Estimating Effective Radiative Properties and In-Depth Radiative Heating of Porous Ablators

2022 ◽  
Author(s):  
Ayan Banerjee ◽  
Alexandre Martin ◽  
Savio J. Poovathingal
Keyword(s):  
Radiative Heating ◽  
Radiative Properties

Evolution of a Florida Cirrus Anvil

2005 ◽  
Vol 62 (7) ◽  
pp. 2352-2372 ◽  
Author(s):  
T. J. Garrett ◽  
B. C. Navarro ◽  
C. H. Twohy ◽  
E. J. Jensen ◽  
D. G. Baumgardner ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Radiative Heating ◽  
Ice Crystals ◽  
Radiative Properties ◽  
Infrared Heating ◽  
Size Distributions ◽  
Regional Study ◽  
University Of North Dakota ◽  
Heating And Cooling ◽  
Anvil Cirrus

Abstract This paper presents a detailed study of a single thunderstorm anvil cirrus cloud measured on 21 July 2002 near southern Florida during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers–Florida Area Cirrus Experiment (CRYSTAL-FACE). NASA WB-57F and University of North Dakota Citation aircraft tracked the microphysical and radiative development of the anvil for 3 h. Measurements showed that the cloud mass that was advected downwind from the thunderstorm was separated vertically into two layers: a cirrus anvil with cloud-top temperatures of −45°C lay below a second, thin tropopause cirrus (TTC) layer with the same horizontal dimensions as the anvil and temperatures near −70°C. In both cloud layers, ice crystals smaller than 50 μm across dominated the size distributions and cloud radiative properties. In the anvil, ice crystals larger than 50 μm aggregated and precipitated while small ice crystals increasingly dominated the size distributions; as a consequence, measured ice water contents and ice crystal effective radii decreased with time. Meanwhile, the anvil thinned vertically and maintained a stratification similar to its environment. Because effective radii were small, radiative heating and cooling were concentrated in layers approximately 100 m thick at the anvil top and base. A simple analysis suggests that the anvil cirrus spread laterally because mixing in these radiatively driven layers created horizontal pressure gradients between the cloud and its stratified environment. The TTC layer also spread but, unlike the anvil, did not dissipate—perhaps because the anvil shielded the TTC from terrestrial infrared heating. Calculations of top-of-troposphere radiative forcing above the anvil and TTC showed strong cooling that tapered as the anvil evolved.

scholarly journals Macrophysical, Microphysical, and Radiative Properties of Tropical Mesoscale Convective Systems over Their Life Cycle

2016 ◽  
Vol 29 (9) ◽  
pp. 3353-3371 ◽  
Author(s):  
Dominique Bouniol ◽  
Rémy Roca ◽  
Thomas Fiolleau ◽  
D. Emmanuel Poan
Keyword(s):  
Life Cycle ◽  
Large Scale ◽  
Radiative Heating ◽  
Radiative Properties ◽  
Mesoscale Convective Systems ◽  
Cloud Base ◽  
Convective Systems ◽  
Mesoscale Convective ◽  
Polar Orbiting Satellite ◽  
The Impact

Abstract Mesoscale convective systems (MCSs) are important drivers of the atmospheric large-scale circulation through their associated diabatic heating profile. Taking advantage of recent tracking techniques, this study investigates the evolution of macrophysical, microphysical, and radiative properties over the MCS life cycle by merging geostationary and polar-orbiting satellite data. These observations are performed in three major convective areas: continental West Africa, the adjacent Atlantic Ocean, and the open Indian Ocean. MCS properties are also investigated according to internal subregions (convective, stratiform, and nonprecipitating anvil). Continental MCSs show a specific life cycle, with more intense convection at the beginning. Larger and denser hydrometeors are thus found at higher altitudes, as well as up to the cirriform subregion. Oceanic MCSs have more constant reflectivity values, suggesting a less intense convective updraft, but more persistent intensity. A layer of small crystals is found in all subregions, but with a depth that varies according to the MCS subregion and life cycle. Radiative properties are also examined. It appears that the evolution of large and dense hydrometeors tends to control the evolution of the cloud albedo and the outgoing longwave radiation. The impact of dense hydrometeors, detrained from the convective towers, is also seen in the radiative heating profiles, in particular in the shortwave domain. A dipole of cooling near the cloud top and heating near the cloud base is found in the longwave; this cooling intensifies near the end of the life cycle.

scholarly journals A comparative study of the response of non-drizzling stratocumulus to meteorological and aerosol perturbations

2012 ◽  
Vol 12 (10) ◽  
pp. 27111-27172
Author(s):  
J. L. Petters ◽  
H. Jiang ◽  
G. Feingold ◽  
D. L. Rossiter ◽  
D. Khelif ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Cloud Droplet ◽  
Radiative Heating ◽  
Radiative Properties ◽  
Liquid Water Path ◽  
Cloud Properties ◽  
Stratiform Clouds ◽  
Order Of Magnitude ◽  
Aerosol State ◽  
The Impact

Abstract. The impact of changes in aerosol and cloud droplet concentration (Na and Nd) on the radiative forcing of stratocumulus-topped boundary layers (STBLs) has been widely studied. How these impacts compare to those due to variations in meteorological context has not been investigated in a systematic fashion. In this study we examine the impact of observed variations in meteorological context and aerosol state on daytime, non-drizzling stratiform evolution, and determine how resulting changes in cloud properties compare. We perturb aerosol and meteorological properties within an observationally-constrained LES and determine the cloud response, focusing on changes in liquid water path (LWP), bulk optical depth (τ) and cloud radiative forcing (CRF). We find that realistic variations in meteorological context (i.e. jump properties) can elicit responses in τ and shortwave (SW) CRF that are on the same order of magnitude as, and at times larger than, those responses found due to similar changes in aerosol state (i.e Nd). Further, we find that one hour differences in the timing of SW radiative heating can lead to substantial changes in LWP and τ. Our results suggest that, for observational studies of aerosol influences on the radiative properties of stratiform clouds, consistency in meteorological context (the cloud top jump properties in particular) and time of observations from day-to-day must be carefully considered.

scholarly journals Variability in individual particle structure and mixing states between the glacier–snowpack and atmosphere in the northeastern Tibetan Plateau

2018 ◽  
Vol 12 (12) ◽  
pp. 3877-3890 ◽  
Author(s):  
Zhiwen Dong ◽  
Shichang Kang ◽  
Dahe Qin ◽  
Yaping Shao ◽  
Sven Ulbrich ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Radiative Forcing ◽  
Morphological Structure ◽  
Deposition Process ◽  
Radiative Heating ◽  
Radiative Properties ◽  
Particle Structure ◽  
Glacier Surface ◽  
Northeastern Tibetan Plateau ◽  
Salt Coating

Abstract. Aerosols affect the Earth's temperature and climate by altering the radiative properties of the atmosphere. Changes in the composition, morphological structure, and mixing state of aerosol components will cause significant changes in radiative forcing in the atmosphere. This work focused on the physicochemical properties of light-absorbing particles (LAPs) and their variability through deposition process from the atmosphere to the glacier–snowpack interface based on large-range observations in the northeastern Tibetan Plateau, and laboratory transmission electron microscope (TEM) and energy dispersive X-ray spectrometer (EDX) measurements. The results showed that LAP particle structures changed markedly in the snowpack compared to those in the atmosphere due to black carbon (BC) and organic matter (OM) particle aging and salt-coating condition changes. Considerably more aged BC and OM particles were observed in the glacier and snowpack surfaces than in the atmosphere, as the concentration of aged BC and OM varied in all locations by 4 %–16 % and 12 %–25 % in the atmosphere, whereas they varied by 25 %–36 % and 36 %–48 % in the glacier–snowpack surface. Similarly, the salt-coated particle ratio of LAPs in the snowpack is lower than in the atmosphere. Albedo change contribution in the Miaoergou, Yuzhufeng, and Qiyi glaciers is evaluated using the SNICAR model for glacier surface-distributed impurities. Due to the salt-coating state change, the snow albedo decreased by 16.7 %–33.9 % compared to that in the atmosphere. Such a great change may cause more strongly enhanced radiative heating than previously thought, suggesting that the warming effect from particle structure and mixing change in glacier–snowpack LAPs may have markedly affected the climate on a global scale in terms of direct forcing in the cryosphere.

scholarly journals Variability in individual particle structure and mixing states between the glacier snowpack and atmosphere interface in the northeast Tibetan Plateau

2018 ◽  
Author(s):  
Zhiwen Dong ◽  
Shichang Kang ◽  
Yaping Shao ◽  
Sven Ulbrich ◽  
Dahe Qin
Keyword(s):  
Tibetan Plateau ◽  
Radiative Forcing ◽  
Global Scale ◽  
Radiative Heating ◽  
Radiative Properties ◽  
Particle Structure ◽  
Glacier Surface ◽  
Coated Particle ◽  
Mixing States ◽  
Salt Coating

Abstract. Aerosol impurities affect the earth's temperature and climate by altering the radiative properties of the atmosphere. Changes in the composition, morphology structure and mixing states of aerosol components will cause significantly varied radiative forcing in the atmosphere. This work focused on the physicochemical properties of light-absorbing impurities (LAIs) and their variability through deposition from the atmosphere to the glacier/snowpack surface interface based on large-range observation in northeastern Tibetan Plateau and laboratory transmission electron microscope (TEM) and laboratory energy dispersive X-ray spectrometer (EDX) measurements. The results showed that LAI particle structures changed markedly in the snowpack compared to those in the atmosphere due to black carbon (BC)/organic matter (OM) particle aging and salt-coating condition changes. Considerably more aged BC and OM particles were observed in glacier/snowpack surfaces than in the atmosphere, as the proportion of aged BC and OM varied in all locations by 4 %–16 % and 12 %–25 % in the atmosphere, respectively, whereas they varied by 25 %–36 % and 36 %–48 %, respectively, in the glacier/snowpack surface. Similarly, the salt-coated particle ratio of LAIs in the snowpack is lower than in the atmosphere. Albedo change contribution in the Miaoergou, Yuzhufeng and Qiyi Glaciers is evaluated using the SNICAR model for glacier surface distributed impurities. Due to salt-coating state change, these values decreased by 30.1 %–56.4 % compared to that in the atmosphere. Such great change may cause more strongly enhanced radiative heating than previously thought, suggesting that the warming effect from particle structure and mixing change of glacier/snowpack LAIs may have markedly affected the climate on a global scale in terms of direct forcing in the cryosphere.

Rate of Sublimation of Ice by Radiative Heating in Freeze-Etching

1980 ◽  
Vol 38 ◽  
pp. 618-619
Author(s):  
Yeshayahu Talmon
Keyword(s):  
Heat Flux ◽  
Freeze Fracture ◽  
Constant Heat Flux ◽  
Radiative Heating ◽  
Constant Heat ◽  
Entire Sample ◽  
Simplified Method ◽  
Freeze Etching ◽  
Sublimation Rates ◽  
Fractured Surface

To bring out details in the fractured surface of a frozen sample in the freeze fracture/freeze-etch technique,the sample or part of it is warmed to enhance water sublimation.One way to do this is to raise the temperature of the entire sample to about -100°C to -90°C. In this case sublimation rates can be calculated by using plots such as Fig.1 (Talmon and Thomas),or by simplified formulae such as that given by Menold and Liittge. To achieve higher rates of sublimation without heating the entire sample a radiative heater can be used (Echlin et al.). In the present paper a simplified method for the calculation of the rates of sublimation under a constant heat flux F [W/m2] at the surface of the sample from a heater placed directly above the sample is described.

Characterizing the convective heat exchange with plastic shading nets under natural arid conditions

2019 ◽  
pp. 11-20
Author(s):  
Ahmed M Abdel-Ghanya ◽  
Ibrahim M Al-Helal
Keyword(s):  
Wind Speed ◽  
Thermal Radiation ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Convective Heat Exchange ◽  
Radiative Properties ◽  
Wooden Frame ◽  
Arid Conditions ◽  
Air Temperatures ◽  
Radiation Fluxes

Plastic nets are extensively used for shading purposes in arid regions such as in the Arabian Peninsula. Quantifying the convection exchange with shading net and understanding the mechanisms (free, mixed and forced) of convection are essential for analyzing energy exchange with shading nets. Unlike solar and thermal radiation, the convective energy, convective heat transfer coefficient and the nature of convection have never been theoretically estimated or experimentally measured for plastic nets under arid conditions. In this study, the convected heat exchanges with different plastic nets were quantified based on an energy balance applied to the nets under outdoor natural conditions. Therefore, each net was tacked onto a wooden frame, fixed horizontally at 1.5-m height over the floor. The downward and upward solar and thermal radiation fluxes were measured below and above each net on sunny days; also the wind speed over the net, and the net and air temperatures were measured, simultaneously. Nets with different porosities, colors and texture structures were used for the study. The short and long wave’s radiative properties of the nets were pre-determined in previous studies to be used. Re and Gr numbers were determined and used to characterize the convection mechanism over each net. The results showed that forced and mixed convection are the dominant modes existing over the nets during most of the day and night times. The nature of convection over nets depends mainly on the wind speed, net-air temperature difference and texture shape of the net rather than its color and its porosity.

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