Evaluation of climate model aerosol trends with ground-based observations over the last 2 decades – an AeroCom  and CMIP6 analysis

Mortier, Augustin; Gliß, Jonas; Schulz, Mıchael; Aas, Wenche; Andrews, Elisabeth; Bian, Huisheng; Chin, Mian; Ginoux, Paul; Hand, Jenny L.; Holben, B. N.; Zhang, Hua; Kipling, Zak; Kirkevåg, Alf; Laj, Paolo; Lurton, Thibault; Myhre, Gunnar; Neubauer, David; Olivié, Dirk; Salzen, Knut von; Skeie, Ragnhild Bieltvedt; Takemura, Toshihiko; Tilmes, Simone

doi:10.5194/acp-20-13355-2020

Cited by 50 publications

(47 citation statements)

References 86 publications

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“…One of the main reasons to update the reference year from 2000 to 2010 was that many more observations became available between 2000 and 2010 and also to account for changes in the present-day climate, for instance, due to changing emissions and composition (e.g. Klimont et al, 2013;Aas et al, 2019;Mortier et al, 2020b). Detailed information about the models on emissions, humidity growth, and particularly their treatment of aerosol optics has been collected from the modelling groups through a questionnaire.…”

Section: Modelsmentioning

confidence: 99%

“…One factor that likely impacts the climatological results is that (1) the site density increased in more recent years (e.g. Laj et al, 2020), particularly in Europe and the United States, and (2) these regions are associated with negative trends in scattering and absorption (Collaud Coen et al, 2020;Mortier et al, 2020b). This could shift the weight in the climatology to more recent measurements or to regions affected by larger changes between 2005-2015.…”

Section: Dry Surface Scattering Coefficient (Sc Dry )mentioning

confidence: 99%

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AeroCom phase III multi-model evaluation of the aerosol life cycle and optical properties using ground- and space-based remote sensing as well as surface in situ observations

et al. 2021

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Abstract. Within the framework of the AeroCom (Aerosol Comparisons between Observations and Models) initiative, the state-of-the-art modelling of aerosol optical properties is assessed from 14 global models participating in the phase III control experiment (AP3). The models are similar to CMIP6/AerChemMIP Earth System Models (ESMs) and provide a robust multi-model ensemble. Inter-model spread of aerosol species lifetimes and emissions appears to be similar to that of mass extinction coefficients (MECs), suggesting that aerosol optical depth (AOD) uncertainties are associated with a broad spectrum of parameterised aerosol processes. Total AOD is approximately the same as in AeroCom phase I (AP1) simulations. However, we find a 50 % decrease in the optical depth (OD) of black carbon (BC), attributable to a combination of decreased emissions and lifetimes. Relative contributions from sea salt (SS) and dust (DU) have shifted from being approximately equal in AP1 to SS contributing about 2∕3 of the natural AOD in AP3. This shift is linked with a decrease in DU mass burden, a lower DU MEC, and a slight decrease in DU lifetime, suggesting coarser DU particle sizes in AP3 compared to AP1. Relative to observations, the AP3 ensemble median and most of the participating models underestimate all aerosol optical properties investigated, that is, total AOD as well as fine and coarse AOD (AODf, AODc), Ångström exponent (AE), dry surface scattering (SCdry), and absorption (ACdry) coefficients. Compared to AERONET, the models underestimate total AOD by ca. 21 % ± 20 % (as inferred from the ensemble median and interquartile range). Against satellite data, the ensemble AOD biases range from −37 % (MODIS-Terra) to −16 % (MERGED-FMI, a multi-satellite AOD product), which we explain by differences between individual satellites and AERONET measurements themselves. Correlation coefficients (R) between model and observation AOD records are generally high (R>0.75), suggesting that the models are capable of capturing spatio-temporal variations in AOD. We find a much larger underestimate in coarse AODc (∼ −45 % ± 25 %) than in fine AODf (∼ −15 % ± 25 %) with slightly increased inter-model spread compared to total AOD. These results indicate problems in the modelling of DU and SS. The AODc bias is likely due to missing DU over continental land masses (particularly over the United States, SE Asia, and S. America), while marine AERONET sites and the AATSR SU satellite data suggest more moderate oceanic biases in AODc. Column AEs are underestimated by about 10 % ± 16 %. For situations in which measurements show AE > 2, models underestimate AERONET AE by ca. 35 %. In contrast, all models (but one) exhibit large overestimates in AE when coarse aerosol dominates (bias ca. +140 % if observed AE < 0.5). Simulated AE does not span the observed AE variability. These results indicate that models overestimate particle size (or underestimate the fine-mode fraction) for fine-dominated aerosol and underestimate size (or overestimate the fine-mode fraction) for coarse-dominated aerosol. This must have implications for lifetime, water uptake, scattering enhancement, and the aerosol radiative effect, which we can not quantify at this moment. Comparison against Global Atmosphere Watch (GAW) in situ data results in mean bias and inter-model variations of −35 % ± 25 % and −20 % ± 18 % for SCdry and ACdry, respectively. The larger underestimate of SCdry than ACdry suggests the models will simulate an aerosol single scattering albedo that is too low. The larger underestimate of SCdry than ambient air AOD is consistent with recent findings that models overestimate scattering enhancement due to hygroscopic growth. The broadly consistent negative bias in AOD and surface scattering suggests an underestimate of aerosol radiative effects in current global aerosol models. Considerable inter-model diversity in the simulated optical properties is often found in regions that are, unfortunately, not or only sparsely covered by ground-based observations. This includes, for instance, the Sahara, Amazonia, central Australia, and the South Pacific. This highlights the need for a better site coverage in the observations, which would enable us to better assess the models, but also the performance of satellite products in these regions. Using fine-mode AOD as a proxy for present-day aerosol forcing estimates, our results suggest that models underestimate aerosol forcing by ca. −15 %, however, with a considerably large interquartile range, suggesting a spread between −35 % and +10 %.

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Section: Modelsmentioning

confidence: 99%

Section: Dry Surface Scattering Coefficient (Sc Dry )mentioning

confidence: 99%

AeroCom phase III multi-model evaluation of the aerosol life cycle and optical properties using ground- and space-based remote sensing as well as surface in situ observations

et al. 2021

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“…trations observed until 0930-1000. PM distribution during the morning traffic rush hours is in the range 15-25 µ g/m 3 and homogeneously distributed in the first 500 m (i.e., no clear gradual decrease in this altitude range) with again a sharp decrease below 5 μg/m 3 when crossing the PBL at 500 m AGL. Interestingly, the development of PBL (from 1030 LT) does not seem to affect the PM vertical distribution, which seems to dilute homogeneously within the boundary layer.…”

Section: Profiling Of Aerosol Properties In Various Marine Regionsmentioning

confidence: 95%

“…In-situ measurements can provide a great deal of information about the atmospheric environment that impacts almost all aspects of human life. Such measurements provide essential input for evaluating satellite retrievals [1,2], establishing long-term datasets for monitoring atmospheric aerosol and gas levels, and assessing atmospheric models by giving insight into the localized air quality [3], long-range transport of pollutants, radiative forcing, cloud formation, etc. [4].…”

Section: Introductionmentioning

confidence: 99%

The Unmanned Systems Research Laboratory (USRL): A New Facility for UAV-Based Atmospheric Observations

et al. 2021

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The Unmanned Systems Research Laboratory (USRL) of the Cyprus Institute is a new mobile exploratory platform of the EU Research Infrastructure Aerosol, Clouds and Trace Gases Research InfraStructure (ACTRIS). USRL offers exclusive Unmanned Aerial Vehicle (UAV)-sensor solutions that can be deployed anywhere in Europe and beyond, e.g., during intensive field campaigns through a transnational access scheme in compliance with the drone regulation set by the European Union Aviation Safety Agency (EASA) for the research, innovation, and training. UAV sensor systems play a growing role in the portfolio of Earth observation systems. They can provide cost-effective, spatial in-situ atmospheric observations which are complementary to stationary observation networks. They also have strong potential for calibrating and validating remote-sensing sensors and retrieval algorithms, mapping close-to-the-ground emission point sources and dispersion plumes, and evaluating the performance of atmospheric models. They can provide unique information relevant to the short- and long-range transport of gas and aerosol pollutants, radiative forcing, cloud properties, emission factors and a variety of atmospheric parameters. Since its establishment in 2015, USRL is participating in major international research projects dedicated to (1) the better understanding of aerosol-cloud interactions, (2) the profiling of aerosol optical properties in different atmospheric environments, (3) the vertical distribution of air pollutants in and above the planetary boundary layer, (4) the validation of Aeolus satellite dust products by utilizing novel UAV-balloon-sensor systems, and (5) the chemical characterization of ship and stack emissions. A comprehensive overview of the new UAV-sensor systems developed by USRL and their field deployments is presented here. This paper aims to illustrate the strong scientific potential of UAV-borne measurements in the atmospheric sciences and the need for their integration in Earth observation networks.

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“…In contrast, high SO 2 and NO x emissions promote the conversion of gaseous NH 3 into particulate ammonium in the NCP. However, a rapid decline of acidic (SO 2 ) emissions over China after 2000, which may not be reflected correctly in HTAP_v2 (Mortier et al, 2020;Tong et al, 2020;Zheng et al, 2018), will lead to higher NH 3 loading due to less partitioning of NH 3 .…”

Section: Comparison Between Surface Nh 3 Measurements and Simulated Nh 3 Concentrations In South And East Asiamentioning

confidence: 99%

Analysis of atmospheric ammonia over South and East Asia based on the MOZART-4 model and its comparison with satellite and surface observations

et al. 2021

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Abstract. Limited availability of atmospheric ammonia (NH3) observations limits our understanding of controls on its spatial and temporal variability and its interactions with the ecosystem. Here we used the Model for Ozone and Related chemical Tracers version 4 (MOZART-4) global chemistry transport model and the Hemispheric Transport of Air Pollution version 2 (HTAP-v2) emission inventory to simulate global NH3 distribution for the year 2010. We presented a first comparison of the model with monthly averaged satellite distributions and limited ground-based observations available across South Asia. The MOZART-4 simulations over South Asia and East Asia were evaluated with the NH3 retrievals obtained from the Infrared Atmospheric Sounding Interferometer (IASI) satellite and 69 ground-based monitoring stations for air quality across South Asia and 32 ground-based monitoring stations from the Nationwide Nitrogen Deposition Monitoring Network (NNDMN) of China. We identified the northern region of India (Indo-Gangetic Plain, IGP) as a hotspot for NH3 in Asia, both using the model and satellite observations. In general, a close agreement was found between yearly averaged NH3 total columns simulated by the model and IASI satellite measurements over the IGP, South Asia (r=0.81), and the North China Plain (NCP), East Asia (r=0.90). However, the MOZART-4-simulated NH3 column was substantially higher over South Asia than East Asia, as compared with the IASI retrievals, which show smaller differences. Model-simulated surface NH3 concentrations indicated smaller concentrations in all seasons than surface NH3 measured by the ground-based observations over South and East Asia, although uncertainties remain in the available surface NH3 measurements. Overall, the comparison of East Asia and South Asia using both MOZART-4 model and satellite observations showed smaller NH3 columns in East Asia compared with South Asia for comparable emissions, indicating rapid dissipation of NH3 due to secondary aerosol formation, which can be explained by larger emissions of acidic precursor gases in East Asia.

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Evaluation of climate model aerosol trends with ground-based observations over the last 2 decades – an AeroCom and CMIP6 analysis

Cited by 50 publications

References 86 publications

AeroCom phase III multi-model evaluation of the aerosol life cycle and optical properties using ground- and space-based remote sensing as well as surface in situ observations

AeroCom phase III multi-model evaluation of the aerosol life cycle and optical properties using ground- and space-based remote sensing as well as surface in situ observations

The Unmanned Systems Research Laboratory (USRL): A New Facility for UAV-Based Atmospheric Observations

Analysis of atmospheric ammonia over South and East Asia based on the MOZART-4 model and its comparison with satellite and surface observations

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