Characteristics of supersaturation in midlatitude cirrus clouds and their adjacent cloud-free air

Dekoutsidis, Georgios; Groß, Silke; Wirth, Martin; Krämer, M.; Rolf, Christian

doi:10.5194/acp-23-3103-2023

Cited by 15 publications

(21 citation statements)

References 77 publications

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“…According to previous laboratory studies (e.g., Bailey and Hallett, 2009), RHi can reach high values of ∼ 160 % at very low temperatures. High RHi values of ∼ 200 % at the tropopause level were also reported in previous field campaign studies (Krämer et al, 2020;Dekoutsidis et al, 2022) but with a very low frequency of occurrence of ∼ 2 %. Simulations overestimate RHi, especially the ISHMAEL scheme.…”

Section: Sensitivity Of Simulated Microphysical Properties To Model C...supporting

confidence: 82%

Sensitivity of convectively driven tropical tropopause cirrus properties to ice habits in high-resolution simulations

Lamraoui

Krämer

Afchine³

et al. 2023

Atmos. Chem. Phys.

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Abstract. Cirrus clouds that form in the tropical tropopause layer (TTL) can play a key role in vertical transport through the upper troposphere and lower stratosphere, which can significantly impact the radiative energy budget and stratospheric chemistry. However, the lack of realistic representation of natural ice cloud habits in microphysical parameterizations can lead to uncertainties in cloud-related processes and cloud–climate feedbacks. The main goal of this study is to investigate the role of different cloud regimes and the associated ice habits in regulating the properties of the TTL. We compare aircraft measurements from the StratoClim field campaign to a set of numerical experiments at the scale of large-eddy simulations (LESs) for the same case study that employ different microphysics schemes. Aircraft measurements over the southern slopes of the Himalayas captured high ice water content (HIWC) up to 2400 ppmv and ice particle aggregates exceeding 700 µm in size with unusually long residence times. The observed ice particles were mainly of liquid origin, with a small amount formed in situ. The corresponding profile of ice water content (IWC) from the ERA5 reanalysis corroborates the presence of HIWC detrained from deep-convective plumes in the TTL but underestimates HIWC by an order of magnitude. In the TTL, only the scheme that predicts ice habits can reproduce the observed HIWC, ice number concentration, and bimodal ice particle size distribution. The lower range of particle sizes is mostly represented by planar and columnar habits, while the upper range is dominated by aggregates. Large aggregates with sizes between 600 and 800 µm have fall speeds of less than 20 cm s−1, which explains the long residence time of the aggregates in the TTL. Planar ice particles of liquid origin contribute substantially to HIWC. The columnar and aggregate habits are in the in situ range with lower IWC and number concentrations. For all habits, the ice number concentration increases with decreasing temperature. For the planar ice habit, relative humidity is inversely correlated with fall speed. This correlation is less evident for the other two ice habits. In the lower range of supersaturation with respect to ice, the columnar habit has the highest fall speed. The difference in ice number concentration across habits can be up to 4 orders of magnitude, with aggregates occurring in much smaller numbers. We demonstrate and quantify the linear relationship between the differential sedimentation of pristine ice crystals and the size of the aggregates that form when pristine crystals collide. The slope of this relationship depends on which pristine ice habit sediments faster. Each simulated ice habit is associated with distinct radiative and latent heating rates. This study suggests that a model configuration nested down to LES scales with a microphysical parameterization that predicts ice shape evolution is crucial to provide an accurate representation of the microphysical properties of TTL cirrus and thus the associated (de)hydration process.

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Section: Sensitivity Of Simulated Microphysical Properties To Model C...supporting

confidence: 82%

Sensitivity of convectively driven tropical tropopause cirrus properties to ice habits in high-resolution simulations

Lamraoui

Krämer

Afchine³

et al. 2023

Atmos. Chem. Phys.

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“…From the vertical profiles of cloud properties and RHi we found that cirrus formed in air masses transported into the Arctic by WAIs have a larger vertical extent compared to cirrus formed in Arctic air masses (Dekoutsidis et al, 2023). WAI cirrus are characterized by high ice supersaturation throughout their whole vertical profile.…”

Section: Arctic Cirrusmentioning

confidence: 87%

Overview: Quasi-Lagrangian observations of Arctic air mass transformations – Introduction and initial results of the HALO–(AC)³ aircraft campaign

Wendisch,

Crewell,

Ehrlich

et al. 2024

Preprint

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Abstract. The global warming is amplified in the Arctic. To collect data that help to constrain weather and climate models, which often do not realistically represent the enhanced Arctic warming, the HALO-(AC)³ aircraft campaign was conducted in March and April 2022 over the Norwegian and Greenland Seas, the Fram Strait, and the central Arctic Ocean. Observations were made over areas of open ocean, the marginal sea ice zone, and the central Arctic sea ice. Two low-flying and one long-range, high-altitude research aircraft have been employed. Whenever possible, the three aircraft were flown in collocated formation. The campaign focused on one specific challenge posed by the models: The reasonable representation of transformations of air masses during their meridional transport into (northward by moist and warm air intrusions, WAIs) and out of (southward via marine cold air outbreaks, CAOs) the Arctic. To observe the air mass transformations, a quasi-Lagrangian flight strategy using trajectory calculations was realized enabling to sample the moving air mass parcels twice along their trajectories. Eight distinct WAI and 12 CAO cases were probed extensively. From the quasi-Lagrangian measurements, we have derived the diabatic heating and moistening of the moving air masses during CAOs and WAIs, the development of cloud macrophysical and microphysical properties along the southward pathways of the air masses during CAOs, and the moisture budget of WAIs. As an example result, we have obtained typical values of the surface-driven diabatic heating between 1–3 K h-1 and of the near-surface moistening between 0.05–0.3 g kg-1 h-1 within the lowest about 0.5 km. From the observations of WAIs, a weak diabatic cooling of up to 0.4 K h-1 and a moisture loss of up to 0.1 g kg-1 h-1 from the ground to about 5 km altitude were derived. In addition, we discuss the frequency of occurrence of the different thermodynamic phases of Arctic low-level clouds, the interaction of Arctic cirrus with sea ice, water vapor, and aerosol particles, and the characteristic microphysical and chemical properties of Arctic aerosol particles. Finally, we provide proof of a concept to measure mesoscale divergence and subsidence in the Arctic using data from dropsondes released during circular flight patterns.

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“…Nevertheless, since the routes considered in this analysis mostly represent heavy-traffic flight paths and as such are chosen so as to avoid extreme atmospheric conditions, typical contrail properties should emerge. Hence, moderate levels of supersaturation, say around 20%, are still those most likely to be encountered at mid-latitude routes [23].…”

Section: Shortcomings Of the Original Contrail Modelmentioning

confidence: 99%

Addressing Confidence in Modeling of Contrail Formation from E-Fuels in Aviation Using Large Eddy Simulation Parametrization

Cabrera,

de Sousa

2024

Energies

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As it becomes increasingly necessary to reduce aviation-related emissions, condensation trails present an additional challenge. These are arguably responsible for the largest contribution to radiative forcing in the sector, but the phenomenon is still not as well understood as those involving other agents. The present study employs a large eddy simulation (LES) parametrization to validate a previously developed contrail model in order to assess the feasibility of a multi-model approach to increase confidence in simulations of contrail cirrus formation. Subsequently, the computational model was used to analyze the impact of e-fuels in contrail dynamics, resulting in reductions of over 7% and 14%, respectively, in average contrail lifetime and optical depth, with such improvements increasing if higher blending limits are utilized. This confirmed the potential for e-fuels as the most viable option for near-future large-scale implementations among all sustainable aviation fuel alternatives.

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Characteristics of supersaturation in midlatitude cirrus clouds and their adjacent cloud-free air

Cited by 15 publications

References 77 publications

Sensitivity of convectively driven tropical tropopause cirrus properties to ice habits in high-resolution simulations

Sensitivity of convectively driven tropical tropopause cirrus properties to ice habits in high-resolution simulations

Overview: Quasi-Lagrangian observations of Arctic air mass transformations – Introduction and initial results of the HALO–(AC)³ aircraft campaign

Addressing Confidence in Modeling of Contrail Formation from E-Fuels in Aviation Using Large Eddy Simulation Parametrization

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Characteristics of supersaturation in midlatitude cirrus clouds and their adjacent cloud-free air

Cited by 15 publications

References 77 publications

Sensitivity of convectively driven tropical tropopause cirrus properties to ice habits in high-resolution simulations

Sensitivity of convectively driven tropical tropopause cirrus properties to ice habits in high-resolution simulations

Overview: Quasi-Lagrangian observations of Arctic air mass transformations – Introduction and initial results of the HALO–(AC)3 aircraft campaign

Addressing Confidence in Modeling of Contrail Formation from E-Fuels in Aviation Using Large Eddy Simulation Parametrization

Contact Info

Product

Resources

About

Overview: Quasi-Lagrangian observations of Arctic air mass transformations – Introduction and initial results of the HALO–(AC)³ aircraft campaign