scholarly journals Evaluation of the sectional aerosol microphysics module SALSA implementation in ECHAM5-HAM aerosol-climate model

2012 ◽  
Vol 5 (3) ◽  
pp. 845-868 ◽  
Author(s):  
T. Bergman ◽  
V.-M. Kerminen ◽  
H. Korhonen ◽  
K. J. Lehtinen ◽  
R. Makkonen ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Size Distribution ◽  
Black Carbon ◽  
Climate Model ◽  
Good Choice ◽  
Sea Salt ◽  
Aerosol Size Distribution ◽  
Chemical Compositions ◽  
Model Framework ◽  
Aerosol Properties

Abstract. We present the implementation and evaluation of a sectional aerosol microphysics module SALSA within the aerosol-climate model ECHAM5-HAM. This aerosol microphysics module has been designed to be flexible and computationally efficient so that it can be implemented in regional or global scale models. The computational efficiency has been achieved by minimising the number of variables needed to describe the size and composition distribution. The aerosol size distribution is described using 10 size classes with parallel sections which can have different chemical compositions. Thus in total, the module tracks 20 size sections which cover diameters ranging from 3 nm to 10 μm and are divided into three subranges, each with an optimised selection of processes and compounds. The implementation of SALSA into ECHAM5-HAM includes the main aerosol processes in the atmosphere: emissions, removal, radiative effects, liquid and gas phase sulphate chemistry, and the aerosol microphysics. The aerosol compounds treated in the module are sulphate, organic carbon, sea salt, black carbon, and mineral dust. In its default configuration, ECHAM5-HAM treats aerosol size distribution using the modal method. In this implementation, the aerosol processes were converted to be used in a sectional model framework. The ability of the module to describe the global aerosol properties was evaluated by comparing against (1) measured continental and marine size distributions, (2) observed variability of continental number concentrations, (3) measured sulphate, organic carbon, black carbon and sea-salt mass concentrations, (4) observations of aerosol optical depth (AOD) and other aerosol optical properties from satellites and AERONET network, (5) global aerosol budgets and concentrations from previous model studies, and (6) model results using M7, which is the default aerosol microphysics module in ECHAM5-HAM. The evaluation shows that the global aerosol properties can be reproduced reasonably well using a coarse resolution of 10 sections in size space. The simulated global aerosol budgets are within the range of previous studies. Surface concentrations of sulphate and carbonaceous species have an annual mean within a factor of two of the observations. The simulated sea-salt concentrations reproduce the observations within a factor of two, apart from the Southern Ocean over which the concentrations are within a factor of five. Regionally, AOD is in a relatively good agreement with the observations (within a factor of two). At mid-latitudes the observed AOD is captured well, while at high-latitudes as well as in some polluted and dust regions the modelled AOD is significantly lower than observed. Regarding most of the investigated aerosol properties, the SALSA and the modal aerosol module M7 perform comparably well against observations. However, SALSA reproduces the observed number concentrations and the size distribution of CCN sized particles much more accurately than M7, and is therefore a good choice for aerosol-cloud interaction studies in global models. Our study also shows that when activation type nucleation in the boundary layer is included, the observed concentration of particles under 50 nm in diameter are reproduced much better compared to when only binary nucleation in the free troposphere is assumed.

scholarly journals Evaluation of the sectional aerosol microphysics module SALSA implementation in ECHAM5-HAM aerosol-climate model

2011 ◽  
Vol 4 (4) ◽  
pp. 3623-3690 ◽  
Author(s):  
T. Bergman ◽  
V.-M. Kerminen ◽  
H. Korhonen ◽  
K. J. Lehtinen ◽  
R. Makkonen ◽  
...  
Keyword(s):  
Climate Model ◽  
Global Scale ◽  
Good Choice ◽  
Sea Salt ◽  
Aerosol Size Distribution ◽  
Size Distributions ◽  
Computationally Efficient ◽  
Model Studies ◽  
Aerosol Module ◽  
Aerosol Properties

Abstract. We present the implementation and evaluation of a sectional aerosol microphysics model SALSA within the aerosol-climate model ECHAM5-HAM. This aerosol microphysics module has been designed to be flexible and computationally efficient so that it can be implemented in regional or global scale models. The computational efficiency has been achieved by keeping the number of variables needed to describe the size and composition distribution to the minimum. The aerosol size distribution is described using 20 size sections with 10 size sections in size space which cover diameters ranging from 3 nm to 10 μm divided to three subranges each having distinct optimised process and compound selection. The ability of the module to describe the global aerosol properties was evaluated by comparison against (1) measured continental and marine size distributions, (2) observed variability of continental modal number concentrations, (3) measured sulphate, organic carbon, black carbon and sea salt mass concentrations, (4) observations of AOD and other aerosol optical properties from satellites and AERONET network, (5) global aerosol budgets and concentrations from previous model studies, and (6) model results using M7 which is the default aerosol microphysics module in ECHAM5-HAM. The evaluation shows that the global aerosol properties can be reproduced reasonably well using the coarse resolution of 10 size sections in size space. The simulated global aerosol budgets are within the range of previous studies. Surface concentrations of sea salt, sulphate and carbonaceous species have an annual mean within a factor of five of the observations, while the simulated sea salt concentrations reproduce the observations less accurately and show high variability. Regionally, AOD is in relatively good agreement with the observations (within a factor of two). At mid-latitudes the observed AOD is captured well, while at high-latitudes as well as in some polluted and dust regions the modeled AOD is significantly lower than the observed. Regarding the most investigated aerosol properties, the performances of SALSA and the modal aerosol module M7 against observations are comparable. However, SALSA reproduces the observed number concentrations and the size distributions of CCN sized particles much more accurately than M7, and is therefore a good choice for aerosol-cloud interaction studies in global models. Our study also shows that when including activation type nucleation process in the boundary layer, the modeled concentrations of particles under 50 nm in diameter are reproduced much better compared to when only binary nucleation is assumed.

scholarly journals Ice Initiation by Aerosol Particles: Measured and Predicted Ice Nuclei Concentrations versus Measured Ice Crystal Concentrations in an Orographic Wave Cloud

2010 ◽  
Vol 67 (8) ◽  
pp. 2417-2436 ◽  
Author(s):  
T. Eidhammer ◽  
P. J. DeMott ◽  
A. J. Prenni ◽  
M. D. Petters ◽  
C. H. Twohy ◽  
...  
Keyword(s):  
Size Distribution ◽  
Ice Nucleation ◽  
Aerosol Size Distribution ◽  
Chemical Compositions ◽  
Ice Crystal ◽  
Model Framework ◽  
Lognormal Distributions ◽  
Ice Nuclei ◽  
Nuclei Number ◽  
Ice Initiation

Abstract The initiation of ice in an isolated orographic wave cloud was compared with expectations based on ice nucleating aerosol concentrations and with predictions from new ice nucleation parameterizations applied in a cloud parcel model. Measurements of ice crystal number concentrations were found to be in good agreement both with measured number concentrations of ice nuclei feeding the clouds and with ice nuclei number concentrations determined from the residual nuclei of cloud particles collected by a counterflow virtual impactor. Using lognormal distributions fitted to measured aerosol size distributions and measured aerosol chemical compositions, ice nuclei and ice crystal concentrations in the wave cloud were reasonably well predicted in a 1D parcel model framework. Two different empirical parameterizations were used in the parcel model: a parameterization based on aerosol chemical type and surface area and a parameterization that links ice nuclei number concentrations to the number concentrations of particles with diameters larger than 0.5 μm. This study shows that aerosol size distribution and composition measurements can be used to constrain ice initiation by primary nucleation in models. The data and model results also suggest the likelihood that the dust particle mode of the aerosol size distribution controls the number concentrations of the heterogeneous ice nuclei, at least for the lower temperatures examined in this case.

scholarly journals Evaluation of biomass burning aerosols in the HadGEM3 climate model with observations from the SAMBBA field campaign

2016 ◽  
Vol 16 (22) ◽  
pp. 14657-14685 ◽  
Author(s):  
Ben T. Johnson ◽  
James M. Haywood ◽  
Justin M. Langridge ◽  
Eoghan Darbyshire ◽  
William T. Morgan ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Size Distribution ◽  
Biomass Burning ◽  
Climate Model ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Aerosol Mass ◽  
Biomass Burning Aerosol ◽  
Aerosol Properties

Abstract. We present observations of biomass burning aerosol from the South American Biomass Burning Analysis (SAMBBA) and other measurement campaigns, and use these to evaluate the representation of biomass burning aerosol properties and processes in a state-of-the-art climate model. The evaluation includes detailed comparisons with aircraft and ground data, along with remote sensing observations from MODIS and AERONET. We demonstrate several improvements to aerosol properties following the implementation of the Global Model for Aerosol Processes (GLOMAP-mode) modal aerosol scheme in the HadGEM3 climate model. This predicts the particle size distribution, composition, and optical properties, giving increased accuracy in the representation of aerosol properties and physical–chemical processes over the Coupled Large-scale Aerosol Scheme for Simulations in Climate Models (CLASSIC) bulk aerosol scheme previously used in HadGEM2. Although both models give similar regional distributions of carbonaceous aerosol mass and aerosol optical depth (AOD), GLOMAP-mode is better able to capture the observed size distribution, single scattering albedo, and Ångström exponent across different tropical biomass burning source regions. Both aerosol schemes overestimate the uptake of water compared to recent observations, CLASSIC more so than GLOMAP-mode, leading to a likely overestimation of aerosol scattering, AOD, and single scattering albedo at high relative humidity. Observed aerosol vertical distributions were well captured when biomass burning aerosol emissions were injected uniformly from the surface to 3 km. Finally, good agreement between observed and modelled AOD was gained only after scaling up GFED3 emissions by a factor of 1.6 for CLASSIC and 2.0 for GLOMAP-mode. We attribute this difference in scaling factor mainly to different assumptions for the water uptake and growth of aerosol mass during ageing via oxidation and condensation of organics. We also note that similar agreement with observed AOD could have been achieved with lower scaling factors if the ratio of organic carbon to primary organic matter was increased in the models toward the upper range of observed values. Improved knowledge from measurements is required to reduce uncertainties in emission ratios for black carbon and organic carbon, and the ratio of organic carbon to primary organic matter for primary emissions from biomass burning.

scholarly journals Arctic smoke – aerosol characteristics during a record air pollution event in the European Arctic and its radiative impact

2007 ◽  
Vol 7 (1) ◽  
pp. 2275-2324 ◽  
Author(s):  
R. Treffeisen ◽  
P. Turnved ◽  
J. Ström ◽  
A. Herber ◽  
J. Bareiss ◽  
...  
Keyword(s):  
Air Pollution ◽  
Size Distribution ◽  
Climate Model ◽  
Atmospheric Stability ◽  
The Arctic ◽  
Aerosol Size Distribution ◽  
Geometric Standard Deviation ◽  
Transfer Model ◽  
Climatic Effects ◽  
Pollution Event

Abstract. In early May 2006 a record high air pollution event was observed at Ny-Ålesund, Spitsbergen. An atypical weather pattern established a pathway for the rapid transport of biomass burning aerosols from agricultural fires in Eastern Europe to the Arctic. Atmospheric stability was such that the smoke was constrained to low levels, within 2 km of the surface during the transport. A description of this smoke event in terms of transport and main aerosol characteristics can be found in Stohl et al. (2007). This study puts emphasis on the radiative effect of the smoke. The aerosol size distribution was characterized as having an accumulation mode centered at 165–185 nm and almost 1.6 for geometric standard deviation of the mode. Nucleation and small Aitken mode particles were almost completely suppressed within the smoke plume measured at Ny-Ålesund. Chemical and microphysical aerosol information obtained at Mt. Zeppelin (474 m.a.s.l) was used to derive input parameters for a one-dimensional radiation transfer model to explore the radiative effects of the smoke. The daily mean heating rate calculated on 2 May 2006 for the average size distribution and measured chemical composition reached 0.55 K day−1 at 0.5 km altitude for the assumed external mixture of the aerosols but showing much higher heating rates for an internal mixture (1.7 K day−1). In comparison a case study for March 2000 showed that the local climatic effects due to Arctic haze, using a regional climate model, HIRHAM, amounts to a maximum of 0.3 K day−1 of heating at 2 km altitude (Treffeisen et al., 2005).

scholarly journals Consistent simulation of bromine chemistry from the marine boundary layer to the stratosphere – Part 1: Model description, sea salt aerosols and pH

2008 ◽  
Vol 8 (19) ◽  
pp. 5899-5917 ◽  
Author(s):  
A. Kerkweg ◽  
P. Jöckel ◽  
A. Pozzer ◽  
H. Tost ◽  
R. Sander ◽  
...  
Keyword(s):  
Size Distribution ◽  
Atmospheric Chemistry ◽  
General Circulation ◽  
Circulation Model ◽  
Reaction Rates ◽  
Sea Salt ◽  
Aerosol Size Distribution ◽  
Model Description ◽  
Aerosol Chemistry ◽  
Coarse Mode

Abstract. This is the first article of a series presenting a detailed analysis of bromine chemistry simulated with the atmospheric chemistry general circulation model ECHAM5/MESSy. Release from sea salt is an important bromine source, hence the model explicitly calculates aerosol chemistry and phase partitioning for coarse mode aerosol particles. Many processes including chemical reaction rates are influenced by the particle size distribution, and aerosol associated water strongly affects the aerosol pH. Knowledge of the aerosol pH is important as it determines the aerosol chemistry, e.g., the efficiency of sulphur oxidation and bromine release. Here, we focus on the simulated sea salt aerosol size distribution and the coarse mode aerosol pH. A comparison with available field data shows that the simulated aerosol distributions agree reasonably well within the range of measurements. In spite of the small number of aerosol pH measurements and the uncertainty in its experimental determination, the simulated aerosol pH compares well with the observations. The aerosol pH ranges from alkaline aerosol in areas of strong production down to pH-values of 1 over regions of medium sea salt production and high levels of gas phase acids, mostly polluted regions over the oceans in the Northern Hemisphere.

scholarly journals One year boundary layer aerosol size distribution data from five Nordic background stations

2003 ◽  
Vol 3 (3) ◽  
pp. 2783-2833 ◽  
Author(s):  
P. Tunved ◽  
H.-C. Hansson ◽  
M. Kulmala ◽  
P. Aalto ◽  
Y. Viisanen ◽  
...  
Keyword(s):  
Size Distribution ◽  
Geographical Area ◽  
Aerosol Size Distribution ◽  
Distribution Data ◽  
Large Variability ◽  
Accumulation Mode ◽  
One Year ◽  
The Impact ◽  
Aitken Mode ◽  
Aerosol Properties

Abstract. Size distribution measurements performed at five different stations have been investigated during a one-year period between 01 June 2000 and 31 May 2001 with focus on diurnal, seasonal and geographical differences of size distribution properties. The stations involved cover a large geographical area ranging from the Finnish Lapland (67° N) down to southern Sweden (56° N) in the order Värriö, Pallas, Hyytiälä, Aspvreten and Vavihill. The shape of the size distribution is typically bimodal during winter with a larger fraction of accumulation mode particles compared to the other seasons. Highest Aitken mode concentration is found during summer and spring. The maximum of nucleation events occur during spring months. Nucleation events occur during other seasons as well, although not as frequently. Large differences were found between different categories of stations. Northerly located stations such as Pallas and Värriö presented well-separated Aitken and accumulation modes, while the two modes often overlap significantly at the two southernmost stations Vavihill and Aspvreten. A method to cluster trajectories was used to analyse the impact of long-range transport on the observed aerosol properties. Clusters of trajectories arriving from the continent were clearly associated with size distributions shifted towards the accumulation mode. This feature was more pronounced the further south the station was located. Marine- or Arctic-type clusters were associated with large variability in the nuclei size ranges. A quasi-lagrangian approach was used to investigate transport related changes in the aerosol properties. Typically, an increase in especially Aitken mode concentrations was observed when advection from the north occurs, i.e. allowing more continental influence on the aerosol when comparing the different measurement sites. When trajectory clusters arrive to the stations from SW, a gradual decrease in number concentration is experienced in all modes as latitude of measurement site increases.

scholarly journals Quantifying the aerosol effect on droplet size distribution at cloud-top

2018 ◽  
Author(s):  
Lianet Hernández Pardo ◽  
Luiz Augusto Toledo Machado ◽  
Micael Amore Cecchini ◽  
Madeleine Sánchez Gácita
Keyword(s):  
Size Distribution ◽  
Initial Conditions ◽  
Droplet Size Distribution ◽  
Cloud Microphysics ◽  
Number Concentration ◽  
Population Characteristics ◽  
Aerosol Size Distribution ◽  
Effective Diameter ◽  
Bin Microphysics ◽  
Aerosol Properties

Abstract. This work uses the number concentration-effective diameter phase-space to test cloud sensitivity to variations in the aerosol population characteristics, such as the aerosol size distribution, number concentration and hygroscopicity. It is based on the information from the top of a cloud simulated by a bin-microphysics single-column model, for initial conditions typical of the Amazon. It is shown that the cloud-top evolution can be very sensitive to aerosol properties, but the relative importance of each parameter is variable. The sensitivity to each aerosol characteristic varies as a function of the tested parameter and is conditioned by the base values of the other parameters. The median radius of the aerosols showed the largest influence on this sensitivity. We show that all aerosol properties can have significant impacts on cloud microphysics, especially if the median radius of the aerosol size distribution is smaller than 0.05 μm.

scholarly journals Toward a minimal representation of aerosols in climate models: description and evaluation in the Community Atmosphere Model CAM5

2012 ◽  
Vol 5 (3) ◽  
pp. 709-739 ◽  
Author(s):  
X. Liu ◽  
R. C. Easter ◽  
S. J. Ghan ◽  
R. Zaveri ◽  
P. Rasch ◽  
...  
Keyword(s):  
Developing Countries ◽  
Optical Properties ◽  
Size Distribution ◽  
Sea Salt ◽  
The Arctic ◽  
Aerosol Size Distribution ◽  
Model Version ◽  
Community Atmosphere Model ◽  
Atmosphere Model ◽  
Aerosol Module

Abstract. A modal aerosol module (MAM) has been developed for the Community Atmosphere Model version 5 (CAM5), the atmospheric component of the Community Earth System Model version 1 (CESM1). MAM is capable of simulating the aerosol size distribution and both internal and external mixing between aerosol components, treating numerous complicated aerosol processes and aerosol physical, chemical and optical properties in a physically-based manner. Two MAM versions were developed: a more complete version with seven lognormal modes (MAM7), and a version with three lognormal modes (MAM3) for the purpose of long-term (decades to centuries) simulations. In this paper a description and evaluation of the aerosol module and its two representations are provided. Sensitivity of the aerosol lifecycle to simplifications in the representation of aerosol is discussed. Simulated sulfate and secondary organic aerosol (SOA) mass concentrations are remarkably similar between MAM3 and MAM7. Differences in primary organic matter (POM) and black carbon (BC) concentrations between MAM3 and MAM7 are also small (mostly within 10%). The mineral dust global burden differs by 10% and sea salt burden by 30–40% between MAM3 and MAM7, mainly due to the different size ranges for dust and sea salt modes and different standard deviations of the log-normal size distribution for sea salt modes between MAM3 and MAM7. The model is able to qualitatively capture the observed geographical and temporal variations of aerosol mass and number concentrations, size distributions, and aerosol optical properties. However, there are noticeable biases; e.g., simulated BC concentrations are significantly lower than measurements in the Arctic. There is a low bias in modeled aerosol optical depth on the global scale, especially in the developing countries. These biases in aerosol simulations clearly indicate the need for improvements of aerosol processes (e.g., emission fluxes of anthropogenic aerosols and precursor gases in developing countries, boundary layer nucleation) and properties (e.g., primary aerosol emission size, POM hygroscopicity). In addition, the critical role of cloud properties (e.g., liquid water content, cloud fraction) responsible for the wet scavenging of aerosol is highlighted.

scholarly journals Using MODIS and AERONET to Determine GCM Aerosol Size

2006 ◽  
Vol 63 (4) ◽  
pp. 1338-1347 ◽  
Author(s):  
Glen Lesins ◽  
Ulrike Lohmann
Keyword(s):  
Size Distribution ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
General Circulation ◽  
Climate Model ◽  
General Circulation Models ◽  
Aerosol Size Distribution ◽  
Error Source ◽  
Fine Mode ◽  
Fine Mode Aerosol

Abstract Aerosol size is still a poorly constrained quantity in general circulation models (GCMs). By using the modal radii of the coarse and fine mode retrieved from 103 stations in the Aerosol Robotic Network (AERONET) and the fine mode aerosol optical depth fraction derived from both the Moderate Resolute Imaging Spectroradiometer (MODIS) Terra and AERONET, a globally and monthly averaged aerosol size distribution dataset was computed assuming internally mixed aerosols. Different methods were employed in creating the size distribution datasets that were input to the ECHAM4 climate model giving a globally averaged aerosol optical depth (AOD) at 500 nm that ranged from 0.11 to 0.20 depending on the method. This translates into a globally averaged direct aerosol top-of-atmosphere forcing range from −1.6 to −3.9 W m−2. Reducing the uncertainty in the aerosol sizes is important when using AOD to validate models since mass burden errors can then be assumed to be the main AOD error source. This paper explores a procedure that can help achieve this goal.

scholarly journals An aerosol activation metamodel of v1.2.0 of the pyrcel cloud parcel model: development and offline assessment for use in an aerosol–climate model

2017 ◽  
Vol 10 (4) ◽  
pp. 1817-1833 ◽  
Author(s):  
Daniel Rothenberg ◽  
Chien Wang
Keyword(s):  
Size Distribution ◽  
Relative Error ◽  
Climate Model ◽  
Cloud Condensation Nuclei ◽  
Full Range ◽  
Model Development ◽  
Cloud Droplet ◽  
Aerosol Size Distribution ◽  
Mean Relative Error ◽  
Distribution Parameters

Abstract. We describe an emulator of a detailed cloud parcel model which has been trained to assess droplet nucleation from a complex, multimodal aerosol size distribution simulated by a global aerosol–climate model. The emulator is constructed using a sensitivity analysis approach (polynomial chaos expansion) which reproduces the behavior of the targeted parcel model across the full range of aerosol properties and meteorology simulated by the parent climate model. An iterative technique using aerosol fields sampled from a global model is used to identify the critical aerosol size distribution parameters necessary for accurately predicting activation. Across the large parameter space used to train them, the emulators estimate cloud droplet number concentration (CDNC) with a mean relative error of 9.2 % for aerosol populations without giant cloud condensation nuclei (CCN) and 6.9 % when including them. Versus a parcel model driven by those same aerosol fields, the best-performing emulator has a mean relative error of 4.6 %, which is comparable with two commonly used activation schemes also evaluated here (which have mean relative errors of 2.9 and 6.7 %, respectively). We identify the potential for regional biases in modeled CDNC, particularly in oceanic regimes, where our best-performing emulator tends to overpredict by 7 %, whereas the reference activation schemes range in mean relative error from −3 to 7 %. The emulators which include the effects of giant CCN are more accurate in continental regimes (mean relative error of 0.3 %) but strongly overestimate CDNC in oceanic regimes by up to 22 %, particularly in the Southern Ocean. The biases in CDNC resulting from the subjective choice of activation scheme could potentially influence the magnitude of the indirect effect diagnosed from the model incorporating it.

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