Aerosol water parameterization: long-term evaluation and importance

Abstract. We scrutinize the importance of aerosol water for the aerosol optical depth (AOD) calculations by a long-term evaluation of the EQuilibrium Simplified Aerosol Model V4 for climate modeling, which was introduced by Metzger et al. (2016a). EQSAM4clim is based on a sin-gle solute coefficient approach that efficiently parameterizes hygroscopic growth, account- ing for aerosol water uptake from the deliquescence relative humidity up to supersaturation. EQSAM4clim extends the single solute coefficient approach to treat water uptake of multi- component mixtures. The gas-aerosol partitioning and the mixed solution water uptake can be solved analytically, preventing the need for iterations, which is computationally efficient. EQSAM4clim has been implemented in the global chemistry climate model EMAC and com- pared to ISORROPIA II (Fountoukis and Nenes, 2007) at climate time-scales. Our global modeling results show that (I) our EMAC results of the aerosol optical depth (AOD) are comparable to independent results of Pozzer et al. (2015) for the period 2000–2010, (II) the results of various aerosol properties of EQSAM4clim and ISORROPIA II are similar and in agreement with AERONET and EMEP observations for the period 2000–2013, and (III) that the underlying assumptions on the aerosol water uptake limitations are important for derived AOD calculations. Sensitivity studies of different levels of chemical aging and associated water uptake show larger effects on AOD calculations for the year 2005 compared to the differences associated with the application of the two gas-liquid-solid partitioning schemes. Altogether, our study reveals the importance of the aerosol water for climate applications.

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Aerosol water parameterization: long-term evaluation and importance for climate studies

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-16747-2018 ◽

2018 ◽

Vol 18 (22) ◽

pp. 16747-16774 ◽

Cited By ~ 6

Author(s):

Swen Metzger ◽

Mohamed Abdelkader ◽

Benedikt Steil ◽

Klaus Klingmüller

Keyword(s):

Water Uptake ◽

Climate Model ◽

Climate Modeling ◽

Mixed Solution ◽

Hygroscopic Growth ◽

Computationally Efficient ◽

Aerosol Model ◽

Term Evaluation ◽

Climate Studies

Abstract. We scrutinize the importance of aerosol water for the aerosol optical depth (AOD) calculations using a long-term evaluation of the EQuilibrium Simplified Aerosol Model v4 for climate modeling. EQSAM4clim is based on a single solute coefficient approach that efficiently parameterizes hygroscopic growth, accounting for aerosol water uptake from the deliquescence relative humidity up to supersaturation. EQSAM4clim extends the single solute coefficient approach to treat water uptake of multicomponent mixtures. The gas–aerosol partitioning and the mixed-solution water uptake can be solved analytically, preventing the need for iterations, which is computationally efficient. EQSAM4clim has been implemented in the global chemistry climate model EMAC and compared to ISORROPIA II on climate timescales. Our global modeling results show that (I) our EMAC results of the AOD are comparable to modeling results that have been independently evaluated for the period 2000–2010, (II) the results of various aerosol properties of EQSAM4clim and ISORROPIA II are similar and in agreement with AERONET and EMEP observations for the period 2000–2013, and (III) the underlying assumptions on the aerosol water uptake limitations are important for derived AOD calculations. Sensitivity studies of different levels of chemical aging and associated water uptake show larger effects on AOD calculations for the year 2005 compared to the differences associated with the application of the two gas–liquid–solid partitioning schemes. Overall, our study demonstrates the importance of aerosol water for climate studies.

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Aerosol water parameterisation: a single parameter framework

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-7213-2016 ◽

2016 ◽

Vol 16 (11) ◽

pp. 7213-7237 ◽

Cited By ~ 13

Author(s):

Swen Metzger ◽

Benedikt Steil ◽

Mohamed Abdelkader ◽

Klaus Klingmüller ◽

Li Xu ◽

...

Keyword(s):

Ammonium Nitrate ◽

Water Uptake ◽

Climate Model ◽

Mixed Solution ◽

Hygroscopic Growth ◽

Simple Method ◽

Aerosol Model ◽

Kohler Theory ◽

Comprehensive Comparison ◽

Term Evaluation

Abstract. We introduce a framework to efficiently parameterise the aerosol water uptake for mixtures of semi-volatile and non-volatile compounds, based on the coefficient, νi. This solute-specific coefficient was introduced in Metzger et al. (2012) to accurately parameterise the single solution hygroscopic growth, considering the Kelvin effect – accounting for the water uptake of concentrated nanometer-sized particles up to dilute solutions, i.e. from the compounds relative humidity of deliquescence (RHD) up to supersaturation (Köhler theory). Here we extend the νi parameterisation from single to mixed solutions. We evaluate our framework at various levels of complexity, by considering the full gas–liquid–solid partitioning for a comprehensive comparison with reference calculations using the E-AIM, EQUISOLV II and ISORROPIA II models as well as textbook examples. We apply our parameterisation in the EQuilibrium Simplified Aerosol Model V4 (EQSAM4clim) for climate simulations, implemented in a box model and in the global chemistry–climate model EMAC. Our results show (i) that the νi approach enables one to analytically solve the entire gas–liquid–solid partitioning and the mixed solution water uptake with sufficient accuracy, (ii) that ammonium sulfate mixtures can be solved with a simple method, e.g. pure ammonium nitrate and mixed ammonium nitrate and (iii) that the aerosol optical depth (AOD) simulations are in close agreement with remote sensing observations for the year 2005. Long-term evaluation of the EMAC results based on EQSAM4clim and ISORROPIA II will be presented separately.

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Aerosol water parameterization: a single parameter framework

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-33493-2015 ◽

2015 ◽

Vol 15 (22) ◽

pp. 33493-33553

Author(s):

S. Metzger ◽

B. Steil ◽

M. Abdelkader ◽

K. Klingmüller ◽

L. Xu ◽

...

Keyword(s):

Ammonium Nitrate ◽

Water Uptake ◽

Climate Model ◽

Mixed Solution ◽

Hygroscopic Growth ◽

Simple Method ◽

Aerosol Model ◽

Kohler Theory ◽

Comprehensive Comparison ◽

Term Evaluation

Abstract. We introduce a framework to efficiently parameterize the aerosol water uptake for mixtures of semi-volatile and non-volatile compounds, based on the coefficient, νi. This solute specific coefficient was introduced in Metzger et al. (2012) to accurately parameterize the single solution hygroscopic growth, considering the Kelvin effect – accounting for the water uptake of concentrated nanometer sized particles up to dilute solutions, i.e., from the compounds relative humidity of deliquescence (RHD) up to supersaturation (Köhler-theory). Here we extend the νi-parameterization from single to mixed solutions. We evaluate our framework at various levels of complexity, by considering the full gas-liquid-solid partitioning for a comprehensive comparison with reference calculations using the E-AIM, EQUISOLV II, ISORROPIA II models as well as textbook examples. We apply our parameterization in EQSAM4clim, the EQuilibrium Simplified Aerosol Model V4 for climate simulations, implemented in a box model and in the global chemistry-climate model EMAC. Our results show: (i) that the νi-approach enables to analytically solve the entire gas-liquid-solid partitioning and the mixed solution water uptake with sufficient accuracy, (ii) that, e.g., pure ammonium nitrate and mixed ammonium nitrate – ammonium sulfate mixtures can be solved with a simple method, and (iii) that the aerosol optical depth (AOD) simulations are in close agreement with remote sensing observations for the year 2005. Long-term evaluation of the EMAC results based on EQSAM4clim and ISORROPIA II will be presented separately.

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Description of EQSAM4: gas-liquid-solid partitioning model for global simulations

Geoscientific Model Development Discussions ◽

10.5194/gmdd-4-2791-2011 ◽

2011 ◽

Vol 4 (4) ◽

pp. 2791-2847 ◽

Cited By ~ 1

Author(s):

S. Metzger ◽

B. Steil ◽

L. Xu ◽

J. E. Penner ◽

J. Lelieveld

Keyword(s):

Water Uptake ◽

Atmospheric Aerosols ◽

Atmospheric Chemistry ◽

Large Scale ◽

Climate Model ◽

Reference Model ◽

Climate Modeling ◽

Box Model ◽

Hygroscopic Growth ◽

Aerosol Model

Abstract. We introduce version 4 of the EQuilibrium Simplified Aerosol Model (EQSAM4), which is part of our aerosol chemistry-microphysics module (GMXe) and chemistry-climate model (EMAC). We focus on the relative humidity of deliquescence (RHD) based water uptake of atmospheric aerosols, as this is important for atmospheric chemistry and climate modeling, e.g. to calculate the aerosol optical depth (AOD). Since the main EQSAM4 applications will involve large-scale, long-term and high-resolution atmospheric chemistry-climate modeling with EMAC, computational efficiency is an important requirement. EQSAM4 parameterizes the composition and water uptake of multicomponent atmospheric aerosols by considering the gas-liquid-solid partitioning of single and mixed solutes. EQSAM4 builds on analytical, and hence CPU efficient, aerosol hygroscopic growth parameterizations to compute the aerosol liquid water content (AWC). The parameterizations are described in the companion paper (Metzger et al., 2011) and only require a compound specific coefficient νi to derive the single solute molality and the AWC for the whole range of water activity (aw). νi is pre-calculated and applied during runtime by using internal look-up tables. Here, the EQSAM4 equilibrium model is described and compared to the more explicit thermodynamic model ISORROPIA II. Both models are imbedded in EMAC/GMXe. Box model inter-comparisons, including the reference model E-AIM, and global simulations with EMAC show that gas-particle partitioning, including semi-volatiles and water, is in good agreement. A more comprehensive box model inter-comparison of EQSAM4 with EQUISOLV II is subject of the revised publication of Xu et al. (2009), i.e. Xu et al. (2011).

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The global aerosol-climate model ECHAM-HAM, version 2: sensitivity to improvements in process representations

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-12-7545-2012 ◽

2012 ◽

Vol 12 (3) ◽

pp. 7545-7615 ◽

Cited By ~ 12

Author(s):

K. Zhang ◽

D. O'Donnell ◽

J. Kazil ◽

P. Stier ◽

S. Kinne ◽

...

Keyword(s):

Aerosol Optical Depth ◽

Optical Depth ◽

Water Uptake ◽

Climate Model ◽

Lower Troposphere ◽

Cloud Microphysics ◽

Aerosol Size Distribution ◽

Microphysics Scheme ◽

Temporal Variance ◽

General Improvement

Abstract. This paper introduces and evaluates the second version of the global aerosol-climate model ECHAM-HAM. Major changes have been brought into the model, including new parameterizations for aerosol nucleation and water uptake, an explicit treatment of secondary organic aerosols, modified emission calculations for sea salt and mineral dust, the coupling of aerosol microphysics to a two-moment stratiform cloud microphysics scheme, and alternative wet scavenging parameterizations. These revisions extend the model's capability to represent details of the aerosol lifecycle and its interaction with climate. Sensitivity experiments are carried out to analyse the effects of these improvements in the process representation on the simulated aerosol properties and global distribution. The new parameterizations that have largest impact on the global mean aerosol optical depth and radiative effects turn out to be the water uptake scheme and cloud microphysics. The former leads to a significant decrease of aerosol water contents in the lower troposphere, and consequently smaller optical depth; the latter results in higher aerosol loading and longer lifetime due to weaker in-cloud scavenging. The combined effects of the new/updated parameterizations are demonstrated by comparing the new model results with those from the earlier version, and against observations. Model simulations are evaluated in terms of aerosol number concentrations against measurements collected from twenty field campaigns as well as from fixed measurement sites, and in terms of optical properties against the AERONET measurements. Results indicate a general improvement with respect to the earlier version. The aerosol size distribution and spatial-temporal variance simulated by HAM2 are in better agreement with the observations. Biases in the earlier model version in aerosol optical depth and in the Ångström parameter have been reduced. The paper also points out the remaining model deficiencies that need to be addressed in the future.

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Aerosol optical depth retrievals at the Izaña Atmospheric Observatory from 1941 to 2013 by using artificial neural networks

Atmospheric Measurement Techniques ◽

10.5194/amt-9-53-2016 ◽

2016 ◽

Vol 9 (1) ◽

pp. 53-62 ◽

Cited By ~ 13

Author(s):

R. D. García ◽

O. E. García ◽

E. Cuevas ◽

V. E. Cachorro ◽

A. Barreto ◽

...

Keyword(s):

Neural Networks ◽

Time Series ◽

Artificial Neural Networks ◽

Aerosol Optical Depth ◽

Optical Depth ◽

Mineral Dust ◽

Dust Particles ◽

Filter Radiometer ◽

Artificial Neural

Abstract. This paper presents the reconstruction of a 73-year time series of the aerosol optical depth (AOD) at 500 nm at the subtropical high-mountain Izaña Atmospheric Observatory (IZO) located in Tenerife (Canary Islands, Spain). For this purpose, we have combined AOD estimates from artificial neural networks (ANNs) from 1941 to 2001 and AOD measurements directly obtained with a Precision Filter Radiometer (PFR) between 2003 and 2013. The analysis is limited to summer months (July–August–September), when the largest aerosol load is observed at IZO (Saharan mineral dust particles). The ANN AOD time series has been comprehensively validated against coincident AOD measurements performed with a solar spectrometer Mark-I (1984–2009) and AERONET (AErosol RObotic NETwork) CIMEL photometers (2004–2009) at IZO, obtaining a rather good agreement on a daily basis: Pearson coefficient, R, of 0.97 between AERONET and ANN AOD, and 0.93 between Mark-I and ANN AOD estimates. In addition, we have analysed the long-term consistency between ANN AOD time series and long-term meteorological records identifying Saharan mineral dust events at IZO (synoptical observations and local wind records). Both analyses provide consistent results, with correlations >  85 %. Therefore, we can conclude that the reconstructed AOD time series captures well the AOD variations and dust-laden Saharan air mass outbreaks on short-term and long-term timescales and, thus, it is suitable to be used in climate analysis.

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Nine years of UV aerosol optical depth measurements at Thessaloniki, Greece

Atmospheric Chemistry and Physics ◽

10.5194/acp-7-2091-2007 ◽

2007 ◽

Vol 7 (8) ◽

pp. 2091-2101 ◽

Cited By ~ 90

Author(s):

S. Kazadzis ◽

A. Bais ◽

V. Amiridis ◽

D. Balis ◽

C. Meleti ◽

...

Keyword(s):

Aerosol Optical Depth ◽

Optical Depth ◽

Back Trajectories ◽

Air Masses ◽

North Eastern ◽

Range Transport ◽

Air Quality Monitoring Stations ◽

Pm 10 ◽

The City

Abstract. Spectral measurements of the aerosol optical depth (AOD) and the Ångström coefficient were conducted at Thessaloniki, Greece (40.5° N, 22.9° E) between January 1997 and December 2005 with a Brewer MKIII double-monochromator spectroradiometer. The dataset was compared with collocated measurements of a second spectroradiometer (Brewer MKII) and a CIMEL sun-photometer, showing correlations of 0.93 and 0.98, respectively. A seasonal variation of the AOD was observed at Thessaloniki, with AOD values at 340 nm of 0.52 and 0.28 for August and December respectively. Back trajectories of air masses for up to 4 days were used to assess the influence of long-range transport from various regions to the aerosol load over Thessaloniki. It is shown that part of the observed seasonality can be attributed to air masses with high AOD originating from North-Eastern and Eastern directions during summertime. The analysis of the long-term record (9 years) of AOD showed a downward tendency. A similar decreasing tendency was found in the record of the PM$_{10}$ aerosol measurements, which are conducted near the surface at 4 air-quality monitoring stations in the area of the city of Thessaloniki.

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