scholarly journals Radiative and chemical implications of the size and composition of aerosol particles in the existing or modified global stratosphere

2021 ◽  
Vol 21 (11) ◽  
pp. 8915-8932
Author(s):  
Daniel M. Murphy ◽  
Karl D. Froyd ◽  
Ilann Bourgeois ◽  
Charles A. Brock ◽  
Agnieszka Kupc ◽  
...  
Keyword(s):  
Surface Area ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Aerosol Particles ◽  
Climate Impact ◽  
Infrared Heating ◽  
Heterogeneous Chemistry ◽  
Radiative Effects ◽  
Four Seasons ◽  
Far Ultraviolet

Abstract. The size of aerosol particles has fundamental effects on their chemistry and radiative effects. We explore those effects using aerosol size and composition data in the lowermost stratosphere along with calculations of light scattering. In the size range between about 0.1 and 1.0 µm diameter (accumulation mode), there are at least two modes of particles in the lowermost stratosphere. The larger mode consists mostly of particles produced in the stratosphere, and the smaller mode consists mostly of particles transported from the troposphere. The stratospheric mode is similar in the Northern and Southern Hemisphere, whereas the tropospheric mode is much more abundant in the Northern Hemisphere. The purity of sulfuric acid particles in the stratospheric mode shows that there is limited production of secondary organic aerosol in the stratosphere, especially in the Southern Hemisphere. Out of eight sets of flights sampling the lowermost stratosphere (four seasons and two hemispheres) there were three with large injections of specific materials: volcanic, biomass burning, or dust. The stratospheric and tropospheric modes have very different roles for radiative effects on climate and for heterogeneous chemistry. Because the larger particles are more efficient at scattering light, most of the radiative effect in the lowermost stratosphere is due to stratospheric particles. In contrast, the tropospheric particles can have more surface area, at least in the Northern Hemisphere. The surface area of tropospheric particles could have significant implications for heterogeneous chemistry because these particles, which are partially neutralized and contain organics, do not correspond to the substances used for laboratory studies of stratospheric heterogeneous chemistry. We then extend the analysis of size-dependent properties to particles injected into the stratosphere, either intentionally or from volcanoes. There is no single size that will simultaneously maximize the climate impact relative to the injected mass, infrared heating, potential for heterogeneous chemistry, and undesired changes in direct sunlight. In addition, light absorption in the far ultraviolet is identified as an issue requiring more study for both the existing and potentially modified stratosphere.

scholarly journals Radiative and chemical implications of the size and composition of aerosol particles in the existing or modified global stratosphere

2020 ◽  
Author(s):  
Daniel M. Murphy ◽  
Karl D. Froyd ◽  
Ilann Bourgeois ◽  
Charles A. Brock ◽  
Agnieszka Kupc ◽  
...  
Keyword(s):  
Surface Area ◽  
Northern Hemisphere ◽  
Aerosol Particles ◽  
Climate Impact ◽  
Infrared Heating ◽  
Heterogeneous Chemistry ◽  
Radiative Effects ◽  
Size Dependent ◽  
Four Seasons ◽  
Far Ultraviolet

Abstract. The size of aerosol particles has fundamental effects on their chemistry and radiative effects. We explore those effects using aerosol size and composition data in the lowermost stratosphere along with calculations of light scattering. In the size range between about 0.1 and 1.0 µm diameter (accumulation mode), there are at least two modes of particles in the lowermost stratosphere. The larger mode consists mostly of particles produced in the stratosphere and the smaller mode consists mostly of particles transported from the troposphere. The stratospheric mode is similar in the Northern and Southern hemispheres whereas the tropospheric mode is much more abundant in the Northern Hemisphere. The two modes have very different roles for radiative effects on climate and for heterogeneous chemistry. Because the larger particles are more efficient at scattering light, most of the radiative effect in the lowermost stratosphere is due to stratospheric particles. In contrast, the tropospheric particles can have more surface area, at least in the Northern Hemisphere. The surface area of tropospheric particles could have significant implications for heterogeneous chemistry because these particles, which are partially neutralized and contain organics, do not correspond to the surfaces used for laboratory studies of stratospheric heterogeneous chemistry. The purity of sulfuric acid particles in the stratospheric mode shows that there is limited production of secondary organic aerosol in the stratosphere, especially in the Southern Hemisphere. Out of eight sets of flights sampling the lowermost stratosphere (four seasons and two hemispheres) there were three with large injections of specific materials: volcanic, biomass burning, or dust. We then extend the analysis of size-dependent properties to particles considered for intentional climate modification. There is no single size that will simultaneously optimize the climate impact relative to the injected mass, infrared heating, potential for heterogeneous chemistry, and undesired changes in direct sunlight. In addition, light absorption in the far ultraviolet is identified as an issue requiring more study for both the existing and potentially modified stratosphere.

scholarly journals In situ observations of aerosol particles remaining from evaporated cirrus crystals: Comparing clean and polluted air masses

2002 ◽  
Vol 2 (5) ◽  
pp. 1599-1633 ◽  
Author(s):  
M. Seifert ◽  
J. Ström ◽  
R. Krejci ◽  
A. Minikin ◽  
A. Petzold ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Aerosol Particles ◽  
Pollution Level ◽  
Size Distributions ◽  
Number Density ◽  
Particle Volume ◽  
The North ◽  
In Situ Observations

Abstract. In situ observations of aerosol particles contained in cirrus crystals are presented and compared to interstitial aerosol size distributions (non-activated particles in between the cirrus crystals). The observations were conducted in cirrus clouds in the Southern and Northern Hemisphere mid-latitudes during the INCA project. The first campaign in March and April 2000 was performed from Punta Arenas, Chile (54° S) in pristine air. The second campaign in September and October 2000 was performed from Prestwick, Scotland (53° N) in the vicinity of the North Atlantic flight corridor. Size distribution measurements of crystal residuals (particles remaining after evaporation of the crystals) show that small aerosol particles (Dp < 0.1µm) dominate the number density of residuals. The crystal residual size distributions were significantly different in the two campaigns. On average the residual size distributions were shifted towards larger sizes in the Southern Hemisphere. For a given integral residual number density, the calculated particle volume was on average three times larger in the Southern Hemisphere. This may be of significance to the vertical redistribution of aerosol mass by clouds in the tropopause region. In both campaigns the mean residual size increased with increasing crystal number density. The observations of ambient aerosol particles were consistent with the expected higher pollution level in the Northern Hemisphere. The fraction of residual particles only contributes to approximately a percent or less of the total number of particles, which is the sum of the residual and interstitial particles.

Large hemispheric difference in ultrafine aerosol concentrations in the lowermost stratosphere

2021 ◽  
Author(s):  
Christina J Williamson ◽  
Agnieszka Kupc ◽  
Andrew Rollins ◽  
Jan Kazil ◽  
Karl D Froyd ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Sulphur Dioxide ◽  
Climate Impact ◽  
Hemispheric Difference ◽  
Aircraft Emissions ◽  
Four Seasons ◽  
Aerosol Distribution ◽  
Ultrafine Aerosols ◽  
Ultrafine Aerosol ◽  
A Current

&lt;p&gt;On the NASA Atmospheric Tomography Mission (ATom), we observed a sharp hemispheric contrast in the concentration of ultrafine aerosols (3-12 nm diameter) in the lowermost stratosphere that persisted through all four seasons. Exploring possible causes, we show that this is likely caused by aircraft, which emit both ultrafine aerosol and precursor gases for new particle formation (NPF) in quantities that agree well with our observations. While aircraft may emit a range of NPF precursors, we focus here on sulphur dioxide (a major source of atmospheric sulphuric acid), of which we have observations from the same mission.&amp;#160; We observe the same hemispheric contrast in sulphur dioxide as ultrafine aerosol, and find that the observed concentrations are in alignment with inventoried aircraft emissions. We present box modeling and thermodynamic calculations that support the plausibility of NPF under the conditions and sulphur dioxide concentrations observed on ATom.&lt;/p&gt;&lt;p&gt;While the direct climate impact of ultrafine aerosol in the lowermost stratosphere (LMS) may currently be small, our observations show a definitive size distribution shift of the background aerosol distribution in the northern hemisphere. This is important for assessing aviation impacts, and the expected impacts of increased air-traffic. Furthermore, climate intervention via injection of sulphate or aerosols into the stratosphere is a current subject of research. Our study shows that NPF is possible and likely already happening in the LMS, which must be accounted for in models for stratospheric modification, and points out that we must consider that any intentional stratospheric modification will be applied to two very different hemispheres: a largely pristine southern hemisphere; and an already anthropogenically modified northern hemisphere.&lt;/p&gt;

scholarly journals In-situ observations of aerosol particles remaining from evaporated cirrus crystals: Comparing clean and polluted air masses

2003 ◽  
Vol 3 (4) ◽  
pp. 1037-1049 ◽  
Author(s):  
M. Seifert ◽  
J. Ström ◽  
R. Krejci ◽  
A. Minikin ◽  
A. Petzold ◽  
...  
Keyword(s):  
Size Distribution ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Aerosol Particles ◽  
Pollution Level ◽  
Size Distributions ◽  
Number Density ◽  
Particle Volume ◽  
In Situ Observations

Abstract. In-situ observations of aerosol particles contained in cirrus crystals are presented and compared to interstitial aerosol size distributions (non-activated particles in between the cirrus crystals). The observations were conducted in cirrus clouds in the Southern and Northern Hemisphere mid-latitudes during the INCA project. The first campaign in March and April 2000 was performed from Punta Arenas, Chile (54°S) in pristine air. The second campaign in September and October 2000 was performed from Prestwick, Scotland (53°N) in the vicinity of the North Atlantic flight corridor. Size distribution measurements of crystal residuals (particles remaining after evaporation of the crystals) show that small aerosol particles (Dp< 0.1 mm) dominate the number density of residuals. The crystal residual size distributions were significantly different in the two campaigns. On average the residual size distributions were shifted towards larger sizes in the Southern Hemisphere. For a given integral residual number density, the calculated particle volume was on average three times larger in the Southern Hemisphere. This may be of significance to the vertical redistribution of aerosol mass by clouds in the tropopause region. In both campaigns the mean residual size increased slightly with increasing crystal number density. The form of the residual size distribution did not depend on temperature as one might have expected considering different modes of nucleation. The observations of ambient aerosol particles were consistent with the expected higher pollution level in the Northern Hemisphere. The fraction of residual particles only contributes to approximately a percent or less of the total number of particles, which is the sum of the residual and interstitial particles. Excellent agreement between the CVI and FSSP-300 probes was found supporting the assumption that each crystal is associated with only one residual particle.

scholarly journals The climate impact of COVID-19-induced contrail changes

2021 ◽  
Vol 21 (12) ◽  
pp. 9405-9416
Author(s):  
Andrew Gettelman ◽  
Chieh-Chieh Chen ◽  
Charles G. Bardeen
Keyword(s):  
Surface Temperature ◽  
Northern Hemisphere ◽  
Land Surface ◽  
Radiative Forcing ◽  
Climate Impact ◽  
Climate Impacts ◽  
Infrared Heating ◽  
Boreal Summer ◽  
Surface Temperature Change ◽  
Standard Deviations

Abstract. The COVID-19 pandemic caused significant economic disruption in 2020 and severely impacted air traffic. We use a state-of-the-art Earth system model and ensembles of tightly constrained simulations to evaluate the effect of the reductions in aviation traffic on contrail radiative forcing and climate in 2020. In the absence of any COVID-19-pandemic-caused reductions, the model simulates a contrail effective radiative forcing (ERF) of 62 ± 59 mW m−2 (2 standard deviations). The contrail ERF has complex spatial and seasonal patterns that combine the offsetting effect of shortwave (solar) cooling and longwave (infrared) heating from contrails and contrail cirrus. Cooling is larger in June–August due to the preponderance of aviation in the Northern Hemisphere, while warming occurs throughout the year. The spatial and seasonal forcing variations also map onto surface temperature variations. The net land surface temperature change due to contrails in a normal year is estimated at 0.13 ± 0.04 K (2 standard deviations), with some regions warming as much as 0.7 K. The effect of COVID-19 reductions in flight traffic decreased contrails. The unique timing of such reductions, which were maximum in Northern Hemisphere spring and summer when the largest contrail cooling occurs, means that cooling due to fewer contrails in boreal spring and fall was offset by warming due to fewer contrails in boreal summer to give no significant annual averaged ERF from contrail changes in 2020. Despite no net significant global ERF, because of the spatial and seasonal timing of contrail ERF, some land regions would have cooled slightly (minimum −0.2 K) but significantly from contrail changes in 2020. The implications for future climate impacts of contrails are discussed.

scholarly journals Climate impact of volcanic eruptions: the sensitivity to eruption season and latitude in MPI-ESM ensemble experiments

2021 ◽  
Vol 21 (17) ◽  
pp. 13425-13442
Author(s):  
Zhihong Zhuo ◽  
Ingo Kirchner ◽  
Stephan Pfahl ◽  
Ulrich Cubasch
Keyword(s):  
Southern Hemisphere ◽  
Regional Climate ◽  
Volcanic Eruptions ◽  
Climate Impact ◽  
Climate Impacts ◽  
Cloud Formation ◽  
Radiative Effects ◽  
Near Surface ◽  
Volcanic Aerosols ◽  
The Impact

Abstract. Explosive volcanic eruptions influence near-surface temperature and precipitation especially in the monsoon regions, but the impact varies with different eruption seasons and latitudes. To study this variability, two groups of ensemble simulations are performed with volcanic eruptions in June and December at 0∘ representing an equatorial eruption (EQ) and at 30∘ N and 30∘ S representing Northern and Southern Hemisphere eruptions (NH and SH). Results show significant cooling especially in areas with enhanced volcanic aerosol content. Compared to the EQ eruption, stronger cooling emerges in the Northern Hemisphere after the NH eruption and in the Southern Hemisphere after the SH eruption. Stronger precipitation variations occur in the tropics than in the high latitudes. Summer and winter eruptions lead to similar hydrological impacts. The NH and the SH eruptions have reversed climate impacts, especially in the regions of the South Asian summer monsoon (SASM). After the NH eruption, direct radiative effects of volcanic aerosols induce changes in the interhemispheric and land–sea thermal contrasts, which move the intertropical convergence zone (ITCZ) southward and weaken the SASM. This reduces the moisture transport from the ocean and reduces cloud formation and precipitation in India. The subsequent radiative feedbacks due to regional cloud cover lead to warming in India. After the SH eruption, vice versa, a northward movement of the ITCZ and strengthening of the SASM, along with enhanced cloud formation, lead to enhanced precipitation and cooling in India. This emphasizes the sensitivity of regional climate impacts of volcanic eruptions to eruption latitude, which relates to the dynamical response of the climate system to radiative effects of volcanic aerosols and the subsequent regional physical feedbacks. Our results indicate the importance of considering dynamical and physical feedbacks to understand the mechanism behind regional climate responses to volcanic eruptions and may also shed light on the climate impact and potential mechanisms of stratospheric aerosol engineering.

Alpha-Effect, Current and Kinetic Helicities for Magnetically Driven Turbulence, and Solar Dynamo

2000 ◽  
Vol 179 ◽  
pp. 387-388
Author(s):  
Gaetano Belvedere ◽  
V. V. Pipin ◽  
G. Rüdiger
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Convection Zone ◽  
Solar Surface ◽  
Momentum Transport ◽  
Angular Momentum Transport ◽  
Magnetic Buoyancy ◽  
Alpha Effect ◽  
Current Helicity

Extended AbstractRecent numerical simulations lead to the result that turbulence is much more magnetically driven than believed. In particular the role ofmagnetic buoyancyappears quite important for the generation ofα-effect and angular momentum transport (Brandenburg &amp; Schmitt 1998). We present results obtained for a turbulence field driven by a (given) Lorentz force in a non-stratified but rotating convection zone. The main result confirms the numerical findings of Brandenburg &amp; Schmitt that in the northern hemisphere theα-effect and the kinetic helicityℋkin= 〈u′ · rotu′〉 are positive (and negative in the northern hemisphere), this being just opposite to what occurs for the current helicityℋcurr= 〈j′ ·B′〉, which is negative in the northern hemisphere (and positive in the southern hemisphere). There has been an increasing number of papers presenting observations of current helicity at the solar surface, all showing that it isnegativein the northern hemisphere and positive in the southern hemisphere (see Rüdigeret al. 2000, also for a review).

The Hemispheric Sign Rule of Current Helicity during the Rising Phase of Cycle 23

2000 ◽  
Vol 179 ◽  
pp. 303-306
Author(s):  
S. D. Bao ◽  
G. X. Ai ◽  
H. Q. Zhang
Keyword(s):  
Solar Cycle ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Active Regions ◽  
Hemispheric Preference ◽  
Current Helicity

AbstractWe compute the signs of two different current helicity parameters (i.e., αbestandHc) for 87 active regions during the rise of cycle 23. The results indicate that 59% of the active regions in the northern hemisphere have negative αbestand 65% in the southern hemisphere have positive. This is consistent with that of the cycle 22. However, the helicity parameterHcshows a weaker opposite hemispheric preference in the new solar cycle. Possible reasons are discussed.

scholarly journals First results of low frequency electromagnetic wave detector of TC-2/Double Star program

2005 ◽  
Vol 23 (8) ◽  
pp. 2803-2811 ◽  
Author(s):  
J. B. Cao ◽  
Z. X. Liu ◽  
J. Y. Yang ◽  
C. X. Yian ◽  
Z. G. Wang ◽  
...  
Keyword(s):  
Electromagnetic Wave ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Geomagnetic Storms ◽  
Low Frequency ◽  
Wave Detector ◽  
Ion Cyclotron Waves ◽  
Satellite Platform ◽  
Ion Cyclotron ◽  
First Results

Abstract. LFEW is a low frequency electromagnetic wave detector mounted on TC-2, which can measure the magnetic fluctuation of low frequency electromagnetic waves. The frequency range is 8 Hz to 10 kHz. LFEW comprises a boom-mounted, three-axis search coil magnetometer, a preamplifier and an electronics box that houses a Digital Spectrum Analyzer. LFEW was calibrated at Chambon-la-Forêt in France. The ground calibration results show that the performance of LFEW is similar to that of STAFF on TC-1. The first results of LFEW show that it works normally on board, and that the AC magnetic interference of the satellite platform is very small. In the plasmasphere, LFEW observed the ion cyclotron waves. During the geomagnetic storm on 8 November 2004, LFEW observed a wave burst associated with the oxygen ion cyclotron waves. This observation shows that during geomagnetic storms, the oxygen ions are very active in the inner magnetosphere. Outside the plasmasphere, LFEW observed the chorus on 3 November 2004. LFEW also observed the plasmaspheric hiss and mid-latitude hiss both in the Southern Hemisphere and Northern Hemisphere on 8 November 2004. The hiss in the Southern Hemisphere may be the reflected waves of the hiss in the Northern Hemisphere.

On a possible geological cause of changes in the position of the axis of the earth's crust

1867 ◽  
Vol 15 ◽  
pp. 46-54 ◽  
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Earth’S Crust ◽  
The Subject ◽  
Earth's Crust ◽  
Geological Observation

At a time when the causes which have led to climatal changes in various parts of the globe are the subject of so much discussion, but little apology is needed for calling the attention of this Society to what possibly may have been one of these causes, though it has apparently hitherto escaped observation. That great changes of climate have taken place, at all events in the northern hemisphere of the globe, is one of the best established facts of geology, and that corresponding changes have not been noticed to the same extent in the southern hemisphere may possibly be considered as due, rather to a more limited amount of geological observation, than to an absence of the phenomena indicative of such alterations in climatal con­ditions having occurred.

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