Microstructure of Atmospheric Clouds and Precipitation

Pruppacher, H. R.; Klett, James D.

doi:10.1007/978-0-306-48100-0_2

Cited by 155 publications

(239 citation statements)

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“…CBW particles activate at a SSact of 0.4 % after 552 and 523 min (line 1 and 2) while CBK particles demand a SSact of 1.6 % for activation after 552 and 584 min (line 20 and 21), respectively. Overall, no CCN-activity of CBK particles could be detected at atmospherically relevant SS (0.3 to 0.8 %;Pruppacher and Klett, 2010) within the maximum aging time of up to 12 h of our 10 experimental setup.…”

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confidence: 65%

“…3 2 × 10 6 molec•cm -3 which is approximately equal to one day of atmospheric aging. Both, the OFRs and the batch-aerosol chamber methods show that equivalent atmospheric aging time spans of several hours to days are required to make soot particles CCN-active at atmospherically relevant super saturations (SS) of below 0.8 % (Pruppacher and Klett, 2010) Another very important atmospheric oxidant is ozone. The effect of ozone oxidation on the CCN-activity of soot particles has been investigated intensively in various laboratory studies.…”

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confidence: 99%

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

Friebel¹,

Lobo²,

Neubauer³

et al. 2019

Preprint

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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&#8201;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&#8201;nm particles rich in organic carbon (OC) that were initially CCN-inactive showed significant CCN-activity at supersaturations (SS) down to 0.3&#8201;% after 10&#8201;h of exposure to 200&#8201;ppb of ozone. While this process was not affected by different levels of relative humidity in the range 5&#8211;75&#8201;%, 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&#8201;h can be achieved in comparably small aerosol chamber volumes (<&#8201;3&#8201;m3). Implementation of our measurement results on the CCN-activity of soot particles retrieved from measurements at atmospherically relevant conditions into a global aerosol-climate model showed a statistically significant increase in the regional and global CCN burden and cloud droplet number concentration (CDNC).

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confidence: 65%

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confidence: 99%

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

Friebel¹,

Lobo²,

Neubauer³

et al. 2019

Preprint

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“…A denitrification scheme is incorporated to account for the sedimentation of HNO 3 containing particles where the NAT particles are assumed to be in equilibrium with gas phase HNO 3 . All the three types of particles – NAT, ice, and liquid aerosols – are considered in the sedimentation module and the sedimentation speed of the particles is calculated according to Pruppacher and Klett [1997]. Nevertheless, recent studies indicate that PSCs do not frequently exist at NAT temperatures [ WMO , 2011; Pitts et al , 2007] and liquid aerosols often dominate heterogeneous halogen processing [ Portmann et al , 1996].…”

Section: Ozone and Tracer Simulationsmentioning

confidence: 99%

Arctic ozone depletion in 2002-2003 measured by ASUR and comparison with POAM observations

et al. 2011

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International audienceWe present ozone loss estimated from airborne measurements in the Arctic winter 2003. The first half of the winter was characterized by unusually cold temperatures and the second half by a major stratospheric sudden warming that culminated around 15-18 January 2003. The potential vorticity maps show a vortex split in the lower stratosphere during the major warming (MW) period in late January and during the minor warming period in mid-February due to wave 1 amplification. The ozone depletion computed from the ASUR measurements sampled inside the vortex shows a maximum of 1.3{plus minus}0.2 ppmv at 450-500 K by late March. The partial column loss derived from the ASUR ozone profiles reaches up to 61{plus minus}4 DU in 400-550 K. The evolution of ozone and ozone loss in the ASUR measurements are in very good agreement with that of POAM observations. This study reveals that the Arctic winter 2003 is unique as it had three minor warmings and a MW, yet showed large loss in ozone, whereas no such feature was observed in any other Arctic winter in 1989-2010. An unusually large ozone loss in December, 0.5{plus minus}0.2 ppmv at 450-500 K or 12{plus minus}1 DU in 400-550 K, was estimated for the first time in the Arctic. A careful and detailed diagnosis of ozone loss from all available published results for this winter exhibits an average loss of about 1.5{plus minus}0.3 ppmv at 450-500 K or 65{plus minus}5 DU at 400-550 K by the end of March, which exactly matches the depletion derived in this study

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“…Ice nucleation by aerosol particles is known to modify cloud properties, hence, playing an important role in modulating the hydrological cycle and climate (Boucher et al, 2013;Seinfeld and Pandis, 2006). There are four mechanisms identified for primary heterogeneous ice nucleation in the atmosphere, which are the immersion, condensation, deposition, and contact modes (Pruppacher and Klett, 2010;Young, 1993). Immersion freezing occurs when an ice-nucleating particle (INP) initiates ice formation when completely immersed in a cloud droplet.…”

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confidence: 99%

“…Condensation freezing happens when ice nucleates as water is condensed on the INP whereas deposition nucleation occurs when water vapour directly forms the ice phase on a particle. Contact freezing is triggered when an INP comes in contact with a supercooled water droplet (from inside or outside) to initiate nucleation and subsequent freezing (Pruppacher and Klett, 2010;Vali et al, 2015). While immersion freezing is relevant in mixed-phase clouds (Murray et al, 2012), the deposition mode mechanism and homogeneous ice nucleation dominate cirrus cloud formation (Hoose and Möhler, 2012).…”

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confidence: 99%

Enhanced ice nucleation activity of coal fly ash aerosol particles initiated by ice-filled pores

Umo¹,

Wagner²,

Ullrich³

et al. 2019

Preprint

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Abstract. Ice-nucleating particles (INPs), which are precursors for ice formation in clouds, can alter the microphysical and optical properties of clouds, hence, impacting the cloud lifetimes and hydrological cycles. However, the mechanisms with which these INPs nucleate ice when exposed to different atmospheric conditions are still unclear for some particles. Recently, some INPs with pores or permanent surface defects of regular or irregular geometries have been reported to initiate ice formation at cirrus temperatures via the liquid phase in a two-step process, involving the condensation and freezing of supercooled water inside these pores. This mechanism has therefore been labelled as pore condensation and freezing (PCF). The PCF mechanism allows formation and stabilization of ice germs in the particle without the formation of macroscopic ice. Coal fly ash (CFA) aerosol particles are known to nucleate ice in the immersion freezing mode and may play a significant role in cloud formation. In our current ice nucleation experiments with CFA particles, which we conducted in the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) aerosol and cloud simulation chamber at the Karlsruhe Institute of Technology, Germany, we partly observed a strong increase in the ice-active fraction for experiments performed at temperatures just below the homogeneous freezing of pure water, which could be related to the PCF mechanism. To further investigate the potential of CFA particles undergoing PCF mechanism, we performed a series of temperature-cycling experiments in AIDA. The temperature-cycling experiments involve exposing CFA particles to lower temperatures (down to ~&#8201;228&#8201;K), then warming them up to higher temperatures (238&#8201;K&#8211;273&#8201;K) before investigating their ice nucleation properties. For the first time, we report the enhancement of the ice nucleation activity of the CFA particles for temperatures up to 263&#8201;K, from which we conclude that it is most likely due to the PCF mechanism. This indicates that ice germs formed in the CFA particles&#8217; pores during cooling remains in the pores during the warming and induces ice crystallization as soon as the pre-activated particles experience ice-supersaturated conditions at warmer temperatures; hence, showing an enhancement in their ice-nucleating ability compared to the scenario where the CFA particles are directly probed at warmer temperatures without temporary cooling. The enhancement in the ice nucleation ability showed a positive correlation with the specific surface area and porosity of the particles. On the one hand, the PCF mechanism could be the prevalent nucleation mode for intrinsic ice formation at cirrus temperatures rather than the previously acclaimed deposition mode. On the other, the PCF mechanism can also play a significant role in mixed-phase cloud formation in a case where the CFA particles are injected from higher altitudes and then transported to lower altitudes after being exposed to lower temperatures.

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Microstructure of Atmospheric Clouds and Precipitation

Cited by 155 publications

References 0 publications

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

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

Arctic ozone depletion in 2002-2003 measured by ASUR and comparison with POAM observations

Enhanced ice nucleation activity of coal fly ash aerosol particles initiated by ice-filled pores

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