scholarly journals Effect of volcanic emissions on clouds during the 2008 and 2018 Kilauea degassing events

2021 ◽  
Vol 21 (10) ◽  
pp. 7749-7771
Author(s):  
Katherine H. Breen ◽  
Donifan Barahona ◽  
Tianle Yuan ◽  
Huisheng Bian ◽  
Scott C. James
Keyword(s):  
Anthropogenic Activities ◽  
Volcanic Eruptions ◽  
Atmospheric Modeling ◽  
Natural Experiments ◽  
Volcanic Emissions ◽  
Aerosol Cloud ◽  
Aerosol Loading ◽  
Cloud Properties ◽  
Satellite Retrievals ◽  
Aerosol Cloud Interactions

Abstract. Volcanic eruptions in otherwise clean environments are “natural experiments” wherein the effects of aerosol emissions on clouds and climate can be partitioned from meteorological variability and anthropogenic activities. In this work, we combined satellite retrievals, reanalysis products, and atmospheric modeling to analyze the mechanisms of aerosol–cloud interactions during two degassing events at the Kilauea volcano in 2008 and 2018. The eruptive nature of the 2008 and 2018 degassing events was distinct from long-term volcanic activity for Kilauea. Although previous studies assessed the modulation of cloud properties from the 2008 event, this is the first time such an analysis has been reported for the 2018 event and that multiple degassing events have been analyzed and compared at this location. Both events resulted in significant changes in cloud effective radius and cloud droplet number concentration that were decoupled from local meteorology and in line with an enhanced cloud albedo. However, it is likely that the effects of volcanic emissions on liquid water path and cloud fraction were largely offset by meteorological variability. Comparison of cloud anomalies between the two events suggested a threshold response of aerosol–cloud interactions to overcome meteorological effects, largely controlled by aerosol loading. In both events, the ingestion of aerosols within convective parcels enhanced the detrainment of condensate in the upper troposphere, resulting in deeper clouds than observed under pristine conditions. Accounting for ice nucleation on ash particles led to enhanced ice crystal concentrations at cirrus levels and a slight decrease in ice water content, improving the correlation of the model results with the satellite retrievals. Overall, aerosol loading, plume characteristics, and meteorology contributed to changes in cloud properties during the Kilauea degassing events.

scholarly journals Effect of volcanic emissions on clouds during the 2008 and 2018 Kilauea degassing events

2020 ◽  
Author(s):  
Katherine H. Breen ◽  
Donifan Barahona ◽  
Tianle Yuan ◽  
Huisheng Bian ◽  
Scott C. James
Keyword(s):  
Volcanic Eruptions ◽  
Atmospheric Modeling ◽  
Natural Experiments ◽  
Volcanic Emissions ◽  
Aerosol Cloud ◽  
Satellite Retrievals ◽  
Aerosol Cloud Interactions ◽  
Aerosol Effects ◽  
Aerosol Emissions ◽  
Ice Water

Abstract. Aerosol emissions from volcanic eruptions in otherwise clean environments are regarded as natural experiments where the aerosol effects on clouds and climate can be partitioned from other effects like meteorology and anthropogenic emissions. In this work, we combined satellite retrievals, reanalysis products, and atmospheric modeling to analyze the mechanism of aerosol-cloud interactions during two degassing events at the Kilauea Volcano in 2008 and 2018. The eruptive nature of the 2008 and 2018 degassing events was distinct from long-term volcanic activity for Kilauea. For both events, we performed a comprehensive investigation on the effects of aerosol emissions on macro and microphysical cloud processes for both liquid and ice clouds. This is the first time such an analysis has been reported for the 2018 event. Similarities between both events suggested that aerosol-cloud interactions related to the cloud albedo modification were likely decoupled from local meteorology. In both events the ingestion of aerosols within convective parcels enhanced the detrainment of condensate in the upper troposphere resulting in deeper clouds than in pristine conditions. Accounting for ice nucleation on ash particles led to enhanced ice crystal concentrations at cirrus levels and a slight decrease in ice water content, improving the correlation of the model results with the satellite retrievals. Overall, aerosol loading, plume characteristics, and meteorology contributed to observed and simulated changes in clouds during the Kilauea degassing events.

scholarly journals Observing the timescales of aerosol-cloud interactions in snapshot satellite images

2020 ◽  
Author(s):  
Edward Gryspeerdt ◽  
Tom Goren ◽  
Tristan W. P. Smith
Keyword(s):  
Satellite Images ◽  
Strong Impact ◽  
Natural Experiments ◽  
Liquid Water Path ◽  
Clear Sky ◽  
Cloud Properties ◽  
Aerosol Cloud Interactions ◽  
Aerosol Source ◽  
Retrieval Bias ◽  
Ship Emission

Abstract. The response of cloud processes to an aerosol perturbation is one of the largest uncertainties in the anthropogenic forcing of the climate. It occurs at a variety of timescales, from the near-instantaneous Twomey effect, to the longer timescales required for cloud adjustments. Understanding the temporal evolution of cloud properties following an aerosol perturbation is necessary to interpret the results of so-called "natural experiments" from a known aerosol source, such as a ship or industrial site. This work uses reanalysis windfields and ship emission information matched to observations of shiptracks to measure the timescales of cloud responses to aerosol in instantaneous (or "snapshot") images taken by polar-orbiting satellites. As found in previous studies, the local meteorological environment is shown to have a strong impact on the occurrence and properties of shiptracks, but there is a strong time dependence in their properties. The largest droplet number concentration (Nd) responses are found within three hours of emission, while cloud adjustments continue to evolve over periods of ten hours or more. Cloud fraction is increased within the early life of shiptracks, with the formation of shiptracks in otherwise clear skies indicating that around 5–10 % of clear-sky cases in this region may be aerosol-limited. The liquid water path (LWP) enhancement and the Nd-LWP sensitivity are also time dependent and strong functions of the background cloud and meteorological state. The near-instant response of the LWP within shiptracks may be evidence of a retrieval bias in previous estimates of the LWP response to aerosol derived from natural experiments. These results highlight the importance of temporal development and the background cloud field for quantifying the aerosol impact on clouds, even in situations where the aerosol perturbation is clear.

scholarly journals Observing the timescales of aerosol–cloud interactions in snapshot satellite images

2021 ◽  
Vol 21 (8) ◽  
pp. 6093-6109
Author(s):  
Edward Gryspeerdt ◽  
Tom Goren ◽  
Tristan W. P. Smith
Keyword(s):  
Strong Impact ◽  
Natural Experiments ◽  
Wind Fields ◽  
Liquid Water Path ◽  
Clear Sky ◽  
Cloud Properties ◽  
Ship Tracks ◽  
Aerosol Cloud Interactions ◽  
Aerosol Source ◽  
Ship Emission

Abstract. The response of cloud processes to an aerosol perturbation is one of the largest uncertainties in the anthropogenic forcing of the climate. It occurs at a variety of timescales, from the near-instantaneous Twomey effect to the longer timescales required for cloud adjustments. Understanding the temporal evolution of cloud properties following an aerosol perturbation is necessary to interpret the results of so-called “natural experiments” from a known aerosol source such as a ship or industrial site. This work uses reanalysis wind fields and ship emission information matched to observations of ship tracks to measure the timescales of cloud responses to aerosol in instantaneous (or“snapshot”) images taken by polar-orbiting satellites. As in previous studies, the local meteorological environment is shown to have a strong impact on the occurrence and properties of ship tracks, but there is a strong time dependence in their properties. The largest droplet number concentration (Nd) responses are found within 3 h of emission, while cloud adjustments continue to evolve over periods of 10 h or more. Cloud fraction is increased within the early life of ship tracks, with the formation of ship tracks in otherwise clear skies indicating that around 5 %–10 % of clear-sky cases in this region may be aerosol-limited. The liquid water path (LWP) enhancement and the Nd–LWP sensitivity are also time dependent and strong functions of the background cloud and meteorological state. The near-instant response of the LWP within ship tracks may be evidence of a bias in estimates of the LWP response to aerosol derived from natural experiments. These results highlight the importance of temporal development and the background cloud field for quantifying the aerosol impact on clouds, even in situations where the aerosol perturbation is clear.

scholarly journals Dual‐FOV Raman and Doppler lidar studies of aerosol‐cloud interactions: Simultaneous profiling of aerosols, warm‐cloud properties, and vertical wind

2014 ◽  
Vol 119 (9) ◽  
pp. 5512-5527 ◽  
Author(s):  
Jörg Schmidt ◽  
Albert Ansmann ◽  
Johannes Bühl ◽  
Holger Baars ◽  
Ulla Wandinger ◽  
...  
Keyword(s):  
Vertical Wind ◽  
Doppler Lidar ◽  
Aerosol Cloud ◽  
Cloud Properties ◽  
Warm Cloud ◽  
Aerosol Cloud Interactions

scholarly journals Incorporation of advanced aerosol activation treatments into CESM/CAM5: model evaluation and impacts on aerosol indirect effects

2014 ◽  
Vol 14 (14) ◽  
pp. 7485-7497 ◽  
Author(s):  
B. Gantt ◽  
J. He ◽  
X. Zhang ◽  
Y. Zhang ◽  
A. Nenes
Keyword(s):  
Indirect Effects ◽  
Radiative Forcing ◽  
Cloud Condensation Nuclei ◽  
Condensation Nuclei ◽  
Activation Kinetics ◽  
Aerosol Cloud ◽  
Model Version ◽  
Cloud Properties ◽  
Aerosol Cloud Interactions ◽  
Aerosol Activation

Abstract. One of the greatest sources of uncertainty in the science of anthropogenic climate change is from aerosol–cloud interactions. The activation of aerosols into cloud droplets is a direct microphysical linkage between aerosols and clouds; parameterizations of this process link aerosol with cloud condensation nuclei (CCN) and the resulting indirect effects. Small differences between parameterizations can have a large impact on the spatiotemporal distributions of activated aerosols and the resulting cloud properties. In this work, we incorporate a series of aerosol activation schemes into the Community Atmosphere Model version 5.1.1 within the Community Earth System Model version 1.0.5 (CESM/CAM5) which include factors such as insoluble aerosol adsorption and giant cloud condensation nuclei (CCN) activation kinetics to understand their individual impacts on global-scale cloud droplet number concentration (CDNC). Compared to the existing activation scheme in CESM/CAM5, this series of activation schemes increase the computation time by ~10% but leads to predicted CDNC in better agreement with satellite-derived/in situ values in many regions with high CDNC but in worse agreement for some regions with low CDNC. Large percentage changes in predicted CDNC occur over desert and oceanic regions, owing to the enhanced activation of dust from insoluble aerosol adsorption and reduced activation of sea spray aerosol after accounting for giant CCN activation kinetics. Comparison of CESM/CAM5 predictions against satellite-derived cloud optical thickness and liquid water path shows that the updated activation schemes generally improve the low biases. Globally, the incorporation of all updated schemes leads to an average increase in column CDNC of 150% and an increase (more negative) in shortwave cloud forcing of 12%. With the improvement of model-predicted CDNCs and better agreement with most satellite-derived cloud properties in many regions, the inclusion of these aerosol activation processes should result in better predictions of radiative forcing from aerosol–cloud interactions.

scholarly journals Aerosol-cloud interactions in mixed-phase convective clouds. Part 2: Meteorological ensemble

2018 ◽  
Author(s):  
Annette K. Miltenberger ◽  
Paul R. Field ◽  
Adrian A. Hill ◽  
Ben J. Shipway ◽  
Jonathan M. Wilkinson
Keyword(s):  
Boundary Conditions ◽  
Cell Number ◽  
Cloud Fraction ◽  
Meteorological Conditions ◽  
Shortwave Radiation ◽  
Precipitation Efficiency ◽  
Aerosol Cloud ◽  
Cloud Properties ◽  
Aerosol Cloud Interactions ◽  
Induced Changes

Abstract. The relative contribution of variations in meteorological and aerosol initial and boundary conditions to the variability in modelled cloud properties are investigated with a high-resolution ensemble (30 members). In the investigated case, moderately deep convection develops along sea-breeze convergence zones over the southwestern peninsula of the UK. A detailed analysis of the mechanism of aerosol cloud interactions in this case has been presented in the first part of this study (Miltenberger et al., 2017). The meteorological ensemble (10 members) varies by about a factor 2 in boundary layer moisture convergence, surface precipitation, and cloud fraction, while aerosol number concentrations are varied by a factor 100 between the three considered aerosol scenarios. If ensemble members are paired according to the meteorological initial and boundary conditions, aerosol-induced changes are consistent across the ensemble. Aerosol-induced changes in CDNC, cloud fraction, cell number and size, outgoing shortwave radiation, instantaneous and mean precipitation rates, and precipitation efficiency are statistically significant at the 5 % level, but changes in cloud top height or condensate gain are not. In contrast, if ensemble members are not paired according to meteorological conditions, aerosol-induced changes are statistically significant only for CDNC, cell number and size, outgoing shortwave radiation, and precipitation efficiency. The significance of aerosol-induced changes depends on the aerosol scenarios compared, i.e. for an increase or decrease relative to the standard scenario. A simple statistical analysis of the results suggests that a large number of realisations (typically > 100) of meteorological conditions within the uncertainty of a single day needs to be consider for retrieving robust aerosol signals in most cloud properties. Only for CDNC and shortwave radiation small samples are sufficient. While the results are strictly only valid for the investigated case, the presented evidence combined with previous studies highlights the necessity for careful consideration of intrinsic predictability, detailed meteorological conditions, and co-variability between aerosol and meteorological conditions for observational or modelling studies of aerosol indirect effects.

scholarly journals Strong constraints on aerosol–cloud interactions from volcanic eruptions

Nature ◽  
2017 ◽  
Vol 546 (7659) ◽  
pp. 485-491 ◽  
Author(s):  
Florent F. Malavelle ◽  
Jim M. Haywood ◽  
Andy Jones ◽  
Andrew Gettelman ◽  
Lieven Clarisse ◽  
...  
Keyword(s):  
Volcanic Eruptions ◽  
Aerosol Cloud ◽  
Aerosol Cloud Interactions

Aerosol-cloud interactions from combined observations with geostationary and polar-orbiting sensors

2020 ◽  
Author(s):  
Matthias Tesche ◽  
Torsten Seelig ◽  
Fani Alexandri ◽  
Peter Bräuer ◽  
Goutam Choudhury ◽  
...  
Keyword(s):  
Rain Rate ◽  
Cloud Condensation Nuclei ◽  
Cloud Formation ◽  
Development Phase ◽  
Time Resolved ◽  
Aerosol Cloud ◽  
Cloud Properties ◽  
The Pacific ◽  
Aerosol Cloud Interactions ◽  
Ice Water

<p>Atmospheric aerosol particles are of great importance for cloud formation in the atmosphere because they are needed to act as cloud condensation nuclei (CCN) in liquid-water clouds and as ice nucleating particles (INP) in ice-containing clouds. Changes in aerosol concentration affect the albedo, development, phase, lifetime and rain rate of clouds. These aerosol-cloud interactions (ACI) and the resulting climate effects still cause the largest uncertainty in assessing climate change as they are understood only with medium confidence.</p><p>The PACIFIC project, which is embedded in the French-German Make Our Planet Great Again (MOPGA) initiative, aims to improve our understanding of ACI by enhancing the representation of those aerosols that are relevant for cloud processes and by quantifying temporal changes in cloud properties throughout the cloud life cycle. PACIFIC uses a three-fold approach for studying ACI based on spaceborne observations by (i) using spaceborne lidar data to obtain unprecedented insight in CCN and INP concentrations at cloud level opposed to using column-integrated parameters, (ii) characterizing the development of clouds by tracking them in time-resolved geostationary observations opposed to resorting to the snap-shot view of polar-orbiting sensors, and (iii) combining the detailed observations from polar-orbiting sensors with the time-resolved observations of geostationary sensors – for clouds observed by both – to study the effects of CCN and INP on the albedo, liquid and ice water content, droplet and crystal size, development, phase and rain rate of clouds within different regimes carefully accounting for the meteorological background.</p><p>This contribution will present the scope of the MOPGA-GRI project PACIFIC and illustrate the first findings.</p>

scholarly journals The scale problem in quantifying aerosol indirect effects

2012 ◽  
Vol 12 (2) ◽  
pp. 1031-1049 ◽  
Author(s):  
A. McComiskey ◽  
G. Feingold
Keyword(s):  
Radiative Forcing ◽  
Process Model ◽  
Full Range ◽  
Liquid Water Path ◽  
Aerosol Cloud ◽  
Cloud Properties ◽  
Wide Range ◽  
Albedo Effect ◽  
Aerosol Cloud Interactions ◽  
The Impact

Abstract. A wide range of estimates exists for the radiative forcing of the aerosol effect on cloud albedo. We argue that a component of this uncertainty derives from the use of a wide range of observational scales and platforms. Aerosol influences cloud properties at the microphysical scale, or the "process scale", but observations are most often made of bulk properties over a wide range of resolutions, or "analysis scales". We show that differences between process and analysis scales incur biases in quantification of the albedo effect through the impact that data aggregation and computational approach have on statistical properties of the aerosol or cloud variable, and their covariance. Measures made within this range of scales are erroneously treated as equivalent, leading to a large uncertainty in associated radiative forcing estimates. Issues associated with the coarsening of observational resolution particular to quantifying the albedo effect are discussed. Specifically, the omission of the constraint on cloud liquid water path and the separation in space of cloud and aerosol properties from passive, space-based remote sensors dampen the measured strength of the albedo effect. We argue that, because of this lack of constraints, many of these values are in fact more representative of the full range of aerosol-cloud interactions and their associated feedbacks. Based on our understanding of these biases we propose a new observationally-based and process-model-constrained, method for estimating aerosol-cloud interactions that can be used for radiative forcing estimates as well as a better characterization of the uncertainties associated with those estimates.

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