Intermittency Effects Research Articles

Modeling and optimization of a novel Oxy-fuel/Solar/Wind/Battery power generation system

• The optimized combined system can perfectly meet the needs of electricity grid. • The cold energy of LNG is used to condense CO 2 and nearly zero CO 2 emissions is achieved. • The optimal model is obtained by considering various wind-solar ratios and scales of battery storage capacity. • The LCOE of the combined system is reduced by 3% to 6% with the employment of solar-wind energy. It is proposed and built a novel oxy-fuel/solar/wind/battery power generation system. It consists of a solar-wind renewable system (SWRS) with battery bank and a liquefied natural gas-fueled oxy-fuel combined cycle (OFCC). The work is unique in that it uses SWRS to power OFCC’s main energy-consuming equipment, such as the recycled CO 2 compressor (RCC) and air separation unit (ASU). SWRS power is consumed locally, avoiding the negative effects of SWRS intermittency and variability on the electricity grid. CO 2 is compressed, cooled and then condensed by evaporating the cold LNG. MATLAB/Simulink and Aspen Plus were used to create the SWRS and OFCC, respectively. In order to find the optimal model of the combined system in terms of economic factors, various wind-solar ratios, scales of SWRS and OFCC, and battery storage capacity have been considered and combined. The results show that the optimized combined system can perfectly meet the needs of the electricity grid while having a high renewable energy utilization efficiency, no negative impact on power grid stability, low power generation costs, and low CO 2 emissions. This work will serve as a guide for the combined power system’s power supply planning.

Species-Specific Abundance Response of Montane Stream Fishes to Drought-Induced Variation in Streamflow

Climate change projections in the western United States suggest that snowpack levels and winter precipitation will decline, but mean annual precipitation levels will remain unchanged. Mountain streams that once saw a constant source of water from snowpack will begin to see large seasonal variation in flow. Increased stream intermittency will create significant conservation risks for fish species; however, few studies have examined the abundance responses of fish in high elevation streams to the shift from perennial to intermittent flow. To determine the effects of stream intermittency on fish abundance in a montane stream, we quantified changes in abundance for five species over a five-year period that exhibited extreme variation in streamflow. Responses varied by species and life stage, suggesting that the shift from perennial to intermittent flow will cause significant declines in abundance for some species. Northern leatherside chub may experience large decreases in their range as the availability of perennial streams decreases. The study of drought effects on fish abundance will be crucial to the conservation of biodiversity in montane regions of the world.

Effects of intermittent flow on biofilms are driven by stream characteristics rather than history of intermittency

Intermittent streams are found all over the world, however most studies focus on intermittency in hot, arid climates. As flow intermittency is expected to increase with climate change, it is important to understand how stream biofilms in temperate regions respond to these changing conditions. In this study, 20 different streams from around Austria were sampled under flowing and non-flowing conditions to evaluate the effect of intermittency on temperate stream biofilms. These streams encompassed two distinct stream types: fine-grained with high agricultural land use and coarse sediments from relatively pristine areas. Half of these streams were historically intermittent and half historically perennial. Samples were taken from all streams during the spring and fall, when the intermittent streams were flowing and dry, respectively. Subsets of the sediments were subjected to controlled drying to evaluate the effects of history of intermittency on the biofilms. Samples were analyzed for respiration, extracellular enzyme activities, and extracellular polysaccharides in the wet and dry sediments from the field, as well as the lab-dried sediments. This study found that lab-dried perennial sediments showed similar responses to the intermittent sediments, indicating that history of intermittency does not affect biofilm response to drought. This study also found that the effects of grain size, seasonal growth, and nutrient levels have a larger impact on the biofilms than moisture content and history of intermittency.

The Link between Obstructive Sleep Apnea and Neurocognitive Impairment: An Official American Thoracic Society Workshop Report.

There is emerging evidence that obstructive sleep apnea (OSA) is a risk factor for preclinical Alzheimer’s disease (AD). An American Thoracic Society workshop was convened that included clinicians, basic scientists, and epidemiologists with expertise in OSA, cognition, and dementia, with the overall objectives of summarizing the state of knowledge in the field, identifying important research gaps, and identifying potential directions for future research. Although currently available cognitive screening tests may allow for identification of cognitive impairment in patients with OSA, they should be interpreted with caution. Neuroimaging in OSA can provide surrogate measures of disease chronicity, but it has methodological limitations. Most data on the impact of OSA treatment on cognition are for continuous positive airway pressure (CPAP), with limited data for other treatments. The cognitive domains improving with CPAP show considerable heterogeneity across studies. OSA can negatively influence risk, manifestations, and possibly progression of AD and other forms of dementia. Sleep-dependent memory tasks need greater incorporation into OSA testing, with better delineation of sleep fragmentation versus intermittent hypoxia effects. Plasma biomarkers may prove to be sensitive, feasible, and scalable biomarkers for use in clinical trials. There is strong biological plausibility, but insufficient data, to prove bidirectional causality of the associations between OSA and aging pathology. Engaging, recruiting, and retaining diverse populations in health care and research may help to decrease racial and ethnic disparities in OSA and AD. Key recommendations from the workshop include research aimed at underlying mechanisms; longer-term longitudinal studies with objective assessment of OSA, sensitive cognitive markers, and sleep-dependent cognitive tasks; and pragmatic study designs for interventional studies that control for other factors that may impact cognitive outcomes and use novel biomarkers.

Short-term solar irradiance forecasting based on a novel Bayesian optimized deep Long Short-Term Memory neural network

Accurate forecasting is indispensable for improving solar renewables integration and minimizing the effects of solar energy's intermittency. Existing research on time series solar forecasting confronts challenges such as determining the accurate hyperparameters and flexibility in considering meteorological parameters. This study proposes a novel deep learning model, namely an optimized stacked Bi-directional Long Short-Term Memory(BiLSTM)/ Long Short-Term Memory(LSTM) model to forecast univariate and multivariate hourly time series data by integrating stacked LSTM layers, drop out architecture, and LSTM based model. The performance of the model is enhanced by Bayesian optimization with the tuning of six relevant hyperparameters. To evaluate the model, standard Global Horizontal Irradiance (GHI) and observed Plane of Array (POA) irradiance with meteorological real-world solar data from Sweihan Photovoltaic Independent Power project in Abu Dhabi, UAE, and NREL solar data for year-round data are forecasted. Furthermore, the performance of the proposed algorithm is also evaluated under weather uncertainty for different climate types. The forecasting accuracy is evaluated based on various performance metrics and it is observed that the proposed model offered the best R2 values, 0.99 for univariate as well as multivariate models using GHI data and 0.97 using POA data. The findings suggest that the proposed model is a reliable technique for solar prediction due to its comparable performance with both GHI and POA in terms of accuracy.

Levelized Full System Costs of Electricity

Different electricity generating technologies are often compared using the Levelized Costs of Electricity (LCOE), which summarize different ratios of fixed to variable costs into a single cost metric. They have been criticized for ignoring the effects of intermittency and non-dispatchability. This paper introduces the Levelized Full System Costs of Electricity (LFSCOE), a novel cost evaluation metric that compares the costs of serving the entire market using just one source plus storage. Like LCOE, and in contrast to alternatives such as System LCOE, LFSCOE condense the cost for each technology into one number per market. The paper calculates LFSCOE for several technologies using data from two different markets. It then discusses some refinements, including the LFSCOE-95 metric that require each technology to supply only 95% of total demand.

Dose-dependent phosphorylation of endogenous Tau by intermittent hypoxia in rat brain.

Intermittent hypoxia, or intermittent low oxygen interspersed with normal oxygen levels, has differential effects that depend on the "dose" of hypoxic episodes (duration, severity, number per day, and number of days). Whereas "low dose" daily acute intermittent hypoxia (dAIH) elicits neuroprotection and neuroplasticity, "high dose" chronic intermittent hypoxia (CIH) similar to that experienced during sleep apnea elicits neuropathology. Sleep apnea is comorbid in >50% of patients with Alzheimer's disease-a progressive, neurodegenerative disease associated with brain amyloid and chronic Tau dysregulation (pathology). Although patients with sleep apnea present with higher Tau levels, it is unknown if sleep apnea through attendant CIH contributes to onset of Tau pathology. We hypothesized CIH characteristic of moderate sleep apnea would increase dysregulation of phosphorylated Tau (phospho-Tau) species in Sprague-Dawley rat hippocampus and prefrontal cortex. Conversely, we hypothesized that dAIH, a promising neurotherapeutic, has minimal impact on Tau phosphorylation. We report a dose-dependent intermittent hypoxia effect, with region-specific increases in 1) phospho-Tau species associated with human Tauopathies in the soluble form and 2) accumulated phospho-Tau in the insoluble fraction. The latter observation was particularly evident with higher CIH intensities. This important and novel finding is consistent with the idea that sleep apnea and attendant CIH have the potential to accelerate the progression of Alzheimer's disease and/or other Tauopathies.NEW & NOTEWORTHY Sleep apnea is highly prevalent in people with Alzheimer's disease, suggesting the potential to accelerate disease onset and/or progression. These studies demonstrate that intermittent hypoxia (IH) induces dose-dependent, region-specific Tau phosphorylation, and are the first to indicate that higher IH "doses" elicit both endogenous, (rat) Tau hyperphosphorylation and accumulation in the hippocampus. These findings are essential for development and implementation of new treatment strategies that minimize sleep apnea and its adverse impact on neurodegenerative diseases.

Impact of circadian time of dosing on cardiomyocyte-autonomous effects of glucocorticoids

ObjectiveMitochondrial capacity is critical to adapt the high energy demand of the heart to circadian oscillations and diseased states. Glucocorticoids regulate the circadian cycle of energy metabolism, but little is known about how circadian timing of exogenous glucocorticoid dosing directly regulates heart metabolism through cardiomyocyte-autonomous mechanisms. While chronic once-daily intake of glucocorticoids promotes metabolic stress and heart failure, we recently discovered that intermittent once-weekly dosing of exogenous glucocorticoids promoted muscle metabolism in normal and obese skeletal muscle. However, the effects of glucocorticoid intermittence on heart metabolism and heart failure remain unknown. Here we investigated the extent to which circadian time of dosing regulates the effects of the glucocorticoid prednisone in heart metabolism and function in conditions of single pulse or chronic intermittent dosing. Methods and ResultsIn WT mice, we found that prednisone improved cardiac content of NAD+ and ATP with light-phase dosing (ZT0), while the effects were blocked by dark-phase dosing (ZT12). The drug effects on mitochondrial function were cardiomyocyte-autonomous, as shown by inducible cardiomyocyte-restricted glucocorticoid receptor (GR) ablation, and depended on an intact cardiomyocyte clock, as shown by inducible cardiomyocyte-restricted ablation of Brain and Muscle ARNT-like 1 (BMAL1). Conjugating time-of-dosing with chronic intermittence, we found that once-weekly prednisone improved metabolism and function in heart after myocardial injury dependent on circadian time of intake, i.e. with light-phase but not dark-phase dosing. ConclusionsOur study identifies cardiac-autonomous mechanisms through which circadian-specific intermittent dosing reconverts glucocorticoid drugs to metabolic boosters for the heart.

Turbulence Hierarchy and Multifractality in the Integer Quantum Hall Transition.

We offer a new perspective on the problem of characterizing mesoscopic fluctuations in the interplateau regions of the integer quantum Hall transition. We found that longitudinal and transverse conductance fluctuations, generated by varying the external magnetic field within a microscopic model, are multifractal and lead to distributions of conductance increments (magnetoconductance) with heavy tails (intermittency) and signatures of a hierarchical structure (cascade) in the corresponding stochastic process, akin to Kolmogorov's theory of fluid turbulence. We confirm this picture by interpreting the stochastic process of the conductance increments in the framework of H theory, which is a continuous-time stochastic approach that incorporates the basic features of Kolmogorov's theory. The multifractal analysis of the conductance "time series," combined with the H-theory formalism, provides strong support for the overall characterization of mesoscopic fluctuations in the quantum Hall transition as a multifractal stochastic phenomenon with multiscale hierarchy, intermittency, and cascade effects.

Predicting jet ignitability using a PDF transport model

For the first time the probability of ignition is calculated successfully using a PDF transport model. At present the model is only accurate where jet intermittency effects are small, away from the jet boundary. A conclusion of this investigation is the probability of ignition field is sensitive to the micro-mixing model used. In this article, four micro-mixing models are implemented and the modified Curl model demonstrated to be the most accurate for the jet ignitability experiments simulated.

A commentary on: Efficacy and time course of acute intermittent hypoxia effects in the upper extremities of people with cervical spinal cord injury

A commentary on: Efficacy and time course of acute intermittent hypoxia effects in the upper extremities of people with cervical spinal cord injury

Bolgiano–Obukhov scaling in two-dimensional isotropic convection

The existence of Bolgiano–Obukhov (BO) scaling in Rayleigh–Bénard convection (RBC) has long been speculated. However, due to the inhomogeneity and anisotropy of the flow, and the lack of clear scale separation, no conclusive evidence has been found. To avoid these non-ideal factors, we construct an idealized isotropic convection system by introducing an additional horizontal buoyancy field to RBC in a doubly periodic domain. We focus on the two-dimensional case so that its upscale kinetic energy flux can enable a long inertial range for detecting the BO scaling. Through direct numerical simulations of this system, we justify the existence of BO scaling using second- and third-order structure functions, which are in good agreement with our theoretically obtained scaling relations from the Kármán–Howarth–Monin equations. These theoretical and numerical results provide direct support for the conjecture that the existence of the BO scaling in RBC is associated with the inverse kinetic energy cascade. For higher-order structure functions, we found strong intermittent effects in the buoyancy field, but not in the velocity. By comparing the present system with the canonical anisotropic RBC in a periodic domain, the effects of anisotropy on the scaling properties are elucidated.

Solar thermochemical fuels: Present status and future prospects

The production of syngas by simultaneous splitting of direct-air-captured CO2 and H2O via a solar thermochemical redox cycle is a competitive alternative to electrolysis-based pathways. Isothermal or near-isothermal operation using high-entropy oxides that are readily available, robust, and flowable is recommended on the basis of practical considerations and improved performance, both mechanical and thermodynamic. Ongoing research efforts should direct attention toward devising compatible thermal energy storage technologies and/or incorporating hybrid solar-electric heating to (1) mitigate the effects of solar intermittency and (2) provide a continuous feed for downstream gas-to-liquid processing. The path forward involves funding the development and characterization of fully integrated laboratory systems.

Unsteady response of performance for centrifugal compressor under pulsating backpressure condition

The intermittent throttling effects of intake valves of internal combustion engine generate pulsations at compressor exit, which has a great impact on the compressor performance. In this paper, the influence of pulsation on the compressor is studied via unsteady 3-D numerical method validated by experiments. Results show that the cycle-average efficiency is lower than the quasi-steady value. The impeller is confirmed as the main reason for efficiency deterioration according to entropy generation analysis, due to the difference of secondary flow patterns. The tip leakage vortex at impeller inlet is alleviated at pulsating condition because of inertia effect, resulting in a lower velocity thus higher incidence angle near splitter. The stronger separation and tip leakage flow at splitter leading edge lead to the wake with higher losses. Moreover, the circumferential distortion at the impeller exit is found to be weaker under pulsation. It is caused by two reasons: the flow field, which is closer to the quasi-steady one with a higher mass flow rate due to the lagging effect; the additional pressure gradient in volute caused by propagation of pulse. It results in an evener flow field and improves impeller stability. Specifically, the recirculation region at impeller inlet shrinks 5% under pulsation.

Effects of ferric citrate and intravenous iron sucrose on markers of mineral, bone, and iron homeostasis in a rat model of CKD-MBD.

Anemia and chronic kidney disease-mineral and bone disorder (CKD-MBD) are common and begin early in CKD. Limited studies have concurrently compared the effects of ferric citrate (FC) versus intravenous (IV) iron on CKD-MBD and iron homeostasis in moderate CKD. We tested the effects of 10 weeks of 2% FC versus IV iron sucrose in rats with moderate CKD (Cy/+ male rat) and untreated normal (NL) littermates. Outcomes included a comprehensive assessment of CKD-MBD, iron homeostasis and oxidative stress. CKD rats had azotemia, elevated phosphorus, parathyroid hormone and fibroblast growth factor-23 (FGF23). Compared with untreated CKD rats, treatment with FC led to lower plasma phosphorus, intact FGF23 and a trend (P=0.07) toward lower C-terminal FGF23. FC and IV iron equally reduced aorta and heart calcifications to levels similar to NL animals. Compared with NL animals, CKD animals had higher bone turnover, lower trabecular volume and no difference in mineralization; these were unaffected by either iron treatment. Rats treated with IV iron had cortical and bone mechanical properties similar to NL animals. FC increased the transferrin saturation rate compared with untreated CKD and NL rats. Neither iron treatment increased oxidative stress above that of untreated CKD. Oral FC improved phosphorus homeostasis, some iron-related parameters and the production and cleavage of FGF23. The intermittent effect of low-dose IV iron sucrose on cardiovascular calcification and bone should be further explored in moderate-advanced CKD.

Quality of Life in Menopausal Women with Dental Restorations and Implants

Aim: This multicenter study examined the relationship, possible interactions, and intermittent effects that dental implants and prostheses can have on menopausal women’s quality of life as well as provided information regarding the possible side effects of therapeutic regimens on menopause and osteoporosis or osteopenia. Materials and Methods: Questionnaires consisted of selected quality of life questions based on specific and additional medical and dental (mainly prosthodontic) questions, which were administered to 100 Greek menopausal/post-menopausal women (Age: Mean Value=63,62 years old) with osteopenia or with or without osteoporosis, with dental implants and implant restorations, or conventional prosthetic restorations visiting two University Hospitals. Menopausal/post-menopausal status was judged on the basis of either secondary, definitive amenorrhoea or based on follicular stimulation hormone ​​(FSH) values, estradiol, and clinical risk factors. Results: Participants had a statistically significantly better “functional” and “psychological” feeling after prosthodontic rehabilitation with and without implants. Three out of four reported that their dentist informed them of the possible implant problems that might arise from osteoporosis and its treatment (medications). Moreover, osteopenia was found to be associated with a very lower problem percentage. The bisphosphonate treatment had the highest rate (80%) of reported implant problems than non-bisphosphonate treatment (30%). The hormone replacement therapy (HRT) for menopause was reported to be more associated with problems in implant placement (19%) than in those without treatment (27.3%). Conclusion: The questionnaires revealed a significant improvement concerning women’s life quality and well-documented information about the problems their dental implants and restorations may cause in association with menopause and/or osteoporosis.

Microstructure evolution and very-high-cycle fatigue crack initiation behavior of a structural steel with two loading intermittence modes

The effects of fatigue loading intermittence on specimens manufactured on two locations in a railway wheel were experimentally investigated: (i) in the rim and (ii) web plate (WP). The specimens with 50 ms pause presented a substantially lower fatigue strength in comparison to those with 300 ms pause. The microstructure evolution indicated the occurrence of martensitic transformation and discontinuous dynamic recrystallization. Rim and WP show respective preference for crack initiation, i.e. inclusion or matrix. Slip on {110} and {112} plane families prevails in ferrite. The pearlitic lamellae aligned at 45° relative to applied tension indicates that crack initiates and propagates along the ferrite-cementite interface due to stress concentration as a result of inhomogeneous deformation.

Tuberculosis treatment intermittency in the continuation phase and mortality in HIV-positive persons receiving antiretroviral therapy

BackgroundSome tuberculosis (TB) treatment guidelines recommend daily TB treatment in both the intensive and continuation phases of treatment in HIV-positive persons to decrease the risk of relapse and acquired drug resistance. However, guidelines vary across countries, and treatment is given 7, 5, 3, or 2 days/week. The effect of TB treatment intermittency in the continuation phase on mortality in HIV-positive persons on antiretroviral therapy (ART), is not well-described.MethodsWe conducted an observational cohort study among HIV-positive adults treated for TB between 2000 and 2018 and after enrollment into the Caribbean, Central, and South America network for HIV epidemiology (CCASAnet; Brazil, Chile, Haiti, Honduras, Mexico and Peru). All received standard TB therapy (2-month initiation phase of daily isoniazid, rifampin or rifabutin, pyrazinamide ± ethambutol) and continuation phase of isoniazid and rifampin or rifabutin, administered concomitantly with ART. Known timing of ART and TB treatment were also inclusion criteria. Kaplan–Meier and Cox proportional hazards methods compared time to death between groups. Missing model covariates were imputed via multiple imputation.Results2303 patients met inclusion criteria: 2003(87%) received TB treatment 5–7 days/week and 300(13%) 2–3 days/week in the continuation phase. Intermittency varied by site: 100% of patients from Brazil and Haiti received continuation phase treatment 5–7 days/week, followed by Honduras (91%), Peru (42%), Mexico (7%), and Chile (0%). The crude risk of death was lower among those receiving treatment 5–7 vs. 2–3 days/week (HR = 0.68; 95% CI = 0.51—0.91; P = 0.008). After adjusting for age, sex, CD4, ART use at TB diagnosis, site of TB disease (pulmonary vs. extrapulmonary), and year of TB diagnosis, mortality risk was lower, but not significantly, among those treated 5–7 days/week vs. 2–3 days/week (HR 0.75, 95%CI 0.55–1.01; P = 0.06). After also stratifying by study site, there was no longer a protective effect (HR 1.42, 95%CI 0.83–2.45; P = 0.20).ConclusionsTB treatment 5–7 days/week was associated with a marginally decreased risk of death compared to TB treatment 2–3 days/week in the continuation phase in multivariable, unstratified analyses. However, little variation in TB treatment intermittency within country meant the results could have been driven by other differences between study sites. Therefore, randomized trials are needed, especially in heterogenous regions such as Latin America.

Intermittent aeration to regulate microbial activities in membrane-aerated biofilm reactors: Energy-efficient nitrogen removal and low nitrous oxide emission

Membrane-aerated biofilm reactors (MABR) are being applied for autotrophic nitrogen removal, yet control of nitrogen turnover remains challenging in MABR counter-diffusion biofilms. In this study, we regulated microbial activities in two lab-scale MABRs by providing continuous versus intermittent aeration. Nitrogen consumption by different functional microbial groups was estimated from bulk measurements via a mass balance approach. Nitrite-oxidizing bacteria (NOB) proliferated under continuous aeration while they were significantly suppressed under intermittent aeration, and NOB suppression activated anaerobic ammonium oxidation. Nitritation performance in the MABR was studied through long-term bulk measurements and in situ biofilm microprofiles of dissolved oxygen (DO) and pH. During intermittent aeration pH effects rather than DO effects determined nitritation success, especially ammonia speciation, which serves as substrate and inhibitor in nitrification processes. Biofilm transition phases were monitored upon aeration switches. Canonical correspondence analysis suggested that the relative transition after anoxia and aeration intermittency were less decisive for biofilm performance than the relative aeration duration. Heterotrophic bacteria displayed minor denitrification rates with aeration control, but contributed to mitigation of nitrous oxide (N2O) emissions. N2O production hotspots were identified at the top of the anoxic biofilm zone under continuous aeration. Instead, under intermittent aeration an anoxic N2O reduction zone was established. Our observations support intermittent aeration control of MABRs as a simple strategy for energy-efficient nitrogen removal with low N2O emission. .

The Detection, Genesis, and Modeling of Turbulence Intermittency in the Stable Atmospheric Surface Layer

Abstract Intermittent transitions between turbulent and nonturbulent states are ubiquitous in the stable atmospheric surface layer (ASL). Data from two field experiments in Utqiaġvik, Alaska, and from direct numerical simulations are used to probe these state transitions so as to (i) identify statistical metrics for the detection of intermittency, (ii) probe the physical origin of turbulent bursts, and (iii) quantify intermittency effects on overall fluxes and their representation in closure models. The analyses reveal three turbulence regimes, two of which correspond to weakly turbulent periods accompanied by intermittent behavior (regime 1: intermittent; regime 2: transitional), while the third is associated with a fully turbulent flow. Based on time series of the turbulence kinetic energy (TKE), two nondimensional parameters are proposed to diagnostically categorize the ASL state into these regimes; the first characterizes the weakest turbulence state, while the second describes the range of turbulence variability. The origins of intermittent turbulence activity are then investigated based on the TKE budget over the identified bursts. While the quantitative results depend on the height, the analyses indicate that these bursts are predominantly advected by the mean flow, produced locally by mechanical shear, or lofted from lower levels by turbulent ejections. Finally, a new flux model is proposed using the vertical velocity variance in combination with different mixing length scales. The model provides improved representation (correlation coefficients with observations of 0.61 for sensible heat and 0.94 for momentum) compared to Monin–Obukhov similarity (correlation coefficients of 0.0047 for sensible heat and 0.49 for momentum), thus opening new pathways for improved parameterizations in coarse atmospheric models. Significance Statement Airflow in the lowest layer of the atmosphere is often modulated by a strong gradient of temperature when the surface is much cooler than the air. Such a regime results in weak turbulence and mixing, and is ubiquitous during nighttime and in polar regions. Understanding and modeling atmospheric flow and turbulence under such conditions are further complicated by “turbulence intermittency,” which manifests as periods of strong turbulent activity interspersed in a more quiescent airflow. The turbulent periods dominate the air–surface exchanges even when they occur over a small fraction of the time. This paper develops approaches to detect and classify such intermittent regimes, examines how the turbulent bursts are generated and advected, and offers guidance on representing such regimes in geophysical models. The findings have the potential to advance weather forecasting and climate modeling, particularly in the all-important polar regions.