New evidence of soot particles affecting past and future cloud formation and climate

2020 ◽  
Author(s):  
Ulrike Lohmann ◽  
Franz Friebel ◽  
Zamin A. Kanji ◽  
Fabian Mahrt ◽  
Amewu A. Mensah ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Hydrological Cycle ◽  
Global Climate ◽  
Cloud Condensation Nuclei ◽  
Critical Role ◽  
Carbon Dioxide Concentration ◽  
Radiative Properties ◽  
Cloud Formation ◽  
Condensation Nuclei ◽  
Soot Particles

<p>Clouds play a critical role in the hydrological cycle and modulating the Earth’s climate via precipitation and radiative forcing. Aerosol particles acting as cloud condensation nuclei and ice nucleating particles aid in cloud formation, shaping their microphysical structure. Previously thought to be unimportant for cloud formation, soot particles that undergo oxidation by ozone and/or aging with aqueous sulfuric acid result in being both good centers for cloud droplets and ice crystals formation. However, the associated changes in cloud radiative properties and the consequences for Earth’s climate remain uncertain, because these processes have not been considered in global climate models. Here we present both past and future global climate simulations, which for the first time consider the effect of such aged soot particles as cloud condensation nuclei and ice nucleating particles. Our results constitute the first evidence that aging of soot particles produce a 0.2 to 0.25 Wm<sup>-2</sup> less negative shortwave indirect aerosol forcing compared to previous estimates. We also conducted equilibrium climate sensitivity simulations representing a future warmer climate in which the carbon dioxide concentration is doubled compared to pre-industrial levels. Accounting for these soot aging processes significantly exacerbates the global mean surface temperature increase by 0.4 to 0.5 K. Thus, reducing emissions of soot particles will be beneficial for many aspects including air pollution and future climate.</p><p> </p>

scholarly journals Impact of isolated atmospheric aging processes on the cloud condensation nuclei activation of soot particles

2019 ◽  
Vol 19 (24) ◽  
pp. 15545-15567 ◽  
Author(s):  
Franz Friebel ◽  
Prem Lobo ◽  
David Neubauer ◽  
Ulrike Lohmann ◽  
Saskia Drossaart van Dusseldorp ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Climate Model ◽  
Cloud Condensation Nuclei ◽  
Particle Diameter ◽  
Cloud Droplet ◽  
High Sensitivity ◽  
Condensation Nuclei ◽  
Soot Particles ◽  
Atmospheric Aging ◽  
Ccn Activity

Abstract. The largest contributors to the uncertainty in assessing the anthropogenic contribution in radiative forcing are the direct and indirect effects of aerosol particles on the Earth's radiative budget. Soot particles are of special interest since their properties can change significantly due to aging processes once they are emitted into the atmosphere. Probably the largest obstacle for the investigation of these processes in the laboratory is the long atmospheric lifetime of 1 week, requiring tailored experiments that cover this time span. This work presents results on the ability of two types of soot, obtained using a miniCAST soot generator, to act as cloud condensation nuclei (CCN) after exposure to atmospherically relevant levels of ozone (O3) and humidity. Aging times of up to 12 h were achieved by successful application of the continuous-flow stirred tank reactor (CSTR) concept while allowing for size selection of particles prior to the aging step. Particles of 100 nm diameter and rich in organic carbon (OC) that were initially CCN inactive showed significant CCN activity at supersaturations (SS) down to 0.3 % after 10 h of exposure to 200 ppb of O3. While this process was not affected by different levels of relative humidity in the range of 5 %–75 %, a high sensitivity towards the ambient/reaction temperature was observed. Soot particles with a lower OC content required an approximately 4-fold longer aging duration to show CCN activity at the same SS. Prior to the slow change in the CCN activity, a rapid increase in the particle diameter was detected which occurred within several minutes. This study highlights the applicability of the CSTR approach for the simulation of atmospheric aging processes, as aging durations beyond 12 h can be achieved in comparably small aerosol chamber volumes (<3 m3). Implementation of our measurement results in a global aerosol-climate model, ECHAM6.3-HAM2.3, showed a statistically significant increase in the regional and global CCN burden and cloud droplet number concentration.

scholarly journals Impact of Isolated Atmospheric Aging processes on the Cloud Condensation Nuclei-activation of Soot Particles

2019 ◽  
Author(s):  
Franz Friebel ◽  
Prem Lobo ◽  
David Neubauer ◽  
Ulrike Lohmann ◽  
Saskia Drossaart van Dusseldorp ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Cloud Condensation Nuclei ◽  
Particle Diameter ◽  
High Sensitivity ◽  
Condensation Nuclei ◽  
Soot Particles ◽  
Atmospheric Aging ◽  
Aerosol Chamber ◽  
Small Aerosol ◽  
Ccn Activity

Abstract. The largest contributors to the uncertainty in assessing the anthropogenic contribution in radiative forcing are the direct and indirect effects of aerosol particles on the Earth's radiative budget. Soot particles are of special interest since their properties can change significantly due to aging processes once they are emitted to the atmosphere. Probably the largest obstacle for the investigation of these processes in the laboratory is the long atmospheric lifetime of one week, demanding tailored experiments that cover this time span. This work presents results on the ability of two types of soot to act as cloud condensation nuclei (CCN) after exposure to atmospherically relevant levels of ozone and humidity. Aging times of up to 12 h were achieved by successful application of the continuous-flow stirred tank reactor (CSTR) concept while allowing for size-selection of particles prior to the aging step. 100 nm particles rich in organic carbon (OC) that were initially CCN-inactive showed significant CCN-activity at supersaturations (SS) down to 0.3 % after 10 h of exposure to 200 ppb of ozone. While this process was not affected by different levels of relative humidity in the range 5–75 %, a high sensitivity towards the ambient/reaction temperature was observed. Soot particles with a lower OC-content demanded an approximately four-fold longer aging duration to show CCN-activity for the same SS. Prior to the slow change in the CCN-activity, a rapid increase in the particle diameter was detected which occurred within several minutes. This study highlights the applicability of the CSTR-approach for the simulation of atmospheric aging processes, as aging durations beyond 12 h can be achieved in comparably small aerosol chamber volumes (

scholarly journals Size-resolved aerosol water uptake and cloud condensation nuclei measurements as measured above a Southeast Asian rainforest during OP3

2011 ◽  
Vol 11 (21) ◽  
pp. 11157-11174 ◽  
Author(s):  
M. Irwin ◽  
N. Robinson ◽  
J. D. Allan ◽  
H. Coe ◽  
G. McFiggans
Keyword(s):  
Water Uptake ◽  
Radiative Forcing ◽  
Tropical Rainforest ◽  
Fine Particles ◽  
Hydrological Cycle ◽  
Cloud Condensation Nuclei ◽  
Tropical Atmosphere ◽  
Condensation Nuclei ◽  
Hygroscopic Properties ◽  
Diameter Range

Abstract. The influence of the properties of fine particles on the formation of clouds and precipitation in the tropical atmosphere is of primary importance to their impacts on radiative forcing and the hydrological cycle. Measurements of aerosol number size distribution, hygroscopicity in both sub- and supersaturated regimes and composition were taken between March and July 2008 in the tropical rainforest in Borneo, Malaysia, marking the first study of this type in an Asian tropical rainforest. Hygroscopic growth factors (GF) at 90 % relative humidity (RH) for the dry diameter range D0 = 32–258 nm, supersaturated water uptake behaviour for the dry diameter range D0 = 45–300 nm and aerosol chemical composition were simultaneously measured using a Hygroscopicity Tandem Differential Mobility Analyser (HTDMA), a Droplet Measurement Technologies Cloud Condensation Nuclei counter (CCNc) and an Aerodyne Aerosol Mass Spectrometer (AMS) respectively. The hygroscopicity parameter κ was derived from both CCNc and HTDMA measurements, with the resulting values of κ ranging from 0.05–0.37, and 0.17–0.37, respectively. Although the total range of κ values is in good agreement, there are inconsistencies between CCNc and HTDMA derived κ values at different dry diameters. Results from a study with similar methodology performed in the Amazon rainforest report values for κ within a similar range to those reported in this work, indicating that the aerosol as measured from both sites shows similar hygroscopic properties. However, the derived number of cloud condensation nuclei (NCCN) were much higher in the present experiment than the Amazon, resulting in part from the increased total particle number concentrations observed in the Bornean rainforest. This contrast between the two environments may be of substantial importance in describing the impacts of particles in the tropical atmosphere.

The key role of aerosol-radiation-interactions on cloud formation and precipitation in the Amazon

2021 ◽  
Author(s):  
Lixia Liu ◽  
Yafang Cheng ◽  
Siwen Wang ◽  
Chao Wei ◽  
Mira Pöhlker ◽  
...  
Keyword(s):  
Energy Balance ◽  
Radiative Forcing ◽  
Amazon Basin ◽  
Hydrological Cycle ◽  
Global Climate ◽  
Cloud Formation ◽  
Emission Rates ◽  
Liquid Water Path ◽  
Aerosol Loading ◽  
The Impact

&lt;p&gt;Biomass burning (BB) aerosols can influence regional and global climate through interactions with radiation, clouds, and precipitation. Here, we investigate the impact of BB aerosols on the energy balance and hydrological cycle over the Amazon Basin during the dry season. We performed WRF-Chem simulations for a range of different BB emission scenarios to explore and characterize nonlinear effects and individual contributions from aerosol&amp;#8211;radiation interactions (ARIs) and aerosol&amp;#8211;cloud interactions (ACIs). For scenarios representing the lower and upper limits of BB emission estimates for recent years (2002&amp;#8211;2016), we obtained total regional BB aerosol radiative forcings of -0.2 and 1.5Wm&lt;sup&gt;-2&lt;/sup&gt;, respectively, showing that the influence of BB aerosols on the regional energy balance can range from modest cooling to strong warming. We find that ACIs dominate at low BB emission rates and low aerosol optical depth (AOD), leading to an increased cloud liquid water path (LWP) and negative radiative forcing, whereas ARIs dominate at high BB emission rates and high AOD, leading to a reduction of LWP and positive radiative forcing. In all scenarios, BB aerosols led to a decrease in the frequency of occurrence and rate of precipitation, caused primarily by ACI effects at low aerosol loading and by ARI effects at high aerosol loading. Overall, our results show that ACIs tend to saturate at high aerosol loading, whereas the strength of ARIs continues to increase and plays a more important role in highly polluted episodes and regions. This should hold not only for BB aerosols over the Amazon, but also for other light-absorbing aerosols such as fossil fuel combustion aerosols in industrialized and densely populated areas. The importance of ARIs at high aerosol loading highlights the need for accurately characterizing aerosol optical properties in the investigation of aerosol effects on clouds, precipitation, and climate.&lt;/p&gt;

scholarly journals Size-resolved aerosol water uptake and cloud condensation nuclei measurements as measured above a Southeast Asian rainforest during OP3

2011 ◽  
Vol 11 (1) ◽  
pp. 3117-3159 ◽  
Author(s):  
M. Irwin ◽  
N. Robinson ◽  
J. D. Allan ◽  
H. Coe ◽  
G. McFiggans
Keyword(s):  
Relative Humidity ◽  
Water Uptake ◽  
Radiative Forcing ◽  
Tropical Rainforest ◽  
Hydrological Cycle ◽  
Cloud Condensation Nuclei ◽  
Tropical Atmosphere ◽  
Condensation Nuclei ◽  
Hygroscopic Properties ◽  
Diameter Range

Abstract. The influence of the properties of fine particles on the formation of clouds and precipitation in the tropical atmosphere is of primary importance to their impacts on radiative forcing and the hydrological cycle. Measurements of aerosol number size distribution, hygroscopicity in both sub- and supersaturated regimes and composition were taken between March and July 2008 in the tropical rainforest in Borneo, Malaysia, marking the first study of this type in an Asian tropical rainforest. Hygroscopic growth factors (GF) at 90% relative humidity (RH) for the dry diameter range D0=32–258 nm, supersaturated water uptake behaviour for the dry diameter range D0=20–300 nm and aerosol chemical composition were simultaneously measured using a Hygroscopicity Tandem Differential Mobility Analyser (HTDMA), a Droplet Measurement Technologies Cloud Condensation Nuclei counter (CCNc) and an Aerodyne Aerosol Mass Spectrometer (AMS), respectively. The derived hygroscopicty parameter κ ranged from between 0.05–0.37 for the supersaturation range 0.11–0.73% compared to those between 0.17–0.37 for measurements performed at a relative humidity of 90%. In contrast, results from a study with similar methodology performed in the Amazon basin report more similar values for κ, indicating that the aerosol as measured from both sites shows similar hygroscopic properties. However, the derived number of cloud condensation nuclei (NCCN) were much higher than those measured in the Amazon, due to the higher particle number concentrations in the rainforests of Borneo. This first contrast between the two environments may be of substantial importance in describing the impacts of particles in the tropical atmosphere.

scholarly journals Measured and modelled cloud condensation nuclei number concentration at the high alpine site Jungfraujoch

2010 ◽  
Vol 10 (16) ◽  
pp. 7891-7906 ◽  
Author(s):  
Z. Jurányi ◽  
M. Gysel ◽  
E. Weingartner ◽  
P. F. DeCarlo ◽  
L. Kammermann ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Hydrological Cycle ◽  
Cloud Condensation Nuclei ◽  
Sensitivity Study ◽  
Research Station ◽  
Condensation Nuclei ◽  
Composition Data ◽  
Particle Mobility ◽  
Kohler Theory ◽  
Highly Correlated

Abstract. Atmospheric aerosol particles are able to act as cloud condensation nuclei (CCN) and are therefore important for the climate and the hydrological cycle, but their properties are not fully understood. Total CCN number concentrations at 10 different supersaturations in the range of SS=0.12–1.18% were measured in May 2008 at the remote high alpine research station, Jungfraujoch, Switzerland (3580 m a.s.l.). In this paper, we present a closure study between measured and predicted CCN number concentrations. CCN predictions were done using dry number size distribution (scanning particle mobility sizer, SMPS) and bulk chemical composition data (aerosol mass spectrometer, AMS, and multi-angle absorption photometer, MAAP) in a simplified Köhler theory. The predicted and the measured CCN number concentrations agree very well and are highly correlated. A sensitivity study showed that the temporal variability of the chemical composition at the Jungfraujoch can be neglected for a reliable CCN prediction, whereas it is important to know the mean chemical composition. The exact bias introduced by using a too low or too high hygroscopicity parameter for CCN prediction was further quantified and shown to be substantial for the lowest supersaturation. Despite the high average organic mass fraction (~45%) in the fine mode, there was no indication that the surface tension was substantially reduced at the point of CCN activation. A comparison between hygroscopicity tandem differential mobility analyzer (HTDMA), AMS/MAAP, and CCN derived κ values showed that HTDMA measurements can be used to determine particle hygroscopicity required for CCN predictions if no suitable chemical composition data are available.

scholarly journals Atmospheric ionization and cloud radiative forcing

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Henrik Svensmark ◽  
Jacob Svensmark ◽  
Martin Bødker Enghoff ◽  
Nir J. Shaviv
Keyword(s):  
Radiative Forcing ◽  
Cloud Condensation Nuclei ◽  
Short Wave ◽  
Satellite Observations ◽  
Cloud Formation ◽  
Wave Radiation ◽  
Substantial Impact ◽  
Radiative Balance ◽  
Cloud Radiative Forcing ◽  
Atmospheric Ionization

AbstractAtmospheric ionization produced by cosmic rays has been suspected to influence aerosols and clouds, but its actual importance has been questioned. If changes in atmospheric ionization have a substantial impact on clouds, one would expect to observe significant responses in Earth’s energy budget. Here it is shown that the average of the five strongest week-long decreases in atmospheric ionization coincides with changes in the average net radiative balance of 1.7 W/m$$^2$$ 2 (median value: 1.2 W/m$$^2$$ 2 ) using CERES satellite observations. Simultaneous satellite observations of clouds show that these variations are mainly caused by changes in the short-wave radiation of low liquid clouds along with small changes in the long-wave radiation, and are almost exclusively located over the pristine areas of the oceans. These observed radiation and cloud changes are consistent with a link in which atmospheric ionization modulates aerosol's formation and growth, which survive to cloud condensation nuclei and ultimately affect cloud formation and thereby temporarily the radiative balance of Earth.

scholarly journals Aerosol characteristics at the Southern Great Plains site during the HI-SCALE campaign

2020 ◽  
Author(s):  
Jiumeng Liu ◽  
Liz Alexander ◽  
Jerome D. Fast ◽  
Rodica Lindenmaier ◽  
John E. Shilling
Keyword(s):  
Mass Spectrometer ◽  
Great Plains ◽  
Biomass Burning ◽  
Radiative Forcing ◽  
Global Climate ◽  
Global Climate Model ◽  
Cloud Formation ◽  
Dominant Factor ◽  
Numerical Representation ◽  
Southern Great Plains

Abstract. Large uncertainties exist in global climate model predictions of radiative forcing due to insufficient understanding and simplified numerical representation of cloud formation and cloud-aerosol interactions. The Holistic Interactions of Shallow Clouds, Aerosols and Land Ecosystems (HI-SCALE) campaign was conducted near the DOE's Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site in north-central Oklahoma to provide a better understanding of land-atmosphere interactions, aerosol and cloud properties, and the influence of aerosol and land-atmosphere interactions on cloud formation. The HI-SCALE campaign consisted of two Intensive Observational Periods (IOPs) (April–May, and August–September, 2016), during which coincident measurements were conducted both on the G-1 aircraft platform and at the SGP ground site. In this study we focus on the observations at the SGP ground site. An Aerodyne HR-ToF Aerosol Mass Spectrometer (AMS) and an Ionicon Proton-Transfer-Reaction Mass Spectrometer (PTR-MS) were deployed, characterizing chemistry of non-refractory aerosol and trace gases, respectively. Contributions from various aerosol sources, including biogenic and biomass burning emissions, were retrieved using factor analysis of the AMS data. In general, the organic aerosols at the SGP site was highly oxidized, with OOA identified as the dominant factor for both the spring and summer IOP though more aged in spring. Cases of IEPOX SOA and biomass burning events were further investigated to understand additional sources of organic aerosol. Unlike other regions largely impacted by IEPOX chemistry, the IEPOX SOA at SGP was more highly oxygenated, likely due to the relatively weak local emissions of isoprene. Biogenic emissions appear to largely control the formation of OA during HI-SCALE campaign. Potential HOM (highly-oxygenated molecule) chemistry likely contributes to the highly-oxygenated feature of aerosols at the SGP site, with impacts on new particle formation and global climate.

Year-long observations of chemical properties of organic aerosols and cloud residuals at the Zeppelin Observatory, Svalbard

2021 ◽  
Author(s):  
Yvette Gramlich ◽  
Sophie Haslett ◽  
Karolina Siegel ◽  
Gabriel Freitas ◽  
Radovan Krejci ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Aerosol Particles ◽  
Trace Gases ◽  
Chemical Properties ◽  
Radiative Properties ◽  
Cloud Formation ◽  
The Arctic ◽  
Arctic Clouds ◽  
Clear Sky ◽  
Air Inlet

&lt;p&gt;The number of cloud seeds, e.g. cloud condensation nuclei (CCN) and ice nucleation particles (INP), in the pristine Arctic shows a large range throughout the year, thereby influencing the radiative properties of Arctic clouds. However, little is known about the chemical properties of CCN and INP in this region. This study aims to investigate the chemical properties of aerosol particles and trace gases that are of importance for cloud formation in the Arctic environment, with focus on the organic fraction.&lt;/p&gt;&lt;p&gt;Over the course of one full year (fall 2019 until fall 2020), we deployed a filter-inlet for gases and aerosols coupled to a chemical ionization high-resolution time-of-flight mass spectrometer (FIGAERO-CIMS) using iodide as reagent ion at the Zeppelin Observatory in Svalbard (480 m a.s.l.), as part of the Ny-&amp;#197;lesund Aerosol Cloud Experiment (NASCENT). The FIGAERO-CIMS is able to measure organic trace gases and aerosol particles semi-simultaneously. The instrument was connected to an inlet switching between a counterflow virtual impactor (CVI) inlet and a total air inlet. This setup allows to study the differences in chemical composition of organic aerosol particles and trace gases at molecular level that are involved in Arctic cloud formation compared to ambient non-activated aerosol.&lt;/p&gt;&lt;p&gt;We observed organic signal above background in both gas and particle phase all year round. A comparison between the gas phase mass spectra of cloud-free and cloudy conditions shows lower signal for some organics inside the cloud, indicating that some trace gases are scavenged by cloud hydrometeors whilst others are not. In this presentation we will discuss the chemical characteristics of the gases exhibiting different behavior during clear sky and cloudy conditions, and the implications for partitioning of organic compounds between the gas, aerosol particle and cloud hydrometeor (droplet/ice) phase.&lt;/p&gt;

scholarly journals An Equatorial Ocean Bottleneck in Global Climate Models

2012 ◽  
Vol 25 (1) ◽  
pp. 343-349 ◽  
Author(s):  
Kristopher B. Karnauskas ◽  
Gregory C. Johnson ◽  
Raghu Murtugudde
Keyword(s):  
Ocean Circulation ◽  
Radiative Forcing ◽  
Climate Models ◽  
Global Climate ◽  
Critical Role ◽  
Tropical Pacific ◽  
Global Climate Models ◽  
Momentum Balance ◽  
Equatorial Ocean ◽  
The Tropical Pacific

Abstract The Equatorial Undercurrent (EUC) is a major component of the tropical Pacific Ocean circulation. EUC velocity in most global climate models is sluggish relative to observations. Insufficient ocean resolution slows the EUC in the eastern Pacific where nonlinear terms should dominate the zonal momentum balance. A slow EUC in the east creates a bottleneck for the EUC to the west. However, this bottleneck does not impair other major components of the tropical circulation, including upwelling and poleward transport. In most models, upwelling velocity and poleward transport divergence fall within directly estimated uncertainties. Both of these transports play a critical role in a theory for how the tropical Pacific may change under increased radiative forcing, that is, the ocean dynamical thermostat mechanism. These findings suggest that, in the mean, global climate models may not underrepresent the role of equatorial ocean circulation, nor perhaps bias the balance between competing mechanisms for how the tropical Pacific might change in the future. Implications for model improvement under higher resolution are also discussed.

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