High Sensitivity of Arctic Liquid Clouds to Long‐Range Anthropogenic Aerosol Transport

Coopman, Quentin; Garrett, Timothy J.; Finch, Douglas; Riédi, J.

doi:10.1002/2017gl075795

Cited by 36 publications

(56 citation statements)

References 77 publications

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“…These observations indicate that changes in T and RH of air masses entering the Arctic will likely have a very large influence on observed CF, to a degree that is much more regionally important than the microphysical effects of the aerosols themselves. In line with previous studies (e.g., Gryspeerdt et al (2016);Coopman et al (2018)), these results also underscore the need for large sample volumes to identify 5 systematic differences in regional air masses between clean and all conditions, and a way to reduce the confounding effects of meteorological co-variation on these samples. To accomplish this, we analyzed over 10 million profiles across the Arctic Ocean, which were binned into similar T and RH groups.…”

Section: Discussionsupporting

confidence: 74%

“…This finding suggests that aerosol microphysical impacts on clouds are more influential at the lower temperatures and/or more stable conditions over sea ice. Previous studies have also observed larger aerosol microphysical effects under more stable conditions in the Arctic (Coopman et al, 2018;Zamora et al, 2017). Possible reasons for the disparate behavior at different altitudes are discussed below.…”

mentioning

confidence: 92%

“…Systematic regional co-variability of aerosols and meteorological factors must be accounted for in order to avoid overestimating aerosol impacts on clouds (Coopman et al, 2018;Gryspeerdt et al, 2016). To illustrate this point, Figure 2 shows the longwave CRE BOA for the upper and lower quartiles of FLEXPART model column BC concentrations during the study period.…”

Section: Aerosol Microphysical Effects On Cloud Fractionmentioning

confidence: 99%

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A satellite-based estimate of aerosol-cloud microphysical effects over the Arctic Ocean

Zamora

Kahn

Huebert

et al. 2018

Preprint

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Abstract. Climate predictions for the rapidly changing Arctic are highly uncertain, largely due to a poor understanding of the processes driving cloud properties. In particular, cloud fraction (CF) and cloud phase (CP) have major impacts on energy 10 budgets, but are poorly represented in most models, often because of uncertainties in aerosol-cloud interactions. Here we use over 10 million satellite observations coupled with aerosol transport model simulations to quantify regional-scale microphysical effects of aerosols on CF and CP over the Arctic Ocean during polar night, when direct and semi-direct aerosol effects are minimal. Combustion aerosols over sea ice are associated with very large (~25 W m -2 ) differences in longwave cloud radiative effects at the sea ice surface. However, co-varying meteorological changes on factors such as CF 15 likely explain much of this signal -for example, explaining up to 91% of the CF differences between the full dataset and the clean-condition subset. After normalizing for meteorological regime, aerosol microphysical effects have small but significant regional-scale impacts on CF, CP, and precipitation frequency. These effects indicate that dominant aerosol-cloud microphysical mechanisms are related to the relative fraction of liquid-containing clouds, with implications for a warming Arctic. 20

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Section: Discussionsupporting

confidence: 74%

mentioning

confidence: 92%

Section: Aerosol Microphysical Effects On Cloud Fractionmentioning

confidence: 99%

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A satellite-based estimate of aerosol-cloud microphysical effects over the Arctic Ocean

Zamora

Kahn

Huebert

et al. 2018

Preprint

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“…When the impact of meteorology is controlled for, these satellite‐based ACI estimates indicate a high sensitivity of Arctic clouds to transported aerosol, though anthropogenic sources appear to make a larger impact than aerosol from biomass burning (Coopman et al, , ). This high sensitivity of Arctic clouds could not solely be explained by overall lower aerosol concentrations compared to lower latitudes and may arise in part due to the strong stability of the Arctic troposphere that inhibits vertical mixing (Coopman et al, ). Importantly, these satellite‐based ACI estimates rely upon comparison to a clean cloud background state and use modeled carbon monoxide concentrations as a proxy for aerosol.…”

Section: Aerosol‐cloud Interactionsmentioning

confidence: 99%

Processes Controlling the Composition and Abundance of Arctic Aerosol

Willis

Leaitch

Abbatt

2018

Reviews of Geophysics

147

154

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The Arctic region is a harbinger of global change and is warming at a rate higher than the global average. While Arctic warming is driven by increases in anthropogenic greenhouse gases' in combination with local feedback mechanisms, short‐lived climate forcing agents, such as tropospheric aerosol, are also important drivers of Arctic climate. Arctic aerosol‐climate impacts vary seasonally as a result of the interplay between aerosol and different cloud types, available solar radiation, sea ice, surface albedo, Arctic and lower latitude removal processes, and atmospheric transport patterns. Photochemistry and efficient wet aerosol removal have low impact in winter but become important in spring to summer, dramatically altering aerosol chemical composition, and driving the size distribution from a pronounced accumulation mode toward a dominance of smaller particles. Retreating sea ice, increasing solar insolation and warmer temperatures in summer result in enhanced emissions from Arctic marine and terrestrial ecosystems, and anthropogenic sources, with impacts on the composition of gas and particle phases. Fractional cloud cover reaches a maximum in Arctic summer, in parallel with decreasing sea ice extent and surface albedo. This seasonal variation corresponds to significant changes in the net cloud radiative effect; changes that are affected by aerosol. This review summarizes our current knowledge of processes that control Arctic aerosol properties. We highlight both natural and anthropogenic processes that will be impacted by current and future sea ice loss. Efforts are needed to better constrain aerosol removal rates, characterize aerosol precursors, and constrain the seasonality and magnitude of aerosol‐cloud‐climate impacts.

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“…Later studies stress the complexity of this mechanism and its efficiency in different geographic locations. For example, Coopman, Garrett, et al () using multiyear satellite, meteorological, and tracer transport model data found that low‐level Arctic cloud response to anthropogenic aerosols are 2 to 8 times higher than in lower latitudes and that the role of biomass aerosols to Arctic clouds response have been overstated in previous studies. Consequently, the relative contribution of aerosol to the radiative forcing of Arctic clouds is still highly uncertain (Coopman, Riedi, et al, ; Flanner, ; Garrett et al, ; Garrett et al, ; Norgren et al, ; Solomon et al, ; Wylie & Hudson, ; Zamora et al, ; Zhao & Garrett, ).…”

Section: Introductionmentioning

confidence: 99%

Aerosol Effect on the Cloud Phase of Low‐Level Clouds Over the Arctic

et al. 2019

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Three years of nighttime Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation data was used in synergy with CloudSat measurements to quantify how strongly aerosol type and aerosol load affect the cloud phase in low‐level clouds over the Arctic. Supercooled liquid layers were present in the majority of observed low‐level clouds (0.75 ≤ z ≤ 3.5 km) between −10 and −25 °C. Furthermore, based on the subset (6%) of data with high quality assurance for aerosol typing, ice formation is more common in the presence of dust or continental aerosols as opposed to marine or elevated smoke aerosols. With the first aerosol group, glaciated clouds were found at cloud top temperatures of 2 to 4 °C warmer than with the latter aerosol types. Further association of the aerosol concentration with the cloud phase showed that the aerosol concentration outweighs the aerosol type effect. Depending on the aerosol load, the temperature at which a cloud completely glaciates can vary by up to 6–10 °C. However, this behavior was most pronounced in stable atmospheric conditions and absent over open ocean with lower tropospheric stability values and probably less stratified clouds. Finally, more mixed‐phase clouds were associated with high aerosol load, suggesting that mixed‐phase clouds have an extended lifetime in the Arctic under high cloud condensation nuclei concentrations. This implies that in a pristine environment, with few or no local aerosol sources, and under the investigated conditions the amount of aerosol particles affects the cloud phase more than the aerosol type does.

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High Sensitivity of Arctic Liquid Clouds to Long‐Range Anthropogenic Aerosol Transport

Cited by 36 publications

References 77 publications

A satellite-based estimate of aerosol-cloud microphysical effects over the Arctic Ocean

A satellite-based estimate of aerosol-cloud microphysical effects over the Arctic Ocean

Processes Controlling the Composition and Abundance of Arctic Aerosol

Aerosol Effect on the Cloud Phase of Low‐Level Clouds Over the Arctic

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