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

Smith, Jacob W.; Bushell, Andrew C.; Butchart, Neal; Haynes, P. H.; Maycock, Amanda C.

doi:10.1029/2021gl097386

Cited by 6 publications

(7 citation statements)

References 37 publications

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“…The results of this study highlight the importance of changes in the large-scale TTL temperature field for the total mass in frozen hydrometeor transported in convective events. They are in agreement with other studies on the vapor-frozen hydrometeor partitioning under other perturbations like seasonal variations [45,46] or climate change [47]. The increase in tropical cold-point tropopause temperatures leads to an increased absolute amount of water vapor within saturated air parcels which can freeze out.…”

Section: Discussionsupporting

confidence: 92%

The impact of stratospheric aerosol heating on the frozen hydrometeor transport pathways in the tropical tropopause layer

Kroll,

Fueglistaler,

Schmidt

et al. 2024

Environ. Res. Lett.

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The exceptionally low temperature in the tropical tropopause layer (TTL) restricts the amount of water vapor entering the stratosphere. However, moisture may also enter the stratosphere in its frozen state, and the amount thereof depends on hydrometeor sedimentation and air vertical velocity. We investigate the sensitivity of frozen hydrometeor transport pathways to substantial perturbationsof the TTL temperature structure in global storm-resolving model simulations. A special focus is laid on the question which process - convection, slow upwelling within the background velocity field, in-cloud radiative processes, gravity waves or turbulence - is responsible for most of the transport. The study shows that the main contribution to the frozen hydrometeor flux is cold-point overshooting convection in both the control and perturbed scenario. The average convective event transports an increased amount of frozen hydrometeors at the cold-point tropopause, when the later is warmed. This finding can be explained by scaling of frozen moisture content with Clausius Clapeyron in a saturated environment.

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Section: Discussionsupporting

confidence: 92%

The impact of stratospheric aerosol heating on the frozen hydrometeor transport pathways in the tropical tropopause layer

Kroll,

Fueglistaler,

Schmidt

et al. 2024

Environ. Res. Lett.

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“…Figure 3 shows the contribution from water vapor and frozen hydrometeors to the total flux for CTL (blue) and PTB (red) (The plot shows unrounded values, the calculated percentage changes therefore deviate slightly from those calculated based on the values reported in the text.). A first inspection of the CTL data reveals that the frozen moisture flux of 0.0006 kg m −2 year −1 contributes with around 20%, a value which is well within the spread of values reported in previous studies (e.g., Dauhut et al., 2015; Dauhut & Hohenegger, 2022; Schoeberl et al., 2018; Smith et al., 2022; Ueyama et al., 2015, 2018). The leading order term however is the water vapor flux of 0.0021 kg m −2 year −1 contributing around 80% to the total flux.…”

Section: Resultssupporting

confidence: 86%

“…Third, they indirectly inferred the frozen moisture contribution, rather than directly calculating fluxes online as in our study. Our result also falls into the range of 2%–32% frozen moisture contribution reported in GCM studies (Schoeberl et al., 2018; Smith et al., 2022; Ueyama et al., 2015, 2018).…”

Section: Discussionsupporting

confidence: 83%

“…The result of roughly constant partitioning may surprise at first, but is consistent with a trajectory model based climate change study (Smith et al., 2022), where ice content was explicitly tracked. Observational based studies analyzing the annual cycle (Fueglistaler et al., 2013; Liu et al., 2010) also found a constant frozen hydrometeor contribution, which can calculated from the offset between observed and modeled water vapor values.…”

Section: Discussionmentioning

confidence: 96%

“…Corresponding estimates for the frozen contribution to the moisture flux can have a low bias if coarse scale wind fields are used. Reported values include Schoeberl et al (2018) with 2% (between 18 and −30 km), Ueyama et al (2015) with 14% (at 100 hPa), Ueyama et al (2018) with 15% (at 100 hPa) and Smith et al (2022) with 26-32% (entry above 18.6 km).…”

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confidence: 99%

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The Sensitivity of Moisture Flux Partitioning in the Cold‐Point Tropopause to External Forcing

Kroll

Fueglistaler

Schmidt

et al. 2023

Geophysical Research Letters

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The dryness of the stratosphere is the result of air entering through the cold tropical tropopause layer (TTL). However, our understanding of the moisture flux partitioning into water vapor and frozen hydrometeors is incomplete. This raises concerns regarding the ability of General Circulation Models to accurately predict changes in stratospheric water vapor following perturbations in the radiative budget due to volcanic aerosol or stratospheric geoengineering. We present the first results using a global storm‐resolving model investigating the sensitivity of moisture fluxes within the TTL to an additional heating source. We address the question how the partitioning of moisture fluxes into water vapor and frozen hydrometeors changes under perturbations. The analysis reveals the resilience of the TTL, keeping the flux partitioning constant even at an average cold‐point warming exceeding 8 K. In the control and perturbed simulations, water vapor contributes around 80% of the moisture entering the stratosphere.

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Stratospheric water vapor affecting atmospheric circulation

et al. 2023

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Water vapor plays an important role in many aspects of the climate system, by affecting radiation, cloud formation, atmospheric chemistry and dynamics. Even the low stratospheric water vapor content provides an important climate feedback, but current climate models show a substantial moist bias in the lowermost stratosphere. Here we report crucial sensitivity of the atmospheric circulation in the stratosphere and troposphere to the abundance of water vapor in the lowermost stratosphere. We show from a mechanistic climate model experiment and inter-model variability that lowermost stratospheric water vapor decreases local temperatures, and thereby causes an upward and poleward shift of subtropical jets, a strengthening of the stratospheric circulation, a poleward shift of the tropospheric eddy-driven jet and regional climate impacts. The mechanistic model experiment in combination with atmospheric observations further shows that the prevailing moist bias in current models is likely caused by the transport scheme, and can be alleviated by employing a less diffusive Lagrangian scheme. The related effects on atmospheric circulation are of similar magnitude as climate change effects. Hence, lowermost stratospheric water vapor exerts a first order effect on atmospheric circulation and improving its representation in models offers promising prospects for future research.

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

Cited by 6 publications

References 37 publications

The impact of stratospheric aerosol heating on the frozen hydrometeor transport pathways in the tropical tropopause layer

The impact of stratospheric aerosol heating on the frozen hydrometeor transport pathways in the tropical tropopause layer

The Sensitivity of Moisture Flux Partitioning in the Cold‐Point Tropopause to External Forcing

Stratospheric water vapor affecting atmospheric circulation

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