scholarly journals Stratospheric aerosol layer perturbation caused by the 2019 Raikoke and Ulawun eruptions and their radiative forcing

2021 ◽  
Vol 21 (1) ◽  
pp. 535-560
Author(s):  
Corinna Kloss ◽  
Gwenaël Berthet ◽  
Pasquale Sellitto ◽  
Felix Ploeger ◽  
Ghassan Taha ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Short Wavelength ◽  
Radiative Forcing ◽  
Stratospheric Aerosol ◽  
Aerosol Layer ◽  
Radiative Forcings ◽  
Clear Sky ◽  
The Earth ◽  
Northern Latitudes ◽  
The Tropics

Abstract. In June 2019 a stratospheric eruption occurred at Raikoke (48∘ N, 153∘ E). Satellite observations show the injection of ash and SO2 into the lower stratosphere and an early entrainment of the plume into a cyclone. Following the Raikoke eruption, stratospheric aerosol optical depth (sAOD) values increased in the whole Northern Hemisphere and tropics and remained enhanced for more than 1 year, with peak values at 0.040 (short-wavelength, high northern latitudes) to 0.025 (short-wavelength, Northern Hemisphere average). Discrepancies between observations and global model simulations indicate that ash may have influenced the extent and evolution of the sAOD. Top of the atmosphere radiative forcings are estimated at values between −0.3 and -0.4Wm-2 (clear-sky) and of −0.1 to -0.2Wm-2 (all-sky), comparable to what was estimated for the Sarychev eruption in 2009. Almost simultaneously two significantly smaller stratospheric eruptions occurred at Ulawun (5∘ S, 151∘ E) in June and August. Aerosol enhancements from the Ulawun eruptions mainly had an impact on the tropics and Southern Hemisphere. The Ulawun plume circled the Earth within 1 month in the tropics. Peak shorter-wavelength sAOD values at 0.01 are found in the tropics following the Ulawun eruptions and a radiative forcing not exceeding −0.15 (clear-sky) and −0.05 (all-sky). Compared to the Canadian fires (2017), Ambae eruption (2018), Ulawun (2019) and the Australian fires (2019/2020), the highest sAOD and radiative forcing values are found for the Raikoke eruption.

scholarly journals Stratospheric aerosol layer perturbation caused by the 2019 Raikoke and Ulawun eruptions and climate impact

2020 ◽  
Author(s):  
Corinna Kloss ◽  
Gwenaël Berthet ◽  
Pasquale Sellitto ◽  
Felix Ploeger ◽  
Ghassan Taha ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Radiative Forcing ◽  
Climate Impact ◽  
Stratospheric Aerosol ◽  
Aerosol Layer ◽  
Radiative Forcings ◽  
Clear Sky ◽  
Northern Latitudes ◽  
One Year ◽  
The Tropics

Abstract. In June 2019 a stratospheric moderate eruption occurred at Raikoke (48° N, 153° E). Satellite observations show the injection of ash and SO2 into the lower stratosphere and an early entrainment of the plume into a cyclone. Following the Raikoke eruption stratospheric Aerosol Optical Depth (sAOD) values increased in the whole northern hemisphere and tropics and remained enhanced for more than one year, with peak values at 0.040 (shorter-wavelength visible, higher northern latitudes) to 0.025 (shorter-wavelength visible, average northern hemisphere). Discrepancies between observations and models indicate that ash has played a role on evolution and sAOD values. Top of the atmosphere radiative forcings are estimated at values between −0.3 and −0.4 W/m2 (clear-sky), and of −0.1 to −0.2 W/m2 (all-sky), comparable to what was estimated for the Sarychev eruption in 2009. Almost simultaneously two significantly smaller stratospheric eruptions occurred at Ulawun (5° S, 151° E) in June and August. Aerosol enhancements from the Ulawun eruptions had mainly an impact on the tropics and southern hemisphere. The Ulawun plume circled the Earth within one month in the tropics. Peak shorter-wavelength sAOD values at 0.01 are found in the tropics following the Ulawun eruptions, and a radiative forcing not exceeding −0.15 (clear-sky) and −0.05 (all-sky). Compared to the Canadian Fires (2017), Ambae eruption (2018), Ulawun (2019) and the Australian fires (2019/2020) highest sAOD values and RF are found for the Raikoke eruption.

scholarly journals Particulate sulfur in the upper troposphere and lowermost stratosphere – sources and climate forcing

2017 ◽  
Vol 17 (18) ◽  
pp. 10937-10953 ◽  
Author(s):  
Bengt G. Martinsson ◽  
Johan Friberg ◽  
Oscar S. Sandvik ◽  
Markus Hermann ◽  
Peter F. J. van Velthoven ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Radiative Forcing ◽  
Chemical Elements ◽  
Volcanic Eruptions ◽  
Stratospheric Aerosol ◽  
Aerosol Layer ◽  
Pixe Analysis ◽  
Upper Troposphere ◽  
Particulate Sulfur ◽  
Fine Mode

Abstract. This study is based on fine-mode aerosol samples collected in the upper troposphere (UT) and the lowermost stratosphere (LMS) of the Northern Hemisphere extratropics during monthly intercontinental flights at 8.8–12 km altitude of the IAGOS-CARIBIC platform in the time period 1999–2014. The samples were analyzed for a large number of chemical elements using the accelerator-based methods PIXE (particle-induced X-ray emission) and PESA (particle elastic scattering analysis). Here the particulate sulfur concentrations, obtained by PIXE analysis, are investigated. In addition, the satellite-borne lidar aboard CALIPSO is used to study the stratospheric aerosol load. A steep gradient in particulate sulfur concentration extends several kilometers into the LMS, as a result of increasing dilution towards the tropopause of stratospheric, particulate sulfur-rich air. The stratospheric air is diluted with tropospheric air, forming the extratropical transition layer (ExTL). Observed concentrations are related to the distance to the dynamical tropopause. A linear regression methodology handled seasonal variation and impact from volcanism. This was used to convert each data point into stand-alone estimates of a concentration profile and column concentration of particulate sulfur in a 3 km altitude band above the tropopause. We find distinct responses to volcanic eruptions, and that this layer in the LMS has a significant contribution to the stratospheric aerosol optical depth and thus to its radiative forcing. Further, the origin of UT particulate sulfur shows strong seasonal variation. We find that tropospheric sources dominate during the fall as a result of downward transport of the Asian tropopause aerosol layer (ATAL) formed in the Asian monsoon, whereas transport down from the Junge layer is the main source of UT particulate sulfur in the first half of the year. In this latter part of the year, the stratosphere is the clearly dominating source of particulate sulfur in the UT during times of volcanic influence and under background conditions.

scholarly journals Transport of the 2017 Canadian wildfire plume to the tropics via the Asian monsoon circulation

2019 ◽  
Vol 19 (21) ◽  
pp. 13547-13567 ◽  
Author(s):  
Corinna Kloss ◽  
Gwenaël Berthet ◽  
Pasquale Sellitto ◽  
Felix Ploeger ◽  
Silvia Bucci ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Asian Monsoon ◽  
Regional Climate ◽  
Climate Impact ◽  
Monsoon Circulation ◽  
Aerosol Layer ◽  
Fire Plume ◽  
Monsoon Area ◽  
The Tropics ◽  
The Impact

Abstract. We show that a fire plume injected into the lower stratosphere at high northern latitudes during the Canadian wildfire event in August 2017 partly reached the tropics. The transport to the tropics was mediated by the anticyclonic flow of the Asian monsoon circulation. The fire plume reached the Asian monsoon area in late August/early September, when the Asian monsoon anticyclone (AMA) was still in place. While there is no evidence of mixing into the center of the AMA, we show that a substantial part of the fire plume is entrained into the anticyclonic flow at the AMA edge and is transported from the extratropics to the tropics, and possibly the Southern Hemisphere particularly following the north–south flow on the eastern side of the AMA. In the tropics the fire plume is lifted by ∼5 km in 7 months. Inside the AMA we find evidence of the Asian tropopause aerosol layer (ATAL) in August, doubling background aerosol conditions with a calculated top of the atmosphere shortwave radiative forcing of −0.05 W m−2. The regional climate impact of the fire signal in the wider Asian monsoon area in September exceeds the impact of the ATAL by a factor of 2–4 and compares to that of a plume coming from an advected moderate volcanic eruption. The stratospheric, trans-continental transport of this plume to the tropics and the related regional climate impact point to the importance of long-range dynamical interconnections of pollution sources.

scholarly journals Exploring accumulation-mode H<sub>2</sub>SO<sub>4</sub> versus SO<sub>2</sub> stratospheric sulfate geoengineering in a sectional aerosol–chemistry–climate model

2019 ◽  
Vol 19 (7) ◽  
pp. 4877-4897 ◽  
Author(s):  
Sandro Vattioni ◽  
Debra Weisenstein ◽  
David Keith ◽  
Aryeh Feinberg ◽  
Thomas Peter ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Climate Model ◽  
Continuous Production ◽  
Stratospheric Aerosol ◽  
So2 Emissions ◽  
Aerosol Chemistry ◽  
Accumulation Mode ◽  
Direct Emission ◽  
Equivalent Mass ◽  
The Tropics

Abstract. Stratospheric sulfate geoengineering (SSG) could contribute to avoiding some of the adverse impacts of climate change. We used the SOCOL-AER global aerosol–chemistry–climate model to investigate 21 different SSG scenarios, each with 1.83 Mt S yr−1 injected either in the form of accumulation-mode H2SO4 droplets (AM H2SO4), gas-phase SO2 or as combinations of both. For most scenarios, the sulfur was continuously emitted at an altitude of 50 hPa (≈20 km) in the tropics and subtropics. We assumed emissions to be zonally and latitudinally symmetric around the Equator. The spread of emissions ranged from 3.75∘ S–3.75∘ N to 30∘ S–30∘ N. In the SO2 emission scenarios, continuous production of tiny nucleation-mode particles results in increased coagulation, which together with gaseous H2SO4 condensation, produces coarse-mode particles. These large particles are less effective for backscattering solar radiation and have a shorter stratospheric residence time than AM H2SO4 particles. On average, the stratospheric aerosol burden and corresponding all-sky shortwave radiative forcing for the AM H2SO4 scenarios are about 37 % larger than for the SO2 scenarios. The simulated stratospheric aerosol burdens show a weak dependence on the latitudinal spread of emissions. Emitting at 30∘ N–30∘ S instead of 10∘ N–10∘ S only decreases stratospheric burdens by about 10 %. This is because a decrease in coagulation and the resulting smaller particle size is roughly balanced by faster removal through stratosphere-to-troposphere transport via tropopause folds. Increasing the injection altitude is also ineffective, although it generates a larger stratospheric burden, because enhanced condensation and/or coagulation leads to larger particles, which are less effective scatterers. In the case of gaseous SO2 emissions, limiting the sulfur injections spatially and temporally in the form of point and pulsed emissions reduces the total global annual nucleation, leading to less coagulation and thus smaller particles with increased stratospheric residence times. Pulse or point emissions of AM H2SO4 have the opposite effect: they decrease the stratospheric aerosol burden by increasing coagulation and only slightly decrease clear-sky radiative forcing. This study shows that direct emission of AM H2SO4 results in higher radiative forcing for the same sulfur equivalent mass injection strength than SO2 emissions, and that the sensitivity to different injection strategies varies for different forms of injected sulfur.

scholarly journals The Interactive Stratospheric Aerosol Model Intercomparison Project (ISA-MIP): motivation and experimental design

2018 ◽  
Vol 11 (7) ◽  
pp. 2581-2608 ◽  
Author(s):  
Claudia Timmreck ◽  
Graham W. Mann ◽  
Valentina Aquila ◽  
Rene Hommel ◽  
Lindsay A. Lee ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Volcanic Eruptions ◽  
Stratospheric Aerosol ◽  
Transport Processes ◽  
Aerosol Layer ◽  
Model Intercomparison ◽  
Aerosol Model ◽  
Model Experiments ◽  
Aerosol Forcing ◽  
Intercomparison Project

Abstract. The Stratospheric Sulfur and its Role in Climate (SSiRC) Interactive Stratospheric Aerosol Model Intercomparison Project (ISA-MIP) explores uncertainties in the processes that connect volcanic emission of sulfur gas species and the radiative forcing associated with the resulting enhancement of the stratospheric aerosol layer. The central aim of ISA-MIP is to constrain and improve interactive stratospheric aerosol models and reduce uncertainties in the stratospheric aerosol forcing by comparing results of standardized model experiments with a range of observations. In this paper we present four co-ordinated inter-model experiments designed to investigate key processes which influence the formation and temporal development of stratospheric aerosol in different time periods of the observational record. The Background (BG) experiment will focus on microphysics and transport processes under volcanically quiescent conditions, when the stratospheric aerosol is controlled by the transport of aerosols and their precursors from the troposphere to the stratosphere. The Transient Aerosol Record (TAR) experiment will explore the role of small- to moderate-magnitude volcanic eruptions, anthropogenic sulfur emissions, and transport processes over the period 1998–2012 and their role in the warming hiatus. Two further experiments will investigate the stratospheric sulfate aerosol evolution after major volcanic eruptions. The Historical Eruptions SO2 Emission Assessment (HErSEA) experiment will focus on the uncertainty in the initial emission of recent large-magnitude volcanic eruptions, while the Pinatubo Emulation in Multiple models (PoEMS) experiment will provide a comprehensive uncertainty analysis of the radiative forcing from the 1991 Mt Pinatubo eruption.

scholarly journals Radiative forcing bias of simulated surface albedo modifications linked to forest cover changes at northern latitudes

2015 ◽  
Vol 12 (7) ◽  
pp. 2195-2205 ◽  
Author(s):  
R. M. Bright ◽  
G. Myhre ◽  
R. Astrup ◽  
C. Antón-Fernández ◽  
A. H. Strømman
Keyword(s):  
Radiative Forcing ◽  
Surface Albedo ◽  
Forest Cover ◽  
Climate Models ◽  
Open Area ◽  
Data Set ◽  
Radiative Forcings ◽  
Open Forest ◽  
Northern Latitudes ◽  
Analytical Time

Abstract. In the presence of snow, the bias in the prediction of surface albedo by many climate models remains difficult to correct due to the difficulties of separating the albedo parameterizations from those describing snow and vegetation cover and structure. This can be overcome by extracting the albedo parameterizations in isolation, by executing them with observed meteorology and information on vegetation structure, and by comparing the resulting predictions to observations. Here, we employ an empirical data set of forest structure and daily meteorology for three snow cover seasons and for three case regions in boreal Norway to compute and evaluate predicted albedo to those based on daily MODIS retrievals. Forest and adjacent open area albedos are subsequently used to estimate bias in top-of-the-atmosphere (TOA) radiative forcings (RF) from albedo changes (Δα, Open–Forest) connected to land use and land cover changes (LULCC). As expected, given the diversity of approaches by which snow masking by tall-statured vegetation is parameterized, the magnitude and sign of the albedo biases varied considerably for forests. Large biases at the open sites were also detected, which was unexpected given that these sites were snow-covered throughout most of the analytical time period, therefore eliminating potential biases linked to snow-masking parameterizations. Biases at the open sites were mostly positive, exacerbating the strength of vegetation masking effects and hence the simulated LULCC Δα RF. Despite the large biases in both forest and open area albedos by some schemes in some months and years, the mean Δα RF bias over the 3-year period (November–May) was considerably small across models (−2.1 ± 1.04 Wm−2; 21 ± 11%); four of six models had normalized mean absolute errors less than 20%. Identifying systematic sources of the albedo prediction biases proved challenging, although for some schemes clear sources were identified.

scholarly journals Variability of the Daily-Mean Shortwave Cloud Radiative Forcing at the Surface at a Midlatitude Site in Southwestern Europe

2014 ◽  
Vol 27 (20) ◽  
pp. 7769-7780 ◽  
Author(s):  
Vanda Salgueiro ◽  
Maria João Costa ◽  
Ana Maria Silva ◽  
Daniele Bortoli
Keyword(s):  
Seasonal Variation ◽  
Radiative Forcing ◽  
Quantitative Relationship ◽  
Mean Values ◽  
Cloud Radiative Forcing ◽  
Radiative Forcings ◽  
Black And White ◽  
Clear Sky ◽  
Surface Measurements ◽  
Multifilter Rotating Shadowband Radiometer

Abstract The shortwave cloud radiative forcing is calculated from surface measurements taken in Évora from 2003 to 2010 with a multifilter rotating shadowband radiometer (MFRSR) and with an Eppley black and white pyranometer. A new approach to estimate the clear-sky irradiance based on radiative transfer calculations is also proposed. The daily-mean values of the cloud radiative forcing (absolute and normalized) as well as their monthly and seasonal variabilities are analyzed. The study shows greater variability of radiative forcing during springtime with respect to the other seasons. The mean daily cloudy periods have seasonal variation proportional to the seasonal variation of the cloud radiative forcing, with maximum values also occurring during springtime. The minimum values found for the daily-mean cloud radiative forcing are −139.5 and −198.4 W m−2 for MFRSR and Eppley data, respectively; the normalized values present about 40% of sample amplitude, both for MFRSR and Eppley. In addition, a quantitative relationship between the MFRSR and Eppley cloud radiative forcings applicable to other locations is proposed.

scholarly journals Extreme temperature and precipitation response to solar dimming and stratospheric aerosol geoengineering

2018 ◽  
Author(s):  
Duoying Ji ◽  
Songsong Fang ◽  
Charles L. Curry ◽  
Hiroki Kashimura ◽  
Shingo Watanabe ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Extreme Temperature ◽  
Stratospheric Aerosol ◽  
Aerosol Direct Effect ◽  
Temperature And Precipitation ◽  
Intercomparison Project ◽  
Lower Maximum ◽  
Maximum Temperatures ◽  
Subtropical Oceans ◽  
The Tropics

Abstract. We examine extreme temperature and precipitation under two potential geoengineering methods forming part of the Geoengineering Model Intercomparison Project (GeoMIP). The solar dimming experiment G1 is designed to completely offset the global mean radiative forcing due to a CO2-quadrupling experiment (abrupt 4 × CO2), while in GeoMIP experiment G4, the radiative forcing due to the representative concentration pathway 4.5 (RCP4.5) scenario is partly offset by a simulated layer of aerosols in the stratosphere. Both G1 and G4 geoengineering simulations lead to lower maximum temperatures at higher latitudes, and on land primarily through feedback effects involving high latitude processes such as snow cover, sea ice and soil moisture. Maximum 5-day precipitation increases over subtropical oceans, whereas warm spells decrease markedly in the tropics, and the number of consecutive dry days decreases in most deserts. The precipitation during the tropical cyclone (hurricane) seasons becomes less intense, whilst the remainder of the year becomes wetter. Aerosol injection is more effective than dimming in moderating extreme precipitation (and flooding), possibly due to stratospheric warming by aerosol injection working in tandem with sea surface temperature reductions to moderate extreme tropical storm cyclogenesis. The differences in the response of temperature extremes between the two types of geoengineering are relatively minor. Despite the magnitude of the radiative forcing applied in G1 being ~ 6.5 times larger than in G4, and differences in the aerosol chemistry and transport schemes amongst the models, one can discern clear differences in the precipitation extremes between the types of geoengineering probably due to the aerosol direct effect and related energetic changes.

scholarly journals Climate system response to stratospheric sulfate aerosols: sensitivity to altitude of aerosol layer

2019 ◽  
Vol 10 (4) ◽  
pp. 885-900 ◽  
Author(s):  
Krishna-Pillai Sukumara-Pillai Krishnamohan ◽  
Govindasamy Bala ◽  
Long Cao ◽  
Lei Duan ◽  
Ken Caldeira
Keyword(s):  
Radiative Forcing ◽  
Stratospheric Aerosol ◽  
System Response ◽  
Substantial Part ◽  
Aerosol Layer ◽  
Sulfate Aerosols ◽  
Cooling Effectiveness ◽  
Aerosol Radiative Forcing ◽  
Stratospheric Water Vapor ◽  
Effective Radiative Forcing

Abstract. Reduction of surface temperatures of the planet by injecting sulfate aerosols in the stratosphere has been suggested as an option to reduce the amount of human-induced climate warming. Several previous studies have shown that for a specified amount of injection, aerosols injected at a higher altitude in the stratosphere would produce more cooling because aerosol sedimentation would take longer. In this study, we isolate and assess the sensitivity of stratospheric aerosol radiative forcing and the resulting climate change to the altitude of the aerosol layer. We study this by prescribing a specified amount of sulfate aerosols, of a size typical of what is produced by volcanoes, distributed uniformly at different levels in the stratosphere. We find that stratospheric sulfate aerosols are more effective in cooling climate when they reside higher in the stratosphere. We explain this sensitivity in terms of effective radiative forcing: volcanic aerosols heat the stratospheric layers where they reside, altering stratospheric water vapor content, tropospheric stability, and clouds, and consequently the effective radiative forcing. We show that the magnitude of the effective radiative forcing is larger when aerosols are prescribed at higher altitudes and the differences in radiative forcing due to fast adjustment processes can account for a substantial part of the dependence of the amount of cooling on aerosol altitude. These altitude effects would be additional to dependences on aerosol microphysics, transport, and sedimentation, which are outside the scope of this study. The cooling effectiveness of stratospheric sulfate aerosols likely increases with the altitude of the aerosol layer both because aerosols higher in the stratosphere have larger effective radiative forcing and because they have higher stratospheric residence time; these two effects are likely to be of comparable importance.

scholarly journals The HNO<sub>3</sub> forming branch of the HO<sub>2</sub> + NO reaction: pre-industrial-to-present trends in atmospheric species and radiative forcings

2011 ◽  
Vol 11 (17) ◽  
pp. 8929-8943 ◽  
Author(s):  
O. A. Søvde ◽  
C. R. Hoyle ◽  
G. Myhre ◽  
I. S. A. Isaksen
Keyword(s):  
Radiative Forcing ◽  
Transport Model ◽  
Three Dimensional ◽  
Branching Ratio ◽  
Pressure Effects ◽  
Atmospheric Composition ◽  
Radiative Forcings ◽  
Atmospheric Species ◽  
Tropospheric O3 ◽  
The Tropics

Abstract. Recent laboratory measurements have shown the existence of a HNO3 forming branch of the HO2 + NO reaction. This reaction is the main source of tropospheric O3, through the subsequent photolysis of NO2, as well as being a major source of OH. The branching of the reaction to HNO3 reduces the formation of these species significantly, affecting O3 abundances, radiative forcing and the oxidation capacity of the troposphere. The Oslo CTM2, a three-dimensional chemistry transport model, is used to calculate atmospheric composition and trends with and without the new reaction branch. Results for the present day atmosphere, when both temperature and pressure effects on the branching ratio are accounted for, show an 11 % reduction in the calculated tropospheric burden of O3, with the main contribution from the tropics. An increase of the global, annual mean methane lifetime by 10.9 %, resulting from a 14.1 % reduction in the global, annual mean OH concentration is also found. Comparisons with measurements show that including the new branch improves the modelled O3 in the Oslo CTM2, but that it is not possible to conclude whether the NOy distribution improves. We model an approximately 11 % reduction in the tropical tropospheric O3 increase since pre-industrial times, and a 4 % reduction of the increase in total tropospheric burden. Also, an 8 % decrease in the trend of OH concentrations is calculated, when the new branch is accounted for. The radiative forcing due to changes in O3 over the industrial era was calculated as 0.33 W m−2, reducing to 0.26 W m−2 with the new reaction branch. These results are significant, and it is important that this reaction branching is confirmed by other laboratory groups.

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