Air Temperature Research Articles

Integrated heating and cooling system with borehole thermal energy storage for a greenhouse in Romania

The IDA Indoor Climate and Energy (IDA ICE) simulation tool is used to model a research greenhouse in Bucharest, Romania, equipped with a recently implemented energy system that includes an integrated heat pump system, Air Handling Units (AHUs), a dry cooler, and boreholes for thermal energy storage. The integrated heat pump system is designed to provide year-round heating and cooling of the greenhouse. The performance of the system is assessed through simulations conducted for one week in summer (July 2023) and one week in winter (December 2023), using recorded weather data for each respective period. Results from the IDA ICE model are compared with values derived from onsite sensor measurements. During the summer week, the model generally aligns with measured air temperatures in the greenhouse compartment. The total cooling simulated in the model is 26.5 kWh/m2, compared to 27.2 kWh/m2 calculated from onsite measurements. Hourly discrepancies were observed, potentially due to the heat pump system operating at reduced capacity during this summer. In the winter week, the measured and simulated temperatures fall within a comparable range. The calculated and simulated cumulative heating show excellent agreement, both at 15.1 kWh/m2.

Less power when more is needed. Climate-related current and possible future problems of the wind energy sector in Poland.

Heat waves, combined with an increasing share of weather-dependent renewable energy sources, lead to disruptions in the operation of energy systems. This paper estimates how energy consumption in Poland changed during four heat waves (2010-2022). It also analyzes how often wind conditions may occur in the summer, that interrupt energy production by land-based wind farms. Moreover, authors are looking at future changes of climate indices responsible for increased energy consumption and possible reduction of energy production in wind farms. During the 2010 heatwave, the increase in energy consumption during the hottest days did not exceed 4%. Later summer demand increased; in 2019, it was 8% higher than during the 2015 heatwave. In 2016-2022, energy consumption at the average daily air temperature above 26°C was over 8% higher on working days than at 18°C. Recently, even in regions with favorable wind conditions, the number of summer days with low wind speed (2 ms-1) exceeds 14. For Poland, the number of days with low wind speeds will increase by about ten. Therefore, the increasing demand for energy on hot days, combined with their more frequent occurrence, may have a negative impact on the stability of the energy system in the future.

Enhancing outdoor comfort in urban hot climates: investigating the cooling impact of two tropical trees through shade provision and transpiration

ABSTRACT One key ecosystem service widely known and attributed to trees in the urban environment is their ability to provide shade through their canopies and undertake evapotranspiration cooling. These in turn contribute to reduced atmospheric temperatures. A lesser-known aspect with little quantitative data is the heterogeneous temperature environment beneath the canopies at pedestrian or street level where the cooling will benefit thermal comfort. This study was conducted throughout 2022. It collected data where air temperature was measured under the canopies of two urban tropical tree species, Samanea saman and Peltophotum pterocarpum, at three different heights, which were 1, 3 and 5 m, respectively, from the ground. This was to investigate whether crown architectures and the associated shade and cooling effects via transpiration can have a significant change in the surrounding temperature. The study observed surface and air temperatures coupled with meteorological data across cool, warm, and hot periods of the year. It was observed that soil temperature increased alongside increases in atmospheric temperatures with a more significant rise observed for P. pterocarpum despite the observation of greater wind speeds for both night and day at the site where this species was situated. The soil moisture potential data indicated the reverse where S. saman showed more negative values with the greatest increase under warm conditions. Interestingly, sap flow rates also indicated that P. pterocarpum had more efficient rates whether conditions were cool, warm, or hot, suggestive of more active transpirational cooling. This was despite a lower leaf area index, smaller crown volume and sap wood area for this species. Relationship analyses between sap flow and air temperatures at different heights under the canopies showed a positive correlation. This demonstrates that apart from shade provided by the canopies, transpiration is also an important parameter for cooling. The mean daytime air temperature indicated that the greatest cooling effect was experienced at the lowest level from the ground (at 1 m), and this was consistent for both species across cool, warm, and hot conditions with a significant cooling effect of between 2.3 and 4°C. Temperature data under the canopy (1 to 5 m from the ground) compared to the air temperature of the grass that was shaded indicated temperature differences of between 2.3 and 7.9°C at 5 m and between 1.9 and 5.6°C at 1 m (for both species) with a bigger reduction attributed to S. saman.

Penerapan IoT dengan Algoritma Fuzzy dan Mikrokontroler ESP32 dalam Monitoring Penyiraman

Smart farming has become a major focus in the development of modern agricultural technology. In this context, the Internet of Things (IoT) offers innovative solutions to increase productivity and efficiency in crop management. This research introduces an IoT-based plant watering monitoring system that uses a fuzzy algorithm and an ESP32 microcontroller. This system is designed to automatically regulate plant watering based on environmental conditions and plant needs. The ESP32 microcontroller acts as the brain of the system, collecting environmental data such as soil moisture, air temperature, and relative humidity. This data is analyzed using a fuzzy algorithm to determine plant watering needs in real-time. Based on the output of the fuzzy algorithm, the system automatically controls the water pump to water the plants according to the specified needs. The application of fuzzy algorithms allows the system to overcome uncertainty in plant watering decisions, especially in the face of complex variations in environmental conditions. With the adoption of IoT technology, farmers can monitor and control crop watering efficiently through web interfaces or mobile applications, even remotely. This research shows that the integration of IoT with fuzzy algorithms and ESP32 microcontrollers can be an effective solution in managing crop watering, increasing overall agricultural productivity, while reducing water and energy consumption.

Predictive heating load management and energy flexibility analysis in residential sector using an archetype gray-box modeling approach: Application to an experimental house in Québec

This paper presents a methodology to develop archetype gray-box models and use them in an economic model-based predictive control algorithm to simulate optimal heating load management in response to a newly-introduced static time-of-use tariff for Québec’s residential sector, rate Flex-D. The methodology is evaluated through a case study, wherein in situ measurements from a two-storey unoccupied research house of Hydro-Québec are used to develop an 11R6C network with a heuristic zoning-by-floor approach and compute the sequence of optimal electric heating input for the next control horizon. Properly-tuned economic model-based predictive control under rate Flex-D shows potential for an approximately 30% reduction in daily heating cost compared to the reference operation, with a minimal average deviation of indoor air temperature from the reference setpoint. Also, the analysis of the response’s sensitivity to weather forecast uncertainties indicates that the most influential uncontrolled input directing the performance of economic model-based predictive control is the structure price signal, rendering the impact of uncertainty in the weather forecast negligible.

The effectiveness of duty cycling technique on air conditioning system during break period for comfort, energy and cost savings: A real case study in health center

This paper investigates the potential of duty cycling techniques for air conditioning (AC) systems in producing energy and cost savings and the impact on the indoor thermal environment, air quality, and environmental sustainability. The real case study concentrated on energy consumption practice during the break period between 13:00 to 14:00 in a lobby area of a Health Center. Site data measurements of electrical input power, energy, indoor air temperature and humidity, and indoor carbon dioxide (CO2) concentration were conducted. Two zero-cost strategies were studied and results were compared to baseline conditions. In general, the results show that all strategies can meet the indoor thermal environment and air quality requirements, except room temperature for Strategy 2 which ranges on average between 26.71 to 26.82C. In addition to the instant payback period (0 years), the results also indicate that as compared to baseline condition, Strategies 1 and 2 led to annual energy and cost savings of around 759.2 kWh (USD 64.40) and 1250.6 kWh (USD 106.08), respectively. In terms of environmental sustainability, Strategies 1 and 2 can avoid environmental CO2 emissions by 444.13 and 731.60 kg of CO2 per year, respectively. Due to these reasons and if the sensitivity of occupant comfort to room temperature during the break period can be tolerated, it is proposed that Strategy 2 is the best option for the AC system operation during the break period. Considering other buildings also adopted the same strategy, this small action can lead to a high impact, not only on energy and cost savings but also on environmental sustainability in the future.

The combined link of the Indian Ocean dipole and ENSO with the North Atlantic-European circulation during early boreal winter in reanalysis and the ECMWF-SEAS5 hindcast

Abstract During early boreal winter, the extra-tropical atmospheric circulation is influenced by Rossby waves propagating from the Indian Ocean towards the North Atlantic-European (NAE) regions, resulting in a North Atlantic Oscillation (NAO)-like pattern. The mechanisms driving these teleconnections are not well understood and are crucial for improving model skills. This study investigates these mechanisms using the ERA5 dataset and tests the predictive capabilities of the ECMWF-SEAS5 hindcast, exploring potential reasons for a weak model response. Linear regression methods are employed to examine the extra-tropical links with the Indian Ocean dipole (IOD), both in isolation and in combination with the El Niño-Southern Oscillation (ENSO). Our findings demonstrate a connection between October IOD sea surface temperature anomalies and December Indian Ocean precipitation patterns. Furthermore, a correlation between the October IOD and December NAO time series suggests a link between the IOD and NAE circulation. The early winter European response to a positive IOD is characterized by a north-south precipitation dipole and a large positive surface air temperature anomaly. Positive feedback from transient eddy forcing reinforces the wavenumber-3-like propagation across extra-tropical regions, with ENSO playing a minor role compared to the IOD. This phenomenon is particularly evident in regions such as the North Pacific and North Atlantic, where wave energy propagation is intensified. Although SEAS5 replicates the NAO response, its magnitude is significantly weaker. The model struggles to simulate the delayed rainfall dipole response to the IOD accurately and shows structural discrepancies compared to reanalysis data.

Frontal effects on the rapid formation of a deep layer of marine fog and cloud in the NW Atlantic

AbstractRapid formation of a deep layer of fog and clouds extending to a height of 2 km was observed over Sable Island off Nova Scotia on 13–14 July 2019. This fog and cloud event was dominantly caused by the rapid intrusion of a trough from a cyclone over NE Canada. The trough quickly moved from SW–W to E–NE and encroached on the coastal waters of Nova Scotia. Due to the warm front in the trough, the air temperature increased up to 4 km in height with increased stability, while the sea‐level pressure at Sable Island dropped by 11 hPa within 12 hours. The moderate to strong winds turned counterclockwise from the N to the SE, converging with the SE winds maintained by the ridge located to the east. There was no indication of an advection‐type fog mechanism because the surface air temperature was not adjusted to the colder sea‐surface temperature that could have resulted in saturation of the surface air. The leading portion of a massive cloud band in the trough passing over Sable Island included precipitation before fog formation. The rain that evaporated in the unsaturated and warm subcloud layer effectively reduced the air temperature and significantly increased the wet‐bulb temperature in this layer. The cloud extended into the moist subcloud layer, while fog formed at 1400 UTC 13 July and lasted until 2327 UTC 13 July (with two brief periods of mist lasting less than two hours). The development of this deep layer of fog and cloud in the NW Atlantic was caused by evolving synoptic conditions through the simultaneous effects of a rapid trough intrusion over coastal waters with a massive cloud band, induced precipitation causing cloud deepening into the subcloud layer, and surface wind convergence forcing vertical mixing in a stable marine boundary layer.

Utilization of waste hot air of medical oxygen plant in solar desalination unit employing jet impingement air heater for water production

ABSTRACT Many oxygen plants have been established specially during COVID-19 period and they are still serving for medical needs. The objective of the present work is to utilize solar and waste thermal energy of medical oxygen plants for water production. Humidification–dehumidification desalination (HDD) has been found suitable for this objective due to low temperature energy need during the process. The layout of an HDD unit has been presented to utilize waste heat, specially when solar energy is not much effective or absent. The system has been configured with a jet impingement solar air heater and a packed bed humidifier. A mathematical model has been developed and validated with the results of our experiments. A comparative study of the proposed unit (HDD-O2) and a conventional unit has been performed in terms of yield and gained output ratio (GOR). The optimum flow rates of working fluids found in the range 0.03–0.04 kg/s and the temperature of air and water resulted in a continuous gain in yield. The average yield and GOR of the HDD-O2 unit were found to be 8.5 kg/d and 1.1 that could reach up to 11 kg/d and 1.4, respectively. The HDD-O2 unit provided yield at the cost of 0.04 $/kg with a payback period of 1.73 years. The findings of the present work indicated the suitability of the HDD-O2 plant for water production.

Temperature Dependence of the Pre-Chromatographic ‘Lawrence’ Method for Bivalves Contaminated with Paralytic Shellfish Poisoning Toxins

AbstractSaxitoxins are potent neurotoxins originating the acute human neurological syndrome of paralytic shellfish poisoning (PSP) via bivalve vectors. The official testing method in the European Union, commonly known as the ‘Lawrence method’, involves pre-column oxidation steps. The Portuguese monitoring adopted the hydrogen peroxide oxidation screening approach for bivalves contaminated with Gymnodinium catenatum toxins, which can quantify chromatographically at once 6 out of 10 analogues commonly found in bivalves. Seasonal fluctuation in the fluorescence yield of calibration curves was observed across years in a consistent manner. It correlated with fluctuations in average monthly air temperature in Lisbon, highlighting the importance of recording the room temperature during the oxidation steps as a matter of routine practice. Incubation experiments also showed an increase in fluorescence yield with temperature, more pronounced for the 11-hydroxysulphate analogues (dcGTX2 + 3, C1 + 2, GTX2 + 3) than for the 11-H toxins (dcSTX, GTX5[B1], STX). Temperature can be exploited to increase fluorescence yield, assisting in spectral confirmation, but must not exceed 40–50 °C to avoid toxin decomposition or production of extra oxidation products.

Baseline survey of environmental parameters, radiation, and drip water hydrochemistry in Niah Caves (Sarawak, Malaysia)

Relict caves in fenglin karst may typically have numerous entrances and openings. Hence, they host a variety of environments in which parameters such as light, airflow, humidity, and temperature may vary significantly over short distances. Similarly, drip water hydrochemistry, including isotopic values, may vary due to different contributions of various sources and residence time in the karst. This study investigated environmental parameters, including radiation, using hand-held instruments, along a transect within several major caves in the Niah karst of Sarawak (Malaysia). This has led to a baseline data set which showed an inverse relationship between humidity and temperature, gamma radiation levels that are about 25% of that in surrounding non-karst region, and high percentages of twilight zones in the studied caves. Airflow was found to be variable, with high values of 530 m3/s in Painted Cave and 122 m2/s in parts of Gan Kira passage, with flow towards the southeast at the time of the study. The hydrochemistry of the drip water and surface water was also analyzed and found to be dominantly Ca–Mg–Cl water type which indicates dissolution of minerals through water–rock interaction. In addition, the cave environment, particularly air temperature, humidity, and ventilation, also influences the drip water composition and isotopic values. Three different origins (precipitation, evaporation, and paleo-recharge) of drip water have been identified through the δ18O-δ2H diagram. Enriched isotopic values were observed in the cave entrance due to increased evaporation caused by lower humidity and higher air temperature. Factor analysis identifies the key geochemical processes responsible for the drip water chemistry. The outcome of this study provides the first baseline environmental data for the Niah caves, which could support future initiatives for sustainable management of this famous archeological site in southeast Asia.

Effect of air preheating temperature on the dynamic behaviour of a swirled spray flame

The effects of the air inlet temperature on the dynamic behaviour of a spray flame are reported for different air flow rates. Dodecane droplets are generated through a pressurised nozzle and introduced in the combustion chamber fed with air via two co-rotating swirlers. The flow rate of dodecane is kept constant (1.24gs-1) while the air flow rate is changed from 28gs-1 to 35gs-1 and its temperature from 70°C to 220°C. Microphones are used to record the different dynamics observed while a camera and a Phase Doppler Anemometry system allow to monitor the flame and the fuel spray.For low flow rates (between 28gs-1 and 32gs-1, leading to an overall equivalence ratio ranging between 0.6 and 0.7), the pressure fluctuations start by increasing with an increase of the temperature until, for a given temperature, the pressure fluctuations suddenly drop. This threshold temperature depends on the air flow rate. When displaying the pressure fluctuation level as a function of the bulk velocity (taking both air flow rate and temperature into account), the curves collapse into a similar shape. The instability frequency monotonically increases with the bulk velocity. For high flow rates (between 32gs-1 and 35gs-1, leading to overall equivalence ratio ranging between 0.5 and 0.6), a hysteresis phenomenon is found. Pressure fluctuations are relatively high for constantly decreasing temperature conditions and have almost similar levels as those obtained for lower flow rates. When constantly increasing the temperature, the levels are much lower, showing a bi-stable behaviour for the pressure fluctuations at a given operating point. A simple analysis based on the acoustic energy balance equation allows to qualitatively retrieve the behaviour of the pressure fluctuations amplitude and frequency for the low flow rate cases.

Seasonal snow–atmosphere modeling: let's do it

Abstract. Mountain snowpack forecasting relies on accurate mass and energy input information in relation to the snowpack. For this reason, coupled snow–atmosphere models, which downscale input fields to the snow model using atmospheric physics, have been developed. These coupled models are often limited in the spatial and temporal extents of their use by computational constraints. In addressing this challenge, we introduce HICARsnow, an intermediate-complexity coupled snow–atmosphere model. HICARsnow couples two physics-based models of intermediate complexity to enable basin-scale snow and atmospheric modeling at seasonal timescales. To showcase the efficacy and capability of HICARsnow, we present results from its application to a high-elevation basin in the Swiss Alps. The simulated snow depth is compared throughout the snow season to aerial lidar data. The model shows reasonable agreement with observations from peak accumulation through late-season melt-out, representing areas of high snow accumulation due to redistribution processes, as well as melt patterns caused by interactions between radiation and topography. HICARsnow is also found to resolve preferential deposition, with model outputs suggesting that parameterizations of the process using surface wind fields may only be inappropriate under certain atmospheric conditions. The two-way coupled model also improves surface air temperatures over late-season snow, demonstrating added value for the atmospheric model as well. Differences between observations and model outputs during the accumulation season indicate a poor representation of redistribution processes away from exposed ridges and steep terrain and a low bias in albedo at high elevations during the ablation season. Overall, HICARsnow shows great promise for applications in operational snow forecasting and in studying the representation of snow accumulation and ablation processes.

Comparing airborne and along-sidewall ground-based measurements to retrieve thermal and PM10 concentration profiles in two Alpine valleys

Abstract The paper aims at investigating the effectiveness of estimating vertical profiles of air temperature and PM10 concentrations in Alpine valleys through ground stations positioned at different altitudes on one valley sidewall (i.e. pseudo-vertical profiles). Two case studies in the Italian Alps are investigated: Chiese Valley in Trentino province and Camonica Valley in Lombardy region. Vertical profiles of temperature and PM10 concentrations were derived from airborne measurements at the center of the two valleys by means of low-cost sensors installed on a drone during summer 2019 and a tethered balloon during winter 2020. At the same time, five stations, equipped with the same kind of low-cost sensors, simultaneously monitored the same variables on one mountain slope. Comparisons between pseudo-profiles and airborne soundings revealed that ground stations well approximated temperature and PM10 soundings during the night and early morning, while temperatures along the slopes were higher than in the center of the valley during daytime, due to solar radiative heating, with larger differences in summer than in winter. On the contrary, some episodes with PM10 concentrations slightly higher in the valley center than on the slope were recorded, due to transport events and upslope winds. Nonetheless, the pseudo-profiles based on slope ground measurements faithfully reproduced the vertical gradients of both air temperature and PM10 if compared to those assessed from the soundings performed at the center of the two valleys. Results show that pseudo-vertical profiles can be a reliable and inexpensive method for continuous monitoring of vertical air temperature and PM10 distribution in mountain valleys.

Net Primary Production of Steppe Ecosystems and the Reasons for its Spatial Variability

The purpose of the article is to analyze the values change of net primary production: aboveground (ANP), belowground (BNP) and total (NPP) for meadow, true and dry steppes. The investigated meadow and true steppes are located between 36 and 116° E, 47 and 56° N. In Tyva, the production of dry steppes is determined on various elements of the relief – from the upper part of the mountain to the depressions located in the bottom of the slope. The value of ANP in the meadow steppes varies from west to east from 10.2 to 3.1, in the true steppes from 5.8 to 0.7 t/ha per year and depends on many factors, including air temperature, precipitation, and soil properties. The soil properties are defined by a set of conditions: the position of the ecosystem on the relief, which leads to different soil moisture. Both, the meadow and true steppes, have irregularities in the decrease of the ANP value from west to east. In some cases, in a series of meadow steppes instead of a decrease, an increase of ANP is observed, which is explaining by changes in soil conditions. The first increase from 4.8 (63° E) to 6.1 t/ha per year (73° E) occurs when Luvic Chernozem (Loamic) is replaced by Inclinigleyic Chernozem (Loamic), as a result of additional soil moistening. The second increase of ANP from 3.6 (75° E) to 6.6 t/ha per year (90° E) is observed when the soil changes from Tonguic Chernozem (Siltic) to Haplic Chernozem (Siltic, Pachic). The increases of ANP were observed in the true steppes: 1) when Skeletic Kastanozem (Siltic) changed to Calcic Chernozem (Siltic), 2) when Haplic Solonetz (Loamic) changed to Calcic Chernozem (Loamic), 3) when soil changes from Mollic Leptosol (Siltic) to Calcic Chernozem (Siltic). The value of BNP in meadow and true steppes in the soil layer of 0–30 cm generally decreases from west to east from 26.8 to 7.7 t/ha per year, varying without a visible pattern. In Tyva, due to the change in the relief, ANP of dry steppes varies from 3.7 to 1.7, BNP – from 27.0 to 8.7 t/ha per year. Consequently, the amount of aboveground production of grass ecosystems is determined not only by air temperature and precipitation, but also by the properties of soils, which vary in structure, Corg content, nutrients, and watering.

Interpretation of the glacial lake outburst floods database in relation to climatic conditions in different world regions

This article investigates the response of glacial lake outburst floods (GLOFs) to climatic conditions since the beginning of the 20th century and during individual seasons based on the data from the publicly available online database recording past GLOFs worldwide. All recorded GLOFs were classified into the regions of Alaska, Western Canada and USA, Central Andes, Southern Andes, Iceland, Scandinavia, Alps, Caucasus, Tian Shan, Central Asia I (west), Central Asia II (east), and New Zealand. In each of these regions, the influence of temperature and precipitation on the frequency of glacial flood occurrences was investigated. It was established that GLOFs occur mainly during the summer months and air temperature is their main triggering factor. Since the frequency of GLOFs is influenced by both temperature and precipitation, a gradual increase in the frequency of GLOFs is expected because of global warming, although the relative importance of each factor will vary across regions.

Seasonal acclimation of photosynthetic thermal tolerances in six woody tropical species along a thermal gradient

Abstract Extreme heat events are becoming increasingly common, and the short‐term acclimation of photosynthesis will have a large impact on plant performance. Trees in lowland tropical forests, which are hypothesized to have limited abilities to tolerate rising temperatures, may need to rely on short‐term acclimation of their more plastic traits, like photosynthetic thermal tolerance, to persist in the face of increasingly variable climates. Here, we investigated seasonal acclimation of thermal tolerances in plant species of the moist Amazon. Specifically, we measured the photosynthetic thermal tolerances of six common woody Amazonian species at the beginning and at the end of the dry season to determine the species' abilities to acclimate to intra‐annual changes to climate. In addition, we used the natural thermal gradient present at our research site to test the acclimation of individual plants to maximum air temperatures not currently observed elsewhere in the moist lowland Amazon (up to ~43°C). Between seasons, there were significant overall increases in the thermal tolerances of three species (i.e. higher thermal tolerances in the hotter dry season), suggesting that leaf megathermy is prominent in these species. Also, three species acclimated their thermal tolerances to microsite‐level differences in seasonal temperature maxima, suggesting closer fidelity between leaf and air temperatures (i.e. limited homeothermy) for these species. Our results show that some woody species from the moist Amazon can acclimate their thermal tolerances over short time‐scales, although acclimation is likely insufficient to overcome thermal stress during extreme temperature events. Some species may therefore be more sensitive to heatwaves than others, which could impact survival and composition of tropical lowland forests into the future. Read the free Plain Language Summary for this article on the Journal blog.

Solar driven atmospheric water harvesting system with integration of desiccant wheel and desiccant bed: An experimental investigation

Solar-driven atmospheric water harvesting (SDAWH) presents a promising solution to address water scarcity issues, particularly in arid and semi-arid regions where conventional water sources are limited. This paper presents a new SDAWH system, integrated with a desiccant wheel and desiccant bed. The desiccant bed adsorbs water vapour during night and desorbs in a day time. Whereas the desiccant wheel performs adsorption and desorption process simultaneously in day time. Therefore, the combination of these offers the potential to enhance water yield and energy efficiency compared to conventional sorption-based SDAWH systems in semi-arid climate. Further, an evacuated tube solar air heater for regeneration and an air-to-air heat exchanger for condensation of water vapour has been integrated. The desiccant bed releases large amount of water vapour in regeneration air but its desorption gradually decreases with time. On the other hand, the desiccant wheel releases a lesser quantity of water vapour into the regeneration air, but its desorption capacity remains almost constant. The system’s performance has been evaluated in a semi-arid climate. As the system is working in closed cycle, the dew point temperature of regeneration air obtained at the outlet of the desiccant wheel is 39.4 °C, which increases to 42.4 °C at the outlet of the desiccant bed. The total yield of water in a day is 7.6 L, with an energy efficiency of 9 %.

Internal Variability Dominated the Extreme Cold Wave Over North America in December 2022

AbstractIn December 2022, North America experienced an unprecedented extreme cold event. However, the underlying physical mechanisms of this cold wave, and the extent to which it is driven by internal variability or external forcing, are not fully understood. Using ERA5 reanalysis data and the HadGEM3‐A‐N216 attribution simulations, we identified internal variability as the main cause, contributing −5.14 K to surface air temperature (SAT) anomalies in North America. External forcing slightly mitigated the cold by 0.42 K. An internally generated wave train from the North Pacific, influenced in combination by Pacific‐North American (PNA) and North Pacific Oscillation (NPO) teleconnection patterns, initiated this intense cyclonic event, contributing −2.18 K and −2.12 K to SAT anomalies, respectively. La Niña‐like sea surface temperature anomalies amplified this wave train and resultant cold wave. Additionally, excessive snow cover in the previous November also intensified the December cold anomalies by enhancing surface albedo and reducing solar radiation.

Surface warming in Svalbard may have led to increases in highly active ice-nucleating particles

The roles of Arctic aerosols as ice-nucleating particles remain poorly understood, even though their effects on cloud microphysics are crucial for assessing the climate sensitivity of Arctic mixed-phase clouds and predicting their response to Arctic warming. Here we present a full-year record of ice-nucleating particle concentrations over Svalbard, where surface warming has been anomalously faster than the Arctic average. While the variation of ice-nucleating particles active at around −30 °C was relatively small, those active at higher temperatures (i.e., highly active ice-nucleating particles) tended to increase exponentially with rising surface air temperatures when the surface air temperatures rose above 0 °C and snow/ice-free barren and vegetated areas appeared in Svalbard. The aerosol population relevant to their increase was largely characterized by dust and biological organic materials that likely originated from local/regional terrestrial sources. Our results suggest that highly active ice-nucleating particles could be actively released from Arctic natural sources in response to surface warming.