A New Concept of Convective Mixing Pattern

A model of internal structure and evolution of the peculiar binary system v Sgr is presented. The model corresponds well to the observed chemical composition of the main component atmosphere (10-4 H, 0.844 He, 0.013 C, 0.042 N by mass). It is supposed that about 5 million years ago the main component passed the stage of hydrogen nuclear burning in the shell over the helium core where the helium-carbon reactions took place. Because of convective mixing, the synthesized carbon diffusing into the hydrogen burning zone was catalyzing the reactions of the CN - cycle. This has resulted in anomalies in the chemical composition, particularly high nitrogen abundance in the layer observed now as the atmosphere of the main component since external layers were thrown off during the evolution. Following the calculated results, the quantitative restrictions of temperature and density in the layers and values of mixing parameters are obtained. It is shown that the best agreement with observations exists if the mass of the matter penetrating from the zone of helium-carbon reactions into the helium layer is 0.25 of the helium-carbon core mass. Moreover, the ratio of mass concentration He/C in this matter should equal 2, and the mass share diffusing into the layer of hydrogen burning should be in the range 0.25 - 0.30 of the layer mass.

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Stability of two-layer systems with respect to convective mixing

Fluid Dynamics ◽

10.1007/bf01090564 ◽

1983 ◽

Vol 18 (3) ◽

pp. 434-438

Author(s):

I. B. Simanovskii

Keyword(s):

Convective Mixing

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Moist-soil response to brief intense radiative heating

Proceedings of the Royal Society of London. Series A: Mathematical and Physical Sciences ◽

10.1098/rspa.1992.0166 ◽

1992 ◽

Vol 439 (1907) ◽

pp. 531-552

Keyword(s):

Interstitial Water ◽

Early Response ◽

Radiative Heating ◽

Heated Layer ◽

Moist Soil ◽

Soil Response ◽

Average Temperature ◽

Convective Mixing ◽

The Stability ◽

Interstitial Air

We consider the early response of a layer of moist soil to a short intense radiative pulse, of duration on the order of one second, and of intensity on the order of 400 J cm -2 s -1 . In the initial stages of the phenomenon, evaporated interstitial water, interstitial air, and possibly soil are lofted into a layer that underlies a somewhat displaced slab of the atmosphere. Then, depending on the stability of that configuration, convective mixing may ensue and may produce, during the next few seconds, a thicker and cooler hot layer. We quantify reliably the thickness and temperature distribution during the radiative phase of the event, and we also estimate much more crudely the thickness and the average temperature at limited later times. With even less detail we quantify the importance of ice, snow or vegetation on the structure of the heated layer.

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Aerosol measurements at the Gual Pahari EUCAARI station: preliminary results from in-situ measurements

Atmospheric Chemistry and Physics ◽

10.5194/acp-10-7241-2010 ◽

2010 ◽

Vol 10 (15) ◽

pp. 7241-7252 ◽

Cited By ~ 41

Author(s):

A.-P. Hyvärinen ◽

H. Lihavainen ◽

M. Komppula ◽

T. S. Panwar ◽

V. P. Sharma ◽

...

Keyword(s):

Rainy Season ◽

In Situ Measurements ◽

Aerosol Size Distribution ◽

Finnish Meteorological Institute ◽

Convective Mixing ◽

Average Fraction ◽

Mode Size ◽

First Time ◽

Pm10 Mass

Abstract. The Finnish Meteorological Institute (FMI), together with The Energy and Resources Institute of India (TERI), contributed to the European Integrated project on Aerosol Cloud Climate and Air Quality Interactions, EUCAARI, by conducting aerosol measurements in Gual Pahari, India, from December 2007 to January 2010. This paper describes the station setup in detail for the first time and provides results from the aerosol in-situ measurements, which include PM and BCe masses, aerosol size distribution from 4 nm to 10 μm, and the scattering and absorption coefficients. The seasonal variation of the aerosol characteristics was very distinct in Gual Pahari. The highest concentrations were observed during the winter and the lowest during the rainy season. The average PM10 concentration (at STP conditions) was 216 μgm−3 and the average PM2.5 concentration was 126 μgm−3. A high percentage (4–9%) of the PM10 mass consisted of BCe which indicates anthropogenic influence. The percentage of BCe was higher during the winter; and according to the diurnal pattern of the BCe fraction, the peak occurred during active traffic hours. Another important source of aerosol particles in the area was new particle formation. The nucleated particles grew rapidly reaching the Aitken and accumulation mode size, thus contributing considerably to the aerosol load. The rainy season decreased the average fraction of particle mass in the PM2.5 size range, i.e. of secondary origin. The other mechanism decreasing the surface concentrations was based on convective mixing and boundary layer evolution. This diluted the aerosol when sun radiation and the temperature was high, i.e. especially during the pre-monsoon day time. The lighter and smaller particles were more effectively diluted.

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Lithium in Capella and Convective Mixing in F and G Giants

Nature ◽

10.1038/204367a0 ◽

1964 ◽

Vol 204 (4956) ◽

pp. 367-368 ◽

Cited By ~ 5

Author(s):

GEORGE WALLERSTEIN

Keyword(s):

Convective Mixing

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Convective and diffusive gas transport in canine intrapulmonary airways

Journal of Applied Physiology ◽

10.1152/jappl.1992.72.4.1557 ◽

1992 ◽

Vol 72 (4) ◽

pp. 1557-1562 ◽

Cited By ~ 37

Author(s):

H. Schulz ◽

P. Heilmann ◽

A. Hillebrecht ◽

J. Gebhart ◽

M. Meyer ◽

...

Keyword(s):

Dead Space ◽

Gas Transport ◽

Inert Gases ◽

Differential Analysis ◽

Mechanically Ventilated ◽

Convective Mixing ◽

Conducting Airways ◽

And Diffusion ◽

Residual Air ◽

Space Dispersion

The significance of convective and diffusive gas transport in the respiratory system was assessed from the response of combined inert gas and particle boluses inhaled into the conducting airways. Particles, considered as “nondiffusing gas,” served as tracers for convection and two inert gases with widely different diffusive characteristics (He and SF6) as tracers for convection and diffusion. Six-milliliter boluses labeled with monodisperse di-2-ethylhexyl sebacate droplets of 0.86-microns aerodynamic diameter, 2% He, and 2% SF6 were inspired by three anesthetized mechanically ventilated beagle dogs to volumetric lung depths up to 170 ml. Mixing between inspired and residual air caused dispersion of the inspired bolus, which was quantified in terms of the bolus half-width. Dispersion of particles increased with increasing lung depth to which the boluses were inhaled. The increase followed a power law with exponents less than 0.5 (mean 0.39), indicating that the effect of convective mixing per unit volume was reduced with depth. Within the pulmonary dead space, the behavior of the inert gases He and SF6 was similar to that of the particles, suggesting that gas transport was almost solely due to convection. Beyond the dead space, dispersion of He and SF6 increased more rapidly than dispersion of particles, indicating that diffusion became significant. The gas and particle bolus technique offers a suitable approach to differential analysis of gas transport in intrapulmonary airways of lungs.

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Erratum to: Observed and Modelled Convective Mixing-Layer Height at Dome C, Antarctica

Boundary-Layer Meteorology ◽

10.1007/s10546-014-9951-1 ◽

2014 ◽

Vol 153 (1) ◽

pp. 163-164 ◽

Cited By ~ 1

Author(s):

Giampietro Casasanta ◽

Ilaria Pietroni ◽

Igor Petenko ◽

Stefania Argentini

Keyword(s):

Mixing Layer ◽

Layer Height ◽

Convective Mixing ◽

Mixing Layer Height

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Tracers confirm downward mixing of Tyrrhenian Sea upper waters associated with the Eastern Mediterranean Transient

Ocean Science Discussions ◽

10.5194/osd-7-1533-2010 ◽

2010 ◽

Vol 7 (4) ◽

pp. 1533-1557

Author(s):

W. Roether ◽

J. E. Lupton

Keyword(s):

Deep Water ◽

Time Scale ◽

Eastern Mediterranean ◽

Western Mediterranean ◽

The Other ◽

Tyrrhenian Sea ◽

Convective Mixing ◽

Deep Waters ◽

Major Process ◽

Gibraltar Strait

Abstract. Observations of tritium and 3He in the Tyrrhenian Sea, 1987–2009, confirm the enhanced convective mixing of intermediate waters into the deep waters that has been noted and associated with the Eastern Mediterranean Transient in previous studies. Our evidence for the mixing rests on increasing tracer concentrations in the Tyrrhenian deep waters, accompanied by decreases in the upper waters, which are supplied from the Eastern Mediterranean. The downward transfer is particularly evident between 1987 and 1997. Later on, information partly rests on increasing tritium-3He ages; here we correct the observed 3He for contributions released from the ocean floor. The Tyrrhenian tracer distributions are fully compatible with data upstream of the Sicily Strait and in the Western Mediterranean. The tracer data show that mixing reached to the bottom and confirm a cyclonic nature of the deep water circulation in the Tyrrhenian. They furthermore indicate that horizontal homogenization of the deep waters occurs on a time scale of several years. Various features point to a reduced impact of Western Mediterranean Deep Water (WMDW) in the Tyrrhenian during the enhanced-convection period. This is an important finding because it implies less upward mixing of WMDW, which has been named a major process to enable the WMDW to leave the Mediterranean via the Gibraltar Strait. On the other hand, the TDW outflow for several years represented a major influx of enhanced salinity and density waters into the deep-water range of the Western Mediterranean.

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Simulations of Black Carbon Over Indian Region: Improvements and Implications of Diurnality in Emissions

10.5194/acp-2019-152 ◽

2019 ◽

Author(s):

Gaurav Govardhan ◽

Sreedharan Krishnakumari Satheesh ◽

Krishnaswamy Krishna Moorthy ◽

Ravi Nanjundiah

Keyword(s):

Boundary Layer ◽

Black Carbon ◽

Radiative Forcing ◽

Regional Scale ◽

Early Morning ◽

Temporal Variations ◽

Indian Region ◽

Near Surface ◽

Aerosol Radiative Forcing ◽

Convective Mixing

Abstract. With a view to improving the performance of WRF-Chem over the Indian region in simulating BC (black Carbon) mass concentrations as well as its short-term variations, especially on diurnal scale, a region-specific diurnal variation scheme has been introduced in the model emissios and the performance of the modified simulations has been evaluated against high-resolution measurements carried out over 8 ARFI (Aerosol Radiative Forcing over India) network observatories spread across India for distinct seasons; pre-monsoon (represented by May), post-monsoon (represented by October) and winter (represented by December). In addition to an overall improvement in the simulated concentrations and their temporal variations, it has also been found that the effects of prescribing diurnally varying emissions on the simulated near-surface concentrations largely depend on the boundary layer turbulence. The effects are perceived fast (within about 2–3 hours) during the evening–early morning hours when the atmospheric boundary layer is shallow and convective mixing is weak, while they are delayed, taking as much as about 5–6 hours, during periods when the boundary layer is deep and convective mixing is strong. This information would also serve as an important input for agencies concerned with urban planning and pollution mitigation. Despite these improvements in the near-surface concentrations, the simulated columnar aerosol optical depth (AOD) still remains largely underestimated vis-a-vis the satellite retrieved products. These modifications will serve as a guideline for further model-improvement initiatives at regional scale.

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