Summer Days Research Articles

Preliminary Effectiveness of a One-Week Summer Day Camp for Improving Children's Health Behaviors and Psychosocial Well-Being Outcomes.

Summer day camp offers children opportunities to grow knowledge and skills, be physically active, and have fun. Compared to healthy children, at-risk children (i.e., overweight, or with obesity and chronic health conditions) typically display less optimal health behaviors and psychosocial well-being, especially during summer months. This study examined the preliminary effectiveness of an American-Diabetes-Association-sponsored summer day camp at improving children's health behaviors (i.e., physical activity, screen time, diet, sleep) and psychosocial well-being outcomes (i.e., quality of life [QoL], enjoyment, weight-related self-efficacy). The sample consisted of 39 participants, including 19 boys and 20 girls, with majority being overweight (n = 4 or 10%) or with obesity (n = 26 or 67%), who attended the day camp for one week. Significant improvements were observed in screen time, quality of life, and physical function. The results further showed significant time by gender interaction effect for overall QoL (p < 0.05, ηp2 = 0.15), physical health (a dimension of QoL; p < 0.05, ηp2 = 0.18), and significant time by household income for the psychosocial health (another dimension of QoL), favoring boys and those from higher income families. The findings indicate a positive preliminary effectiveness of the summer camp at reducing children's screen time and improving their QoL, especially in boys and those from higher-income families. Future research should focus on health disparities and expansion of this camp for the potential of longer-term and more robust effects related to wellness, nutrition literacy, physical activity promotion, and obesity prevention.

Enhanced Cooling Efficiency of Urban Trees on Hotter Summer Days in 70 Cities of China

Increasing the urban tree cover percentage (TCP) is widely recognized as an efficient way to mitigate the urban heat island effect. The cooling efficiency of urban trees can be either enhanced or attenuated on hotter days, depending on the physiological response of urban trees to rising ambient temperature. However, the response of urban trees’ cooling efficiency to rising urban temperature remains poorly quantified for China’s cities. In this study, we quantify the response of urban trees’ cooling efficiency to rising urban temperature at noontime [∼1330 LT (local time), LT=UTC+8] in 17 summers (June, July, and August) from 2003–19 in 70 economically developed cities of China based on satellite observations. The results show that urban trees have stronger cooling efficiency with increasing temperature, suggesting additional cooling benefits provided by urban trees on hotter days. The enhanced cooling efficiency values of urban trees range from 0.002 to 0.055°C %−1 per 1°C increase in temperature across the selected cities, with larger values for the low-TCP-level cities. The response is also regulated by background temperature and precipitation, as the additional cooling benefit tends to be larger in warmer and wetter cities at the same TCP level. The positive response of urban trees’ cooling efficiency to rising urban temperature is explained mainly by the stronger evapotranspiration of urban trees on hotter days. These results have important implications for alleviating urban heat risk by utilizing urban trees, particularly considering that extreme hot days are becoming more frequent in cities under global warming.

Battery energy storage with renewable energy sources integration in unbalanced distribution network considering time of use pricing

The increasing demand for sustainable energy solutions and the escalating energy demand have facilitated the emergence of renewable energy sources (RES), such as photovoltaic (PV) sources. Combining RES with battery energy storage system (BESS) technology reduces peak hour demand and allows for economical charging and discharging for time-based energy pricing. Integrating PV and BESS in an unbalanced system with multiple RES sources is a challenging task. It requires a robust algorithm to minimise power loss in the distribution system and decrease the voltage unbalance factor (VUF). This paper presents a new multi-objective Pelican optimisation algorithm (MOPOA) for the optimal allocation of PV and BESS. The MOPOA helps find the best placement of PV and BESS in an IEEE-33 bus unbalanced radial distribution system (URDS). The proposed algorithm combines multiple benefits from a lower net present cost (NPC) and a higher voltage profile enhancement index (VPEI). The case studies and simulation results show that the proposed method places PV and BESS in IEEE 33-bus URDS optimally, satisfying all of the system’s requirements. The results indicate an improvement in the minimum VUF factor of 4.4% in a winter day and 4.3% in a summer day; a reduction in active power loss of 16% in a winter day and 7.1% in a summer day; and a reduction in reactive power loss of 7.5% in a winter day and 7.2% in a summer day. Thus, the recommended strategy effortlessly accelerates to a suboptimal solution.

BN fiber aerogels with high solar reflectivity and thermal insulation for green buildings

There exists more than one-third of the stock of buildings that do not meet energy-saving building standards, so there is an urgent need for breakthroughs in the field of green buildings. Herein, we successfully prepared boron nitride (BN) fiber aerogels by sol-gel, freeze-drying and high-temperature pyrolysis. When the molar ratio of C3N6H6 to H3BO3 was 1:2 and the roasting temperature was 1000 °C, the BN fiber aerogel was produced with high specific surface area (257.690 m2/g) and high porosity (99 %). BN fiber aerogels, with their low thermal conductivity (0.043 W/(m·K)) and stable mechanical properties (no change after 45 cycles at 30 % strain), offered possibilities for thermal insulation in green buildings. Its hydrophobic properties protect the wall from the natural environment. In particular, it had a solar reflectivity of 98.6 %, which exceeds most reflective coating materials, enabling the cooling of green construction on hot summer days. The high-temperature resistance of BN fiber aerogels could be applied in special environments such as blast furnace plants and thermoelectric power plants.

We Were Two Girls

Abstract: Two young girls visit a public pool on a hot summer day when they witness a child get hit by a car. The girls, along with others from the pool, gather around while they wait for paramedics to arrive. As they see the aftermath of the accident, the girls confront their emotions and their vulnerability.

Assessing Past and Future Heat and Cold Waves over Iraq Using CMIP6 Model

The United Nations classified Iraq as one of the most vulnerable countries to climate change. Temperatures continue to rise leading to more heat waves, droughts, sandstorms, and desertification. This study aims to investigate the characteristics of heat waves over Iraq from 1982 to 2050 using CMIP6 model at RCP4.5 scenarios. The results clearly showed that the effects of climatic changes were evident in the maximum and minimum temperatures inside Iraq. Average temperature increased of 1.9°C between 1982 and 2020. During 1999, there was a sharp increase in summer days for all stations. The annual number of summer days for the stations (Basra, Nasiriyah, Baghdad, Rutba, Sulaymaniyah, and Mosul) was (195, 193, 177, 108, 106, and 142), while in 2039 the number of summer days was found to be (212, 206, 194, 143, 144, and 149), respectively. The increase in the number of discrete heat wave events began in 2020 and will continue until 2050 for almost the entire territory of Iraq. The warmest day in Basra was in July 2016 with 53.2°C, while the projection of the warmest day was found in July 2046 with 55.7°C. The coldest daily temperature reached -5.03 °C for Baghdad in 1997 and -10.1°C for Sulaymaniyah in 1985, while the projection of the coldest day was -16.2°C over Sulaymaniyah in 2039. The trend of the number of days contributing to cold wave events was decreasing for all stations whereas the coldest year for all stations was 1992 for the entire period (1982 to 2020). Heat waves accelerated from the beginning of the study period in 1982 and continued to increase until the end of the study in 2050 in Iraq.

Intra-Urban Induced Heating Assessment in Kuwait’s Desert Metropolis Using Explainable Machine Learning

Intra-urban induced heating (IUIH) in hot desert cities exhibits distinct patterns and complex diurnal interactions with built environment features, differing significantly from those in temperate areas and remains not fully understood. Understanding how various built environment features contribute to intra-urban thermal variability is an essential first step in developing sub-diurnal targeted heat mitigation strategies. This study presents a data-driven examination of IUIH dynamics in Kuwait’s desert metropolis. Near-surface air temperature observations were collected using high-resolution loop-type traverses at selected hours during a representative summer day to determine IUIH variability. The diurnal impacts of built environment features were modeled using an ensemble learning approach and interpreted with SHapley Additive exPlanations. Among several candidate machine learning regressors evaluated, Random Forest demonstrated strong predictive power (R2 = 0.954) with acceptable error (RMSE = 0.096, MAPE = 0.001) and least bias (MBE = 0.008). The study’s significance lies in its assessment framework that emphasizes explainability of sub-diurnal dynamics, offering detailed insights that challenge traditional assumptions and inform both immediate local climate interventions and strategic urban planning. The findings reveal that simple day-evening comparatives might overlook nuanced sub-diurnal dynamics, such as potential irrigation-induced warming by shrubs observed at mid-day and the complex trade-offs between radiative and transpirative processes by trees in the afternoon and evening. Additionally, the study identifies cooling effects associated with natural land cover, presenting a critical optimization challenge between compact and open urban forms to effectively modulate near-surface air temperatures.

Physiological Responses to Acute Heat Stress in Rohu, Labeo rohita: Insights from Liver Proteomics.

Heat stress is a major problem in aquaculture species, causing changes in physiology such as decreased feed intake, growth rate, reproduction, and internal cellular damage, thereby affecting fish's health. The effects of an acute heat stress simulating a daily rise and fall in temperature on summer days were evaluated in the liver proteome of rohu (Labeo rohita) fingerlings in the present study. The fish maintained at 30°C were gradually exposed to a higher temperature of 36°C at an increment rate of 1°C per 1.5h, and after 3h at that temperature, it was gradually reduced to 30°C. The liver tissue samples were collected at 5 am, 5pm, and 5 am the next day from the exposed and control fish. Protein samples were prepared from the liver tissues, and the extracted proteins were compared using 2-dimensional (2D) gel electrophoresis (2DGE) and mass spectrometry (MS) using a MALDI-TOF/TOF mass spectrometer. A total of 44 differentially expressed protein spots were visualized in 2D gel analysis from heat stress exposed fish at three time points, out of which 21 proteins including one hypothetical protein could be identified by MS. The abundance of five selected differentially expressed proteins (DEPs) was validated using qPCR. The majority of DEPs were found to be involved primarily in lipid, protein and energy metabolism, immune system regulation, cytoskeletal stability, and ROS management. The findings of this study would help in the development of strategies to mitigate heat stress in L. rohita.

A GIS-Based Approach for Urban Building Energy Modeling under Climate Change with High Spatial and Temporal Resolution

The energy demand and associated greenhouse gas (GHG) emissions of buildings are significantly affected by the characteristics of the building and local climate conditions. While energy use datasets with high spatial and temporal resolution are highly needed in the context of climate change, energy use monitoring data are not available for most cities. This study introduces an approach combining building energy simulation, climate change modeling, and GIS spatial analysis techniques to develop an energy demand data inventory enabling assessment of the impacts of climate change on building energy consumption in Shanghai, China. Our results suggest that all types of buildings exhibit a net increase in their annual energy demand under the projected future (2050) climate conditions, with the highest increase in energy demand attributed to Heating, Ventilation, and Cooling (HVAC) systems. Variations in building energy demand are found across building types. Due to the large number of residential buildings, they are the main contributor to the increases in energy demand and associated CO2 emissions. The hourly residential building energy demand on a typical hot summer day (29 July) under the 2050 climate condition at 1 p.m. is found to increase by more than 40%, indicating a risk of energy supply shortage if no actions are taken. The spatial pattern of total annual building energy demand at the individual building level exhibited high spatial heterogeneity with some hotspots. This study provides an alternative method to develop a building energy demand inventory with high temporal resolution at the individual building scale for cities lacking energy use monitoring data, supporting the assessment of building energy and GHG emissions under both current and future climate scenarios at minimal cost.

Self-Cooling Textiles—Substrate Independent Energy-Free Method Using Radiative Cooling Technology

Due to climate change, population increase, and the urban heat island effect (UHI), the demand for cooling energy, especially in urban areas, has increased and will further increase in the future. Technologies such as radiative cooling offer a sustainable and energy-free solution by using the wavelength ranges of the atmosphere that are transparent to electromagnetic radiation, the so-called atmospheric window (8–13 µm), to emit thermal radiation into the colder (3 K) outer space. Previous publications in the field of textile building cooling have focused on specific fiber structures and textile substrate materials as well as complex multi-layer constructions, which restrict the use for highly scaled outdoor applications. This paper describes the development of a novel substrate-independent coating with spectrally selective radiative properties. By adapting the coating parameters and combining low-emitting and solar-reflective particles, along with a matrix material emitting strongly in the mid-infrared range (MIR), substrate-independent cooling below ambient temperature is achieved. Moreover, the coating is designed to be easily applicable, with a low thickness, to ensure high flexibility and scalability, making it suitable for various applications such as membrane architecture, textile roofs, or tent construction. The results show a median daytime temperature reduction (7 a.m.–7 p.m.) of 2 °C below ambient temperature on a hot summer day.

Assessing Climate Change Projections through High-Resolution Modelling: A Comparative Study of Three European Cities

Climate change is expected to influence urban living conditions, challenging cities to adopt mitigation and adaptation measures. This paper assesses climate change projections for different urban areas in Europe –Eindhoven (The Netherlands), Genova (Italy) and Tampere (Finland)—and discusses how nature-based solutions (NBS) can help climate change adaptation in these cities. The Weather Research and Forecasting Model was used to simulate the climate of the recent past and the medium-term future, considering the RCP4.5 scenario, using nesting capabilities and high spatial resolution (1 km2). Climate indices focusing on temperature-related metrics are calculated for each city: Daily Temperature Range, Summer Days, Tropical Nights, Icing Days, and Frost Days. Despite the uncertainties of this modelling study, it was possible to identify some potential trends for the future. The strongest temperature increase was found during winter, whereas warming is less distinct in summer, except for Tampere, which could experience warmer summers and colder winters. The warming in Genova is predicted mainly outside of the main urban areas. Results indicate that on average the temperature in Eindhoven will increase more than in Genova, while in Tampere a small reduction in annual average temperature was estimated. NBS could help mitigate the increase in Summer Days and Tropical Nights projected for Genova and Eindhoven in the warmer months, and the increase in the number of Frost Days and Icing Days in Eindhoven (in winter) and Tampere (in autumn). To avoid undesirable impacts of NBS, proper planning concerning the location and type of NBS, vegetation characteristics and seasonality, is needed.

Using geographic effect measure modification to examine socioeconomic-related surface temperature disparities in New York City.

Lower socioeconomic (SES) communities are more likely to be situated in urban heat islands and have higher heat exposures than their higher SES counterparts, and this inequality is expected to intensify due to climate change. To examine the relationship between surface temperatures and SES in New York City (NYC) by employing a novel analytical approach. Through incorporating modifiable features, this study aims to identify potential locations where mitigation interventions can be implemented to reduce heat disparities associated with SES. Using the 2013-2017 American Community Survey, U.S Landsat-8 Analysis Ready Data surface temperatures (measured on 8/12/2016), and the NYC Land Cover Dataset at the census tract level (2098 tracts), this study examines the association between two components of tract-level SES (percentage of individuals living below the poverty line and the percentage of individuals without a high school degree) and summer day surface temperature in NYC. First, we examine this association with an unrestricted NYC linear regression, examining the city-wide association between the two SES facets and summer surface temperature, with additional models adjusting for altitude, shoreline, and nature-cover. Then, we assess geographic effect measure modification by employing the same models to three supplemental regression model strategies (borough-restricted and community district-restricted linear regressions, and geographically weighted regression (GWR)) that examined associations within smaller intra-city areas. All regression strategies identified areas where lower neighborhood SES composition is associated with higher summer day surface temperatures. The unrestricted NYC regressions revealed widespread disparities, while the borough-restricted and community district-restricted regressions identified specific political boundaries within which these disparities existed. The GWR, addressing spatial autocorrelation, identified significant socioeconomic heat disparities in locations such as northwest Bronx, central Brooklyn, and uptown Manhattan. These findings underscore the need for targeted policies and community interventions, including equitable urban planning and cooling strategies, to mitigate heat exposure in vulnerable neighborhoods. This study redefines previous research on urban socioeconomic disparities in heat exposure by investigating both modifiable (nature cover) and non-modifiable (altitude and shoreline) built environment factors affecting local temperatures at the census tract level in New York City. Through a novel analytical approach, the research aims to highlight intervention opportunities to mitigate heat disparities related to socioeconomic status. By examining the association between surface temperatures and socioeconomic status, as well as investigating different geographic and governmental scales, this study offers actionable insights for policymakers and community members to address heat exposure inequalities effectively across different administrative boundaries. The objective is to pinpoint potential sites for reducing socioeconomic heat exposure disparities at various geographic and political levels.

Projected changes in high temperatures in coastal tourism destinations: A case study of the Turquoise Coast

The effects of climate change may manifest themselves in different ways, but when it comes to coastal tourism, extreme temperatures, which are the unavoidable consequences of climate change, come to the fore. The study examined the changes that extreme temperatures can make on major coastal tourism destinations by using such indices as hot summer days, tropical nights, and days with dangerous apparent temperature (&gt; 40.6 °C). Under the RCP4.5 and RCP8.5 scenarios, increases in these indices are expected for Antalya, Aydın, Balıkesir, İzmir, and Muğla on the Turquoise Coast in the near (2021-2050) and distant (2071-2100) future. The projections based on both scenarios indicate that there might be a rise in the number of hot summer days, tropical nights, and days exceeding the critical human thermal comfort conditions on the Turquoise Coast. Expected increases may reach the highest values under the pessimistic scenario at the end of the century. The increase in these indices caused by rising temperatures may adversely affect the tourism sector due to changes in tourism demands, destinations, and seasonal shifts.

A Simplified Evaluation Framework for Adaptation Measures to Urban Heat Islands

Adaptation measures to urban heat islands are classified into the following three categories: measures to reduce solar radiation incident on the human body, measures to control and cool ground and wall surface temperature, and measures to control and cool the air and human body temperature. Case studies are conducted to evaluate the effects of the implementation of a cool water circulation sunshade and to examine the adverse effects of cool pavements on the human thermal environment, in addition to the effects of mist sprays on the human body. The effect of the sunshade, watering road, and mist spray, which are typical adaptation measures to urban heat islands, on the human thermal environment was estimated using Wet Bulb Globe Temperature (WBGT) as an indicator for heat stroke prevention and Standard New Effective Temperature (SET*) as an indicator for thermal comfort assessment. The effect of solar radiation shielding on improving the human thermal environment was the most significant, with a large decrease in the amount of solar radiation absorbed by the human body, resulting in a large decrease in SET* and WBGT of 2.7 °C and 1.0 °C, respectively, on fine summer days.

Photoperiodic dependent regulation of photosynthesis in the polar diatom Fragilariopsis cylindrus

Introduction: Polar microalgae are exposed to dramatic seasonal changes in light availability, from continuous summer days to winter nights with rapid changes of the daylength in spring and fall. Under this challenging light climate, large diatoms spring blooms occur at the bottom sea-ice and underneath the icepack, accounting for a significant proportion of the annual marine primary production in the Arctic Ocean. The on-going earlier melt down of the snow and ice covers result in a stronger light penetration and consequent increase in irradiance at the bottom of the sea ice leading to earlier seasonal sea-ice diatom blooms under shorter daylengths. Therefore, elucidating the response of polar diatoms to different photoperiods will help to better understand the consequences of the changing arctic climate on their photosynthetic productivity.Methods: In this study, we characterized the response of F. cylindrus, a model polar diatom, across five different photoperiods with similar light and temperature conditions (30 μmol photons m-2 s-1 and 0°C respectively).Results: We report different photoacclimative strategies under shorter and longer daylengths, with the special case of prolonged darkness (mimicking winter polar night). We also observed a repeated daily regulation of the photochemistry and photoprotection parameters when cells were exposed to a light:darkness alternation, despite the constant and optimal light intensity during the light periods.Discussion: Our results highlight the ability of F. cylindrus to grow efficiently under a wide range of daylengths, finely adjusting the balance between photochemistry and photoprotection to make the best use of the available light, supporting sustained production and growth despite low light and temperature.

Theoretical analysis of upward-heating multiple-effect diffusion solar still with parabolic dish concentrator

Upward-heating multiple-effect diffusion solar still (UHMEDS) coupled with a parabolic dish concentrator (PDC) was proposed and analyzed theoretically. UHMEDS has cover glass, several partitions and preheating cover, and wicks are placed on the upper surfaces of partitions and preheating cover. Saline water preheated on the preheating cover flows down the partitions by gravitational force. The lowermost partition of UHMEDS was heated by solar energy collected by PDC. The basic behavior of UHMEDS at Fukuoka, Japan was analyzed theoretically by modeling heat and mass transfer in the still. The theoretical results show that PDC can collect the sunrays to the lowermost partition of UHMEDS effectively, and the overall daily productivity of the still was predicted to be about 18.5, 24.5 and 10.4 kg/m2day on spring equinox, summer and winter solstice days, respectively, which values are almost equivalent to those of other types of multiple-effect diffusion solar still.

Extreme Heat in the Caribbean: Impacts on Wellbeing and Buildings Energy Infrastructure—The 2023 Summer Case

Abstract The summer of 2023 in Puerto Rico and US Virgin Islands witnessed an unprecedented surge in extreme heat, surpassing historical norms prompting the analysis of the broader implications for the Caribbean region. This study presents the initial analysis of this remarkable heatwave, the broader context of global climate change, and its potential impacts on people's well-being and energy demand. Historical and 2023 summer daily maximum heat index (HI) are calculated using local stations and regional gridded data. The results show that summer 2023 exhibited a significant departure from the historical climate. For about 70% of summer days, HI values above 100 °F were recorded. It was found that the extreme summer is part of a broader regional pattern. The summer of 2023 recorded higher sea surface temperatures with anomalies above 2.07 °C and the weakening of the Azores High resulting in reduced wind speed in the region. This diminished the cooling effect associated with cooler maritime air aiding the stagnation of air masses over the region. The analysis sets a threshold of HI of 103 °F to assess human exposure. A significant portion of the region's population, especially in urban areas, was exposed to HI above this threshold. Concurrently, the intense heat led to increased energy demands, with about a 25% increase in peak energy demand in buildings. Per capita consumption exceeded 200 kWh/month for cooling and human comfort and anomalies adding around 15 kWh/month. The study is a step forward in developing adaptive strategies to safeguard vulnerable communities due to global warming-induced extreme events.

Examining the impact of dry climates temperature on citrus fruit internal ripening

High temperatures alter the ripening process of citrus fruit, affecting quality, flavor, harvest time and marketing period. For example, citrus fruits ripen faster and are sweeter in tropical hot-humid climates than in Mediterranean warm-dry climates due to higher sugar accumulation and organic acid catabolism. Considering that: 1) over 60 % of the world's citrus exports come from countries with warm Mediterranean climates, and 2) the Mediterranean region is warming 20 % faster than the global average, the citrus industry will face significant challenges in the coming years. The range of high temperatures and the timing at which they determine sugar and acid content in dry climates have not been studied under field conditions. Therefore, a study was undertaken over 6 years to determine the relationship between high temperature and citrus ripening in two dry macroclimates, hot (Arid, in Morocco) and warm (Mediterranean, in Spain), and 5 microclimates of the Mediterranean region.Heat stress in these dry climates correlates with changes in fruit quality (lower juice and sugar content, and higher organic acids), depending on the maximum temperature threshold and the time of onset and duration of heat. In the arid climate, the heat stress threshold was found to be a significant number of days above 35 °C. This was particularly important at the beginning of summer (July in the northern hemisphere). However, in the current Mediterranean climate of Spain, the percentage of summer days above 35 °C is still low indicating that other microclimatic conditions are involved in determining fruit quality. In particular, an increase in the number of days with temperatures between 27 °C and 33 °C in late summer and early autumn was found to correlate with reduced citric acid concentration. Microclimate did not determine sucrose, fructose, and glucose concentrations.

On the Role of the Building Envelope on the Urban Heat Island Mitigation and Building Energy Performance in Mediterranean Cities: A Case Study in Southern Italy

The urban heat island (UHI) effect is one of the largest climate-related issues concerning our cities due to the localized temperature increase in highly urbanized areas. This paper aims to investigate the impact of UHI mitigation techniques in promoting climate resilience, by reducing urban air temperatures and cooling energy consumption in buildings. To this end, four mitigation solutions regarding the building envelope—green roofs, green walls, cool roofs, and cool walls—were investigated for the city of Bari in Southern Italy and compared with the current baseline scenario. Hence, five scenarios were simulated—using the ENVI-met microclimate software—during three representative summer days, and the resulting microclimate changes were assessed. Based on these analyses, new climate files—one for each scenario—were generated and used as input to run energy simulations in EnergyPlus to estimate the building cooling consumption. Coupling the microclimate and the consumption outcomes, the mitigation strategies were evaluated from both an urban and building point of view. The study shows that urban characteristics, mainly geometry and materials, are crucial for the UHI phenomenon. All the applied technologies seem to be effective. However, green walls proved to be more efficient in reducing outdoor temperatures (1 °C reduction in daily temperatures), while cool walls performed better in reducing cooling energy consumption, with an overall saving of 6% compared to the current scenario.

Can we identify tipping points of resilience loss in Mediterranean rangelands under increased summer drought?

Mediterranean ecosystems are predicted to undergo longer and more intense summer droughts. The mechanisms underlying the response of herbaceous communities to such drier environments should be investigated to identify the resilience thresholds of Mediterranean rangelands. A 5-year experiment was conducted in deep and shallow soil rangelands of southern France. A rainout shelter for 75 days in summer imposed drier and warmer conditions. Total soil water content was measured monthly to model available daily soil water. Aboveground net primary production (ANPP), forage quality, and the proportion of graminoids in ANPP were measured in spring and autumn. Plant senescence and plant cover were assessed in summer and spring, respectively. The experimental years were among the driest ever recorded at the site. Therefore, manipulated summer droughts were drier than long-term ambient conditions. Interactions between treatment, community type, and experimental year were found for most variables. In shallow soil communities, spring plant cover decreased markedly with time. This legacy effect, driven by summer plant mortality and the loss of perennial graminoids, led to an abrupt loss of resilience when the extreme water stress index exceeded 37 mm 10 day-1, characterized by a reduction of spring plant cover below 50% and a decreased ANPP in rainy years. Conversely, the ANPP of deep soil communities remained unaffected by increased summer drought, although the presence of graminoids increased and forage nutritive value decreased. This study highlights the role of the soil water reserve of Mediterranean plant communities in modulating ecosystem responses to chronically intensified summer drought. Communities on deep soils were resilient, but communities on shallow soils showed a progressive, rapid, and intense degradation associated with a loss of resilience capacity. Notably, indexes of extreme stress were a better indicator of tipping points than indexes of integrated annual stress. Considering the role of soil water availability in other herbaceous ecosystems should improve the ability to predict the resilience of plant communities under climate change.