Apparent Seasonal Bias in Delta Outflow Estimates as Revealed in the Historical Salinity Record of the San Francisco Estuary: Implications for Delta Net Channel Depletion Estimates

Accurate estimates of freshwater flow to the San Francisco Estuary are important in successfully regulating this water body, in protecting its beneficial uses, and in accurately modeling its hydrodynamic and water-quality transport regime. For regulatory purposes, freshwater flow to the estuary is not directly measured; rather, it is estimated from a daily balance of upstream Delta inflows, exports, and in-Delta water use termed the net Delta outflow index (NDOI). Field research in the 1960s indicated that NDOI estimates are biased low in summer–fall and biased high in winter–spring as a result of conflating Delta island evapotranspiration estimates with the sum of ungauged hydrologic interactions between channels and islands referred to as net channel depletions. In this work, we employed a 50-year observed salinity record along with gauged tidal flows and an ensemble of five empirical flow-salinity (X2) models to test whether a seasonal bias in Delta outflow estimates could be inferred. We accomplished this objective by conducting statistical analyses and evaluating whether model skill could be improved through seasonal NDOI flow adjustments. Assuming that model residuals are associated with channel depletion uncertainty, our findings corroborate the 1960s research and suggest that channel depletions are biased low in winter months (i.e., NDOI is biased high) and biased high in late summer and early fall months (i.e., NDOI is biased low). The magnitude of seasonal bias, which can reach 1,000 cfs, is a small percentage of typical winter outflow but represents a significant percentage of typical summer outflow. Our findings were derived from five independently developed models, and are consistent with the physical understanding of water exchanges on the islands. This work provides motivation for improved characterization of these exchanges to improve Delta outflow estimates, particularly during drought periods when water supplies are scarce and must be carefully managed.

Seasonal variation of dry and wet islands in Beijing considering urban artificial water dissipation

Urbanization has resulted in dry/wet island effects in built-up areas. Compared to the limited number of observational datasets, simulations can provide data with richer spatial distribution, thereby proving to be more helpful for revealing the spatial distribution of dry/wet islands. This study simulated dry/wet island effects during typical summer and winter conditions in Beijing by coupling the Artificial Water Dissipation Urban Canopy Model with the Weather Research and Forecasting model. Observations of relative humidity, absolute humidity, and temperature from weather stations in Beijing were used to verify the model. The results showed that in 2020, Beijing was prone to be a dry island during summer, with the relative humidity approximately 5–10% lower than the surrounding suburbs. The dry island effect was not obvious in winter, and Beijing tended to be a wet island. The influence of artificial water dissipation on dry/wet islands is higher in winter than in summer. By considering the water vapor from artificial water dissipation, humidity in urban areas can be simulated more accurately.

Permanent Thermal and Chemical Stratification in a Restored Urban Meromictic Lake

Meromictic lakes are unique aquatic ecosystems that occur extremely rarely. The phenomenon of meromixis can result from both natural and anthropogenic factors. The aim of this study was to analyse thermal and chemical stratification in a small, deep (6 ha, H max = 24.5 m) lake. The evaluated lake had a typical summer thermal profile with a shallow epilimnion, a sharp thermocline, and a distinct monimolimnion layer in the hypolimnion, which was also maintained during circulation. The lake had a clinograde oxygen profile, with an oxygen deficit in the metalimnion and permanent anoxic conditions in the deeper layers, including during circulation. A redox zone was identified during summer stagnation. The monimolimnion formed a thermally isolated layer at a depth of around 15 m, and the chemocline was situated above the monimolimnion. In the chemocline, the EC gradient ranged from 61 to 77 μS·cm−1 per meter of depth in the summer and from 90 to 130 μS·cm−1 per meter of depth during circulation. EC was significantly correlated with Ca2+ concentration (r2 = 0.549). Chemical stratification, particularly with regard to organic matter distribution, was observed in the chemocline. The monimolimnion severely limited nutrient internal loading.

SPECIAL ASPECTS OF DEFORMATION OF COASTAL PROFILE DURING A FULL STORM CYCLE

Deformations of the coastal accumulative profile during a full storm cycle can be related both to the special aspects of individual storms and to seasonal cycles of wave activity. There is a concept of a “winter” and a “summer” type of coastal profile. The difference between these types of profiles is the isolation of the outer underwater berm in winter due to the transfer of sand material to depth and an increase of slopes in the surf zone in summer due to the transfer of sand material to the shore. In this case, the post-storm relief is determined by the character of the wave intensity reduction phase, i.e., the storm attenuation phase. The attenuation of the storm can be prolonged and accompanied by local peaks in wave heights, which will decrease gradually. In this case, the storm has a high potential for beach recovery and the underwater berm may shift toward the shore. In another case, storm attenuation can occur relatively quickly – the original profile is not recovered and at the end of the storm, the profile shape reflects the erosion in the peak phase. Relevant is the determination of the special features of the resulting deformations at the end of the storm cycle, in particular at the end of the storm attenuation phase. In this paper, the special features of storm deformations of the coastal sand profile, which were observed during field experiment on the Bulgarian coast and during monitoring observations on the Baltic Spit, are considered. In one case (the Bulgarian coast) it is a transition from the typical “summer” profile to the “winter” profile. In another case (Baltic Spit), a shift of the outer underwater berm toward the shore was revealed, which can be considered as a transition to the “summer” profile. It is revealed that the features of the storm attenuation stage in the two cases under consideration have specific differences. It is shown that transformations of the coastal profile, characterized as seasonal, can occur during the full cycle of a single storm event.

Evaluating the Effect of Window-to-Wall Ratios on Cooling-Energy Demand on a Typical Summer Day

The window-to-wall ratio (WWR) significantly affects the indoor thermal environment, causing changes in buildings’ energy demands. This research couples the “Envi-met” model and the “TRNSYS” model to predict the impact of the window-to-wall ratio on indoor cooling energy demands in south Hunan. With the coupled model, “Envi-met + TRNSYS”, fixed meteorological parameters around the exterior walls are replaced by varied data provided by Envi-met. This makes TRNSYS predictions more accurate. Six window-to-wall ratios are considered in this research, and in each scenario, the electricity demand for cooling is predicted using “Envi-met + TRNSYS”. Based on the classification of thermal perception in south Hunan, the TRNSYS predictions of the electricity demand start with 30 °C as the threshold of refrigeration. The analytical results reveal that in a 6-storey residential building with 24 households, in order to maintain the air temperature below 30 °C, the electricity required for cooling buildings with 0% WWR, 20% WWR, 40% WWR, 60% WWR, 80% WWR, and 100% WWR are respectively 0 KW·h, 19.6 KW·h, 133.7 KW·h, 273.1 KW·h, 374.5 KW·h, and 461.9 KW·h. This method considers the influence of microclimate on the exterior wall and improves the accuracy of TRNSYS in predicting the energy demand for indoor cooling.

Analysis of Urban Greening Scenarios for Improving Outdoor Thermal Comfort in Neighbourhoods of Lecce (Southern Italy)

This study analyses the interactions and impacts between multiple factors i.e., urban greening, building layout, and meteorological conditions that characterise the urban microclimate and thermal comfort in the urban environment. The focus was on two neighbourhoods of Lecce city (southern Italy) characterised through field campaigns and modelling simulations on a typical hot summer day. Field campaigns were performed to collect greening, building geometry, and microclimate data, which were employed in numerical simulations of several greening scenarios using the Computational Fluid Dynamics-based and microclimate model ENVI-met. Results show that, on a typical summer day, trees may lead to an average daily decrease of air temperature by up to 1.00 °C and an improvement of thermal comfort in terms of Mean Radiant Temperature (MRT) by up to 5.53 °C and Predicted Mean Vote (PMV) by up to 0.53. This decrease is more evident when the urban greening (in terms of green surfaces and trees) is increased by 1266 m2 in the first neighbourhood and 1988 m2 in the second one, with respect to the current scenario, proving that shading effect mainly contributes to improving the urban microclimate during daytime. On the contrary, the trapping effect of heat, stored by the surfaces during the day and released during the evening, induces an increase of the spatially averaged MRT by up to 2 °C during the evenings and a slight deterioration of thermal comfort, but only locally where the concentration of high LAD trees is higher. This study contributes to a better understanding of the ecosystem services provided by greening with regard to microclimate and thermal comfort within an urban environment for several hours of the day. It adds knowledge about the role of green areas in a Mediterranean city, an important hot spot of climate change, and thus it can be a guide for important urban regeneration plans.

Forest Fires in Madeira Island and the Fire Weather Created by Orographic Effects

Understanding the effects of weather and topography on fire spread in specific contexts, such as oceanic islands, is critical for supporting fire prevention and suppression strategies. In this study, we analyse the atmospheric conditions associated with historical forest fires that have occurred over complex terrain in Madeira Island, Portugal. The atmospheric Meso-NH model was used to identify the mesoscale environment during three forest fires events. The model was configured into two nested horizontal domains, the outer domain at 2.5 km resolution and the inner domain at 500 m. The paper brings a comprehensive analysis on the factors favouring the evolution of significant large fires occurring in Madeira Island in August 2010, July 2012 and August 2016. These fire events were selected because they are characterized by their large size (between 324.99 ha and 7691.67 ha) that expanded in a short-time period, threatening people and property in the wildland-urban interfaces. The study highlights that local terrain produce orographic effects that enhance the fire danger over the southern slope during typical summer atmospheric conditions.

Summer Thermal Conditions in Outdoor Public Spaces: A Case Study in a Mediterranean Climate

Comfort in public spaces is essential to their attractiveness and continued role in improving human quality of life. Acceptable thermal conditions are determinant to ensuring users’ comfort. This study undertakes an assessment of three urban sites in Arouca, in the north of Portugal, using ENVI-met software. Simulations test the influence of pavement and façade covering material, vegetation, and site morphology. The climate of the region is classified as Mediterranean Csb, with rainy winters and dry and mildly warm summers. A typical summer day is considered. The results reveal that a combination of factors might lead to thermal discomfort even in this mild climate on an average day, mainly due to heat exchange by radiation. In addition, the impact of alterations to surface properties depends on the morphological characteristics of the site, e.g., high albedo of the pavement may lead to a decrease or an increase in mean radiant temperature, depending on the space. This variability is present in the effects observed at the studied sites. A high façade albedo always contributes, in these cases, to thermal discomfort. The conclusions of the present study highlight the importance of performing a specific study for each urban site whenever an intervention is to be planned.

Sustainable Guidelines for Enhancing Indoor Thermal Comfort in Coptic Churches in Egypt Using Passive Design Strategies; Case Study St. Barbarah and Virgin Mary Churches

Since the 20th century, the temperature has risen, worldwide, due to climate change causing global warming. Such phenomena have resulted in thermal dissatisfaction within various buildings indoor spaces including Egyptian Coptic Orthodox churches. Heritage churches designs have always implemented passive strategies to provide indoor thermal comfort. However, modern churches design tend to use active strategies to provide indoor thermal satisfaction instead of referring to the use of passive designs. Accordingly, the main purpose of this research is to identify a set of guidelines to enhance indoor thermal comfort in modern Coptic Orthodox churches using passive design strategies. The research has adapted a mixed method approach where an in-depth literature review resulting a qualitative summary of passive techniques used in heritage Coptic churches, then followed by a comparative analysis between two Egyptian case studies; the first is a heritage church (St. Barbarah church) and the other is modern which is (Virgin Mary church) based on the deducted passive strategies from the literature. Moreover, an applicable simulation for varying the methodology, using Design Builder, where the modern church will be simulated and tested for thermal comfort before and after modifying it using the passive strategies deducted from the literature. The research’s main findings were the list of passive techniques that could be used to enhance the indoor thermal comfort, while the simulation experimental results where related to a typical summer week, showing that for the average air temperature and the average solar gains, the triple glazing was the most effective in causing indoor thermal comfort. But, for the average relative humidity and average of total fresh air, insulation has shown to be most effective in providing enhanced indoor thermal comfort. To conclude, a set of guidelines has been deduced from the methods adapted in the research showing the most suitable and applicable passive design strategies that could be used inside Coptic Orthodox churches to enhance indoor thermal comfort.