Dehydration of the stratosphere

Abstract. Domain filling, forward trajectory calculations are used to examine the global dehydration processes that control stratospheric water vapor. As with most Lagrangian models of this type, water vapor is instantaneously removed from the parcel to keep the relative humidity (RH) with respect to ice from exceeding saturation or a specified super-saturation value. We also test a simple parameterization of stratospheric convective moistening through ice lofting and the effect of gravity waves as a mechanism that can augment dehydration. Comparing diabatic and kinematic trajectories driven by the MERRA reanalysis, we find that, unlike the results from Liu et al. (2010), the additional transport due to the vertical velocity "noise" in the kinematic calculation creates too dry a stratosphere and a too diffuse a water-vapor tape recorder signal compared observations. We also show that the kinematically driven parcels are more likely to encounter the coldest tropopause temperatures than the diabatic trajectories. The diabatic simulations produce stratospheric water vapor mixing ratios close to that observed by Aura's Microwave Limb Sounder and are consistent with the MERRA tropical tropopause temperature biases. Convective moistening, which will increase stratospheric HDO, also increases stratospheric water vapor while the addition of parameterized gravity waves does the opposite. We find that while the Tropical West Pacific is the dominant dehydration location, but dehydration over Tropical South America is also important. Antarctica makes a small contribution to the overall stratospheric water vapor budget as well by releasing very dry air into the Southern Hemisphere stratosphere following the break up of the winter vortex.

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Dehydration of the stratosphere

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-10159-2011 ◽

2011 ◽

Vol 11 (3) ◽

pp. 10159-10190

Author(s):

M. Schoeberl ◽

A. Dessler

Keyword(s):

Water Vapor ◽

Gravity Waves ◽

The Other ◽

Stratospheric Water Vapor ◽

Dry Air ◽

Mixing Ratios ◽

Trajectory Calculations ◽

Type Water ◽

Dehydration Processes ◽

Water Vapor Budget

Abstract. Domain filling, forward trajectory calculations are used to examine the global dehydration processes that control stratospheric water vapor. As with most Lagrangian models of this type, water vapor is instantaneously removed from the parcel to keep the relative humidity with respect to ice from exceeding saturation or a specified super-saturation value. We also test a simple parameterization of stratospheric convective moistening through ice lofting and the effect of gravity waves as a mechanism that can augment dehydration. Comparing diabatic and kinematic trajectories, we find, in agreement with previous authors, that the additional transport due to the vertical velocity "noise" in the kinematic calculation creates too dry a stratosphere and a too diffuse a water-vapor tape recorder signal compared observations. The diabatic simulations, on the other hand, produce stratospheric water vapor mixing ratios very close to that observed by Aura's Microwave Limb Sounder. Convective moistening, which will increases stratospheric HDO, also increases stratospheric water vapor while gravity waves do the opposite. We find that while the Tropical West Pacific is the dominant dehydration location, dehydration over Tropical South America is also important. Antarctica also makes a contribution to the overall stratospheric water vapor budget by releasing very dry air into the Southern Hemisphere stratosphere following the break up of the winter vortex.

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Processes Controlling Tropical Tropopause Temperature and Stratospheric Water Vapor in Climate Models

Journal of Climate ◽

10.1175/jcli-d-15-0075.1 ◽

2015 ◽

Vol 28 (16) ◽

pp. 6516-6535 ◽

Cited By ~ 29

Author(s):

Steven C. Hardiman ◽

Ian A. Boutle ◽

Andrew C. Bushell ◽

Neal Butchart ◽

Mike J. P. Cullen ◽

...

Keyword(s):

Water Vapor ◽

Climate Models ◽

Atmospheric Composition ◽

Stratospheric Water Vapor ◽

Vertical Advection ◽

Radiative Processes ◽

Microphysical Properties ◽

Tropical Tropopause ◽

The Tropics ◽

Tropopause Temperature

Abstract A warm bias in tropical tropopause temperature is found in the Met Office Unified Model (MetUM), in common with most models from phase 5 of CMIP (CMIP5). Key dynamical, microphysical, and radiative processes influencing the tropical tropopause temperature and lower-stratospheric water vapor concentrations in climate models are investigated using the MetUM. A series of sensitivity experiments are run to separate the effects of vertical advection, ice optical and microphysical properties, convection, cirrus clouds, and atmospheric composition on simulated tropopause temperature and lower-stratospheric water vapor concentrations in the tropics. The numerical accuracy of the vertical advection, determined in the MetUM by the choice of interpolation and conservation schemes used, is found to be particularly important. Microphysical and radiative processes are found to influence stratospheric water vapor both through modifying the tropical tropopause temperature and through modifying upper-tropospheric water vapor concentrations, allowing more water vapor to be advected into the stratosphere. The representation of any of the processes discussed can act to significantly reduce biases in tropical tropopause temperature and stratospheric water vapor in a physical way, thereby improving climate simulations.

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Impact of convectively lofted ice on the seasonal cycle of tropical lower stratospheric water vapor

10.5194/acp-2019-302 ◽

2019 ◽

Author(s):

Xun Wang ◽

Andrew E. Dessler ◽

Mark R. Schoeberl ◽

Wandi Yu ◽

Tao Wang

Keyword(s):

Water Vapor ◽

Seasonal Cycle ◽

Climate Model ◽

Boreal Summer ◽

Small Contribution ◽

Asian Monsoon Region ◽

Stratospheric Water Vapor ◽

Trajectory Model ◽

Tropical Tropopause ◽

Important Region

Abstract. We use a forward Lagrangian trajectory model to diagnose mechanisms that produce the tropical lower stratospheric (LS) water vapor seasonal cycle observed by the Microwave Limb Sounder (MLS) and reproduced by the Goddard Earth Observing System Chemistry Climate Model (GEOSCCM) in the tropical tropopause layer (TTL). We confirm in both the MLS and GEOSCCM that the seasonal cycle of water vapor is primarily determined by the seasonal cycle of TTL temperatures. However, we find that the seasonal cycle of temperature predicts a smaller seasonal cycle of LS water vapor between 10° N–40° N than observed by MLS. We show that including evaporation of convectively lofted ice in the trajectory model increases the simulated maximum value in the 10° N–40° N water vapor seasonal cycle by 1.9 ppmv (47 %) and increases the seasonal amplitude by 1.26 ppmv (123 %), which improves the prediction of LS water vapor annual cycle. We conclude that the moistening effect from convective ice evaporation in the TTL plays a key role regulating and maintaining the tropical LS water vapor seasonal cycle. Most of the convective moistening in the 10° N–40° N range comes from convective ice evaporation occurring at the same latitudes. A small contribution to the moistening comes from convective ice evaporation occurring between 10° S–10° N. Within 10° N–40° N, the Asian monsoon region is the most important region for convective ice evaporation and convective moistening during boreal summer and autumn.

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Impacts of Ozone Changes in the Tropopause Layer on Stratospheric Water Vapor

Atmosphere ◽

10.3390/atmos12030291 ◽

2021 ◽

Vol 12 (3) ◽

pp. 291

Author(s):

Jinpeng Lu ◽

Fei Xie ◽

Hongying Tian ◽

Jiali Luo

Keyword(s):

Water Vapor ◽

Ozone Depletion ◽

Climate Model ◽

Global Climate ◽

Stratospheric Water Vapor ◽

Radiative Processes ◽

Low Latitudes ◽

Cold Point ◽

The Impact ◽

Tropopause Temperature

Stratospheric water vapor (SWV) changes play an important role in regulating global climate change, and its variations are controlled by tropopause temperature. This study estimates the impacts of tropopause layer ozone changes on tropopause temperature by radiative process and further influences on lower stratospheric water vapor (LSWV) using the Whole Atmosphere Community Climate Model (WACCM4). It is found that a 10% depletion in global (mid-low and polar latitudes) tropopause layer ozone causes a significant cooling of the tropical cold-point tropopause with a maximum cooling of 0.3 K, and a corresponding reduction in LSWV with a maximum value of 0.06 ppmv. The depletion of tropopause layer ozone at mid-low latitudes results in cooling of the tropical cold-point tropopause by radiative processes and a corresponding LSWV reduction. However, the effect of polar tropopause layer ozone depletion on tropical cold-point tropopause temperature and LSWV is opposite to and weaker than the effect of tropopause layer ozone depletion at mid-low latitudes. Finally, the joint effect of tropopause layer ozone depletion (at mid-low and polar latitudes) causes a negative cold-point tropopause temperature and a decreased tropical LSWV. Conversely, the impact of a 10% increase in global tropopause layer ozone on LSWV is exactly the opposite of the impact of ozone depletion. After 2000, tropopause layer ozone decreased at mid-low latitudes and increased at high latitudes. These tropopause layer ozone changes at different latitudes cause joint cooling in the tropical cold-point tropopause and a reduction in LSWV. Clarifying the impacts of tropopause layer ozone changes on LSWV clearly is important for understanding and predicting SWV changes in the context of future global ozone recovery.

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Effect of the Indo-Pacific Warm Pool on Lower-Stratospheric Water Vapor and Comparison with the Effect of ENSO

Journal of Climate ◽

10.1175/jcli-d-17-0575.1 ◽

2018 ◽

Vol 31 (3) ◽

pp. 929-943 ◽

Cited By ~ 6

Author(s):

Fei Xie ◽

Xin Zhou ◽

Jianping Li ◽

Quanliang Chen ◽

Jiankai Zhang ◽

...

Keyword(s):

Water Vapor ◽

Climate Model ◽

Southern Oscillation ◽

Deep Convection ◽

Warm Pool ◽

Latent Heat Release ◽

Stratospheric Water Vapor ◽

Asymmetric Effects ◽

Pacific Warm Pool ◽

Tropopause Temperature

Abstract Time-slice experiments with the Whole Atmosphere Community Climate Model, version 4 (WACCM4), and composite analysis with satellite observations are used to demonstrate that the Indo-Pacific warm pool (IPWP) can significantly affect lower-stratospheric water vapor. It is found that a warmer IPWP significantly dries the stratospheric water vapor by causing a broad cooling of the tropopause, and vice versa for a colder IPWP. Such imprints in tropopause temperature are driven by a combination of variations in the Brewer–Dobson circulation in the stratosphere and deep convection in the troposphere. Changes in deep convection associated with El Niño–Southern Oscillation (ENSO) reportedly have a small zonal mean effect on lower-stratospheric water vapor for strong zonally asymmetric effects on tropopause temperature. In contrast, IPWP events have zonally uniform imprints on tropopause temperature. This is because equatorial planetary waves forced by latent heat release from deep convection project strongly onto ENSO but weakly onto IPWP events.

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Modeling upper tropospheric and lower stratospheric water vapor anomalies

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-13-9653-2013 ◽

2013 ◽

Vol 13 (4) ◽

pp. 9653-9679 ◽

Cited By ~ 1

Author(s):

M. R. Schoeberl ◽

A. E. Dessler ◽

T. Wang

Keyword(s):

Water Vapor ◽

Lower Stratosphere ◽

Calculation Model ◽

Vapor Concentration ◽

Cold Temperatures ◽

Tropical Tropopause Layer ◽

Stratospheric Water Vapor ◽

Tropical Tropopause ◽

Minimum Displacement ◽

Asian Monsoons

Abstract. The domain-filling, forward trajectory calculation model developed by Schoeberl and Dessler (2011) is used to further investigate processes that produce upper tropospheric and lower stratospheric water vapor anomalies. We examine the pathways parcels take from the base of the tropical tropopause layer (TTL) to the lower stratosphere. Most parcels found in the lower stratosphere arise from East Asia, the Tropical West Pacific (TWP) and the Central/South America. The belt of TTL parcel origins is very wide compared to the final dehydration zones near the top of the TTL. This is due to the convergence of rising air as a result of the stronger diabatic heating near the tropopause relative to levels above and below. The observed water vapor anomalies – both wet and dry – correspond to regions where parcels have minimal displacement from their initialization. These minimum displacement regions include the winter TWP and the Asian and American monsoons. To better understand the stratospheric water vapor concentration we introduce the water vapor spectrum and investigate the source of the wettest and driest components of the spectrum. We find that the driest air parcels that originate below the TWP, moving upward to dehydrate in the TWP cold upper troposphere. The wettest air parcels originate at the edges of the TWP as well as the summer American and Asian monsoons. The wet air parcels are important since they skew the mean stratospheric water vapor distribution toward higher values. Both TWP cold temperatures that produce dry parcels as well as extra-TWP processes that control the wet parcels determine stratospheric water vapor.

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Intercomparison of midlatitude tropospheric and lower-stratospheric water vapor measurements and comparison to ECMWF humidity data

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-16729-2018 ◽

2018 ◽

Vol 18 (22) ◽

pp. 16729-16745 ◽

Cited By ~ 4

Author(s):

Stefan Kaufmann ◽

Christiane Voigt ◽

Romy Heller ◽

Tina Jurkat-Witschas ◽

Martina Krämer ◽

...

Keyword(s):

Water Vapor ◽

Climate Impact ◽

Cloud Formation ◽

Mean Values ◽

Stratospheric Water Vapor ◽

Mixing Ratios ◽

Quality Of Water ◽

Research Aircraft ◽

German Aerospace

Abstract. Accurate measurement of water vapor in the climate-sensitive region near the tropopause is very challenging. Unexplained systematic discrepancies between measurements at low water vapor mixing ratios made by different instruments on airborne platforms have limited our ability to adequately address a number of relevant scientific questions on the humidity distribution, cloud formation and climate impact in that region. Therefore, during the past decade, the scientific community has undertaken substantial efforts to understand these discrepancies and improve the quality of water vapor measurements. This study presents a comprehensive intercomparison of airborne state-of-the-art in situ hygrometers deployed on board the DLR (German Aerospace Center) research aircraft HALO (High Altitude and LOng Range Research Aircraft) during the Midlatitude CIRRUS (ML-CIRRUS) campaign conducted in 2014 over central Europe. The instrument intercomparison shows that the hygrometer measurements agree within their combined accuracy (±10 % to 15 %, depending on the humidity regime); total mean values agree within 2.5 %. However, systematic differences on the order of 10 % and up to a maximum of 15 % are found for mixing ratios below 10 parts per million (ppm) H2O. A comparison of relative humidity within cirrus clouds does not indicate a systematic instrument bias in either water vapor or temperature measurements in the upper troposphere. Furthermore, in situ measurements are compared to model data from the European Centre for Medium-Range Weather Forecasts (ECMWF) which are interpolated along the ML-CIRRUS flight tracks. We find a mean agreement within ±10 % throughout the troposphere and a significant wet bias in the model on the order of 100 % to 150 % in the stratosphere close to the tropopause. Consistent with previous studies, this analysis indicates that the model deficit is mainly caused by too weak of a humidity gradient at the tropopause.

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Water-vapor Measurements in the Lower Stratosphere

Canadian Journal of Chemistry ◽

10.1139/v74-224 ◽

1974 ◽

Vol 52 (8) ◽

pp. 1527-1531 ◽

Cited By ~ 44

Author(s):

H. J. Mastenbrook

Keyword(s):

Water Vapor ◽

Lower Stratosphere ◽

Marked Decrease ◽

Vapor Concentration ◽

Water Vapor Concentration ◽

Mixing Ratio ◽

Stratospheric Water Vapor ◽

Mixing Ratios ◽

Natural Concentration ◽

General Range

Nearly 10 years of water-vapor measurements to heights of 30 km provide a basis for assessing the natural concentration of stratospheric water vapor and its variability. The measurements which began in 1964 have been made at monthly intervals from the mid-latitude location of Washington, D.C, using a balloon-borne frost-point hygrometer. The observations show the mixing ratio of water-vapor mass to air mass in the stratosphere to be in the general range of 1 to 4 p.p.m. with a modal concentration between 2 and 3 p.p.m. An annual cycle of mixing ratio is evident for the low stratosphere. A trend of water-vapor increase observed during the first 6 years does not persist beyond 1969 or 1970. The 6 year increase was followed by a marked decrease in 1971, with mixing ratios remaining generally below 3 p.p.m. thereafter. The measurements of recent years suggest that the series of observations may have begun during a period of low water-vapor concentration in the stratosphere.

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Response of trace gases to the disrupted 2015–2016 quasi-biennial oscillation

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-6813-2017 ◽

2017 ◽

Vol 17 (11) ◽

pp. 6813-6823 ◽

Cited By ~ 22

Author(s):

Olga V. Tweedy ◽

Natalya A. Kramarova ◽

Susan E. Strahan ◽

Paul A. Newman ◽

Lawrence Coy ◽

...

Keyword(s):

Water Vapor ◽

Chemical Constituents ◽

Trace Gases ◽

Quasi Biennial Oscillation ◽

Data Set ◽

Uv Index ◽

Stratospheric Water Vapor ◽

Northern Summer ◽

Tropical Tropopause ◽

Biennial Oscillation

Abstract. The quasi-biennial oscillation (QBO) is a quasiperiodic alternation between easterly and westerly zonal winds in the tropical stratosphere, propagating downward from the middle stratosphere to the tropopause with a period that varies from 24 to 32 months ( ∼  28 months on average). The QBO wind oscillations affect the distribution of chemical constituents, such as ozone (O3), water vapor (H2O), nitrous oxide (N2O), and hydrochloric acid (HCl), through the QBO-induced meridional circulation. In the 2015–2016 winter, radiosonde observations revealed an anomaly in the downward propagation of the westerly phase, which was disrupted by the upward displacement of the westerly phase from ∼  30 hPa up to 15 hPa and the sudden appearance of easterlies at 40 hPa. Such a disruption is unprecedented in the observational record from 1953 to the present. In this study we show the response of trace gases to this QBO disruption using O3, HCl, H2O, and temperature from the Aura Microwave Limb Sounder (MLS) and total ozone measurements from the Solar Backscatter Ultraviolet (SBUV) Merged Ozone Data Set (MOD). Results reveal the development of positive anomalies in stratospheric equatorial O3 and HCl over ∼  50–30 hPa in May–September of 2016 and a substantial decrease in O3 in the subtropics of both hemispheres. The SBUV observations show near-record low levels of column ozone in the subtropics in 2016, resulting in an increase in the surface UV index during northern summer. Furthermore, cold temperature anomalies near the tropical tropopause result in a global decrease in stratospheric water vapor.

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