scholarly journals Atmospheric Processing of Iron in Mineral and Combustion Aerosols: Development of an Intermediate-Complexity Mechanism Suitable for Earth System Models

2018 ◽  
Author(s):  
Rachel A. Scanza ◽  
Natalie M. Mahowald ◽  
Carlos Perez Garcia-Pando ◽  
Clifton Buck ◽  
Alex Baker ◽  
...  
Keyword(s):  
Oxalic Acid ◽  
Earth System ◽  
Reference Case ◽  
Iron Solubility ◽  
Soluble Iron ◽  
System Models ◽  
Intermediate Complexity ◽  
Atmospheric Processing ◽  
Combustion Aerosols ◽  
Earth System Models

Abstract. Atmospheric processing of iron in dust and combustion aerosols is simulated using an intermediate-complexity soluble iron mechanism designed for Earth system models. The solubilization mechanism includes both a dependence on aerosol water pH and in-cloud oxalic acid. The simulations of size resolved total, soluble and fractional iron solubility indicate that this mechanism captures many but not all of the features seen from cruise observations of labile iron. The primary objective was to determine the extent to which our solubility scheme could adequately match observations of fractional iron solubility. We define a semi-quantitative metric as the model mean at points with observations divided by the observational mean (MMO); fractional iron solubility MMO is 0.8, indicating that while the model is not capturing all of the observational variability, it is within range of the observational mean. Several sensitivity studies are performed to ascertain the degree of complexity needed to match observations; including the oxalic acid enhancement is necessary while different parameterizations for calculating model oxalate concentrations are less important. The percent change in soluble iron deposition between the reference case and the simulation with acidic processing alone is 63.8 %, which is consistent with previous studies. Upon deposition to global oceans, global mean combustion iron solubility to total fractional iron solubility is 8.2 %; however, the contribution of fractional iron solubility from combustion sources to ocean basins below 15° S is approximately 50 %. We conclude that in many remote ocean regions, sources of iron from combustion and dust aerosols are equally important. Our estimates of changes in deposition of soluble iron to the ocean since preindustrial suggest roughly a doubling due to a combination of higher dust and combustion iron emissions along with more efficient atmospheric processing.

scholarly journals Atmospheric processing of iron in mineral and combustion aerosols: development of an intermediate-complexity mechanism suitable for Earth system models

2018 ◽  
Vol 18 (19) ◽  
pp. 14175-14196 ◽  
Author(s):  
Rachel A. Scanza ◽  
Douglas S. Hamilton ◽  
Carlos Perez Garcia-Pando ◽  
Clifton Buck ◽  
Alex Baker ◽  
...  
Keyword(s):  
Oxalic Acid ◽  
Earth System ◽  
Reference Case ◽  
Iron Solubility ◽  
Soluble Iron ◽  
System Models ◽  
Intermediate Complexity ◽  
Atmospheric Processing ◽  
Combustion Aerosols ◽  
Earth System Models

Abstract. Atmospheric processing of iron in dust and combustion aerosols is simulated using an intermediate-complexity soluble iron mechanism designed for Earth system models. The solubilization mechanism includes both a dependence on aerosol water pH and in-cloud oxalic acid. The simulations of size-resolved total, soluble and fractional iron solubility indicate that this mechanism captures many but not all of the features seen from cruise observations of labile iron. The primary objective was to determine the extent to which our solubility scheme could adequately match observations of fractional iron solubility. We define a semi-quantitative metric as the model mean at points with observations divided by the observational mean (MMO). The model is in reasonable agreement with observations of fractional iron solubility with an MMO of 0.86. Several sensitivity studies are performed to ascertain the degree of complexity needed to match observations; including the oxalic acid enhancement is necessary, while different parameterizations for calculating model oxalate concentrations are less important. The percent change in soluble iron deposition between the reference case (REF) and the simulation with acidic processing alone is 63.8 %, which is consistent with previous studies. Upon deposition to global oceans, global mean combustion iron solubility to total fractional iron solubility is 8.2 %; however, the contribution of fractional iron solubility from combustion sources to ocean basins below 15∘ S is approximately 50 %. We conclude that, in many remote ocean regions, sources of iron from combustion and dust aerosols are equally important. Our estimates of changes in deposition of soluble iron to the ocean since preindustrial climate conditions suggest roughly a doubling due to a combination of higher dust and combustion iron emissions along with more efficient atmospheric processing.

scholarly journals Improved methodologies for Earth system modelling of atmospheric soluble iron and observation comparisons using the Mechanism of Intermediate complexity for Modelling Iron (MIMI v.1.0)

2019 ◽  
Author(s):  
Douglas S. Hamilton ◽  
Rachel A. Scanza ◽  
Yan Feng ◽  
Joe Guinness ◽  
Jasper F. Kok ◽  
...  
Keyword(s):  
Reaction Scheme ◽  
Comprehensive Treatment ◽  
System Modelling ◽  
Earth System ◽  
Aerosol Model ◽  
Soluble Iron ◽  
Intermediate Complexity ◽  
Atmospheric Processing ◽  
Definition Of ◽  
Log Normal

Abstract. Herein, we present the description of the Mechanism of Intermediate complexity for Modelling Iron (MIMI). This iron processing module was developed for use within Earth system models and has been updated within a modal aerosol framework from the original implementation in a bulk aerosol model. MIMI simulates the emission and atmospheric processing of two main sources of iron in aerosol prior to deposition: mineral dust and combustion processes. Atmospheric dissolution of insoluble to soluble iron is parametrized by an acidic interstitial reaction and a separate in-cloud reaction scheme based on observations of enhanced aerosol iron solubility in the presence of oxalate. Updates include a more comprehensive treatment of combustion iron emissions, improvements to the iron dissolution scheme, and an improved physical dust mobilization scheme. An extensive dataset consisting predominantly of cruise-based observations was compiled to compare to the model. The annual mean modelled concentration of surface-level total iron compared well with observations, but less so in the soluble fraction where observations are much more variable in space and time. Comparing model and observational data is sensitive to the definition of the average and the temporal and spatial range over which it is calculated. Through statistical analysis and examples, we show that a median or log-normal distribution is preferred when comparing with soluble iron observations. We redefined ocean deposition regions based on dominant iron emission sources and found that the daily variability in soluble iron simulated by MIMI was larger than that of previous model simulations. MIMI simulated a general increase in soluble iron deposition to Southern Hemisphere oceans by a factor of two to four compared with the previous version, which has implications for our understanding of the ocean biogeochemistry of these predominantly iron limited ocean regions.

scholarly journals Improved methodologies for Earth system modelling of atmospheric soluble iron and observation comparisons using the Mechanism of Intermediate complexity for Modelling Iron (MIMI v1.0)

2019 ◽  
Vol 12 (9) ◽  
pp. 3835-3862 ◽  
Author(s):  
Douglas S. Hamilton ◽  
Rachel A. Scanza ◽  
Yan Feng ◽  
Joseph Guinness ◽  
Jasper F. Kok ◽  
...  
Keyword(s):  
Comprehensive Treatment ◽  
System Modelling ◽  
Earth System ◽  
Time Step ◽  
Mean Values ◽  
Iron Solubility ◽  
Aerosol Model ◽  
Soluble Iron ◽  
Intermediate Complexity ◽  
Ocean Biogeochemistry

Abstract. Herein, we present a description of the Mechanism of Intermediate complexity for Modelling Iron (MIMI v1.0). This iron processing module was developed for use within Earth system models and has been updated within a modal aerosol framework from the original implementation in a bulk aerosol model. MIMI simulates the emission and atmospheric processing of two main sources of iron in aerosol prior to deposition: mineral dust and combustion processes. Atmospheric dissolution of insoluble to soluble iron is parameterized by an acidic interstitial aerosol reaction and a separate in-cloud aerosol reaction scheme based on observations of enhanced aerosol iron solubility in the presence of oxalate. Updates include a more comprehensive treatment of combustion iron emissions, improvements to the iron dissolution scheme, and an improved physical dust mobilization scheme. An extensive dataset consisting predominantly of cruise-based observations was compiled to compare to the model. The annual mean modelled concentration of surface-level total iron compared well with observations but less so in the soluble fraction (iron solubility) for which observations are much more variable in space and time. Comparing model and observational data is sensitive to the definition of the average as well as the temporal and spatial range over which it is calculated. Through statistical analysis and examples, we show that a median or log-normal distribution is preferred when comparing with soluble iron observations. The iron solubility calculated at each model time step versus that calculated based on a ratio of the monthly mean values, which is routinely presented in aerosol studies and used in ocean biogeochemistry models, is on average globally one-third (34 %) higher. We redefined ocean deposition regions based on dominant iron emission sources and found that the daily variability in soluble iron simulated by MIMI was larger than that of previous model simulations. MIMI simulated a general increase in soluble iron deposition to Southern Hemisphere oceans by a factor of 2 to 4 compared with the previous version, which has implications for our understanding of the ocean biogeochemistry of these predominantly iron-limited ocean regions.

scholarly journals Earth system models of intermediate complexity: closing the gap in the spectrum of climate system models

2002 ◽  
Vol 18 (7) ◽  
pp. 579-586 ◽  
Author(s):  
Claussen M. ◽  
Mysak L. ◽  
Weaver A. ◽  
Crucifix M. ◽  
Fichefet T. ◽  
...  
Keyword(s):  
Climate System ◽  
Earth System ◽  
System Models ◽  
Intermediate Complexity ◽  
Closing The Gap ◽  
Earth System Models ◽  
Climate System Models

scholarly journals Biogeophysical effects of historical land cover changes simulated by six Earth system models of intermediate complexity

2006 ◽  
Vol 26 (6) ◽  
pp. 587-600 ◽  
Author(s):  
V. Brovkin ◽  
M. Claussen ◽  
E. Driesschaert ◽  
T. Fichefet ◽  
D. Kicklighter ◽  
...  
Keyword(s):  
Land Cover ◽  
Land Cover Changes ◽  
Earth System ◽  
System Models ◽  
Intermediate Complexity ◽  
Earth System Models
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