scholarly journals Rotational spectral modulation of cloudless atmospheres for L/T brown dwarfs and extrasolar giant planets

2020 ◽  
Vol 643 ◽  
pp. A23
Author(s):  
P. Tremblin ◽  
M. W. Phillips ◽  
A. Emery ◽  
I. Baraffe ◽  
B. W. P. Lew ◽  
...  
Keyword(s):  
Temperature Gradient ◽  
Spectral Characteristics ◽  
Brown Dwarfs ◽  
Temperature Fluctuations ◽  
Absorption Feature ◽  
Photometric Variability ◽  
Temperature Variations ◽  
Spectral Modulation ◽  
Spectral Flux ◽  
The Impact

Aims. The rotational spectral modulation (spectro-photometric variability) of brown dwarfs is usually interpreted as a sign indicating the presence of inhomogeneous cloud covers in the atmosphere. This paper is aimed at exploring the role of temperature fluctuations in these spectral modulations. These fluctuations could naturally arise in a convective atmosphere impacted by such diabatic processes as complex chemistry, namely, a mechanism recently proposed to explain the L/T transition: CO/CH4 radiative convection. Methods. After exploring the observed spectral-flux ratios between different objects along the cooling sequence, we used the 1D radiative-convective code ATMO, with ad hoc modifications of the temperature gradient, to model the rotational spectral modulation of 2MASS 1821, 2MASS 0136, and PSO 318.5-22. We also explored the impact of CH4 abundance fluctuations on the spectral modulation of 2MASS 0136. Results. The spectral-flux ratio of different objects along the cooling sequence and the rotational spectral modulation within individual objects at the L/T transition have similar characteristics. This strongly suggests that the main parameter varying along the cooling sequence, namely, temperature, might play a key role in the rotational spectral modulations at the L/T transition. Modeling the spectral bright-to-faint ratio of the modulation of 2MASS 1821, 2MASS 0136, and PSO 318.5-22 shows that most spectral characteristics can be reproduced by temperature variations alone. Furthermore, the approximately anti-correlated variability between different wavelengths can be easily interpreted as a change in the temperature gradient in the atmosphere, which is a consequence we expect from CO/CH4 radiative convection as an explanation of the L/T transition. The deviation from an exact anti-correlation could then be interpreted as a phase shift similar to the hot-spot shift at different bandpasses in the atmospheres of hot Jupiters. Conclusions. Our results suggest that the rotational spectral modulation from cloud opacity and temperature variations are degenerate. If the nearly anti-correlated signal between different wavelengths is, indeed, a strong sign of a change in the temperature gradient, the detection of direct cloud spectral signatures, for instance, the silicate absorption feature at 10 μm, would help to confirm the presence of clouds and their contribution to spectral modulations (which does not exclude temperature variations or other mechanisms that may also be at play). Future studies considering the differences in the spectral modulation of objects with and without the silicate absorption feature may give us some insight into how to distinguish cloud-opacity fluctuations from temperature fluctuations.

scholarly journals Impact of scale, nuclear PDF and temperature variations on the interpretation of medium-modified jet production data from the LHC

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
A. Andronic ◽  
J. Honermann ◽  
M. Klasen ◽  
C. Klein-Bösing ◽  
J. Salomon
Keyword(s):  
Distribution Functions ◽  
Production Data ◽  
Crossover Temperature ◽  
Parton Distribution Functions ◽  
Temperature Variations ◽  
Nuclear Modification Factor ◽  
Nuclear Modification ◽  
Modification Factor ◽  
The Impact ◽  
Jet Structure

Abstract In this paper we present a study of in-medium jet modifications performed with JEWEL and PYTHIA 6.4, focusing on the uncertainties related to variations of the perturbative scales and nuclear parton distribution functions (PDFs) and on the impact of the initial and crossover temperature variations of the medium. The simulations are compared to LHC data for the jet spectrum and the nuclear modification factor. We assess the interplay between the choice of nuclear PDFs and different medium parameters and study the impact of nuclear PDFs and the medium on the jet structure via the Lund plane.

Characteristics of Flame Bases for V-Gutters Stabilized Premixed Flames

2013 ◽  
Author(s):  
Fan Gong ◽  
Yong Huang
Keyword(s):  
Thermal Conductivity ◽  
Temperature Gradient ◽  
Equivalence Ratio ◽  
Premixed Flames ◽  
Flame Stabilization ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Heat Conducting ◽  
Inlet Velocity ◽  
The Impact

The objective of this work is to investigate the flame stabilization mechanism and the impact of the operating conditions on the characteristics of the steady, lean premixed flames. It’s well known that the flame base is very important to the existence of a flame, such as the flame after a V-gutter, which is typically used in ramjet and turbojet or turbofan afterburners and laboratory experiments. We performed two-dimensional simulations of turbulent premixed flames anchored downstream of the heat-conducting V-gutters in a confined passage for kerosene-air combustion. The flame bases are symmetrically located in the shear layers of the recirculation zone immediately after the V-gutter’s trailing edge. The effects of equivalence ratio of inlet mixture, inlet temperature, V-gutter’s thermal conductivity and inlet velocity on the flame base movements are investigated. When the equivalence ratio is raised, the flame base moves upstream slightly and the temperature gradient dT/dx near the flame base increases, so the flame base is strengthened. When the inlet temperature is raised, the flame base moves upstream very slightly, and near the flame base dT/dx increases and dT/dy decreases, so the flame base is strengthened. As the V-gutter’s thermal conductivity increases, the flame base moves downstream, and the temperature gradient dT/dx near the flame base decreases, so the flame base is weakened. When the inlet velocity is raised, the flame base moves upstream, and the convection heat loss with inlet mixture increases, so the flame base is weakened.

scholarly journals The Impact of Morphological Features on Summer Temperature Variations on the Example of Two Residential Neighborhoods in Ljubljana, Slovenia

2017 ◽  
Vol 9 (1) ◽  
pp. 122 ◽  
Author(s):  
Alenka Fikfak ◽  
Saja Kosanović ◽  
Miha Konjar ◽  
Janez Grom ◽  
Martina Zbašnik-Senegačnik
Keyword(s):  
Summer Temperature ◽  
Morphological Features ◽  
Temperature Variations ◽  
The Impact

scholarly journals Turbulence coherence and its impact on wind-farm power fluctuations

2018 ◽  
Vol 855 ◽  
pp. 1116-1129 ◽  
Author(s):  
Nicolas Tobin ◽  
Leonardo P. Chamorro
Keyword(s):  
Power Spectrum ◽  
Atmospheric Turbulence ◽  
Turbulent Diffusion ◽  
Wind Farm ◽  
Spectral Characteristics ◽  
Wind Farms ◽  
High Frequencies ◽  
Power Fluctuations ◽  
The Impact ◽  
Coherence Spectrum

Using a physics-based approach, we infer the impact of the coherence of atmospheric turbulence on the power fluctuations of wind farms. Application of the random-sweeping hypothesis reveals correlations characterized by advection and turbulent diffusion of coherent motions. Those contribute to local peaks and troughs in the power spectrum of the combined units at frequencies corresponding to the advection time between turbines, which diminish in magnitude at high frequencies. Experimental inspection supports the results from the random-sweeping hypothesis in predicting spectral characteristics, although the magnitude of the coherence spectrum appears to be over-predicted. This deviation is attributed to the presence of turbine wakes, and appears to be a function of the turbulence approaching the first turbine in a pair.

scholarly journals Thermal history and comfort in a Brazilian subtropical climate: a 'cool' addiction hypothesis

2016 ◽  
Vol 16 (1) ◽  
pp. 7-20 ◽  
Author(s):  
Renata De Vecchi ◽  
Christhina Maria Cândido ◽  
Roberto Lamberts
Keyword(s):  
Air Temperature ◽  
Indoor Air ◽  
Thermal History ◽  
Air Conditioning ◽  
Prolonged Exposure ◽  
Temperature Fluctuations ◽  
Subtropical Climate ◽  
Indoor Thermal Comfort ◽  
Air Speed ◽  
The Impact

Abstract Currently, there is a rising trend for commercial buildings to use air conditioning to provide indoor thermal comfort. This paper focuses on the impact of prolonged exposure to indoor air-conditioned environments on occupants' thermal acceptability and preferences in a mixed-mode building in Brazil. Questionnaires were administered while indoor microclimatic measurements were carried out (i.e., air temperature, radiant air temperature, air speed and humidity). Results suggest significant differences in occupants' thermal acceptability and cooling preferences based on thermal history; differences were found between groups based on different physical characteristics (i.e., different gender and body condition). The findings also indicated a significant potential to implement temperature fluctuations indoors when occupants are exposed to air conditioning environments in warm and humid climates.

scholarly journals Evapotranspiration of Indonesia Tropical Area

2019 ◽  
Vol 16 (3) ◽  
pp. 106-116
Author(s):  
Dyah Marganingrum ◽  
Heru Santoso
Keyword(s):  
Air Temperature ◽  
Potential Evapotranspiration ◽  
Small Islands ◽  
Climate Variables ◽  
Temperature Variations ◽  
Heterogeneous Landscape ◽  
Tropical Area ◽  
Climate Patterns ◽  
Region Data ◽  
The Impact

Indonesia is an archipelago country with a tropical climate. The region of Indonesia is quite large and located between two continents (Asia and Australia) and between two oceans (Indian and Pacific), making the territory of Indonesia has a unique climate pattern. One of the climate variables that quite important to be studied in this chapter is evapotranspiration. The Thornthwaite method was used to estimate potential evapotranspiration based on average air temperature. The relationships between evapotranspiration, precipitation, and elevation were then examined. Besides, temperature variations that affect climate patterns between monsoonal and equatorial regions were compared, between the mainland and small islands, and between mountain and coastal area. The impact of global warming was also examined on the climate and potential evapotranspiration of the Indonesian region. Data analysis showed that evapotranspiration correlates weakly with precipitation, and the contrary, the evapotranspiration correlates strongly with elevation, with correlation indices of 0.02 and 0.89, respectively. The study confirmed that air temperature is the primary controlling variable of the evapotranspiration in this very heterogeneous landscape. Under a global temperature increase of 1.5 °C above the pre-industrialized year (1765), the evapotranspiration is expected to increase in a range from 4.8 to 11.1%. In general, the excess of water to restore soil moisture in the future tends to decrease, i.e., drier.

scholarly journals Impacts of Late-Spring North Eurasian Soil Moisture Variation on Summer Rainfall Anomalies in Northern East Asia

2021 ◽  
Author(s):  
Yinghan Sang ◽  
Hong-Li Ren ◽  
Yi Deng ◽  
Xiaofeng Xu ◽  
Xueli Shi ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Temperature Gradient ◽  
East Asia ◽  
Summer Rainfall ◽  
Low Pressure ◽  
Late Spring ◽  
Boreal Summer ◽  
Pressure Center ◽  
North Eurasia ◽  
The Impact

Abstract This paper reports findings from a diagnostic and modeling analysis that investigates the impact of the late-spring soil moisture anomaly over North Eurasia on the boreal summer rainfall over northern East Asia (NEA). Soil moisture in May in the region from the Kara-Laptev Sea coasts to Central Siberian Plateau is found to be negatively correlated with the summer rainfall from Mongolia to Northeast China. The atmospheric circulation anomalies associated with the anomalously dry soil are characterized by a pressure dipole with the high-pressure center located over North Eurasia and the low-pressure center over NEA, where an anomalous lower-level moisture convergence occurs, favoring rainfall formation. Diagnoses and Modeling experiments demonstrate that the effect of the spring low soil moisture over North Eurasia may persist into the following summer through modulating local surface latent and sensible heat fluxes, increasing low-level air temperature at higher latitudes, and effectively reducing the meridional temperature gradient. The weakened temperature gradient could induce the decreased zonal wind and the generation of a low-pressure center over NEA, associated with a favorable condition of local synoptic activity. The above relationships and mechanisms are vice versa for the prior wetter soil and decreased NEA rainfall. These findings suggest that soil moisture anomalies over North Eurasia may act as a new precursor providing an additional predictability source for better predicting the summer rainfall in NEA.

scholarly journals Экспериментальное и теоретическое исследование осциллятора с соударениями

2020 ◽  
Vol 90 (10) ◽  
pp. 1672
Author(s):  
В.В. Нарожнов
Keyword(s):  
Theoretical Model ◽  
Equations Of Motion ◽  
Spectral Characteristics ◽  
Contact Theory ◽  
Hertz Contact ◽  
Mechanical Oscillator ◽  
Impact Oscillator ◽  
Fourier Filtering ◽  
Nonlinear Mechanical ◽  
The Impact

The results of a study of a nonlinear mechanical oscillator with elastic impacts are presented. The experiment was carried out using an electromechanical impact oscillator. The theoretical model is based on the equations of motion, taking into account the elastic force, which is calculated under the Hertz contact theory. It is shown that bifurcations and attractors of the “stable focus” and “limit cycle” types can occur for the impact oscillator. Fourier filtering was used to analyze the spectral characteristics of the signals.

Management and Handling of Commercial Crustaceans

2020 ◽  
pp. 496-524
Author(s):  
Adam Powell ◽  
Sara Barrento ◽  
Daniel M. Cowing
Keyword(s):  
Stress Responses ◽  
Public Perception ◽  
Temperature Fluctuations ◽  
First Century ◽  
Behavioral Analysis ◽  
Ethical Considerations ◽  
Point Of Sale ◽  
Immunological Stress ◽  
The Individual ◽  
The Impact

Current crustacean production (~14 Mt) and value (up to USD60 billion) is significant and likely to increase further during the twenty-first century. Satisfactory management and handling of live crustaceans are important to safeguard the value, security, safety, and sustainability of wild-caught and aquaculture-sourced fisheries and increasingly to foster improved welfare and public perception of both industries. Decapod crustaceans are frequently transported live and internationally over long distances and experience anthropogenic stressors from point of capture to point of sale. Physical handling, emersion in air, and temperature fluctuations are key examples of stressors, which elicit progressive behavioral, physiological, and immunological stress responses in crustaceans. Stress responses are initiated to return the individual to a state of homeostasis; if these fail, then physiological collapse, a loss of vitality, and death will likely occur. There are several ways to mitigate the impact of stressors, reduce associated stress responses, and thus maintain quantity (survival, weight) and quality (vitality, sensorial perception) of live crustaceans. These include improved fishing techniques, better handling and operating procedures, and the introduction of proven equipment and facilities during the supply chain. The action of stressors and the effectiveness of potential mitigating strategies have been studied intensively via behavioral analysis and hemolymph sampling to ascertain changes in metabolites and the immune system. Finally, improved handling and management include global and ethical considerations, supported by relevant research, which may be achieved by adopting best practices and standards and by ensuring welfare and disease regulations.

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