Passive evaporative cooling technology using the building envelope is a crucial measure to mitigate the urban heat island effect. This study aims to enhance the cooling efficiency of the surface of enclosure structures by utilizing volcanic ash, potassium–sodium stone powder, and silica-based mesoporous oxide (SMO) as primary materials. These components are incorporated into the ceramic brick production process to create innovative humidity-controlling ceramic bricks (HCCTs). This study extensively investigates the impact of SMO and the amount of applied glaze on the physical and mechanical characteristics of these HCCTs. Additionally, it examines the water absorption and evaporative cooling properties of the studied materials under optimal substitution conditions. Numerical calculations are used to determine the heat and moisture transfer properties of HCCTs. The results indicate that incorporating 2% SMO and applying 70 g/m2 of glaze results in a moisture absorption capacity of 385 g/m2 and a moisture discharge capacity of 370 g/m2. These conditions also yield a notable flexural strength of 15.2 MPa. Importantly, the HCCTs exhibit significantly enhanced capillary water absorption and water retention capabilities. Increased water absorption reduces surface temperature by 2–3 °C, maintaining the evaporative cooling effect for 20 to 30 h. It is also found that the temperature of HCCTs decreases linearly with increasing water content and porosity, while the temperature difference gradually decreases with thickness. Water migration in HCCTs with greater thickness is notably influenced by gravity, with water moving from top to bottom. Therefore, it is recommended that brick thickness does not exceed 15 mm.

Mist spraying is a technique for locally lowering air temperature by spraying fine mist into the air and using the latent heat of evaporation immediately after spraying. This study focuses on the conditions under which mist spraying contributes to the increase in sensible heat release from the human body, using the ratio of air temperature decrease and humidity increase in the space where mist is sprayed. From the measurement results in front of the air-conditioning condenser unit, humidity increased by about 10 g/kg(DA), while air temperature decreased by about 10 °C. From the measurement results in an open space in a park, air temperature decreased by about 0.5 to 1 °C within 2 m of the mist spray and humidity increased by about 0.5 to 1 g/kg(DA) at the height of the mist spray, regardless of the distance from the mist spray. From the measurement results at semi-open bus stops, air temperature decreased slightly to 1 °C and humidity increased slightly to 1 g/kg(DA) under low-wind conditions. Unfortunately, the measured results of air temperature decrease in relation to humidity increase, which the human body perceives as cooler, were not available. [ABSTRACT FROM AUTHOR]

An analysis of the crop microclimate is essential for assessing the climate’s appropriateness for cultivation. Here, the Bowen ratio (BR) was used to characterize the energy balance in an irrigated wheat field in a hot, arid environment in Sudan. The hourly BR was calculated using micrometeorological data, including net radiation (Rn) and soil heat flux (G), observed in the 2021–2022 and 2022–2023 growing seasons (December–March) and used to compute hourly daytime latent heat (LE) and sensible heat (H) fluxes during the days before and after irrigation. In both seasons, the observed significant evaporative cooling effect of irrigation led to a daily maximum temperature difference of 2.5–5.7 °C between the wheat field and a nearby meteorological station in a non-vegetated desert area. The energy balance calculation results showed that LE was dominant over H and G. Because BR tended to be negative, H was negative; thus, LE was larger than Rn because of sensible heat advection from the surrounding area. Further, a decrease in G after irrigation indicated an alteration in the soil’s thermal properties. These results provide insights into the micrometeorological response of irrigated wheat to a hot, arid environment and useful information for understanding soil–plant–atmosphere interactions in hot, dry environments.

The purpose of this study is to evaluate the potential for using the spaces integrating the roads and sidewalks in the street canyon as human-centered spaces, and to investigate more appropriate measures to improve the thermal environment for pedestrians and visitors in these spaces. Based on the spatial distribution of SET* throughout the day, as possible human-centered street space uses, north–south streets with restricted widths and south sidewalks on east–west streets are candidates. Spatiotemporal distributions of SET* were calculated when water was sprinkled on the road surface in the street canyon and when water surface, sunshade, and trees were introduced in the street canyon. Assuming people walk or stay on the water surface, the MRT decreases, causing SET* to be below 31.5 °C at any time, so if a continuous supply of water is guaranteed and people can approach the water surface, the water surface can be expected to have a significant impact anywhere at any time. On the east–west street, shading by sunshades and trees occurs along the lanes at any time, allowing pedestrians moving through the lanes to pass through the shaded areas on a periodic cycle. On north–south street, the time required for the countermeasures is limited to around noon, so the measure is effective even if the shade does not occur in the target lanes only around noon. [ABSTRACT FROM AUTHOR]

The purpose of this study is to evaluate the potential for using the spaces integrating the roads and sidewalks in the street canyon as human-centered spaces, and to investigate more appropriate measures to improve the thermal environment for pedestrians and visitors in these spaces. Based on the spatial distribution of SET* throughout the day, as possible human-centered street space uses, north–south streets with restricted widths and south sidewalks on east–west streets are candidates. Spatiotemporal distributions of SET* were calculated when water was sprinkled on the road surface in the street canyon and when water surface, sunshade, and trees were introduced in the street canyon. Assuming people walk or stay on the water surface, the MRT decreases, causing SET* to be below 31.5 °C at any time, so if a continuous supply of water is guaranteed and people can approach the water surface, the water surface can be expected to have a significant impact anywhere at any time. On the east–west street, shading by sunshades and trees occurs along the lanes at any time, allowing pedestrians moving through the lanes to pass through the shaded areas on a periodic cycle. On north–south street, the time required for the countermeasures is limited to around noon, so the measure is effective even if the shade does not occur in the target lanes only around noon.

As cities and their population are subjected to climate change and urban heat islands, it is paramount to have the means to understand the local urban climate and propose mitigation measures, especially at neighbourhood, local and building scales. A framework is presented, where the urban climate is studied by coupling a meteorological model to a building-resolved local urban climate model, and where an urban climate model is coupled to a building energy simulation model. The urban climate model allows for studies at local scale, combining modelling of wind and buoyancy with computational fluid dynamics, radiative exchange and heat and mass transport in porous materials including evaporative cooling at street canyon and neighbourhood scale. This coupled model takes into account the hygrothermal behaviour of porous materials and vegetation subjected to variations of wetting, sun, wind, humidity and temperature. The model is driven by climate predictions from a mesoscale meteorological model including urban parametrisation. Building energy demand, such as cooling demand during heat waves, can be evaluated. This integrated approach not only allows for the design of adapted buildings, but also urban environments that can mitigate the negative effects of future climate change and increased urban heat islands. Mitigation solutions for urban heat island effect and heat waves, including vegetation, evaporative cooling pavements and neighbourhood morphology, are assessed in terms of pedestrian comfort and building (cooling) energy consumption.

Desert coolers have attracted much attention as an alternative to mechanical air conditioning systems, as they are proving to be of lower initial cost and significantly lower operating cost. However, the uncontrolled increase in the moisture content of the supply air is still a great issue for indoor air quality and human thermal comfort concerns. This paper represents an experimental and numerical investigation of a modified desert air cooler into a liquid desiccant air conditioner (LDAC). An experimental setup was established to explore the supply air properties for an adapted commercial desert cooler. Several experiments were performed for air−water and air−desiccant as flow media, at several solutions to air mass ratios. Furthermore, the experimental results were compared with the result of a numerical simplified effectiveness model. The outcomes indicate a sharp reduction in the air humidity ratio by applying the desiccant solutions up to 5.57 g/kg and up to 4.15 g/kg, corresponding to dew point temperatures of 9.5 °C and 12.4 °C for LiCl and CaCl2, respectively. Additionally, the experimental and the numerical results concurred having shown the same pattern, with a maximal deviation of about 18% within the experimental uncertainties.

The Yarnell Hill Fire, triggered by dry lightning on 28 June 2013, was initiated by hot and dry westerly winds, which rapidly shifted to north-northeast by convective-induced outflows. This sudden wind shift led to the demise of 19 firefighters. This study focuses on the environment and its predictive potential in terms of erratically changing the fire spread. Three numerical sensitivity tests are performed investigating the evolving synoptic-meso-β scale environmental wind flow: (1) deactivating the evaporative cooling, (2) deactivating surface-driven diurnal heating/cooling, and (3) removing the mountain. Results show the strong north-northeasterly wind induced by the density current(s) and the diurnal surface sensible heating played the most significant roles in enhancing the mesoscale environment conducive to the rapid change in the fire spread direction. While the mountain played a less significant role in weakening the magnitude of the airflow affecting the fire, it still had an impact. Additionally, the Hot-Dry-Windy (HDW) index is calculated to determine its predictor role with respect to the atmosphere affecting the fire. The focus is not on feedback from explicit fire heating on the larger environment but rather the role of the environmental physical processes in causing the convectively induced rapid wind shifts. [ABSTRACT FROM AUTHOR]

During 19–20 October 2004, a series of spectacular arc-shaped rainbands developed south or southeast of southwestern Japan when Typhoon Tokage (TY0423) approached the region from the southwest. As the typhoon moved closer and the upstream Froude number (Fr) continued to increase, these rainbands first remained quasi-stationary but eventually retreated backward. Using the Nagoya University Cloud-Resolving Storm Simulator (CReSS) at 1-km grid size, these rainbands were successfully simulated, and their behavior during the transition period from a relatively low-Fr to a high-Fr regime was investigated and compared with idealized two-dimensional (2D) model results from theoretical studies. In the present case, the rainbands were found to develop along a low-level frontal convergence zone between the southerly flow associated with the typhoon and the northerly flow from the Sea of Japan. The northeasterly winds accelerated through gaps between topography and fed the offshore flow at the backside of the rainbands, producing a strong resistance that allowed the rainbands to remain stationary under significantly higher Fr values (at least 1.2) than predicted by 2D simulations (of about 0.3–0.5) for the retreat to occur in conditionally unstable flow with a convective available potential energy of about 1300 J kg−1. Typically ≤ 500 m in depth with a potential temperature (θ) deficit of 2–4 K across the rainband, the cooler offshore flow was also found to be enhanced by evaporative cooling as in some other events. The cooling effect helped the rainbands to hold their position until Fr of the upstream flow became too large, and the rainband with stronger cooling behind was able to withstand a higher Fr before retreat. Once the retreat started, the offshore layer became thinner and the θ deficit also reduced, and the rainbands were washed back by the strengthening upcoming flow. [ABSTRACT FROM AUTHOR]

The use of air conditioning technology is accompanied by an increase in electricity consumption, which is linked to an intensification of fossil fuel extraction. This in turn calls for developing cooling solutions of higher energy efficiency. The aim of this study is to examine energy consumption reduction of direct evaporative cooling technology for generating cool air in hot-dry climate regions. At the initial stage, already-installed air cooling equipment with a direct evaporative cooling system was studied for the creation of two regression models of electricity consumption representing the "on" and "off" sequences. Water consumption for system operation was taken into consideration. In the following stage, inlet water temperature dependence for pre-cooling purposes for the direct evaporative cooling system was studied. A mathematical model was developed and the subsequent calculations suggested that there is no need to pre-cool water before it enters the system and therefore consume additional energy. Practical application of this study is evaluated based on the case study in Dubai. The results of this study present significant energy saving potential for system operations of the direct evaporative cooling system of approximately 122 MWh per year. The return on investment for the equipment with direct evaporative cooling in case of an office building in Dubai featuring a hot desert climate is around 4.2 years. The purpose of this study is to examine the potential advantage of air cooling equipment with direct evaporative cooling technology compared to cooling equipment without this technology. The results provide the expediency of conducting further research in this area, in particular with regards to analyzing various materials for the adiabatic precooling pads, as well as the possibility of using a newly developed metal precooling pad. [ABSTRACT FROM AUTHOR]

Green infrastructure has a role to play in climate change adaptation strategies in cities. Alternative urban spaces should be designed considering new requirements in terms of urban microclimate and thermal comfort. Pervious pavements such as green parking lots can contribute to this goal through solar evaporative cooling. However, the cooling benefits of such systems remain under debate during dry and warm periods. The aim of this study was to compare experimentally the thermal behavior of different parking lot types (PLTs) with vegetated urban soil. Four parking lots were instrumented, with temperature probes buried at different depths. Underground temperatures were measured during summer 2019, and the hottest days of the period were analyzed. Results show that the less mineral used in the surface coating, the less it warms up. The temperature difference at the upper layer can reach 10 °C between mineral and non-mineral PLTs. PLTs can be grouped into three types: (i) high surface temperature during daytime and nighttime, important heat transfer toward the sublayers, and low time shift (asphalt system); (ii) high (resp. low) surface temperature during daytime (resp. nighttime), weak heat transfer toward the sublayers, and important time shift (paved stone system); and (iii) low surface temperature during daytime and nighttime, weak heat transfer toward the sublayers, and important time shift (vegetation and substrate system, wood chips system, vegetated urban soil). The results of this study underline that pervious pavements demonstrate thermal benefits under warm and dry summer conditions compared to conventional parking lot solutions. The results also indicate that the hygrothermal properties of urban materials are crucial for urban heat island mitigation. [ABSTRACT FROM AUTHOR]

As cities and their population are subjected to climate change and urban heat islands, it is paramount to have the means to understand the local urban climate and propose mitigation measures, especially at neighbourhood, local and building scales. A framework is presented, where the urban climate is studied by coupling a meteorological model to a building-resolved local urban climate model, and where an urban climate model is coupled to a building energy simulation model. The urban climate model allows for studies at local scale, combining modelling of wind and buoyancy with computational fluid dynamics, radiative exchange and heat and mass transport in porous materials including evaporative cooling at street canyon and neighbourhood scale. This coupled model takes into account the hygrothermal behaviour of porous materials and vegetation subjected to variations of wetting, sun, wind, humidity and temperature. The model is driven by climate predictions from a mesoscale meteorological model including urban parametrisation. Building energy demand, such as cooling demand during heat waves, can be evaluated. This integrated approach not only allows for the design of adapted buildings, but also urban environments that can mitigate the negative effects of future climate change and increased urban heat islands. Mitigation solutions for urban heat island effect and heat waves, including vegetation, evaporative cooling pavements and neighbourhood morphology, are assessed in terms of pedestrian comfort and building (cooling) energy consumption. [ABSTRACT FROM AUTHOR]

The bow echo, a mesoscale convective system (MCS) responsible for much hail and wind damage across the United States, is associated with poor skill in convection-allowing numerical model forecasts. Given the decrease in convection-allowing grid spacings within many operational forecasting systems, we investigate the effect of finer resolution on the character of bowing-MCS development in a real-data numerical simulation. Two ensembles were generated: one with a single domain of 3-km horizontal grid spacing, and another nesting a 1-km domain with two-way feedback. Ensemble members were generated from their control member with a stochastic kinetic-energy backscatter scheme, with identical initial and lateral-boundary conditions. Results suggest that resolution reduces hindcast skill of this MCS, as measured with an adaptation of the object-based Structure–Amplitude–Location method. The nested 1-km ensemble produces a faster system than in both the 3-km ensemble and observations. The nested 1-km simulation also produced stronger cold pools, which could be enhanced by the increased (fractal) cloud surface area with higher resolution, allowing more entrainment of dry air and hence increased evaporative cooling. [ABSTRACT FROM AUTHOR]

Desert coolers have attracted much attention as an alternative to mechanical air conditioning systems, as they are proving to be of lower initial cost and significantly lower operating cost. However, the uncontrolled increase in the moisture content of the supply air is still a great issue for indoor air quality and human thermal comfort concerns. This paper represents an experimental and numerical investigation of a modified desert air cooler into a liquid desiccant air conditioner (LDAC). An experimental setup was established to explore the supply air properties for an adapted commercial desert cooler. Several experiments were performed for air–water and air–desiccant as flow media, at several solutions to air mass ratios. Furthermore, the experimental results were compared with the result of a numerical simplified effectiveness model. The outcomes indicate a sharp reduction in the air humidity ratio by applying the desiccant solutions up to 5.57 g/kg and up to 4.15 g/kg, corresponding to dew point temperatures of 9.5 °C and 12.4 °C for LiCl and CaCl2, respectively. Additionally, the experimental and the numerical results concurred having shown the same pattern, with a maximal deviation of about 18% within the experimental uncertainties. [ABSTRACT FROM AUTHOR]