scholarly journals The mineral dust cycle in EMAC 2.40: sensitivity to the spectral resolution and the dust emission scheme

2011 ◽  
Vol 11 (10) ◽  
pp. 27285-27325
Author(s):  
G. Gläser ◽  
A. Kerkweg ◽  
H. Wernli
Keyword(s):  
Atmospheric Chemistry ◽  
Mineral Dust ◽  
Dust Emission ◽  
Dust Particles ◽  
Global Maximum ◽  
Polar Regions ◽  
Model Resolution ◽  
Dust Source ◽  
Wind Speeds ◽  
Grid Points

Abstract. This first detailed analysis of the mineral dust cycle in the ECHAM5/MESSy Atmospheric Chemistry (EMAC) model system investigates the performance of two dust emission schemes, following the approach of Balkanski et al. (2004) and Tegen et al. (2002), respectively, and the influence of the horizontal model resolution. Here the spectral resolutions T42, T63, T85, and T106 are investigated. A basic sulphur chemistry, enabling the coating of insoluble dust particles to make them soluble, is employed in order to realistically describe the scavenging and wet deposition of mineral dust. Independent of the dust emission scheme the five-year simulations with the horizontal resolutions T42 and T63 produce unrealistically high emissions at some grid points in the Tarim Basin in Central Asia, leading to very high dust loads in polar regions. In these coarse resolutions dust source grid points in the basin and elevated grid points of the Himalayas with high wind speeds can not be distinguished, causing this overestimation. In T85 and T106 these regions are well separated and considerably less dust is emitted there. With the chosen model setup, the dust emission scheme by Balkanski et al. (2004) places the global maximum of emissions in the Thar Desert in India. This is unrealistic as the Sahara Desert is known to be the largest dust source in the world. This is the main deficiency of this scheme compared to the one by Tegen et al. (2002), which produces very reasonable distributed emissions and dust loads in simulations with resolutions T85 and T106. For future climate simulations with EMAC that focus on mineral dust, we recommend to use the dust emission scheme by Tegen et al. (2002), and a model resolution of at least T85. Simulations of two selected episodes and comparison to observational data sets show that in this model configuration EMAC is able to realistically simulate also intense, episodic events of dust emission and long-range transport.

scholarly journals The Mineral Dust Cycle in EMAC 2.40: sensitivity to the spectral resolution and the dust emission scheme

2012 ◽  
Vol 12 (3) ◽  
pp. 1611-1627 ◽  
Author(s):  
G. Gläser ◽  
A. Kerkweg ◽  
H. Wernli
Keyword(s):  
Atmospheric Chemistry ◽  
Mineral Dust ◽  
Dust Emission ◽  
Dust Particles ◽  
Global Maximum ◽  
Polar Regions ◽  
Model Resolution ◽  
Qualitative Comparison ◽  
Dust Source ◽  
Grid Points

Abstract. This first detailed analysis of the mineral dust cycle in the ECHAM5/MESSy Atmospheric Chemistry (EMAC) model system investigates the performance of two dust emission schemes, following the approach of Balkanski et al. (2004) and Tegen et al. (2002), respectively, and the influence of the horizontal model resolution. Here the spectral resolutions T42, T63, T85, and T106 are investigated. A basic sulphur chemistry, enabling the coating of insoluble dust particles to make them soluble, is employed in order to realistically describe the ageing and wet deposition of mineral dust. Independent of the dust emission scheme the five-year simulations with the horizontal resolutions T42 and T63 produce unrealistically high emissions at some grid points in the Tarim Basin in Central Asia, leading to very high dust loads in polar regions. With these coarse resolutions, dust source grid points in the basin and elevated grid points of the Himalayas with high wind speeds cannot be distinguished, causing this overestimation. In T85 and T106 these regions are well separated and considerably less dust is emitted there. With the chosen model setup, the dust emission scheme by Balkanski et al. (2004) places the global maximum of emissions in the Thar Desert in India. This is unrealistic as the Sahara Desert is known to be the largest dust source in the world. This is the main deficiency of this scheme compared to the one by Tegen et al. (2002), which, based on a qualitative comparison to AEROCOM data, produces a very reasonable distribution of emissions and dust loads in simulations with resolutions T85 and T106. For future climate simulations with EMAC focusing on mineral dust, we recommend to use the dust emission scheme by Tegen et al. (2002) and a model resolution of at least T85. Simulations of two selected episodes and comparison to observational data sets show that in this model configuration EMAC is able to realistically simulate also intense, episodic events of dust emission and long-range transport.

scholarly journals Mineral dust modelling with MADE3 in EMAC v2.54

2020 ◽  
Author(s):  
Christof G. Beer ◽  
Johannes Hendricks ◽  
Mattia Righi ◽  
Bernd Heinold ◽  
Ina Tegen ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
General Circulation ◽  
Climate Models ◽  
Mineral Dust ◽  
Dust Emission ◽  
Circulation Model ◽  
Dust Particles ◽  
Model Resolution ◽  
Time Step ◽  
Dust Emissions

Abstract. Mineral dust particles play an important role in the climate system, by e.g. interacting with solar and terrestrial radiation or facilitating the formation of cloud droplets. Additionally, dust particles can act as very efficient ice nuclei in cirrus clouds. Many Global Chemistry Climate Models (GCCMs) use prescribed monthly mean mineral dust emissions representative of a specific year, based on a climatology. It was hypothesized that using dust emission climatologies may lead to misrepresentations of strong dust burst episodes, resulting in a negative bias of model dust concentrations compared to observations for these episodes. Here, we apply the aerosol microphysics submodel MADE3 (Modal Aerosol Dynamics model for Europe, adapted for global applications, third generation) as part of the ECHAM/MESSy Atmospheric Chemistry (EMAC) general circulation model. We employ two different representations of mineral dust for our model simulations: i) a prescribed monthly-mean climatology of dust emissions representative of the year 2000; ii) an online dust parametrization which calculates wind-driven mineral dust emissions at every model time-step. We evaluate model results for these two dust representations by comparison with observations of aerosol optical depth from ground-based station data. The model results show a better agreement with the observations for strong dust burst events when using the online dust representation compared to the prescribed dust emissions setup. Furthermore, we analyse the effect of increasing the vertical and horizontal model resolution on mineral dust properties in our model. The model is evaluated against airborne in situ measurements performed during the SALTRACE mineral dust campaign (Saharan Aerosol Long-range Transport and Aerosol-Cloud Interaction Experiment, June/July 2013), i.e. observations of dust transported from the Sahara to the Caribbean. Results show that an increased horizontal and vertical model resolution is able to better represent the spatial distribution of airborne mineral dust, especially in the upper troposphere (above 400 hPa). Additionally, we analyse the effect of varying assumptions for the size distribution of emitted dust. The results of this study will help to identify the model setup best suited for future studies and to further improve the representation of mineral dust particles in EMAC-MADE3.

scholarly journals Modelling mineral dust emissions and atmospheric dispersion with MADE3 in EMAC v2.54

2020 ◽  
Vol 13 (9) ◽  
pp. 4287-4303
Author(s):  
Christof G. Beer ◽  
Johannes Hendricks ◽  
Mattia Righi ◽  
Bernd Heinold ◽  
Ina Tegen ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
General Circulation ◽  
Climate Models ◽  
Mineral Dust ◽  
Dust Emission ◽  
Circulation Model ◽  
Dust Particles ◽  
Model Resolution ◽  
Time Step ◽  
Dust Emissions

Abstract. It was hypothesized that using mineral dust emission climatologies in global chemistry climate models (GCCMs), i.e. prescribed monthly-mean dust emissions representative of a specific year, may lead to misrepresentations of strong dust burst events. This could result in a negative bias of model dust concentrations compared to observations for these episodes. Here, we apply the aerosol microphysics submodel MADE3 (Modal Aerosol Dynamics model for Europe, adapted for global applications, third generation) as part of the ECHAM/MESSy Atmospheric Chemistry (EMAC) general circulation model. We employ two different representations of mineral dust emissions for our model simulations: (i) a prescribed monthly-mean climatology of dust emissions representative of the year 2000 and (ii) an online dust parametrization which calculates wind-driven mineral dust emissions at every model time step. We evaluate model results for these two dust representations by comparison with observations of aerosol optical depth from ground-based station data. The model results show a better agreement with the observations for strong dust burst events when using the online dust representation compared to the prescribed dust emissions setup. Furthermore, we analyse the effect of increasing the vertical and horizontal model resolution on the mineral dust properties in our model. We compare results from simulations with T42L31 and T63L31 model resolution (2.8∘×2.8∘ and 1.9∘×1.9∘ in latitude and longitude, respectively; 31 vertical levels) with the reference setup (T42L19). The different model versions are evaluated against airborne in situ measurements performed during the SALTRACE mineral dust campaign (Saharan Aerosol Long-range Transport and Aerosol-Cloud Interaction Experiment, June–July 2013), i.e. observations of dust transported from the Sahara to the Caribbean. Results show that an increased horizontal and vertical model resolution is able to better represent the spatial distribution of airborne mineral dust, especially in the upper troposphere (above 400 hPa). Additionally, we analyse the effect of varying assumptions for the size distribution of emitted dust but find only a weak sensitivity concerning these changes. The results of this study will help to identify the model setup best suited for future studies and to further improve the representation of mineral dust particles in EMAC-MADE3.

scholarly journals The spatial distribution of mineral dust and its shortwave radiative forcing over North Africa: modeling sensitivities to dust emissions and aerosol size treatments

2010 ◽  
Vol 10 (18) ◽  
pp. 8821-8838 ◽  
Author(s):  
C. Zhao ◽  
X. Liu ◽  
L. R. Leung ◽  
B. Johnson ◽  
S. A. McFarlane ◽  
...  
Keyword(s):  
North Africa ◽  
Radiative Forcing ◽  
Mineral Dust ◽  
Regional Climate ◽  
Dust Emission ◽  
Radiative Properties ◽  
Lower Atmosphere ◽  
Dust Particles ◽  
Dust Emissions ◽  
Sahel Region

Abstract. A fully coupled meteorology-chemistry-aerosol model (WRF-Chem) is applied to simulate mineral dust and its shortwave (SW) radiative forcing over North Africa. Two dust emission schemes (GOCART and DUSTRAN) and two aerosol models (MADE/SORGAM and MOSAIC) are adopted in simulations to investigate the modeling sensitivities to dust emissions and aerosol size treatments. The modeled size distribution and spatial variability of mineral dust and its radiative properties are evaluated using measurements (ground-based, aircraft, and satellites) during the AMMA SOP0 campaign from 6 January to 3 February of 2006 (the SOP0 period) over North Africa. Two dust emission schemes generally simulate similar spatial distributions and temporal evolutions of dust emissions. Simulations using the GOCART scheme with different initial (emitted) dust size distributions require ~40% difference in total emitted dust mass to produce similar SW radiative forcing of dust over the Sahel region. The modal approach of MADE/SORGAM retains 25% more fine dust particles (radius<1.25 μm) but 8% less coarse dust particles (radius>1.25 μm) than the sectional approach of MOSAIC in simulations using the same size-resolved dust emissions. Consequently, MADE/SORGAM simulates 11% higher AOD, up to 13% lower SW dust heating rate, and 15% larger (more negative) SW dust radiative forcing at the surface than MOSAIC over the Sahel region. In the daytime of the SOP0 period, the model simulations show that the mineral dust heats the lower atmosphere with an average rate of 0.8 ± 0.5 K day−1 over the Niamey vicinity and 0.5 ± 0.2 K day−1 over North Africa and reduces the downwelling SW radiation at the surface by up to 58 W m−2 with an average of 22 W m−2 over North Africa. This highlights the importance of including dust radiative impact in understanding the regional climate of North Africa. When compared to the available measurements, the WRF-Chem simulations can generally capture the measured features of mineral dust and its radiative properties over North Africa, suggesting that the model is suitable for more extensive simulations of dust impact on regional climate over North Africa.

scholarly journals The potential influence of Asian and African mineral dust on ice, mixed-phase and liquid water clouds

2010 ◽  
Vol 10 (2) ◽  
pp. 4027-4077 ◽  
Author(s):  
A. Wiacek ◽  
T. Peter ◽  
U. Lohmann
Keyword(s):  
Liquid Water ◽  
Mineral Dust ◽  
Dust Emission ◽  
Ice Nucleation ◽  
Mixed Phase ◽  
Specific Humidity ◽  
Dust Particles ◽  
Ice Clouds ◽  
Cloud Processing ◽  
Mixed Phase Clouds

Abstract. This modelling study explores the availability of mineral dust particles as ice nuclei for interactions with ice, mixed-phase and liquid water clouds, also tracking the particles' history of cloud-processing. We performed 61 320 one-week forward trajectory calculations originating near the surface of major dust emitting regions in Africa and Asia using high-resolution meteorological analysis fields for the year 2007. Without explicitly modelling dust emission and deposition processes, dust-bearing trajectories were assumed to be those coinciding with known dust emission seasons. We found that dust emissions from Asian deserts lead to a higher potential for interactions with high clouds, despite being the climatologically much smaller dust emission source. This is due to Asian regions experiencing significantly more ascent than African regions, with strongest ascent in the Asian Taklimakan desert at ~25%, ~40% and 10% of trajectories ascending to 300 hPa in spring, summer and fall, respectively. The specific humidity at each trajectory's starting point was transported in a Lagrangian manner and relative humidities with respect to water and ice were calculated in 6-h steps downstream, allowing us to estimate the formation of liquid, mixed-phase and ice clouds. Practically none of the simulated air parcels reached regions where homogeneous ice nucleation can take place (T≲−40 °C) along trajectories that have not experienced water saturation first. By far the largest fraction of cloud forming trajectories entered conditions of mixed-phase clouds, where mineral dust will potentially exert the biggest influence. The majority of trajectories also passed through regions supersaturated with respect to ice but subsaturated with respect to water, where "warm" (T≳−40 °C) ice clouds may form prior to supercooled water or mixed-phase clouds. The importance of "warm" ice clouds and the general influence of dust in the mixed-phase cloud region are highly uncertain due to considerable scatter in recent laboratory data from ice nucleation experiments, which we briefly review in this work. For "classical" cirrus-forming temperatures, our results show that only mineral dust IN that underwent mixed-phase cloud-processing previously are likely to be relevant, and, therefore, we recommend further systematic studies of immersion mode ice nucleation on mineral dust suspended in atmospherically relevant coatings.

scholarly journals Effects of mineral dust on global atmospheric nitrate concentrations

2016 ◽  
Vol 16 (3) ◽  
pp. 1491-1509 ◽  
Author(s):  
V. A. Karydis ◽  
A. P. Tsimpidi ◽  
A. Pozzer ◽  
M. Astitha ◽  
J. Lelieveld
Keyword(s):  
Chemical Composition ◽  
Size Distribution ◽  
Atmospheric Chemistry ◽  
Mineral Dust ◽  
Dust Particles ◽  
Metallic Ions ◽  
Atmospheric Nitrate ◽  
Inorganic Aerosol ◽  
Aerosol State ◽  
Nitrate Aerosol

Abstract. This study assesses the chemical composition and global aerosol load of the major inorganic aerosol components, focusing on mineral dust and aerosol nitrate. The mineral dust aerosol components (i.e., Ca2+, Mg2+, K+, Na+) and their emissions are included in the ECHAM5/MESSy Atmospheric Chemistry model (EMAC). Gas/aerosol partitioning is simulated using the ISORROPIA-II thermodynamic equilibrium model that considers K+, Ca2+, Mg2+, NH4+, Na+, SO42−, NO3−, Cl−, and H2O aerosol components. Emissions of mineral dust are calculated online by taking into account the soil particle size distribution and chemical composition of different deserts worldwide. Presence of metallic ions can substantially affect the nitrate partitioning into the aerosol phase due to thermodynamic interactions. The model simulates highest fine aerosol nitrate concentration over urban and industrialized areas (1–3 µg m−3), while coarse aerosol nitrate is highest close to deserts (1–4 µg m−3). The influence of mineral dust on nitrate formation extends across southern Europe, western USA, and northeastern China. The tropospheric burden of aerosol nitrate increases by 44 % when considering interactions of nitrate with mineral dust. The calculated global average nitrate aerosol concentration near the surface increases by 36 %, while the coarse- and fine-mode concentrations of nitrate increase by 53 and 21 %, respectively. Other inorganic aerosol components are affected by reactive dust components as well (e.g., the tropospheric burden of chloride increases by 9 %, ammonium decreases by 41 %, and sulfate increases by 7 %). Sensitivity tests show that nitrate aerosol is most sensitive to the chemical composition of the emitted mineral dust, followed by the soil size distribution of dust particles, the magnitude of the mineral dust emissions, and the aerosol state assumption.

scholarly journals Uncertainty in modeling dust mass balance and radiative forcing from size parameterization

2013 ◽  
Vol 13 (7) ◽  
pp. 19649-19700 ◽  
Author(s):  
C. Zhao ◽  
S. Chen ◽  
L. R. Leung ◽  
Y. Qian ◽  
J. Kok ◽  
...  
Keyword(s):  
Mass Balance ◽  
Radiative Forcing ◽  
Dust Emission ◽  
Dust Particles ◽  
Mass Loading ◽  
Dust Source ◽  
Deposition Fluxes ◽  
Source Regions ◽  
Dust Mass ◽  
The Difference

Abstract. This study examines the uncertainties in simulating mass balance and radiative forcing of mineral dust due to biases in the dust size parameterization. Simulations are conducted quasi-globally (180° W–180° E and 60° S–70° N) using the WRF-Chem model with three different approaches to represent dust size distribution (8-bin, 4-bin, and 3-mode). The biases in the 3-mode or 4-bin approaches against a relatively more accurate 8-bin approach in simulating dust mass balance and radiative forcing are identified. Compared to the 8-bin approach, the 4-bin approach simulates similar but coarser size distributions of dust particles in the atmosphere, while the 3-mode approach retains more fine dust particles but fewer coarse dust particles due to its prescribed σg of each mode. Although the 3-mode approach yields up to 10 days longer dust mass lifetime over the remote oceanic regions than the 8-bin approach, the three size approaches produce similar dust mass lifetime (3.2 days to 3.5 days) on quasi-global average, reflecting that the global dust mass lifetime is mainly determined by the dust mass lifetime near the dust source regions. With the same global dust emission (∼6000 Tg yr-1), the 8-bin approach produces a dust mass loading of 39 Tg, while the 4-bin and 3-mode approaches produce 3% (40.2 Tg) and 25% (49.1 Tg) higher dust mass loading, respectively. The difference in dust mass loading between the 8-bin approach and the 4-bin or 3-mode approaches has large spatial variations, with generally smaller relative difference (<10%) near the surface over the dust source regions. The three size approaches also result in significantly different dry and wet deposition fluxes and number concentrations of dust. The difference in dust aerosol optical depth (AOD) (a factor of 3) among the three size approaches is much larger than their difference (25%) in dust mass loading. Compared to the 8-bin approach, the 4-bin approach yields stronger dust absorptivity, while the 3-mode approach yields weaker dust absorptivity. Overall, on quasi-global average, the three size parameterizations result in a significant difference of a factor of 2∼3 in dust surface cooling (-1.02∼-2.87 W m-2) and atmospheric warming (0.39∼0.96 W m-2) and in a tremendous difference of a factor of ∼10 in dust TOA cooling (-0.24∼-2.20 W m-2). An uncertainty of a factor of 2 is quantified in dust emission estimation due to the different size parameterizations. This study also highlights the uncertainties in modeling dust mass and number loading, deposition fluxes, and radiative forcing resulting from different size parameterizations, and motivates further investigation of the impact of size parameterizations on modeling dust impacts on air quality, climate, and ecosystem.

scholarly journals Development of a global model of mineral dust aerosol microphysics

2008 ◽  
Vol 8 (6) ◽  
pp. 18765-18802
Author(s):  
Y. H. Lee ◽  
K. Chen ◽  
P. J. Adams
Keyword(s):  
Mineral Dust ◽  
Dust Particles ◽  
Base Case ◽  
Dust Source ◽  
Deposition Fluxes ◽  
Surface Mass ◽  
Remote Areas ◽  
Source Regions ◽  
Mass Concentrations

Abstract. A mineral dust module is developed and implemented into the global aerosol microphysics model, GISS-TOMAS. The model is evaluated against long-term measurements of dust surface mass concentrations and deposition fluxes. Predicted mass concentrations and deposition fluxes are in error on average by a factor of 3 and 5, respectively. The comparison shows that the model performs better near the dust source regions but underestimates surface concentrations and deposition fluxes in more remote regions. For example, including only sites with measured dust concentrations of at least 0.5 μg m−3, the model prediction agrees with observations to within a factor of 2. It was hypothesized that the lifetime of dust, 2.6 days in our base case, is too short and causes the underestimation in remote areas. However, a sensitivity simulation with smaller dust particles and increased lifetime, 3.7 days, does not significantly improve the comparison. We conclude that the underestimation of mineral dust in remote areas results from local factors and sources not well described by the dust source function and/or the GCM meteorology. The effect of dust aerosols on CCN(0.2%) concentrations is negligible in most regions of the globe; however, CCN(0.2%) concentrations decrease by 10–20% in dusty regions as a result of coagulational scavenging of CCN particles by dust and a decrease in H2SO4 condensation to CCN particles due to the additional surface area of dust.

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