scholarly journals Modelling the size distribution of geoengineered stratospheric aerosols

2010 ◽  
Vol 12 (2) ◽  
pp. 168-175 ◽  
Author(s):  
René Hommel ◽  
Hans-F. Graf
Keyword(s):  
Size Distribution ◽  
Stratospheric Aerosols

scholarly journals Dependency of the impacts of geoengineering on the stratospheric sulfur injection strategy – Part 1: Intercomparison of modal and sectional aerosol modules

2022 ◽  
Vol 22 (1) ◽  
pp. 93-118
Author(s):  
Anton Laakso ◽  
Ulrike Niemeier ◽  
Daniele Visioni ◽  
Simone Tilmes ◽  
Harri Kokkola
Keyword(s):  
Sulfuric Acid ◽  
Solar Radiation ◽  
Size Distribution ◽  
Radiative Forcing ◽  
Local Minimum ◽  
Climate Impacts ◽  
Injection Strategy ◽  
Injection Strategies ◽  
Stratospheric Aerosols ◽  
Injection Rates

Abstract. Injecting sulfur dioxide into the stratosphere with the intent to create an artificial reflective aerosol layer is one of the most studied options for solar radiation management. Previous modelling studies have shown that stratospheric sulfur injections have the potential to compensate for the greenhouse-gas-induced warming at the global scale. However, there is significant diversity in the modelled radiative forcing from stratospheric aerosols depending on the model and on which strategy is used to inject sulfur into the stratosphere. Until now, it has not been clear how the evolution of the aerosols and their resulting radiative forcing depends on the aerosol microphysical scheme used – that is, if aerosols are represented by a modal or sectional distribution. Here, we have studied different spatio-temporal injection strategies with different injection magnitudes using the aerosol–climate model ECHAM-HAMMOZ with two aerosol microphysical modules: the sectional module SALSA (Sectional Aerosol module for Large Scale Applications) and the modal module M7. We found significant differences in the model responses depending on the aerosol microphysical module used. In a case where SO2 was injected continuously in the equatorial stratosphere, simulations with SALSA produced an 88 %–154 % higher all-sky net radiative forcing than simulations with M7 for injection rates from 1 to 100 Tg (S) yr−1. These large differences are identified to be caused by two main factors. First, the competition between nucleation and condensation: while injected sulfur tends to produce new particles at the expense of gaseous sulfuric acid condensing on pre-existing particles in the SALSA module, most of the gaseous sulfuric acid partitions to particles via condensation at the expense of new particle formation in the M7 module. Thus, the effective radii of stratospheric aerosols were 10 %–52 % larger in M7 than in SALSA, depending on the injection rate and strategy. Second, the treatment of the modal size distribution in M7 limits the growth of the accumulation mode which results in a local minimum in the aerosol number size distribution between the accumulation and coarse modes. This local minimum is in the size range where the scattering of solar radiation is most efficient. We also found that different spatial-temporal injection strategies have a significant impact on the magnitude and zonal distribution of radiative forcing. Based on simulations with various injection rates using SALSA, the most efficient studied injection strategy produced a 33 %–42 % radiative forcing compared with the least efficient strategy, whereas simulations with M7 showed an even larger difference of 48 %–116 %. Differences in zonal mean radiative forcing were even larger than that. We also show that a consequent stratospheric heating and its impact on the quasi-biennial oscillation depend on both the injection strategy and the aerosol microphysical model. Overall, these results highlight the crucial impact of aerosol microphysics on the physical properties of stratospheric aerosol which, in turn, causes significant uncertainties in estimating the climate impacts of stratospheric sulfur injections.

scholarly journals Dependency of the impacts of geoengineering on the stratospheric sulfur injection strategy part 1: Intercomparison of modal and sectional aerosol module

2021 ◽  
Author(s):  
Anton Laakso ◽  
Ulrike Niemeier ◽  
Daniele Visioni ◽  
Simone Tilmes ◽  
Harri Kokkola
Keyword(s):  
Sulfuric Acid ◽  
Solar Radiation ◽  
Size Distribution ◽  
Radiative Forcing ◽  
Local Minimum ◽  
Injection Rate ◽  
Climate Impacts ◽  
Solar Radiation Management ◽  
Injection Strategy ◽  
Stratospheric Aerosols

Abstract. Injecting sulfur dioxide into the stratosphere with the intent to create an artificial reflective aerosol layer is one of the most studied option for solar radiation management. Previous modelling studies have shown that stratospheric sulfur injections have the potential to compensate the greenhouse gas induced warming at the global scale. However, there is significant diversity in the modelled radiative forcing from stratospheric aerosols depending on the model and on which strategy is used to inject sulfur into the stratosphere. Until now it has not been clear how the evolution of the aerosols and their resulting radiative forcing depends on the aerosol microphysical scheme used, that is, if aerosols are represented by modal or sectional distribution. Here, we have studied different spatio-temporal injections strategies with different injection magnitudes by using the aerosol-climate model ECHAM-HAMMOZ with two aerosol microphysical modules: the sectional module SALSA and the modal module M7. We found significant differences in model responses depending on the used aerosol microphysical module. In a case where SO2 was injected continuously in the equatorial stratosphere, simulations with SALSA produced 88 %–154 % higher all-sky net radiative forcing than simulations with M7 for injection rates from 1 to 1 to 100 Tg(S) yr−1. These large differences are identified to be caused by two main factors. First, the competition between nucleation and condensation: while in SALSA injected sulfur tends to produce new particles at the expense of gaseous sulfuric acid condensing on pre-existing particles, in M7 most of the gaseous sulfuric acid partitions to particles via condensation at the expense of new particle formation. Thus, the effective radii of stratospheric aerosols were 10–52% larger in M7 than in SALSA, depending on injection rate and strategy. Second, the treatment of the modal size distribution in M7 limits the growth of the accumulation mode which results in a local minimum in aerosol number size distribution between the accumulation and the coarse modes. This local minimum is in the size range where the scattering of solar radiation is most efficient. We also found that different spatial-temporal injection strategies have a significant impact on the magnitude and zonal distribution of radiative forcing. Based on simulations with various injection rate using SALSA, the most efficient studied injection strategy produced 33–42 % radiative forcing compared to the least efficient strategy while simulations with M7 showed even larger difference of 48–76 %. Differences in zonal mean radiative forcing were even larger than that. We also show that a consequent stratospheric heating and its impact on the quasi-biennial oscillation depends both on the injection strategy and the aerosol microphysical model. Overall, these results highlight a crucial role of aerosol microphysics on the physical properties of stratospheric aerosol which in turn causes significant uncertainties in estimating climate impacts of stratospheric sulfur injections.

Retrieval of aerosol particle size distributions in the stratosphere from SCIAMACHY limb observations and comparison to balloon-borne measurements and ECHAM5-HAM simulations

2021 ◽  
Author(s):  
Christine Pohl ◽  
Alexei Rozanov ◽  
Elizaveta Malinina-Rieger ◽  
Terry Deshler ◽  
Ulrike Niemeier ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Aerosol Particle ◽  
Atmospheric Chemistry ◽  
Physical Models ◽  
Climate Modelling ◽  
Distribution Width ◽  
Aerosol Particle Size ◽  
Stratospheric Aerosols

<p>Stratospheric aerosols play an important role in the climate system and the atmospheric chemistry. They alter the radiative budget of the Earth affecting the global temperature and interact with stratospheric trace gases leading to ozone depletion. Effects are most noticeable after vulcanic eruptions enhancing the amount of aerosols in the stratosphere. Thus, vertically and spatially resolved knowledge about stratospheric aerosols, such as the particle size distribution and extinction coefficient, is crucial for the initialization of climate models, investigation of geoengineering, validation of aerosol micro-physical models, and improvement of trace gas retrievals. We present an algorithm to retrieve aerosol particle size distribution parameters (mode radius and distribution width, number density) from limb observations of SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric ChartograpHY) operated aboard Envisat between 2002 and 2012. SCIAMACHY retrieved particle size distribution profiles are compared with in-situ balloon-borne measurements from Laramie, Wyoming. Both data-sets show good agreement. The stratospheric plume evolution after the eruption of Sarychev in the Kuril Islands, Russia, in June 2009 is investigated and compared to the output from the aerosol-climate modelling system ECHAM5-HAM.</p>

scholarly journals Stratospheric Aerosol Climatology over Ethiopia and Retrieval of its Size Distribution

2017 ◽  
Author(s):  
Milkessa Gebeyehu Homa ◽  
Gizaw Mengistu Tsidu ◽  
Derese Tekestebrihan Nega
Keyword(s):  
Size Distribution ◽  
Optical Depth ◽  
Anthropogenic Activities ◽  
Maximum Size ◽  
Stratospheric Aerosol ◽  
Radiation Budget ◽  
Aerosol Size Distribution ◽  
Traffic Density ◽  
The Earth ◽  
Stratospheric Aerosols

Abstract. Stratospheric aerosols play significant role both positively and negatively in Earths energy balance and climate change. Its main sources are particulate matters which arises from either of natural or anthropogenic activities. In the context of our country, Ethiopia, the stratospheric aerosol climatology has not been studied yet. However, Ethiopia is undergoing a boom of infrastructural development like increase of urbanization, which comes with a boom of development like building and road constructions, expansion of industries, traffic density, etc, which contributes to air pollution and influences the solar radiation budget of the earth-atmosphere system, which in turn influences the climate on the surface of the Earth by different ways. Hence, this study aimed to provide the stratospheric aerosol climatology for nearly 21 years extending from Oct., 1984 to Sept., 2005. The study was carried out by defining the stratospheric region from the temperature profile of the study area provided by Stratospheric Aerosols and Gas Experiment II (SAGEII) instrument aboard on Earths Radiation Budget Satellite (ERBS). Then, the data was filtered out over Ethiopian region at four aerosol channels and the optical depth is used as input to the Mie algorithm for aerosol size distribution (ASD) retrieval. Finally, it was observed that the spectral and vertical variation of the extinction is maximum between 17–25 km and the total column aerosol optical depth (AOD) temporal variation shows nearly steadily increasing trend with maximum variation during spring. Furthermore, from the ASD result it was observed that the maximum size distribution was in April. This paves a clue about their sources to be mechanical process on the ground and gas to particle conversion in the stratosphere with the dominant size distribution in the range of 0.452–0.525 μm radius.

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