A simple model to assess the impact of gravity waves on ice crystal populations in the tropical tropopause layer

Corcos, Milena; Hertzog, Albert; Plougonven, Riwal; Podglajen, Aurélien

doi:10.5194/egusphere-2022-1444

Cited by 4 publications

(4 citation statements)

References 39 publications

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“…Some of the balloons carry a microlidar system that can detect even the thinnest TTL cirrus (Ravetta et al, 2020). Dynamical information inferred from balloons has already been used in several studies of TTL cirrus (Jensen et al, 2016;Corcos et al, 2023) and offers further insight into the tropical cirrus life cycle Sect. 6.3.…”

Section: In Situ Measurementsmentioning

confidence: 99%

Opinion: Tropical cirrus – from micro-scale processes to climate-scale impacts

Gasparini,

Sullivan,

Sokol

et al. 2023

Atmos. Chem. Phys.

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Abstract. Tropical cirrus clouds, i.e., any type of ice cloud with tops above 400 hPa, play a critical role in the climate system and are a major source of uncertainty in our understanding of global warming. Tropical cirrus clouds involve processes spanning a wide range of spatial and temporal scales, from ice microphysics on cloud scales to mesoscale convective organization and planetary wave dynamics. This complexity makes tropical cirrus clouds notoriously difficult to model and has left many important questions stubbornly unanswered. At the same time, their multi-scale nature makes them well-positioned to benefit from the rise of global, high-resolution simulations of Earth's atmosphere and a growing abundance of remotely sensed and in situ observations. Rapid progress on our understanding of tropical cirrus requires coordinated efforts to take advantage of these modern computational and observational abilities. In this opinion paper, we review recent progress in cirrus studies, highlight important unanswered questions, and discuss promising paths forward. Significant progress has been made in understanding the life cycle of convectively generated “anvil” cirrus and the response of their macrophysical properties to large-scale controls. On the other hand, much work remains to be done to fully understand how small-scale anvil processes and the climatological anvil radiative effect will respond to global warming. Thin, in situ formed cirrus clouds are now known to be closely tied to the thermal structure and humidity of the tropical tropopause layer, but microphysical uncertainties prevent a full understanding of this link, as well as the precise amount of water vapor entering the stratosphere. Model representation of ice-nucleating particles, water vapor supersaturation, and ice depositional growth continue to pose great challenges to cirrus modeling. We believe that major advances in the understanding of tropical cirrus can be made through a combination of cross-tool synthesis and cross-scale studies conducted by cross-disciplinary research teams.

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Section: In Situ Measurementsmentioning

confidence: 99%

Opinion: Tropical cirrus – from micro-scale processes to climate-scale impacts

Gasparini,

Sullivan,

Sokol

et al. 2023

Atmos. Chem. Phys.

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“…As noted above, previous modeling studies investigated the influence of waves on ice nucleation and showed that high‐frequency gravity waves can enhance ice concentrations in cirrus (Corcos et al., 2023; Jensen et al., 2010; Spichtinger & Krämer, 2013). Here, we show that the influence of waves after ice nucleation has ceased is to decrease ice concentrations.…”

Section: Summary and Discussionmentioning

confidence: 96%

“…(2016) developed probabilistic models describing the MTF. We note that previous studies have directly used the super‐pressure balloon temperature time series for simulations of temperature fluctuation influence on TTL cirrus (Corcos et al., 2023; Dinh et al., 2016). Whereas we are using ensembles of the essentially equivalent synthetic temperature time series.…”

Section: Impact Of Stochastic Mesoscale Temperature Fluctuationsmentioning

confidence: 99%

The Impact of Gravity Waves on the Evolution of Tropical Anvil Cirrus Microphysical Properties

Jensen,

Kärcher,

Woods

et al. 2024

JGR Atmospheres

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Anvil cirrus generated by deep convection covers large fractions of the tropics and has important impacts on the Earth's radiation budget and climate. In situ measurements made with high‐altitude aircraft indicate a rapid transition in ice crystal size distributions and habits as anvil cirrus ages. We use numerical simulations to investigate the impact of high‐frequency gravity waves on the evolution of anvil cirrus microphysical properties. The impacts of both monochromatic gravity waves and ubiquitous stochastic mesoscale temperature fluctuations are simulated. In both cases, the interplay between wave‐driven temperature fluctuations, deposition growth/sublimation, and sedimentation causes accelerated removal of both small ice crystals (diameters less than about 10 μm) and large crystals (diameters larger than ≈30 μm). These changes are consistent with the observed evolution of anvil cirrus microphysical properties. The Kelvin effect (higher saturation vapor pressure over curved surfaces) is a critical factor in the anvil evolution, driving mass transfer from small to large ice crystals. The wave‐driven decrease in ice concentration is much faster for typical anvil cirrus detrained at ≃11.5–12.5 km than for less frequent anvils at 15.5–17.5 km because of the strong temperature dependence of deposition growth and sublimation rates. The simulations also show that waves, along with the Kelvin effect, drive growth of mid‐sized (5–20 μm) ice crystals, which is consistent with the observed transition to bullet rosette habits in aging anvil cirrus. We conclude that high‐frequency gravity waves, which are generally not resolved in large‐scale models, likely have important impacts on anvil cirrus microphysical properties and lifetimes.

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“…Clearly, compared to idealized simulations based on constant updrafts, the GW forcing of ice supersaturation results in a more realistic evolution of cirrus clouds. In particular, stochastic cooling and warming phases act to extend cirrus lifetimes compared to a constant, slow updraft scenario (Corcos et al., 2023). In our specific case, a small range of ice crystal radii around 20 μm happens to be a sweet spot in the MUT PSD that is neither significantly affected by sublimation nor by sedimentation over 3 hr of simulation time.…”

Section: Idealized Simulationsmentioning

confidence: 99%

Ice Supersaturation Variability in Cirrus Clouds: Role of Vertical Wind Speeds and Deposition Coefficients

Kärcher,

Jensen,

Pokrifka

et al. 2023

JGR Atmospheres

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Aircraft measurements reveal ice supersaturation statistics in cirrus (ISSs) with broad maxima around ice saturation and pronounced variance. In this study, processes shaping ISSs in midlatitude and tropical upper tropospheric conditions are systematically investigated. Water vapor deposition and sublimation of size‐resolved ice crystal populations are simulated in an air parcel framework. Mesoscale temperature fluctuations (MTFs) due to gravity waves force the temporal evolution of supersaturation. Various levels of background wave forcing and cirrus thickness are distinguished in stochastic ensemble simulations. Kinetic limitations to ice mass growth are brought about by supersaturation‐dependent deposition coefficients that represent efficient and inefficient growth modes as a function of ice crystal size. The simulations identify a wide range of deposition coefficients in cirrus, but most values stay above 0.01 such that kinetic limitations to water uptake remain moderate. Supersaturation quenching times are long, typically 0.5–2 hr. The wave forcing thus causes a remarkably large variability in ISSs and cirrus microphysical properties except in the thickest cirrus, producing ensemble‐mean ISSs in line with in‐situ measurements. ISS variance is controlled by MTFs and increases with decreasing cirrus integral radii. In comparison, the impact of ice crystal growth rates on ISSs is small. These results contribute to efforts directed at identifying and solving issues associated with ice‐supersaturated areas and non‐equilibrium cirrus physics in global models.

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A simple model to assess the impact of gravity waves on ice crystal populations in the tropical tropopause layer

Cited by 4 publications

References 39 publications

Opinion: Tropical cirrus – from micro-scale processes to climate-scale impacts

Opinion: Tropical cirrus – from micro-scale processes to climate-scale impacts

The Impact of Gravity Waves on the Evolution of Tropical Anvil Cirrus Microphysical Properties

Ice Supersaturation Variability in Cirrus Clouds: Role of Vertical Wind Speeds and Deposition Coefficients

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