Cirrus cloud formation and ice supersaturated regions in a global climate model

Lohmann, Ulrike; Spichtinger, Peter; Jess, Stephanie; Peter, Thomas; Smit, H. G. J.

doi:10.1088/1748-9326/3/4/045022

Cited by 125 publications

(184 citation statements)

References 62 publications

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“…Water vapor concentrations in the upper troposphere should decrease as this moisture is exported to lower levels, decreasing the water vapor greenhouse effect. Indeed, this is what was observed in two GCM experiments when the ice fall-speed was increased (Lohmann et al 2008. The globally averaged clear-sky OLR was decreased by ~ 0.7 W m -2 in the Lohmann et al study (MF2009) due to small changes in the ice fall-speed.…”

Section: Reducing Upper Tropospheric Water Vaporsupporting

confidence: 68%

“…In MF2009, two GCM studies (Lohmann et al 2008 andMitchell et al 2008) are discussed that lend credibility to this cirrus engineering idea. The study by Lohmann et al contrasted ECHAM5 GCM simulations based on homogeneous freezing nucleation with simulations based on either heterogeneous nucleation or a combination of homo-and heterogeneous nucleation.…”

Section: Gcm Studiesmentioning

confidence: 98%

“…In section 2.4 a GCM study by Lohmann et al (2008) was discussed that demonstrated that a substantial global cooling effect might be possible through seeding with heterogeneous ice nuclei that activate at ~ RH i = 130%. This produced an 11% increase in effective ice particle size and a corresponding increase in the ice fall-speed, which resulted in a mean global net cooling of ~ 2.7 W m -2 .…”

Section: Over-cooling the Planetmentioning

confidence: 99%

See 2 more Smart Citations

Cirrus Clouds and Climate Engineering: New Findings on Ice Nucleation and Theoretical Basis

Mitchell¹,

Mishra²,

Lawson³

2011

Planet Earth 2011 - Global Warming Challenges and Opportunities for Policy and Practice

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Section: Reducing Upper Tropospheric Water Vaporsupporting

confidence: 68%

Section: Gcm Studiesmentioning

confidence: 98%

Section: Over-cooling the Planetmentioning

confidence: 99%

See 1 more Smart Citation

Cirrus Clouds and Climate Engineering: New Findings on Ice Nucleation and Theoretical Basis

Mitchell¹,

Mishra²,

Lawson³

2011

Planet Earth 2011 - Global Warming Challenges and Opportunities for Policy and Practice

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“…The size of the monodisperse crystals is calculated depending on the ice water content and the ICNC as described in Lohmann et al (2008). The collection kernels are taken from Miller and Wang (1991) in units of cm 3 s −1 and are compiled in look-up tables in our model.…”

Section: New Size-dependent In-cloud Impaction Scavengingmentioning

confidence: 99%

“…The collection kernels are taken from Miller and Wang (1991) in units of cm 3 s −1 and are compiled in look-up tables in our model. For temperatures less than 238.15 K, we assume that all crystals are columns, and for temperatures greater than 238.15 K, all crystals are assumed to be plates (Lohmann et al, 2008).…”

Section: New Size-dependent In-cloud Impaction Scavengingmentioning

confidence: 99%

Influences of in-cloud aerosol scavenging parameterizations on aerosol concentrations and wet deposition in ECHAM5-HAM

et al. 2010

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Abstract.A diagnostic cloud nucleation scavenging scheme, which determines stratiform cloud scavenging ratios for both aerosol mass and number distributions, based on cloud droplet, and ice crystal number concentrations, is introduced into the ECHAM5-HAM global climate model. This scheme is coupled with a size-dependent in-cloud impaction scavenging parameterization for both cloud droplet-aerosol, and ice crystal-aerosol collisions. The aerosol mass scavenged in stratiform clouds is found to be primarily (>90%) scavenged by cloud nucleation processes for all aerosol species, except for dust (50%). The aerosol number scavenged is primarily (>90%) attributed to impaction. 99% of this impaction scavenging occurs in clouds with temperatures less than 273 K. Sensitivity studies are presented, which compare aerosol concentrations, burdens, and deposition for a variety of incloud scavenging approaches: prescribed fractions, a more computationally expensive prognostic aerosol cloud processing treatment, and the new diagnostic scheme, also with modified assumptions about in-cloud impaction and nucleation scavenging. Our results show that while uncertainties in the representation of in-cloud scavenging processes can lead to differences in the range of 20-30% for the predicted annual, global mean aerosol mass burdens, and near to 50% for accumulation mode aerosol number burden, the differences in predicted aerosol mass concentrations can be up to Correspondence to: B. Croft (croft@mathstat.dal.ca) one order of magnitude, particularly for regions of the middle troposphere with temperatures below 273 K where mixed and ice phase clouds exist. Different parameterizations for impaction scavenging changed the predicted global, annual mean number removal attributed to ice clouds by seven-fold, and the global, annual dust mass removal attributed to impaction by two orders of magnitude. Closer agreement with observations of black carbon profiles from aircraft (increases near to one order of magnitude for mixed phase clouds), midtroposphere 210 Pb vertical profiles, and the geographic distribution of aerosol optical depth is found for the new diagnostic scavenging scheme compared to the prescribed scavenging fraction scheme of the standard ECHAM5-HAM. The diagnostic and prognostic schemes represent the variability of scavenged fractions particularly for submicron size aerosols, and for mixed and ice phase clouds, and are recommended in preference to the prescribed scavenging fractions method.

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Perturbed physics ensemble simulations of cirrus on the cloud system‐resolving scale

et al. 2014

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In this study, the effect of uncertainties in the parameterization of ice microphysical processes and initial conditions on the variability of cirrus microphysical and radiative properties are investigated in a series of cloud system‐resolving perturbed physics ensemble (PPE) and initial condition ensemble (ICE) simulations. Three cirrus cases representative of midlatitude, subtropical, and tropical anvil cirrus are examined. The variability in cirrus properties induced by perturbing uncertain parameters in ice microphysics parameterizations outweighs the variability induced by perturbing the initial conditions in midlatitude and subtropical cirrus. However, in tropical anvil cirrus the variability spanned by the PPE and ICE simulations is on the same order of magnitude. Uncertainties in the parameterization of ice microphysical processes affect the vertical distribution of cloud fraction, ice water content, and cloud thickness, whereas cirrus cloud cover is only marginally affected. The top three uncertainties controlling the microphysical variability and radiative impact of cirrus clouds are the mode of ice nucleation, the number concentrations of ice nuclei available for heterogeneous freezing, and the threshold size of the parameterized ice autoconversion process. Uncertainties in ice fall speeds are of minor importance. Changes in the ice deposition coefficient induce only transient effects on the microphysical properties and radiative impacts of cirrus except in cases of very low ice deposition coefficients of about 0.05. Changes in the sulfate aerosol number concentration available for homogeneous freezing have virtually no effect on the microphysical properties and radiative impact of midlatitude and subtropical cirrus but a minor effect on tropical anvil cirrus.

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Cirrus cloud formation and ice supersaturated regions in a global climate model

Cited by 125 publications

References 62 publications

Cirrus Clouds and Climate Engineering: New Findings on Ice Nucleation and Theoretical Basis

Cirrus Clouds and Climate Engineering: New Findings on Ice Nucleation and Theoretical Basis

Influences of in-cloud aerosol scavenging parameterizations on aerosol concentrations and wet deposition in ECHAM5-HAM

Perturbed physics ensemble simulations of cirrus on the cloud system‐resolving scale

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