Ice nucleation and cloud microphysical properties in tropical tropopause layer cirrus

Jensen, E. J.; Pfister, Leonhard; Bui, T. Paul; Lawson, Paul A.; Baumgardner, Darrel

doi:10.5194/acp-10-1369-2010

Cited by 111 publications

(136 citation statements)

References 65 publications

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“…High-altitude aircraft sampling in various tropical locations indicated ice concentrations almost exclusively less than 100 L −1 (11)(12)(13)(14)(15)(16). This result is in conflict with theoretical expectations.…”

Section: Attrex | Ice Nucleicontrasting

confidence: 55%

“…This result is in conflict with theoretical expectations. Given the ubiquitous presence of mesoscale-wave temperature fluctuations in the TTL, the conventional theory of ice nucleation via homogeneous freezing of aqueous aerosols predicts much higher ice concentrations (13,15,17). Ice concentrations of approximately 4,000 L −1 in midlatitude wave clouds with strong updrafts have been shown to be consistent with homogeneous freezing theory (18).…”

Section: Attrex | Ice Nucleisupporting

confidence: 50%

“…However, we find that large supersaturations can persist in the low ice concentration cirrus. The ATTREX measurements, as well as measurements from several previous high-altitude aircraft campaigns, indicate that these low-concentration cirrus are prevalent throughout the TTL (11)(12)(13)(14)(15)(16). The high ice concentration cirrus reported here seem to occur much less frequently.…”

Section: Resultsmentioning

confidence: 76%

“…Alternatively, TTL ice production may be dominated by heterogeneous nucleation, in which case the concentration of ice crystals could be limited by the abundance of effective ice nuclei (IN) because growth of the ice crystals nucleated on the IN could quench the supersaturation in cooling air parcels such that further nucleation does not occur (21). Candidate sources of IN include dust particles, dry ammonium sulfate particles, and glassy organiccontaining aerosols (15,22). Measurements of ice crystal residuals indicate no preference for particular aerosol compositions acting as IN (23).…”

Section: Attrex | Ice Nucleimentioning

confidence: 99%

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Ice nucleation and dehydration in the Tropical Tropopause Layer

Jensen

Diskin

Lawson

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

135

174

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Optically thin cirrus near the tropical tropopause regulate the humidity of air entering the stratosphere, which in turn has a strong influence on the Earth's radiation budget and climate. Recent highaltitude, unmanned aircraft measurements provide evidence for two distinct classes of cirrus formed in the tropical tropopause region: (i) vertically extensive cirrus with low ice number concentrations, low extinctions, and large supersaturations (up to ∼70%) with respect to ice; and (ii) vertically thin cirrus layers with much higher ice concentrations that effectively deplete the vapor in excess of saturation. The persistent supersaturation in the former class of cirrus is consistent with the long time-scales (several hours or longer) for quenching of vapor in excess of saturation given the low ice concentrations and cold tropical tropopause temperatures. The low-concentration clouds are likely formed on a background population of insoluble particles with concentrations less than 100 L −1 (often less than 20 L −1 ), whereas the high ice concentration layers (with concentrations up to 10,000 L −1 ) can only be produced by homogeneous freezing of an abundant population of aqueous aerosols. These measurements, along with past high-altitude aircraft measurements, indicate that the low-concentration cirrus occur frequently in the tropical tropopause region, whereas the high-concentration cirrus occur infrequently. The predominance of the low-concentration clouds means cirrus near the tropical tropopause may typically allow entry of air into the stratosphere with as much as ∼1.7 times the ice saturation mixing ratio. ATTREX | ice nucleiA lthough the stratosphere is extremely dry compared with the troposphere, stratospheric humidity plays crucial roles in both atmospheric chemistry and climate. As the primary source of hydroxyl (OH) radicals, H 2 O plays an important role in the regulation of stratospheric ozone. Small changes in stratospheric humidity can have significant influence on the Earth's radiation budget and climate (1, 2). Model simulations show that increases in stratospheric humidity enhance the rate of ozone destruction, cool the lower stratosphere, and warm the surface (3, 4).Air enters the stratospheric overworld (above 380 K potential temperature) almost exclusively via ascent across the tropical tropopause. This fact has motivated interest in understanding processes occurring in the transition layer between the tropical troposphere and stratosphere, a region of the atmosphere referred to as the Tropical Tropopause Layer (TTL). Physical processes occurring in this layer set the boundary condition for the composition and humidity of the stratosphere. It is well established that the aridity of the stratosphere is associated with "freeze-drying" of air as it passes through the cold TTL (5, 6). Deposition growth of ice crystals in optically thin, laminar TTL cirrus depletes vapor in excess of saturation, and the ice crystals sediment relative to the slowly ascending air. The common occurrence of these thin, ...

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Section: Attrex | Ice Nucleicontrasting

confidence: 55%

Section: Attrex | Ice Nucleisupporting

confidence: 50%

Section: Resultsmentioning

confidence: 76%

Section: Attrex | Ice Nucleimentioning

confidence: 99%

See 2 more Smart Citations

Ice nucleation and dehydration in the Tropical Tropopause Layer

Jensen

Diskin

Lawson

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

135

174

View full text Add to dashboard Cite

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“…Potter and Holton, 1995). High frequency gravity waves influence the cooling rates undergone by air parcels, which has an overwhelming impact on the properties of newly nucleated clouds (Jensen et al, 2010;Dinh et al, 2016;Jensen et al, 2016). 20 So far, most studies investigating the impact of waves on ice clouds have been focusing on temperature anomalies.…”

Section: Introductionmentioning

confidence: 99%

Impact of gravity waves on the motion and distribution of atmospheric ice particles

Podglajen¹,

Plougonven²,

Hertzog³

et al. 2017

Preprint

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Abstract. Gravity waves are an ubiquitous feature of the atmosphere and influence clouds in multiple ways. Regarding cirrus clouds, many studies have emphasized the impact of wave-induced temperature fluctuations on the nucleation of ice crystals. This paper investigates the impact of the waves on the motion and distribution of ice particles, using the idealized 2-D framework of a monochromatic gravity wave. Contrary to previous studies, a special attention is given to the impact of the wind field induced by the wave. 5Assuming no feedback of the ice on the water vapor content, theoretical and numerical analyses both show the existence of a wave-driven localization of ice crystals, where some ice particles remain confined in a specific phase of the wave. The precise location where the confinement occurs depends on the background relative humidity, but it is always characterized by a relative humidity near saturation and a positive vertical wind anomaly. Hence, the wave has an impact on the mean motion of the crystals and may reduce dehydration in cirrus by slowing down the sedimentation of the ice particles. The results also 10 provide a new insight into the relation between relative humidity and ice crystals presence.The wave-driven localization is consistent with temperature-cirrus relationships recently observed in the tropical tropopause layer (TTL) over the Pacific during the Airborne Tropical Tropopause EXperiment (ATTREX). It is argued that this effect may explain such observations. Finally, the impact of the described interaction on TTL cirrus dehydration efficiency is quantified using ATTREX observations of clouds and temperature lapse rate.

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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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Ice nucleation and cloud microphysical properties in tropical tropopause layer cirrus

Cited by 111 publications

References 65 publications

Ice nucleation and dehydration in the Tropical Tropopause Layer

Ice nucleation and dehydration in the Tropical Tropopause Layer

Impact of gravity waves on the motion and distribution of atmospheric ice particles

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

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