Persistence of moist plumes from overshooting convection in the Asian monsoon anticyclone

Khaykin, Sergey; Moyer, Elizabeth; Krämer, M.; Clouser, Benjamin; Bucci, Silvia; Legras, Bernard; Lykov, Alexey; Afchine, Armin; Cairo, F.; Formanyuk, Ivan; Mitev, Valentin; Matthey, Renaud; Rolf, Christian; Singer, Clare E.; Spelten, N.; Volkov, V. V.; Yushkov, V.; Stroh, F.

doi:10.5194/acp-22-3169-2022

Cited by 29 publications

(29 citation statements)

References 99 publications

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“…The in situ measurements used in this study are aircraft data from the StratoClim campaign, which took place over the Indian subcontinent from 27 July to 10 August 2017. The M55-Geophysica high-flying research aircraft deployed in Kathmandu, Nepal, was equipped with a comprehensive set of instruments to capture high-quality data sets, which include, but are not limited to, water vapor, number densities, size distributions of ice particles, and meteorological parameters in the subtropical upper troposphere-lower stratosphere (UTLS) region (Khaykin et al, 2022).…”

Section: Field Campaign and Observational Data Setsmentioning

confidence: 99%

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: Field Campaign and Observational Data Setsmentioning

confidence: 99%

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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“…The influence of deep convection on stratospheric water vapor has been long debated. Though there has been occasional observational evidence for convective dehydration (e.g., Khaykin et al, 2022), convective penetration and accompanying hydration by transport of ice and water vapor above the local cold point have been frequently observed (e.g., Khaykin et al, 2009;Lee et al, 2019) and modeled (e.g., Dauhut et al, 2018). An important role for convective injection of ice in determining lower stratospheric humidity has been observed outside of the tropics (e.g., Schwartz et al, 2013;Werner et al, 2020).…”

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confidence: 99%

The Effect of Convective Injection of Ice on Stratospheric Water Vapor in a Changing Climate

Smith

Bushell

Butchart

et al. 2022

Geophysical Research Letters

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Current climate models in phase six of the Coupled Model Intercomparsion Project (CMIP6) show a large spread in stratospheric water vapor concentrations in the present day and in future projections (Keeble et al., 2021). This in turn implies large uncertainty in the climate feedback induced by future changes in stratospheric water vapor (Banerjee et al., 2019). It is therefore important to understand the processes that control stratospheric water vapor concentrations and their representation in general circulation models (GCMs) to develop strategies to reduce the uncertainty in projections.Water vapor concentrations in the stratospheric overworld (above ∼380 K potential temperature) are largely determined by freeze-drying processes in the tropical tropopause layer (TTL;Fueglistaler et al., 2009) and moistening due to methane oxidation. In the lowermost extratropical stratosphere, an additional influence is mixing of air from the stratospheric overworld with moist air from the troposphere. This paper will focus on the freeze-drying

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“…The in-situ measurements used in this study are aircraft data from the StratoClim campaign, which took place in the Indian subcontinent from July 27 to August 10, 2017. The M55-Geophysica high-flying research aircraft deployed in Kathmandu, Nepal, was equipped with a comprehensive set of instruments to capture high quality datasets which include but are not limited to, water vapor, number densities, size distributions of ice particles, as well as meteorological parameters in the subtropical upper troposphere/lower stratosphere (UTLS) region (Khaykin et al, 2022).…”

Section: Field Campaign and Observational Data Setsmentioning

confidence: 99%

“…The ice water content (IWC) is derived from the particle size distribution with a lower detection limit of ~ 0.05 ppmv (Krämer at al., 2020;Afchine et al, 2018). Gas-phase water was measured with the sampling rate of 1 Hz by means of the Lyman-Alpha hygrometer FLASH (Khaykin et al, 2022).…”

Section: Field Campaign and Observational Data Setsmentioning

confidence: 99%

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Sensitivity of convectively driven tropical tropopause cirrus to ice habit

Lamraoui

Krämer

Afchine³

et al. 2022

Preprint

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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. The main scientific objectives of this work are to (a) investigate the influence of predefined versus non-predefined categories of ice hydrometeors and ice habit on convectively driven TTL cirrus in simulations of the Asian summer monsoon, and (b) determine the optimal model configuration to adequately simulate TTL cirrus clouds. During the StratoClim field campaign in 2017, aircraft measurements from 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 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. We compare the aircraft measurements to a set of numerical experiments at the scales of large-eddy simulations (LES) of the same case study that employ different microphysics schemes. 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 aggregates habits are in the in-situ range with lower IWC and number concentration. 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, columnar habit has the highest fall speed. The difference in ice number concentration across habits can be up to four orders of magnitude, and 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.

show abstract

Persistence of moist plumes from overshooting convection in the Asian monsoon anticyclone

Cited by 29 publications

References 99 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

The Effect of Convective Injection of Ice on Stratospheric Water Vapor in a Changing Climate

Sensitivity of convectively driven tropical tropopause cirrus to ice habit

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