The role of snow interception in winter-time radiation processes of a coniferous sub-alpine forest

2009 ◽  
Vol 23 (17) ◽  
pp. 2498-2512 ◽  
Author(s):  
Manfred Stähli ◽  
Tobias Jonas ◽  
David Gustafsson
Keyword(s):  
Alpine Forest ◽  
Radiation Processes ◽  
Winter Time

scholarly journals On the violation of local thermodynamic equilibrium in the plasma jet of an argon arc two-jet plasmatron

2019 ◽  
Vol 85 (1II)) ◽  
pp. 145-150
Author(s):  
A. S. Cherevko ◽  
A. A. Morozova
Keyword(s):  
Energy Level ◽  
Equilibrium State ◽  
Thermodynamic Equilibrium ◽  
Local Thermodynamic Equilibrium ◽  
Plasma Jet ◽  
Saha Equation ◽  
Radiation Processes ◽  
Unconventional Method

The degree and nature of the violation of local thermodynamic equilibrium (LTE) in the analytical zone of a plasma jet generated by an argon arc two-jet plasmatron (TJP) was estimated using an unconventional method based on determination of the nonequilibrium parameterbiequal to the ratio of the experimentally determined actual population of the energy level (ni) of the element to the population of the same level calculated from the Saha equation (nis). Partial ionizing deviation of plasma under study from the equilibrium state takes place only when low-lying atomic levels are overpopulated. The distinct dependence ofbion the ionization potential of the considered element (e.g., Ca, Mg, and Be) is shown. The results were interpreted in the light of the increasing role of radiation processes upon excitation of spectra in the argon arc two-jet plasmatron.

scholarly journals Supplementary material to "Non Methane Hydrocarbons variability in Athens during winter-time: The role of traffic and heating"

2017 ◽  
Author(s):  
Anastasia Panopoulou ◽  
Eleni Liakakou ◽  
Valérie Gros ◽  
Stéphane Sauvage ◽  
Nadine Locoge ◽  
...  
Keyword(s):  
Supplementary Material ◽  
Winter Time

scholarly journals Persistence of upper stratospheric winter time tracer variability into the Arctic spring and summer

2016 ◽  
Author(s):  
David E. Siskind ◽  
Gerald E. Nedoluha ◽  
Fabrizio Sassi ◽  
Pingping Rong ◽  
Scott M. Bailey ◽  
...  
Keyword(s):  
The Arctic ◽  
Solar Occultation ◽  
Reservoir Species ◽  
Ozone Trends ◽  
Transport And Mixing ◽  
Using Data ◽  
Winter Time ◽  
Atomic Chlorine ◽  
Polar Ozone

Abstract. Using data from the Aeronomy of Ice in the Mesosphere (AIM) and the Aura satellites, we have categorized the interannual variability of winter and spring time upper stratospheric CH4. We further show the effects of this variability on the chemistry of the upper stratosphere throughout the following summer. Years with strong mesospheric descent followed by dynamically quiet springs, such as 2009, lead to the lowest summertime CH4. Years with relatively weak descent, but strong springtime planetary wave activity, such as 2011, have the highest summertime CH4. By sampling the Aura Microwave Limb Sounder according to the occultation pattern of the AIM Solar Occultation for Ice Experiment, we show that summertime upper stratospheric ClO almost perfectly anticorrelates with the CH4. This is consistent with the reaction of atomic chlorine with CH4 to form the reservoir species, HCl. The summertime ClO for years with strong, uninterrupted mesospheric descent is about 50 % greater than in years with strong horizontal transport and mixing of high CH4 air from lower latitudes. Small, but persistent effects on ozone are also seen such that between 1–2 hPa, ozone is about 4–5 % higher in summer for the years with the highest CH4 relative to the lowest. This is consistent with the role of the chlorine catalytic cycle on ozone. These dependencies may offer a means to monitor dynamical effects on the high latitude upper stratosphere using summertime ClO measurements as a proxy. Also, these chlorine controlled ozone decreases, which are seen to maximize after years with strong uninterrupted wintertime descent, represent a new mechanism by which mesosospheric descent can affect polar ozone. Finally, given that the effects on ozone appear to persist much of the rest of the year, the consideration of winter/spring dynamical variability may also be relevant in studies of ozone trends.

scholarly journals Simulating the role of acceleration and radiation processes in X-ray binaries.

2009 ◽  
Author(s):  
Renaud Belmont ◽  
Julien Malzac ◽  
Alexandre Marcowith
Keyword(s):  
X Ray ◽  
Radiation Processes ◽  
X Ray Binaries

Bedrock outcrops: A window for enhanced midwinter recharge

2021 ◽  
Author(s):  
Stephanie Wright ◽  
Kent Novakowski
Keyword(s):  
Moisture Content ◽  
Element Model ◽  
Frozen Soil ◽  
Climate Data ◽  
Soil Permeability ◽  
Time Step ◽  
Near Surface ◽  
Flow Transport ◽  
Winter Time

<p>As midwinter melt and rain-on-snow events become more common occurrences in the northern hemisphere under climate change, incorporating frozen processes when simulating winter-time recharge is increasingly necessary. The activation of infiltration pathways and recharge dynamics of shallow bedrock environments under frozen conditions has received relatively little attention. Over the 2019-2020 winter, hydrogeologic and cryospheric conditions of the surface, unsaturated, and saturated zones were monitored around a low-lying granitic outcrop in eastern Ontario, Canada. Interpretation of the data indicated that the soil-rock contact around outcrop margins was the key pathway enabling midwinter infiltration and recharge. To support this conceptual model and further explore the role of outcrops in enhancing midwinter bedrock recharge, a numerical investigation was undertaken. Measured climate data (hourly time step) was used to govern the surface energy and water balances of a 1D finite difference model that incorporates frozen processes. Measured snow depth, soil moisture content, and soil temperature profiles were simulated. Simulations with vertical infiltration alone could not account for observed increases in moisture content in the deepest soil horizons. This is attributed to additional lateral flow along the unfrozen soil-rock contact that bypasses the frozen soil layers. Preliminary results support the concept that bedrock outcrops provide a window for midwinter infiltration since repeated winter melts reduce frozen soil permeability and inhibits vertical infiltration until the ground thaws. Results from the surface/near-surface simulations are used to guide the development of a 2D finite element model that includes heat and flow transport and ground freeze-thaw. The impacts to bedrock recharge under different rainfall and snowmelt scenarios as well as various outcrop geometries are explored. Results from these numerical experiments help provide greater insight into the processes driving enhanced midwinter bedrock recharge under conditions of warmer winters.</p>

scholarly journals Conditions for the onset of the current filamentation instability in the laboratory

2018 ◽  
Vol 84 (3) ◽  
Author(s):  
N. Shukla ◽  
J. Vieira ◽  
P. Muggli ◽  
G. Sarri ◽  
R. Fonseca ◽  
...  
Keyword(s):  
Minor Role ◽  
Beam Emittance ◽  
Particle In Cell ◽  
Electron Positron ◽  
Astrophysical Objects ◽  
Filamentation Instability ◽  
Radiation Processes ◽  
A Minor ◽  
Stream Instability

The current filamentation instability (CFI) is capable of generating strong magnetic fields relevant to the explanation of radiation processes in astrophysical objects and leads to the onset of particle acceleration in collisionless shocks. Probing such extreme scenarios in the laboratory is still an open challenge. In this work, we investigate the possibility of using neutral$e^{-}~e^{+}$beams to explore the CFI with realistic parameters, by performing two-dimensional particle-in-cell simulations. We show that CFI can occur unless the rate at which the beam expands due to finite beam emittance is larger than the CFI growth rate and as long as the role of the competing electrostatic two-stream instability (TSI) is negligible. We also show that the longitudinal energy spread, typical of plasma-based accelerated electron–positron fireball beams, plays a minor role in the growth of CFI in these scenarios.

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