scholarly journals Competition for water vapour results in suppression of ice formation in mixed phase clouds

2017 ◽  
Author(s):  
Emma L. Simpson ◽  
Paul J. Connolly ◽  
Gordon B. McFiggans
Keyword(s):  
Water Vapour ◽  
Elevated Temperatures ◽  
Dominant Role ◽  
Cloud Condensation Nuclei ◽  
Radiation Budget ◽  
Ice Formation ◽  
Condensed Water ◽  
Mixed Phase Clouds ◽  
Earth’S Radiation Budget ◽  
Made In

Abstract. The formation of ice in clouds can initiate precipitation and influence a cloud's reflectivity and lifetime, affecting climate to a highly uncertain degree. Nucleation of ice at elevated temperatures requires an ice nucleating particle (INP): so-called heterogeneous freezing. Previously reported measurements for the ability of a particle to nucleate ice have been made in the absence of other aerosol which will act as cloud condensation nuclei (CCN) and are ubiquitous in the atmosphere. Here we show that CCN can outcompete INPs for available water vapour thus suppressing ice formation, which has the potential to significantly affect the Earth's radiation budget. The magnitude of this suppression is shown to be dependent on the mass of condensed water required for freezing. Here we show that ice formation in a state-of-the-art cloud parcel model is strongly dependent on the criteria for heterogeneous freezing selected from those previously hypothesised. We have developed two alternative criteria which agree well with observations from cloud chamber experiments. This study highlights the dominant role that competition for water vapour can play in ice formation, highlighting both a need for clarity in the requirements for heterogeneous freezing and for measurements under atmospherically appropriate conditions.

scholarly journals Competition for water vapour results in suppression of ice formation in mixed-phase clouds

2018 ◽  
Vol 18 (10) ◽  
pp. 7237-7250 ◽  
Author(s):  
Emma L. Simpson ◽  
Paul J. Connolly ◽  
Gordon McFiggans
Keyword(s):  
Water Vapour ◽  
Elevated Temperatures ◽  
Dominant Role ◽  
Cloud Condensation Nuclei ◽  
Radiation Budget ◽  
Ice Formation ◽  
Condensed Water ◽  
Mixed Phase Clouds ◽  
Earth’S Radiation Budget ◽  
Made In

Abstract. The formation of ice in clouds can initiate precipitation and influence a cloud's reflectivity and lifetime, affecting climate to a highly uncertain degree. Nucleation of ice at elevated temperatures requires an ice nucleating particle (INP), which results in so-called heterogeneous freezing. Previously reported measurements for the ability of a particle to nucleate ice have been made in the absence of other aerosol which will act as cloud condensation nuclei (CCN) and are ubiquitous in the atmosphere. Here we show that CCN can outcompete INPs for available water vapour thus suppressing ice formation, which has the potential to significantly affect the Earth's radiation budget. The magnitude of this suppression is shown to be dependent on the mass of condensed water required for freezing. Here we show that ice formation in a state-of-the-art cloud parcel model is strongly dependent on the criteria for heterogeneous freezing selected from those previously hypothesised. We have developed an alternative criteria which agrees well with observations from cloud chamber experiments. This study demonstrates the dominant role that competition for water vapour can play in ice formation, highlighting both a need for clarity in the requirements for heterogeneous freezing and for measurements under atmospherically appropriate conditions.

scholarly journals Measurement of the water vapour vertical profile and of the Earth's outgoing far infrared flux

2008 ◽  
Vol 8 (11) ◽  
pp. 2885-2894 ◽  
Author(s):  
L. Palchetti ◽  
G. Bianchini ◽  
B. Carli ◽  
U. Cortesi ◽  
S. Del Bianco
Keyword(s):  
Water Vapour ◽  
Far Infrared ◽  
Radiation Budget ◽  
Accurate Information ◽  
Spectral Radiation ◽  
Uncooled Detectors ◽  
Upper Troposphere ◽  
Atmospheric State ◽  
Spectrally Resolved ◽  
Earth’S Radiation Budget

Abstract. Our understanding of global warming depends on the accuracy with which the atmospheric components that modulate the Earth's radiation budget are known. Many uncertainties still exist as regards the radiative effect of water in the different spectral regions, among which is the far infrared, where very few observations have been made. An assessment is shown of the atmospheric outgoing flux obtained from a balloon-borne platform with wideband spectrally-resolved nadir measurements at the top of the atmosphere over the full spectral range, from 100 to 1400 cm−1, made by a Fourier transform spectrometer with uncooled detectors. From these measurements, we retrieved 15 pieces of information regarding water vapour and temperature profiles and surface temperature, with a major improvement in our knowledge of water vapour in the upper troposphere. The retrieved atmospheric state made it possible to calculate the emitted radiance also at frequencies and zenith angles that have not been observed and to determine the outgoing spectral radiation flux. This proves that spectrally resolved observations can be used to derive accurate information on the integrated flux. While the retrieved temperature was in agreement with ECMWF analysis, the retrieved water vapour profile differed significantly; depending on the time and the location, the derived flux in the far infrared (20–600 cm−1) differed by 2–3.5 W/m2 from that calculated using ECMWF. The error with which the far infrared flux is determined by REFIR-PAD is about 0.4 W/m2 and is caused mainly by calibration uncertainties, while detector noise has a negligible effect. This proves that uncooled detectors are adequate for top-of-the-atmosphere radiometry.

scholarly journals Measurement of the water vapour vertical profile and of the Earth's outgoing far infrared flux

2007 ◽  
Vol 7 (6) ◽  
pp. 17741-17767 ◽  
Author(s):  
L. Palchetti ◽  
G. Bianchini ◽  
B. Carli ◽  
U. Cortesi ◽  
S. Del Bianco
Keyword(s):  
Water Vapour ◽  
Radiative Forcing ◽  
Far Infrared ◽  
Radiation Budget ◽  
Accurate Information ◽  
Uncooled Detectors ◽  
The Mean ◽  
Spectrally Resolved ◽  
Earth’S Radiation Budget ◽  
Good Agreement

Abstract. Our understanding of global warming depends on the accuracy with which the atmospheric components that modulate the Earth's radiation budget are known. Many uncertainties still exist on the radiative effect of water in the different spectral regions, among which the far infrared where few observations have been made. An assessment is shown of the atmospheric outgoing flux obtained from a balloon-borne platform with wideband spectrally resolved nadir measurements at the top-of-atmosphere over the full spectral range, including the far infrared, from 100 to 1400 cm−1, made by a Fourier transform spectrometer with uncooled detectors. From these measurements, we retrieve 15 pieces of information about water vapour and temperature profiles, and surface temperature, with a precision of 5% for the mean water vapour profile and a major improvement of the upper troposphere-lower stratosphere knowledge. The retrieved atmospheric state makes it possible to calculate the emitted radiance as a function of the zenith angle and to determine the outgoing radiation flux, proving that spectrally resolved observations can be used to derive accurate information on the integrated flux. While the retrieved temperature is in good agreement with ECMWF analysis, the retrieved water vapour profile differs significantly, and, depending on time and location, the derived flux differs in the far infrared (0–600 cm−1) from that derived from ECMWF by 2–3.5 W/m2±0.4 W/m2. The observed discrepancy is larger than current estimates of radiative forcing due to CO2 increases since pre-industrial time. The error with which the flux is determined is caused mainly by calibration uncertainties while detector noise has a negligible effect, proving that uncooled detectors are adequate for top of the atmosphere radiometry.

scholarly journals Internal Factors Affecting the Surface Rumpling of a β-NiAlHf Coating

Coatings ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 436
Author(s):  
Liang Liu ◽  
Jian He ◽  
Yaoge Dong ◽  
Hongbo Guo
Keyword(s):  
Physical Vapor Deposition ◽  
Elevated Temperatures ◽  
Coefficient Of Thermal Expansion ◽  
Dominant Role ◽  
Cyclic Loads ◽  
Internal Factor ◽  
Internal Factors ◽  
Factors Affecting ◽  
Mismatch Stress ◽  
Thermal Mismatch Stress

β-NiAl coatings on a superalloy substrate will inevitably result in severe rumpling at elevated temperatures; however, the associated rumpling mechanisms are not completely understood. The scale rumpling behavior of a β-NiAlHf coating deposited by electron beam physical vapor deposition (EB-PVD) on single crystal superalloy IC21 was investigated in this work. Some internal factors, including the mismatch in the coefficient of thermal expansion and the stress induced by the growth of oxide scale and the phase transformation, were taken into consideration. The thermal mismatch stress between the coating and substrate was the main internal factor responsible for rumpling behavior during thermal cyclic loads, while the phase degradation from β-NiAl to γ’-Ni3Al in the coating played a dominant role during static thermal loads.

scholarly journals Recent advances in the electrochemical construction of heterocycles

2014 ◽  
Vol 10 ◽  
pp. 2858-2873 ◽  
Author(s):  
Robert Francke
Keyword(s):  
Heterocyclic Compounds ◽  
Elevated Temperatures ◽  
Ring Formation ◽  
Environmentally Benign ◽  
Heterocyclic Chemistry ◽  
Ambient Conditions ◽  
Recent Developments ◽  
Strong Acids ◽  
Selection Of ◽  
Made In

Due to the fact that the major portion of pharmaceuticals and agrochemicals contains heterocyclic units and since the overall number of commercially used heterocyclic compounds is steadily growing, heterocyclic chemistry remains in the focus of the synthetic community. Enormous efforts have been made in the last decades in order to render the production of such compounds more selective and efficient. However, most of the conventional methods for the construction of heterocyclic cores still involve the use of strong acids or bases, the operation at elevated temperatures and/or the use of expensive catalysts and reagents. In this regard, electrosynthesis can provide a milder and more environmentally benign alternative. In fact, numerous examples for the electrochemical construction of heterocycles have been reported in recent years. These cases demonstrate that ring formation can be achieved efficiently under ambient conditions without the use of additional reagents. In order to account for the recent developments in this field, a selection of representative reactions is presented and discussed in this review.

scholarly journals Air Temperature and Anthropogenic Forcing: Insights from the Solid Earth

2011 ◽  
Vol 24 (2) ◽  
pp. 569-574 ◽  
Author(s):  
Jean O. Dickey ◽  
Steven L. Marcus ◽  
Olivier de Viron
Keyword(s):  
Air Temperature ◽  
Decadal Variability ◽  
Surface Air Temperature ◽  
Radiation Budget ◽  
Cloud Formation ◽  
Length Of Day ◽  
Anthropogenic Forcing ◽  
The Core ◽  
Earth’S Radiation Budget ◽  
Gas Effect

Abstract Earth’s rotation rate [i.e., length of day (LOD)], the angular momentum of the core (CAM), and surface air temperature (SAT) all have decadal variability. Previous investigators have found that the LOD fluctuations are largely attributed to core–mantle interactions and that the SAT is strongly anticorrelated with the decadal LOD. It is shown here that 1) the correlation among these three quantities exists until 1930, at which time anthropogenic forcing becomes highly significant; 2) correcting for anthropogenic effects, the correlation is present for the full span with a broadband variability centered at 78 yr; and 3) this result underscores the reality of anthropogenic temperature change, its size, and its temporal growth. The cause of this common variability needs to be further investigated and studied. Since temperature cannot affect the CAM or LOD to a sufficient extent, the results favor either a direct effect of Earth’s core-generated magnetic field (e.g., through the modulation of charged-particle fluxes, which may impact cloud formation) or a more indirect effect of some other core process on the climate—or yet another process that affects both. In all three cases, their signals would be much smaller than the anthropogenic greenhouse gas effect on Earth’s radiation budget during the coming century.

Increasing the Efficacy and Extending the Effective Application Period of a Granular Turf Bioherbicide by Covering with Jute Fabric

2009 ◽  
Vol 23 (4) ◽  
pp. 524-530 ◽  
Author(s):  
Mohammed H. Abu-Dieyeh ◽  
Alan K. Watson
Keyword(s):  
Elevated Temperatures ◽  
Ground Cover ◽  
Sclerotinia Minor ◽  
Jute Fabric ◽  
Effective Application ◽  
Jute Fibers ◽  
Application Rates ◽  
Warm Summer ◽  
Favorable Conditions ◽  
Made In

Progress in bioherbicide development has been hindered by the strict moisture and temperature requirements of the living active ingredient. Application of a jute fabric to areas treated with aSclerotinia minorgranular bioherbicide improved broadleaf weed control and broadened the effective application period to include the warm summer season. When turfgrass plots treated with the bioherbicide were covered with burlap fabric for 3 d, broadleaf weed (dandelion, white clover, broadleaf plantain, buckhorn plantain, ground ivy, and prostrate knotweed) control was greatly enhanced. The cover was made of natural jute fibers that retained water but had sufficient transparency to allow 33% light penetration for continued growth of the grass. Virulence of the bioherbicide was maintained under elevated temperatures that would otherwise reduce efficacy. The bioherbicide was ineffective in the summer unless covered, but dandelion density, broadleaf weed ground cover, and dandelion survival were all reduced by the bioherbicide when plots were covered, even if applications were made in July. The efficacy of the bioherbicide was also enhanced under favorable conditions, and covering permitted reduced application rates without loss of efficacy. When applied at a rate of 20 g/m2and covered,S. minorgranules exerted significantly greater biocontrol of dandelion than 40 g/m2without covering. Covering for up to 5 d did not cause any adverse effects on the turfgrass. This approach may overcome one obstacle to the commercialization of theSclerotinia minorbioherbicide, permitting its deployment under challenging environmental conditions.

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