scholarly journals Sulfate geoengineering: a review of the factors controlling the needed injection of sulfur dioxide

2016 ◽  
Author(s):  
Daniele Visioni ◽  
Giovanni Pitari ◽  
Valentina Aquila
Keyword(s):  
Lower Stratosphere ◽  
Effective Means ◽  
Climate Engineering ◽  
Radiative Effects ◽  
Stratospheric Water Vapor ◽  
Long Wave ◽  
Engineering Technique ◽  
Aerosol Effects ◽  
Induced Changes ◽  
Fine Tune

Abstract. Sulfate geoengineering has been proposed as an affordable and climate-effective means for temporarily offset the warming produced by the increase of well mixed greenhouse gases (WMGHG). This climate engineering technique has been planned for a timeframe of a few decades needed to implement global inter-governmental measures needed to achieve stabilization of the atmospheric content of WMGHGs (CO2 in particular). The direct radiative effects of sulfur injection in the tropical lower stratosphere can be summarized as increasing shortwave scattering with consequent tropospheric cooling and increasing long- wave absorption with stratospheric warming. Indirect radiative effects are related to induced changes in the ozone distribution, stratospheric water vapor abundance, formation and size of upper tropospheric cirrus ice particles and lifetime of longlived species, namely CH4 in connection with OH changes through several photochemical mechanisms. A direct comparison of the net effects of WMGHG increase with direct and indirect effects of sulfate geoengineering may help fine-tune the best amount of sulfate to be injected in an eventual realization of the experiment. However, we need to take into account large uncertainties in the estimate of some of these aerosol effects, such as cirrus ice particle size modifications.

scholarly journals Sulfate geoengineering: a review of the factors controlling the needed injection of sulfur dioxide

2017 ◽  
Vol 17 (6) ◽  
pp. 3879-3889 ◽  
Author(s):  
Daniele Visioni ◽  
Giovanni Pitari ◽  
Valentina Aquila
Keyword(s):  
Sulfur Dioxide ◽  
Lower Stratosphere ◽  
Effective Means ◽  
Atmospheric Models ◽  
Radiative Effects ◽  
Stratospheric Water Vapor ◽  
Wide Range ◽  
Volcanic Aerosols ◽  
Aerosol Effects ◽  
Induced Changes

Abstract. Sulfate geoengineering has been proposed as an affordable and climate-effective means to temporarily offset the warming produced by the increase of well-mixed greenhouse gases (WMGHGs). This technique would likely have to be applied while and after global intergovernmental measures on emissions of WMGHGs are implemented in order to achieve surface temperature stabilization. The direct radiative effects of sulfur injection in the tropical lower stratosphere can be summarized as increasing shortwave scattering with consequent tropospheric cooling and increasing longwave absorption with stratospheric warming. Indirect radiative effects are related to induced changes in the ozone distribution; stratospheric water vapor abundance,;formation and size of upper-tropospheric cirrus ice particles; and lifetime of long-lived species, namely CH4 in connection with OH changes through several photochemical mechanisms. Direct and indirect effects of sulfate geoengineering both concur to determine the atmospheric response. A review of previous studies on these effects is presented here, with an outline of the important factors that control the amount of sulfur dioxide to be injected in an eventual realization of the experiment. However, we need to take into account that atmospheric models used for these studies have shown a wide range of climate sensitivity and differences in the response to stratospheric volcanic aerosols. In addition, large uncertainties exist in the estimate of some of these aerosol effects.

scholarly journals The Influence of Atmospheric Cloud Radiative Effects on the Large-Scale Stratospheric Circulation

2017 ◽  
Vol 30 (15) ◽  
pp. 5621-5635 ◽  
Author(s):  
Ying Li ◽  
David W. J. Thompson ◽  
Yi Huang
Keyword(s):  
Large Scale ◽  
Lower Stratosphere ◽  
Static Stability ◽  
Wave Activity ◽  
Radiative Effects ◽  
Dynamic Component ◽  
Cloud Radiative Effects ◽  
Stratospheric Circulation ◽  
Induced Changes ◽  
Stratospheric Variability

Previous studies have explored the influence of atmospheric cloud radiative effects (ACRE) on the tropospheric circulation. Here the authors explore the influence of ACRE on the stratospheric circulation. The response of the stratospheric circulation to ACRE is assessed by comparing simulations run with and without ACRE. The stratospheric circulation response to ACRE is reproducible in a range of different GCMs and can be interpreted in the context of both a dynamically driven and a radiatively driven component. The dynamic component is linked to ACRE-induced changes in the vertical and meridional fluxes of wave activity. The ACRE-induced changes in the vertical flux of wave activity into the stratosphere are consistent with the ACRE-induced changes in tropospheric baroclinicity and thus the amplitude of midlatitude baroclinic eddies. They account for a strengthening of the Brewer–Dobson circulation, a cooling of the tropical lower stratosphere, a weakening and warming of the polar vortex, a reduction of static stability near the tropical tropopause transition layer, and a shortening of the time scale of extratropical stratospheric variability. The ACRE-induced changes in the equatorward flux of wave activity in the low-latitude stratosphere account for a strengthening of the zonal wind in the subtropical lower to midstratosphere. The radiative component is linked to ACRE-induced changes in the flux of longwave radiation into the lower stratosphere. The changes in radiative fluxes lead to a cooling of the extratropical lower stratosphere, changes in the static stability and cloud fraction near the extratropical tropopause, and a shortening of the time scales of extratropical stratospheric variability. The results highlight a previously overlooked pathway through which tropospheric climate influences the stratosphere.

scholarly journals Modeling upper tropospheric and lower stratospheric water vapor anomalies

2013 ◽  
Vol 13 (4) ◽  
pp. 9653-9679 ◽  
Author(s):  
M. R. Schoeberl ◽  
A. E. Dessler ◽  
T. Wang
Keyword(s):  
Water Vapor ◽  
Lower Stratosphere ◽  
Calculation Model ◽  
Vapor Concentration ◽  
Cold Temperatures ◽  
Tropical Tropopause Layer ◽  
Stratospheric Water Vapor ◽  
Tropical Tropopause ◽  
Minimum Displacement ◽  
Asian Monsoons

Abstract. The domain-filling, forward trajectory calculation model developed by Schoeberl and Dessler (2011) is used to further investigate processes that produce upper tropospheric and lower stratospheric water vapor anomalies. We examine the pathways parcels take from the base of the tropical tropopause layer (TTL) to the lower stratosphere. Most parcels found in the lower stratosphere arise from East Asia, the Tropical West Pacific (TWP) and the Central/South America. The belt of TTL parcel origins is very wide compared to the final dehydration zones near the top of the TTL. This is due to the convergence of rising air as a result of the stronger diabatic heating near the tropopause relative to levels above and below. The observed water vapor anomalies – both wet and dry – correspond to regions where parcels have minimal displacement from their initialization. These minimum displacement regions include the winter TWP and the Asian and American monsoons. To better understand the stratospheric water vapor concentration we introduce the water vapor spectrum and investigate the source of the wettest and driest components of the spectrum. We find that the driest air parcels that originate below the TWP, moving upward to dehydrate in the TWP cold upper troposphere. The wettest air parcels originate at the edges of the TWP as well as the summer American and Asian monsoons. The wet air parcels are important since they skew the mean stratospheric water vapor distribution toward higher values. Both TWP cold temperatures that produce dry parcels as well as extra-TWP processes that control the wet parcels determine stratospheric water vapor.

A Trial of Detecting Impending Access-graft Failure by Simplified Weekly Flow Monitoring

2005 ◽  
Vol 28 (3) ◽  
pp. 237-243 ◽  
Author(s):  
D. Vilkomerson ◽  
T. Chilipka ◽  
H. Rafi ◽  
P. Homel ◽  
G. Ghadari ◽  
...  
Keyword(s):  
Graft Failure ◽  
Controlled Trial ◽  
Effective Means ◽  
New Method ◽  
Control Group ◽  
Flow Monitoring ◽  
Monitoring Procedure ◽  
Two Stages ◽  
Induced Changes ◽  
Access Graft

Access graft failure is a major problem in hemodialysis. Monitoring the flow through the access so that impending failure can be detected and prevented seems reasonable, but recent clinical trials have failed to show any benefit of such monitoring. Described here are plans for a clinical trial of a new flow monitoring procedure that measures access flow weekly instead of monthly and, being performed before dialysis, avoids the dialysis-induced changes in graft flow that may have affected earlier trials. The planned trial is to be carried out in two stages, the first to establish the sensitivity and specificity of the new method, and the second (if the results of the first stage warrant it) a controlled trial comparing access-costs and hospitalization days between a monitored group and a matched standard care control group. It is hoped that this trial of the new method will establish it as an effective means of extending access-graft life.

scholarly journals Maintenance of polar stratospheric clouds in a moist stratosphere

2008 ◽  
Vol 4 (1) ◽  
pp. 69-78 ◽  
Author(s):  
D. B. Kirk-Davidoff ◽  
J.-F. Lamarque
Keyword(s):  
Water Vapor ◽  
Particle Number Density ◽  
Water Vapor Transport ◽  
Number Density ◽  
Radiative Effects ◽  
Polar Stratospheric Clouds ◽  
Substantial Impact ◽  
Stratospheric Water Vapor ◽  
Microphysical Parameters ◽  
Stratospheric Clouds

Abstract. Previous work has shown that polar stratospheric clouds (PSCs) could have acted to substantially warm high latitude regions during past warm climates such as the Eocene (55 Ma). Using a simple model of stratospheric water vapor transport and polar stratospheric cloud (PSC) formation, we investigate the dependence of PSC optical depth on tropopause temperature, cloud microphysical parameters, stratospheric overturning, and tropospheric methane. We show that PSC radiative effects can help slow removal of water from the stratosphere via self-heating. However, we also show that the ability of PSCs to have a substantial impact on climate depends strongly on the PSC particle number density and the strength of the overturning circulation. Thus even a large source of stratospheric water vapor (e.g. from methane oxidation) will not result in substantial PSC radiative effects unless PSC ice crystal number density is high compared to most current observations, and stratospheric overturning (which modulates polar stratospheric temperatures) is low. These results are supported by analysis of a series of runs of the NCAR WACCM model with methane concentrations varying up to one thousand times present levels.

Climate engineering–induced changes in correlations between Earth system variables—implications for appropriate indicator selection

2019 ◽  
Vol 153 (3) ◽  
pp. 305-322 ◽  
Author(s):  
Nadine Mengis ◽  
David P. Keller ◽  
Wilfried Rickels ◽  
Martin Quaas ◽  
Andreas Oschlies
Keyword(s):  
Earth System ◽  
Climate Engineering ◽  
Indicator Selection ◽  
System Variables ◽  
Induced Changes

Water-vapor Measurements in the Lower Stratosphere

1974 ◽  
Vol 52 (8) ◽  
pp. 1527-1531 ◽  
Author(s):  
H. J. Mastenbrook
Keyword(s):  
Water Vapor ◽  
Lower Stratosphere ◽  
Marked Decrease ◽  
Vapor Concentration ◽  
Water Vapor Concentration ◽  
Mixing Ratio ◽  
Stratospheric Water Vapor ◽  
Mixing Ratios ◽  
Natural Concentration ◽  
General Range

Nearly 10 years of water-vapor measurements to heights of 30 km provide a basis for assessing the natural concentration of stratospheric water vapor and its variability. The measurements which began in 1964 have been made at monthly intervals from the mid-latitude location of Washington, D.C, using a balloon-borne frost-point hygrometer. The observations show the mixing ratio of water-vapor mass to air mass in the stratosphere to be in the general range of 1 to 4 p.p.m. with a modal concentration between 2 and 3 p.p.m. An annual cycle of mixing ratio is evident for the low stratosphere. A trend of water-vapor increase observed during the first 6 years does not persist beyond 1969 or 1970. The 6 year increase was followed by a marked decrease in 1971, with mixing ratios remaining generally below 3 p.p.m. thereafter. The measurements of recent years suggest that the series of observations may have begun during a period of low water-vapor concentration in the stratosphere.

scholarly journals A global modeling study on carbonaceous aerosol microphysical characteristics and radiative effects

2010 ◽  
Vol 10 (15) ◽  
pp. 7439-7456 ◽  
Author(s):  
S. E. Bauer ◽  
S. Menon ◽  
D. Koch ◽  
T. C. Bond ◽  
K. Tsigaridis
Keyword(s):  
Organic Carbon ◽  
Black Carbon ◽  
Radiative Flux ◽  
Radiative Effects ◽  
Carbonaceous Particle ◽  
Flux Change ◽  
Aerosol Effects ◽  
The Impact ◽  
Carbon Aerosols ◽  
Black Carbon Aerosols

Abstract. Recently, attention has been drawn towards black carbon aerosols as a short-term climate warming mitigation candidate. However the global and regional impacts of the direct, indirect and semi-direct aerosol effects are highly uncertain, due to the complex nature of aerosol evolution and the way that mixed, aged aerosols interact with clouds and radiation. A detailed aerosol microphysical scheme, MATRIX, embedded within the GISS climate model is used in this study to present a quantitative assessment of the impact of microphysical processes involving black carbon, such as emission size distributions and optical properties on aerosol cloud activation and radiative effects. Our best estimate for net direct and indirect aerosol radiative flux change between 1750 and 2000 is −0.56 W/m2. However, the direct and indirect aerosol effects are quite sensitive to the black and organic carbon size distribution and consequential mixing state. The net radiative flux change can vary between −0.32 to −0.75 W/m2 depending on these carbonaceous particle properties at emission. Taking into account internally mixed black carbon particles let us simulate correct aerosol absorption. Absorption of black carbon aerosols is amplified by sulfate and nitrate coatings and, even more strongly, by organic coatings. Black carbon mitigation scenarios generally showed reduced radiative fluxeswhen sources with a large proportion of black carbon, such as diesel, are reduced; however reducing sources with a larger organic carbon component as well, such as bio-fuels, does not necessarily lead to a reduction in positive radiative flux.

Morphology of Tropical Upwelling in the Lower Stratosphere

2008 ◽  
Vol 65 (7) ◽  
pp. 2360-2374 ◽  
Author(s):  
Marvin A. Geller ◽  
Tiehan Zhou ◽  
Kevin Hamilton
Keyword(s):  
Interannual Variability ◽  
Climate Models ◽  
Lower Stratosphere ◽  
Surf Zone ◽  
Mechanistic Model ◽  
Wave Drag ◽  
Geophysical Fluid Dynamics Laboratory ◽  
Stratospheric Water Vapor ◽  
Sensitivity Tests ◽  
Mean Meridional Circulation

Abstract Sensitivity tests of a mechanistic model of the mean meridional circulation driven by specified eddy forcing are conducted to investigate how the morphology of tropical upwelling in the lower stratosphere is related to the structure of the forcing expected to be associated with the stratospheric surf zone. The basic morphology of tropical upwelling is found to be similar among the mechanistic model forced with reasonable eddy fluxes, the Geophysical Fluid Dynamics Laboratory (GFDL) SKYHI GCM, U.K. Met Office (UKMO) analyses, and other climate models, indicating the robustness of the upwelling features. Atmospheric data are analyzed to characterize the interannual variability of wave drag. The influence of such variations on the interannual variability of tropical upwelling in the lower stratosphere is explored, which may help explain the observed interannual variability of stratospheric water vapor.

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