Cold Air Temperatures Research Articles

Leveraging machine learning techniques and in-situ measurements for precise predicting the energy performance of regenerative counter-flow indirect evaporative cooler in a semi-arid climate building

This study explores the performance augmentation of a regenerative counterflow indirect evaporative cooler (RCFIEC) both experimentally and numerically. A counter flow heat/mass exchanger between the dry channel and the wet channel is effectively designed using a silica gel wet material. The RCFIECS is examined under different operational scenarios and thoroughly assessed in terms of wet-point effectiveness, and dew-point effectiveness, energy efficiency ratio, and cooling capacity. More so, leveraging machine learning models including Categorical Boosting Regressor (CatBR), Extra Tree Regressor (ETR), Random Forest Regressor (RFR), Voting Hybrid Regressor (VHR), Support Vector Regressor (SVR), and SVR coupled with Particle Swarm Optimization (PSO) are also developed to predict the performance parameters of the RCFIECS. Furthermore, the robustness of the six models is assessed using eight different statistical measures. The experimental findings indicated that the wet-bulb effectiveness of the proposed RCFIEC varied from 65 % to 110 %, while the dew-point effectiveness varied from 45 % to 80 %, at inlet air velocity varied from 0.15 to 0.90 m/s, respectively. Additionally, the system maintained improved cooling performance in which the averaged values of dew effectiveness, energy efficiency ratio, cooling capacity, and average cold air temperature are 0.60, 0.788, 31.6 W, and 25.0 °C, respectively. Furthermore, the statistical analyses prove that the optimal prediction accuracy achieved by ETR, followed by SVR-PSO, CatBR, VHR, and RFR, respectively, while the least accuracy yielded by the standalone SVR method. Specifically, the deterministic coefficient and RMSE of the predictive wet Effectiveness are 0.9978 and 0.0103 for ETR, and 0.9977 and 0.0128 for SVR-PSO, and 0.5515 and 0.1509 for typical SVR, respectively. Conclusively, the ETR approach can be deemed a potent optimization tool not only for forecasting the energetic performance of building cooling systems but is also valuable for various real-time applications.

Model-based control strategy with linear parameter-varying state-space model for rack-based cooling data centers

Cooling system energy consumption occupies approximately 40% of the total energy consumption in data centers, and efficient control is crucial for improving cooling efficiency and reducing the operational costs of data centers. This paper introduced a novel economic model predictive control (EMPC) strategy based on a linear parameter-varying state-space model. The primary objective was to maintain the thermal environment of data centers while minimizing the energy consumption of the cooling system. Therein, a linear parameter-varying state-space model was developed based on the parameter identification method to precisely predict the temperature field of the rack-based cooling data center in real-time. The energy management and thermal regulation performance of the EMPC and the proportion integration differentiation (PID) controller were comparatively analyzed through simulation experiments. Moreover, the impacts of the server workload level and optimization time domain on the performance of EMPC were comprehensively investigated. The results show that, the proposed EMPC was able to minimize the energy consumption by optimizing the supplied cold air temperature and airflow rate simultaneously. In comparison with the PID controller, EMPC not only achieves a 9.7% energy saving by preventing server over-cooling but also diminishes server temperature fluctuations, promoting the safe and stable operation of the server. The research shows that the EMPC reveals excellent performance along with all server workload levels. In addition, the length of the prediction horizon has a notable impact and three minutes is suggested for the rack-based cooling system.

Study of design methods and heat transfer characteristics of combined cooling structure for turbine blades with turbine inter-vane burner

The turbine inter-vane burner can greatly increase the engine thrust but brings about a harsh thermal environment to the turbine blades. Fuel-air combined cooling structure is an effective way to solve the thermal protection problem of the blades. There is a lack of research on the thermal protection of turbine blades with turbine inter-vane burner, especially systematic research on the fuel–air combined cooling structure. In this paper, the design methods of the fuel–air combined cooling structure of turbine blades with turbine inter-vane burner are proposed, and one-dimensional empirical formulas are used to design specific parameters. The heat transfer characteristics of the designed combined cooling structure are numerically investigated and analyzed without turbine inter-vane combustion, where the mainstream temperature varies from 818 K to 1414 K, the cold air temperature ranges from 500 K to 700 K, and the mass flow rate of cold air changes from 0.005 kg/s to 0.02 kg/s. The results show that in the combined cooling structure with embedded fuel channels, the heat absorbed by fuel is mostly influenced by cold air temperature compared to mainstream temperature and mass flow rate of cold air. The proportion of fuel heat absorption to overall heat absorption decreases from 0.25 to 0.13 when mainstream temperature increases from 818 K to 1418 K, as the increase of mainstream temperature has a minimal effect on the heat flux of the fuel channels, but can significantly increase the overall heat absorption. The proportion of fuel heat absorption to the overall heat absorption changes from 0.15 to 0.31 when cold air temperature increases from 500 K to 700 K, as the increase of cold air temperature enhances the heat exchange between the fuel channels and the cold air but decreases the heat exchange between the mainstream and the cold air. Besides, the flow and heat transfer performance of the combined cooling structure of turbine blades with turbine inter-vane combustion is numerically studied. The results show that the temperature of blade and fuel channels are maintained within the safe range with turbine inter-vane combustion, providing research support for subsequent studies on the fuel–air combined cooling structure of turbine blades with turbine inter-vane burner.

Precipitation and relative humidity favours tree growth while air temperature and relative humidity respectively drive winter stem shrinkage and expansion

Forest ecosystems have a major role in sequestering atmospheric CO2 and as such, their resilience is of upmost importance. In the boreal forest, trees grow only during a short period when air temperature is favourable. During winter, trees have specific mechanisms to survive in the cold air temperature. In order to understand the response of trees to a changing climate, this study assessed the influence of environmental variables on three phases of tree radial variation (i.e., growth, shrinkage and expansion) during three periods of the year (i.e., growing season, freeze–thaw period, and winter). The three phases were extracted from stem radial variation measured for as much as 11 years on 12 balsam fir [Abies balsamea (L.) Mill.] trees located in a cold and humid boreal forest of eastern Canada. The random forest algorithm was used to model each phase during each period. Our results show that tree growth increased with high precipitation and high relative humidity. Stem shrinkage was affected mostly by solar radiation, precipitation and vapour pressure deficit during the growing season and was likely caused by tree transpiration. During both the freeze–thaw and winter season periods, stem shrinkage increased with decreasing air temperature. During the growing season, stem expansion was related to 1-day-lag solar radiation and 1-day-lag vapour pressure deficit, which are the same variables associated with shrinkage the preceding day. Stem expansion increased with increasing air temperature and relative humidity during the freeze–thaw and winter season periods, respectively. This study shows that sink-driven tree growth is promoted mostly under humid conditions while antecedent dry and warm conditions are required during the growing season for trees to assimilate carbon through photosynthesis.

Synoptic Climatology of Central U.S. Snowfall

Abstract Prior research evaluating snowfall conditions and temporal trends in the United States often acknowledges the role of various synoptic-scale weather systems in governing snowfall variability. While synoptic classifications have been performed in other regions of North America in applications to snowfall, there remains a need for enhanced understanding of the atmospheric mechanisms of snowfall in the central United States. Here we conduct a novel synoptic climatological investigation of the weather systems responsible for snowfall in the central United States from 1948 to 2021 focused on their identification and the quantification of associated snowfall totals and events. Ten unique synoptic weather types (SWTs) were identified, each resulting in distinct regions of enhanced snowfall across the study domain aligning with regions of sufficiently cold air temperatures and forcing mechanisms. While a substantial proportion of seasonal snowfall is attributed to SWTs associated with surface troughs and/or midlatitude cyclones, in portions of the southeastern and western study domain, as much as 70% of seasonal snowfall occurs during systems with high pressure centers as the domain’s synoptic-scale forcing. Easterly flow, potentially resulting in topographic uplift from high pressure to east of the domain, was associated with between 15% and 25% of seasonal snowfall in Nebraska and South Dakota. On average, 64.8% of the SWT occurrences resulted in snowfall within the study region, ranging between 40.1% and 93.5% by SWT. Synoptic climatological investigations provide valuable insights into the unique weather systems that generate hydroclimatic variability. Significance Statement By evaluating the weather patterns that are responsible for snowfall in the central United States, key insights can be gained into how and why snowfall varies and potentially changes over space and time. Using an approach that categorizes weather patterns based on their similarities, here 10 unique snowfall-producing weather patterns are identified and analyzed from 1948 to 2021. Each pattern resulted in different snowfall amounts across the central United States, varying substantially spatially and within the calendar year. Approximately 65% of the time that these weather patterns occur, snowfall is observed in the region. The majority of snowfall-producing weather patterns are associated with low pressure systems, but in some regions up to 70% of snowfall is associated with instances of high pressure in which winds can cause upward motions associated with topography.

Experimental evaluation on pre-swirling cold air for flue cooling

The operation of a diesel engine leads to the emission of a substantial amount of waste heat flue gas, resulting in a continuous increase in the wall temperature of the exhaust system. To mitigate this continuous rise in temperature, a pre-swirling device has been developed to enhance the heat exchange between cold air and the wall, thus averting heating wall by the hot air. In this study, an experimental system was devised and implemented to analyze the dynamic behavior of the wall temperature in an air duct. The system considered both with and without the pre-swirling device, incorporating different cold air temperatures and flow rates to examine its impact on the increase in wall temperature. The results revealed a gradual rise in wall temperature after reaching a steady state, particularly demonstrating lower wall temperatures at 19 measurement points in the presence of pre-swirl compared to without swirl. Notably, the maximum temperature rise in the air duct wall was reduced by 55.7 %, from 7.9 °C without pre-swirl to 3.5 °C with the inclusion of the pre-swirling device, highlighting the significant thermal protection it provides and suggesting potential applications in exhaust thermal protection engineering. Moreover, the experimental findings consistently indicate that the incorporation of a pre-swirling device effectively diminishes the increase in wall temperature across different cold air flow rates and temperatures.

Abiotic Factors Impact on the Honey Bees Distribution in the Submontane Zone

With the onset of the autumn season, a decrease in air temperature gradually weakens the vital activity of bees from the summer months. With a decrease in air temperature, the laying of eggs of Mother bees decreases and stops. The exchange of substances in bees slows down, they begin to prepare for cold air temperatures. As soon as the cold weather comes, they begin to fill the entire box holes with propolis. As a result of the studies carried out, it was also observed that Wasps grown at low temperatures have a short female, a short canoe, and in some cases the wing is completely absent. It has been studied that the temperature in bee hives rises above 35°С, negatively affects the development of worms, sometimes leading to their death.

Delayed onset of the tropical Asian summer monsoon in CMIP6 can be linked to the cold bias over the Tibetan Plateau

Most global circulation models (GCMs) from the Coupled Model Intercomparison Project Phase 6 (CMIP6) simulate a delayed onset of the tropical Asian summer monsoon of 3–6 pentads when compared with the observations. However, a clear explanation of this model bias has yet to be developed. This study indicates that 23 of the 31 of CMIP6 models generate both the Tibetan Plateau (TP) cold bias and the delayed monsoon onset across tropical Asia. The aloft TP cold air temperature associated with these models tends to reduce the land–sea thermal contrast and monsoon circulation, and hence it generates a delayed onset for the tropical summer monsoon. Two sensitivity experiments based on a coupled ocean–atmosphere–land GCM, together with additional data analysis, further confirm the underlying connection between monsoon onset and temperature anomaly over the TP. Therefore, it is of great importance that we attempt to reduce the model bias associated with the simulation of monsoon onset by improving the physical process parameterization scheme related to the TP temperatures.

Simulation and experiment on pneumatic defrosting of evaporators with heat storage

In order to solve the problem of frosting on surface of the evaporators in rapid freezing equipment, a new defrosting system was proposed based on pneumatic defrosting and heat storage defrosting. A three-dimensional flow model including an evaporator and a thermal flow defrosting system was established to observe the temperature distributions of the fins and gas flowing outside the evaporator and to reflect the defrosting effect. The correctness of the model was verified by a freezing experiment. On this basis, the effects of the nozzle placement hole sizes, hot air inlet temperatures and velocities on the fins and cold air temperatures were simulated. The results show that the appropriate horizontal distance between the nozzle and the evaporator is 40 mm considering the large area of heat transfer. The initial temperatures of the hot gas and nozzle sizes have little effects on the heat exchange areas, but the initial velocities of the hot gas have great effects on the heat exchange areas. It takes 180 s for the air outlet temperature of the heat accumulator with the decrease of the temperature from 44 °C to 25 °C. The frost on the surface of the fin melts rapidly within the time that the heat accumulator can maintain a certain temperature range. More studies are required to perform defrosting experiments by choosing appropriate heat storage materials and elevating gas pressure and temperature.

Diagnosing the Radiation Biases in Global Climate Models Using Radiative Kernels

AbstractRadiation energy balance at the top of the atmosphere (TOA) is a critical boundary condition for the Earth climate. It is essential to validate it in the global climate models (GCM) on both global and regional scales. However, the comparison of overall radiation field is known to conceal compensating errors. Here we use a new set of radiative kernels to diagnose the radiation biases caused by different geophysical variables in the GCMs of the Coupled Model Intercomparison Project. We find although clouds remain a primary cause of radiation biases, the radiation biases caused by non‐cloud variables are of comparable magnitudes. Many GCMs have a cold air temperature bias and a moist tropospheric humidity bias, which lead to considerable biases in TOA radiation budget but are compensated by cloud biases. These findings signify the importance of validating the GCM simulations in terms of both the overall and component radiation biases.

The effect of load and binding position on the friction of cross-country skis

This study investigates the effect of moving the binding and adjusting the normal load on friction for a modern cross-country ski. The binding was moved 10 cm forward and backward from the normal position. The results showed that moving the binding backward on the ski reduced the friction at cold (−10 °C) and warm air temperatures (+5 °C). At intermediate temperatures (−2 °C), neither changes to the binding position nor the total load affected the friction coefficient. Measurement of pressure zone profiles revealed that moving the binding backward reduced the apparent contact area, increased the average contact pressure, increased the peak pressure in the rear zone and increased the spacing between the front and rear contact zones of the ski.

Water and heat recovery for greenhouses in cold climates using a solid sorption system

Greenhouses are basically used to create a protected growing environment for crops. In winter climates, cold air temperature and high humidity level are two major problems for greenhouse production, which induce plant diseases and yield losses. In this research, we proposed a climate control system which integrates solid sorption and sensible thermal storage. During the sorption phase, indoor vapor was captured by sorbents while sorption heat was used to increase the air temperature. During the desorption phase, vapor was released and condensed into liquid water. Heat exchanged through the water-cooling condenser was recovered and stored for nocturnal space heating. In the comparative filed experiments, pure silica gels (SG) and composite sorbents CaCl2@SG were chosen as sorbent materials, respectively. During experiments using SG, the averaged nocturnal air temperature was increased by 3.23 °C and the averaged nocturnal relative humidity was decreased by 16.91%. During experiments using CaCl2@SG, the changes were 2.58 °C and 17.39%, respectively. Moreover, CaCl2@SG significantly decreased the averaged humidity ratio by 0.40 g/kg, while SG imposed tiny effect on this parameter. The energy-saving effect of the prosed system was further discussed through simulation.

The indoor environmental quality and energy savings potential of room ventilation units compared to exhaust-only ventilation systems in France

Humidity-controlled mechanical exhaust ventilation (RH-MEV) has been widely used in France for over 35 years, demonstrating high durability and robustness. This exhaust-only ventilation strategy is widely used as an energy-saving measure, replacing constant mechanical exhaust ventilation (Constant-MEV) systems in residential buildings. It demonstrates energy savings due to the restricted airflows, but as a downside, the building’s indoor air quality (IAQ) often deteriorates. Moreover, it is impossible to recover heat with exhaust-only ventilation systems, which means that energy consumption for space heating is still quite significant and cold supply air temperatures are frequently introduced to the heated spaces. Room ventilation units (RVUs) with heat recovery represent an alternative ventilation solution allowing simple installation through the façade and providing fresh outdoor air and exhaust ventilation to each room. This study investigates these units’ energy saving potential and indoor environmental quality performance as an alternative solution to centralized exhaust-only ventilation systems. The dynamic simulations were performed for a reference residential building under various French climatic conditions for a heating season. The three ventilation strategies investigated were Constant-MEV, RH-MEV and room-based ventilation with RVUs. The results demonstrated 61–85% savings in space heating demand with the RVUs, compared to Constant-MEV under all climatic conditions. Compared to RH-MEV, the RVUs saved 44–75% energy for space heating while the CO2 concentration and relative humidity levels were decreased due to RVUs’ constant air exchange rate. In all cases, RVUs provided considerably higher supply air temperatures due to the implemented heat recovery, which can potentially improve indoor thermal comfort.

Association of Prenatal and Postnatal Exposures to Warm or Cold Air Temperatures With Lung Function in Young Infants

Little is known about long-term associations of early-life exposure to extreme temperatures with child health and lung function. To investigate the association of prenatal and postnatal heat or cold exposure with newborn lung function and identify windows of susceptibility. This population-based cohort study (SEPAGES) recruited pregnant women in France between July 8, 2014, and July 24, 2017. Data on temperature exposure, lung function, and covariates were available from 343 mother-child dyads. Data analysis was performed from January 1, 2021, to December 31, 2021. Mean, SD, minimum, and maximum temperatures at the mother-child's residence, estimated using a state-of-the-art spatiotemporally resolved model. Outcome measures were tidal breathing analysis and nitrogen multiple-breath washout test measured at 2 months of age. Adjusted associations between both long-term (35 gestational weeks and first 4 weeks after delivery) and short-term (7 days before lung function test) exposure to ambient temperature and newborn lung function were analyzed using distributed lag nonlinear models. A total of 343 mother-child pairs were included in the analyses (median [IQR] maternal age at conception, 32 [30.0-35.2] years; 183 [53%] male newborns). A total of 246 mothers and/or fathers (72%) held at least a master's degree. Among the 160 female newborns (47%), long-term heat exposure (95th vs 50th percentile of mean temperature) was associated with decreased functional residual capacity (-39.7 mL; 95% CI, -68.6 to -10.7 mL for 24 °C vs 12 °C at gestational weeks 20-35 and weeks 0-4 after delivery) and increased respiratory rate (28.0/min; 95% CI, 4.2-51.9/min for 24 °C vs 12 °C at gestational weeks 14-35 and weeks 0-1 after delivery). Long-term cold exposure (5th vs 50th percentile of mean temperature) was associated with lower functional residual capacity (-21.9 mL; 95% CI, -42.4 to -1.3 mL for 1 °C vs 12 °C at gestational weeks 15-29), lower tidal volume (-23.8 mL; 95% CI, -43.1 to -4.4 mL for 1 °C vs 12 °C at gestational weeks 14-35 and weeks 0-4 after delivery), and increased respiratory rate (45.5/min; 95% CI, 10.1-81.0/min for 1 °C vs 12 °C at gestational weeks 6-35 and weeks 0-1 after delivery) in female newborns as well. No consistent association was observed for male newborns or short-term exposure to cold or heat. In this cohort study, long-term heat and cold exposure from the second trimester until 4 weeks after birth was associated with newborn lung volumes, especially among female newborns.

Environmental and Hydrogeochemical Controls of Spicular Geyserite in Opaline Hot Spring Deposits

AbstractSiliceous spicules are micro‐laminated geyserite deposits, or micro‐stromatolites, found around high temperature hot‐springs and geysers, associated with intermittent splashes of water. Understanding conditions of formation of these structures will give insights of critical parameters involved in prebiotic environments and early life. We provide a new data set around two geysers from the El Tatio hydrothermal field, Atacama Desert, Chile, a modern analogue for habitable environments on early Earth and Mars. Small spicules (<5 mm diameter) dominate in the near vent areas, whereas larger spicules (>5 mm diameter) form complex columnar structures in the distal vent (>0.3 m distance from the vent). Hydrodynamics, eruption periodicity, and environmental conditions modulate the temperature and cooling patterns around vents. During geyser eruptions, the temperature of water reaching the ground decreases with the distance from the vent. Cooling is stronger during the evenings, due to strong winds and cold air temperature. Rapid water cooling drives supersaturation of amorphous silica, and therefore precipitation rates increase significantly with distance from the vent. Cooling also controls changes in the bacterial communities, from thin filaments <1 μm diameter predominating closer to the vent, to 1–2 μm diameter filaments in the distal vent. Changes in the silica precipitation rate and biota may control the growth of spicules and the transition to columns. Estimated precipitation rates of silica provide a first approximation of the longevity of these structures and the timing for the formation of internal laminations. Microlamination will form in year time‐scales closer to the vent, and weeks farther from the vent.

A data-driven subspace predictive control method for air-cooled data center thermal modelling and optimization

This paper presents a data-driven predictive control method for optimizing the energy consumption of air-cooled data centers with unknown system model parameters. First, based on the measurable data of the studied system, the subspace predictive control (SPC) method is adopted to improve the energy use efficiency of the data center by regulating the power allocation of the server racks and the supply temperature of cold air, while ensuring the safe operating environment of the electronic equipment. Furthermore, a reasonable event-triggered law is designed to solve the problem of the low computational efficiency of the conventional SPC method. The simulation results illustrate that the designed event-triggered law can improve the computational efficiency of the algorithm while maintaining the control performance of the algorithm, which verifies its application prospect in practice.

Urgent Notification Of High Temperature Induced Mortality of Patients with Diabetes and Hypertension in Hodeidah Governorate ،Yemen

Dear Editor: Many researches and studies have shown a relationship between high and cold air temperature and an increase in mortality, especially for patients with cardiovascular disease.[5,6] Recently, associations between ambient temperature and morbidity have also been reported,[7,8] even though these associations have not always been similar in magnitude to mortality,[8] and null findings have also been reported.[9] Also, while the association between temperature and cardiovascular mortality has been reported to be U- shaped in many studies,[10] the association with cardiovascular hospitalization was reported to be linear in the US [7]. Increased blood pressure (BP) is a risk factor for cardiovascular mortality [14,15] and for coronary heart disease and stroke morbidity [16,17]. Therefore changes in BP might also play a part in the development of cardiovascular events that are associated with changes in temperature. The mechanisms behind temperature-related cardiovascular mortality and morbidity are not fully established. As elevated BP is a known risk factor for cardiovascular disease and stroke events, BP can also be part of the mechanism leading to temperature-related deaths. Epidemiological studies have shown that cardiovascular diseases rank first among the causes of death in China and have become a major disease within the Chinese population [18]. The effects of type 1 and type 2 diabetes on the body's physiological response to thermal stress is a relatively new topic in research. Diabetes tends to place individuals at greater risk for heat- related illness during heat waves and physical activity due to an impaired capacity to dissipate heat. Specifically, individuals with diabetes have been reported to have lower skin blood flow and sweating responses during heat exposure and this can have important consequences on cardiovascular regulation and glycemic control. Those who are particularly vulnerable include individuals with poor glycemic control and who are affected by diabetes-related complications [19]. As a result of the war and the siege on Yemen, the deterioration of living and health conditions, the interruption of electricity, the suspension of salaries for six years, and the arrival of about 80% of the population of Al-Hodeidah Governorate to a level below the poverty line. We have monitored as a result of the high temperature, which reached 48 degrees Celsius in the city of Hodeidah, 28 deaths of people with diabetes and arterial hypertension were monitored for the period from 5-6-2022 to 25-6-2022. This catastrophe occurred due to the government power outage as a result of the war and the siege on Yemen and the inability of people to buy expensive commercial electricity. This is considered a humanitarian disaster that requires a serious stand by the government, international organizations and the international community to save Hodeidah residents from extreme heat and poverty by providing electricity and humanitarian aid to contribute to improving the health and living situation in the governorate and supporting hospitals with fuel by the World Health Organization.

Interannual Variations of Sea-ice Extent in the Okhotsk Sea – A Pan-Okhotsk Climate System Perspective

ABSTRACT This study investigated interannual variations in the late winter (January–March) sea-ice extent in the Okhotsk Sea (OS) and its relationship with the atmospheric circulation from 1971 to 2018. During heavy sea-ice years, negative air temperature anomalies are broadly discernable between the northeastern part of Eurasia and the North Pacific including the coastal polynyas adjacent to the northern and western coast of the OS. Cold air mass (CAM) genesis indicates the importance of the insulation effect of sea-ice in the persistent cold air temperatures in the OS. Light sea-ice years are marked by anomalous southeasterly winds and the resultant warm air advection associated with increases in extratropical cyclones. Southeasterly anomalies are associated with the weakening of the Aleutian low. Upper-tropospheric anticyclones dominating around the OS are closely connected with intensified convection in the vicinity of the South China Sea through propagation of a stationary Rossby wave relevant to La Niña-like warm sea surface temperature anomalies. The seasonal evolution of the CAM amount, sea ice in the Sea of Okhotsk, and the Aleutian low suggest that there may be chain feedback between them.

Relationship between cold season air temperature in the Baltic sea region and the Arctic sea ice extent

The variability of the atmospheric circulation described by the AO and NAO indices has a significant impact on the fluctuations of climate parameters in the Baltic Sea region. Many research show, that a decline in Arctic Sea ice extent increases the likelihood of negative phases of the Arctic Oscillation (AO) and North Atlantic Oscillation (NAO) in winter, and in the future could lead to more frequent relatively cold weather events during winter months in Baltic Sea region. This research is important for understanding possible teleconnections between Arctic Sea ice and atmospheric circulation (AO and NAO). In addition, this research helps to better understand the dynamics of Arctic Sea ice extent and Baltic Sea region air temperature, as well as AO and NAO circulation impact on the air temperature in the Baltic Sea region. A statistically significant decrease in the Arctic Sea ice extent and a statistically significant increase in the air temperature in the Baltic Sea region have been determined. The obtained results show that the expansion of the Arctic Sea ice in January-February with a delay of one month determines the AO and NAO values (correlation coefficients vary from 0.32 to 0.55). This means that if Arctic Sea ice decreases during winter months, AO and NAO indices are more likely to become negative as well. However, as the obtained correlations are not very strong, the results are insufficient to confirm the hypothesis that the Arctic Sea ice extent impacts negative AO and NAO phases likelihood and requires further research. A strong correlation between the Baltic Sea region air temperature and the values of AO/NAO indices has been established. The obtained results show that the Baltic Sea region air temperature variability in December-March is greatly influenced by the AO and NAO phases. Keywords: teleconnections, Arctic Sea ice, AO, NAO, Baltic Sea region, air temperature.

Modeling of high voltage induction motor cooling system using linear regression mathematical models.

Achieving reliable power efficiency from a high voltage induction motor (HVIM) is a great challenge, as the rigorous control strategy is susceptible to unexpected failure. External cooling is commonly used in an HVIM cooling system, and it is a vital part of the motor that is responsible for keeping the motor at the proper operating temperature. A malfunctioning cooling system component can cause motor overheating, which can destroy the motor and cause the entire plant to shut down. As a result, creating a dynamic model of the motor cooling system for quality performance, failure diagnosis, and prediction is critical. However, the external motor cooling system design in HVIM is limited and separately done in the past. With this issue in mind, this paper proposes a combined modeling approach to the HVIM cooling system which consists of integrating the electrical, thermal, and cooler model using the mathematical model for thermal performance improvement. Firstly, the development of an electrical model using an established mathematical model. Subsequently, the development of a thermal model using combined mathematical and linear regression models to produce motor temperature. Then, a modified cooler model is developed to provide cold air temperature for cooling monitoring. All validated models are integrated into a single model called the HVIM cooling system as the actual setup of the HVIM. Ultimately, the core of this modeling approach is integrating all models to accurately represent the actual signals of the motor cooler temperature. Then, the actual signals are used to validate the whole structure of the model using Mean Absolute Percentage Error (MAPE) and Root Mean Square Error (RMSE) analysis. The results demonstrate the high accuracy of the HVIM cooling system representation with less than 1% error tolerance based on the industrial plant experts. Thus, it will be helpful for future utilization in quality maintenance, fault identification and prediction study.