Development of aerosol activation in the double-moment Unified Model and evaluation with CLARIFY measurements

Gordon, Hamish; Field, Paul R.; Abel, Steven J.; Barrett, Paul A.; Bower, Keith; Crawford, Ian; Cui, Zhiqiang; Grosvenor, Daniel P.; Hill, Adrian A.; Taylor, Jonathan; Wilkinson, Jonathan; Wu, Huihui; Carslaw, K. S.

doi:10.5194/acp-20-10997-2020

Cited by 14 publications

(38 citation statements)

References 96 publications

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“…In our previous model evaluations, although the model is generally able to well simulate the horizontal and vertical distribution of aerosols in the SEA, aerosols are slightly underestimated at higher altitudes and overestimated west of 5 °W (Che et al, 2021). The latter is also confirmed by studies with the same model (though with different configurations), which also shown an overestimation of aerosol concentrations in the western part of SEA (Gordon et al, 2020;Ranjithkumar et al, 2021). These model biases introduce some uncertainties into our results, particularly with respect to the effects of BB aerosols on CCN and clouds.…”

Section: Discussionsupporting

confidence: 59%

Source attribution of cloud condensation nuclei and their impact on stratocumulus clouds and radiation in the south-eastern Atlantic

Che

Stier

Watson-Parris

et al. 2022

Preprint

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Abstract. The semi-permanent stratocumulus clouds over the South-eastern Atlantic Ocean (SEA) can act as an “air conditioners” to the regional and global climate system. The interaction of aerosols and clouds become important in this region, and can lead to negative radiative effects, partially offsetting the positive radiative forcing of greenhouse gases. A key pathway of aerosols affecting cloud properties is by acting as cloud condensation nuclei (CCN). In this paper, we use the United Kingdom Earth System Model to investigate the sources of CCN (from atmospheric processes and emission sources) in the SEA, and the response of cloud droplet number concentration (CDNC), cloud liquid water path (LWP), and radiative forcing to those sources. Overall, total nucleation (binary nucleation) is the most important source of CCN0.2 % in the marine boundary layer, contributing an annual average of 50 % of CCN0.2 %. In terms of emission sources, anthropogenic emissions (from energy, industry, agriculture, etc.) contribute the most to the annual average CCN0.2 % in the marine boundary layer, followed by BB. In the free troposphere, however, BB becomes the dominant source of CCN0.2 %, accounting for 64 % of the annual average. The contribution of aerosols from different sources to CDNC is consistent with their contribution to CCN0.2 % within the marine boundary layer, with total nucleation being the most important source of CDNC overall. In terms of emissions, anthropogenic sources are also the largest contributors to the annual average of CDNC, closely followed by BB. The contribution of BB to CDNC is more significant than its increase to CCN0.2 %, mainly because BB aerosol also can increase CDNC by enhancing the maximum supersaturation through the radiative effect of shortwave absorption. For an aerosol source that shows an increase in CDNC, it also shows an increase in LWP resulting from a reduction in autoconversion. BB aerosol, due to the absorption effect, can enhance existing temperature inversions and reduce the entrainment of sub-saturated air, leading to a further increase in LWP. As a result, the contribution of BB to LWP is second only to total nucleation. These findings demonstrate that BB is not the dominant source of CCN within the marine boundary layer from an emission source perspective. However, its contribution to clouds increases due to its absorption effect (about the same as anthropogenic sources for CDNC and more than anthropogenic sources for LWP), highlighting the crucial role of its radiative effect on clouds. The results on the radiative effects of aerosols show that BB aerosol exhibits an overall positive RFari (radiative forcing associated with aerosol-radiation interaction), but its net effective radiative forcing remains negative due to its effect on clouds (mainly by absorbing effect). By quantifying aerosol and cloud properties affected by different sources, this paper provides a framework to understand aerosol sources effects on the marine cirrocumulus clouds and radiation in the SEA.

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Section: Discussionsupporting

confidence: 59%

Source attribution of cloud condensation nuclei and their impact on stratocumulus clouds and radiation in the south-eastern Atlantic

Che

Stier

Watson-Parris

et al. 2022

Preprint

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“…Global bulk aerosol models and empirical representations of aerosol indirect effects are being replaced with microphysical aerosol models such as ECHAM5-HAM (Stier et al, 2005) and GLOMAP (also known as UKCA mode) (e.g. Mann et al, 2010;Bellouin et al, 2013), and more explicit representations of cloud and precipitation processes (Hill et al, 2015;Grosvenor et al, 2017) have also been developed. Such schemes require extensive evaluation, which is often achieved through multi-model intercomparison studies (e.g.…”

Section: Aerosol-cloud Interactions (Aci)mentioning

confidence: 99%

The CLoud–Aerosol–Radiation Interaction and Forcing: Year 2017 (CLARIFY-2017) measurement campaign

et al. 2021

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Abstract. The representations of clouds, aerosols, and cloud–aerosol–radiation impacts remain some of the largest uncertainties in climate change, limiting our ability to accurately reconstruct past climate and predict future climate. The south-east Atlantic is a region where high atmospheric aerosol loadings and semi-permanent stratocumulus clouds are co-located, providing an optimum region for studying the full range of aerosol–radiation and aerosol–cloud interactions and their perturbations of the Earth's radiation budget. While satellite measurements have provided some useful insights into aerosol–radiation and aerosol–cloud interactions over the region, these observations do not have the spatial and temporal resolution, nor the required level of precision to allow for a process-level assessment. Detailed measurements from high spatial and temporal resolution airborne atmospheric measurements in the region are very sparse, limiting their use in assessing the performance of aerosol modelling in numerical weather prediction and climate models. CLARIFY-2017 was a major consortium programme consisting of five principal UK universities with project partners from the UK Met Office and European- and USA-based universities and research centres involved in the complementary ORACLES, LASIC, and AEROCLO-sA projects. The aims of CLARIFY-2017 were fourfold: (1) to improve the representation and reduce uncertainty in model estimates of the direct, semi-direct, and indirect radiative effect of absorbing biomass burning aerosols; (2) to improve our knowledge and representation of the processes determining stratocumulus cloud microphysical and radiative properties and their transition to cumulus regimes; (3) to challenge, validate, and improve satellite retrievals of cloud and aerosol properties and their radiative impacts; (4) to improve the impacts of aerosols in weather and climate numerical models. This paper describes the modelling and measurement strategies central to the CLARIFY-2017 deployment of the FAAM BAe146 instrumented aircraft campaign, summarizes the flight objectives and flight patterns, and highlights some key results from our initial analyses.

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“…The single-moment cloud microphysics scheme will also be replaced by the Cloud-AeroSol Interacting Microphysics (CASIM) scheme in DM-Chem, where both cloud and aerosol particles have double-moment representations with prognostic number and mass. This scheme has been implemented for fog in large eddy simulations by Poku et al (2019) and coupled to GLOMAP by Gordon et al (2020). Finally, the visibility scheme needs improvement, for example a more sophisticated representation of the extinction efficiency Q.…”

Section: Discussionmentioning

confidence: 99%

“…(2019) and coupled to GLOMAP by Gordon et al . (2020). Finally, the visibility scheme needs improvement, for example a more sophisticated representation of the extinction efficiency Q .…”

Section: Discussionmentioning

confidence: 99%

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Delhi Model with Chemistry and aerosol framework (DM‐Chem) for high‐resolution fog forecasting

Jayakumar

Gordon

Francis

et al. 2021

Quart J Royal Meteoro Soc

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We introduce here the Delhi Model with Chemistry and aerosol framework (DM-Chem), a high-resolution (330 m) visibility and fog forecasting model with the UK Chemistry and Aerosol scheme. DM-Chem is developed at the National Centre for Medium-Range Weather Forecasting (NCMRWF) in collaboration with UK Met Office and Carnegie Mellon University. We present a revised visibility scheme here which uses prognostic aerosols (mass and number concentration) from the two-moment prognostic Global Model of Aerosol Processes (GLOMAP) -mode aerosol scheme. This scheme represents aerosol microphysical processes and the internal mixing of chemical components within five log-normal size modes. The cloud microphysics parameterization also makes use of the GLOMAP scheme to predict cloud droplet number concentration (N d ).Therefore we are able to evaluate the performance of the scheme indirectly by comparing the predicted N d with that derived from Moderate-Resolution Imaging Spectroradiometer (MODIS) retrievals over the Indo-Gangetic Plain. Aerosol emissions for the inner (330 m) nest are prescribed with a high-resolution inventory for Delhi, from the System of Air Quality and Weather Forecasting project (SAFAR). Winter-time stubble burning is represented using the MODIS-based Fire Energetics and Emissions Research inventory, updated daily. In this article we consider case studies spanning both foggy and haze days of winter 2019-2020. The model compares well with the observed visibility and its spatial and diurnal patterns. The SAFAR emissions help improve the near-surface model fields. For the "haze" case, the single scattering albedo (SSA) is high along the regions of high AOD, and the surface radiative cooling is enhanced. During the "foggy" case, the SSA is not clearly related to AOD, but aerosol absorption does lead to a minor surface warming via the semi-direct effect at the time of onset of fog. The DM-Chem entered operational mode at NCMRWF from winter 2020 and provides high-resolution visibility forecast for Delhi and the adjoining region.

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Development of aerosol activation in the double-moment Unified Model and evaluation with CLARIFY measurements

Cited by 14 publications

References 96 publications

Source attribution of cloud condensation nuclei and their impact on stratocumulus clouds and radiation in the south-eastern Atlantic

Source attribution of cloud condensation nuclei and their impact on stratocumulus clouds and radiation in the south-eastern Atlantic

The CLoud–Aerosol–Radiation Interaction and Forcing: Year 2017 (CLARIFY-2017) measurement campaign

Delhi Model with Chemistry and aerosol framework (DM‐Chem) for high‐resolution fog forecasting

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