Diagnosing Observed Stratospheric Water Vapor Relationships to the Cold Point Tropical Tropopause

Past and future climate simulations from the Goddard Earth Observing System Chemistry–Climate Model (GEOS CCM), with specified boundary conditions for sea surface temperature, sea ice, and trace gas emissions, have been analyzed to assess trends and possible causes of changes in stratospheric water vapor. The simulated distribution of stratospheric water vapor in the 1990s compares well with observations. Changes in the cold point temperatures near the tropical tropopause can explain differences in entry stratospheric water vapor. The average saturation mixing ratio of a 20° latitude by 15° longitude region surrounding the minimum tropical saturation mixing ratio is shown to be a useful diagnostic for entry stratospheric water vapor and does an excellent job reconstructing the annual average entry stratospheric water vapor over the period 1950–2100. The simulated stratospheric water vapor increases over the 50 yr between 1950 and 2000, primarily because of changes in methane concentrations, offset by a slight decrease in tropical cold point temperatures. Stratospheric water vapor is predicted to continue to increase over the twenty-first century, with increasing methane concentrations causing the majority of the trend to midcentury. Small increases in cold point temperature cause increases in the entry water vapor throughout the twenty-first century. The increasing trend in future water vapor is tempered by a decreasing contribution of methane oxidation owing to cooling stratospheric temperatures and by increased tropical upwelling, leading to a near-zero trend for the last 30 yr of the twenty-first century.

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The impact of temperature vertical structure on trajectory modeling of stratospheric water vapor

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-3517-2015 ◽

2015 ◽

Vol 15 (6) ◽

pp. 3517-3526 ◽

Cited By ~ 15

Author(s):

T. Wang ◽

A. E. Dessler ◽

M. R. Schoeberl ◽

W. J. Randel ◽

J.-E. Kim

Keyword(s):

Water Vapor ◽

Vertical Structure ◽

Vertical Resolution ◽

Tropical Tropopause Layer ◽

Stratospheric Water Vapor ◽

Dry Air ◽

Tropical Tropopause ◽

Cold Point ◽

The Impact ◽

Modern Era

Abstract. Lagrangian trajectories driven by reanalysis meteorological fields are frequently used to study water vapor (H2O) in the stratosphere, in which the tropical cold-point temperatures regulate the amount of H2O entering the stratosphere. Therefore, the accuracy of temperatures in the tropical tropopause layer (TTL) is of great importance for understanding stratospheric H2O abundances. Currently, most reanalyses, such as the NASA MERRA (Modern Era Retrospective – analysis for Research and Applications), only provide temperatures with ~ 1.2 km vertical resolution in the TTL, which has been argued to miss finer vertical structure in the tropopause and therefore introduce uncertainties in our understanding of stratospheric H2O. In this paper, we quantify this uncertainty by comparing the Lagrangian trajectory prediction of H2O using MERRA temperatures on standard model levels (traj.MER-T) to those using GPS temperatures at finer vertical resolution (traj.GPS-T), and those using adjusted MERRA temperatures with finer vertical structures induced by waves (traj.MER-Twave). It turns out that by using temperatures with finer vertical structure in the tropopause, the trajectory model more realistically simulates the dehydration of air entering the stratosphere. But the effect on H2O abundances is relatively minor: compared with traj.MER-T, traj.GPS-T tends to dry air by ~ 0.1 ppmv, while traj.MER-Twave tends to dry air by 0.2–0.3 ppmv. Despite these differences in absolute values of predicted H2O and vertical dehydration patterns, there is virtually no difference in the interannual variability in different runs. Overall, we find that a tropopause temperature with finer vertical structure has limited impact on predicted stratospheric H2O.

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Influence of ENSO on entry stratospheric water vapor in coupled chemistry-ocean CCMI and CMIP6 models

10.5194/egusphere-egu21-619 ◽

2021 ◽

Author(s):

Ohad Harari ◽

Chaim garfinkel ◽

Shlomi Ziskin

Keyword(s):

Water Vapor ◽

Climate Model ◽

Temperature Response ◽

Coupled Model ◽

Dominant Mode ◽

Central Pacific ◽

Stratospheric Water Vapor ◽

Tropical Tropopause ◽

Tropical Troposphere ◽

Cold Point

The connection between the dominant mode of interannual variability in the tropical troposphere, El Ni&#241;o Southern Oscillation (ENSO), and entry of stratospheric water vapor, is analyzed in a set of the model simulations archived for the Chemistry-Climate Model Initiative (CCMI) project and for phase 6 of the Coupled Model Intercomparison Project. While the models agree on the temperature response to ENSO in the tropical troposphere and lower stratosphere, and all models also agree &#160;on the zonal structure of the response in the tropical tropopause layer, the only aspect of the entry water vapor with consensus is that La Ni&#241;a leads to moistening in winter relative to neutral ENSO. For El Ni&#241;o and for other seasons there are significant differences among the models. For example, some models find that the enhanced water vapor for La Ni&#241;a in the winter of the event reverses in spring and summer, other models find that this moistening persists, while some show a nonlinear response with both El Ni&#241;o and La Ni&#241;a leading to enhanced water vapor in both winter, spring, and summer. A moistening in the spring &#160;following El Ni&#241;o events, perhaps the strongest signal in observations, is simulated by only half of the models. Focusing on Central Pacific ENSO versus East Pacific ENSO, or temperatures in the mid-troposphere as compared to temperatures near the surface, does not narrow the inter-model discrepancies. Despite this diversity in response, the temperature response near the cold point can explain the response of water vapor when each model is considered separately. While the observational record is too short to fully constrain the response to ENSO, it is clear that most models suffer from biases in the magnitude of interannual variability of entry water vapor. This bias could be due to biased cold point temperatures in some models, but others appear to be missing forcing processes that contribute to observed variability near the cold point

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The Tropical Tropopause Layer 1960–2100

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-1621-2009 ◽

2009 ◽

Vol 9 (5) ◽

pp. 1621-1637 ◽

Cited By ~ 59

Author(s):

A. Gettelman ◽

T. Birner ◽

V. Eyring ◽

H. Akiyoshi ◽

S. Bekki ◽

...

Keyword(s):

Water Vapor ◽

Climate Models ◽

Basic Structure ◽

Historical Trends ◽

Tropical Tropopause Layer ◽

Stratospheric Water Vapor ◽

Temperature Anomalies ◽

Tropical Tropopause ◽

Stratospheric Temperature ◽

Cold Point

Abstract. The representation of the Tropical Tropopause Layer (TTL) in 13 different Chemistry Climate Models (CCMs) designed to represent the stratosphere is analyzed. Simulations for 1960–2005 and 1980–2100 are analyzed. Simulations for 1960–2005 are compared to reanalysis model output. CCMs are able to reproduce the basic structure of the TTL. There is a large (10 K) spread in annual mean tropical cold point tropopause temperatures. CCMs are able to reproduce historical trends in tropopause pressure obtained from reanalysis products. Simulated historical trends in cold point tropopause temperatures are not consistent across models or reanalyses. The pressure of both the tropical tropopause and the level of main convective outflow appear to have decreased (increased altitude) in historical runs as well as in reanalyses. Decreasing pressure trends in the tropical tropopause and level of main convective outflow are also seen in the future. Models consistently predict decreasing tropopause and convective outflow pressure, by several hPa/decade. Tropical cold point temperatures are projected to increase by 0.09 K/decade. Tropopause anomalies are highly correlated with tropical surface temperature anomalies and with tropopause level ozone anomalies, less so with stratospheric temperature anomalies. Simulated stratospheric water vapor at 90 hPa increases by up to 0.5–1 ppmv by 2100. The result is consistent with the simulated increase in temperature, highlighting the correlation of tropopause temperatures with stratospheric water vapor.

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The Tropical Tropopause Layer 1960–2100

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-8-1367-2008 ◽

2008 ◽

Vol 8 (1) ◽

pp. 1367-1413 ◽

Cited By ~ 8

Author(s):

A. Gettelman ◽

T. Birner ◽

V. Eyring ◽

H. Akiyoshi ◽

D. A. Plummer ◽

...

Keyword(s):

Water Vapor ◽

Climate Models ◽

Basic Structure ◽

Complex Nature ◽

Historical Trends ◽

Tropical Tropopause Layer ◽

Stratospheric Water Vapor ◽

Tropical Tropopause ◽

Stratospheric Cooling ◽

Cold Point

Abstract. The representation of the Tropical Tropopause Layer in 13 different Chemistry Climate Models designed to represent the stratosphere is analyzed. Simulations for 1960–present and 1980–2100 are analyzed and compared to reanalysis model output. Results indicate that the models are able to reproduce the basic structure of the TTL. There is a large spread in cold point tropopause temperatures that may be linked to variation in TTL ozone values. The models are generally able to reproduce historical trends in tropopause pressure obtained from reanalysis products. Simulated historical trends in cold point tropopause temperatures and in the meridional extent of the TTL are not consistent across models. The pressure of both the tropical tropopause and the level of main convective outflow appear to be decreasing (increasing altitude) in historical runs. Similar trends are seen in the future. Models consistently predict decreasing tropopause and convective outflow pressure, by several hPa/decade. Tropical cold point temperatures increase by 0.2 K/decade. This indicates that tropospheric warming dominates stratospheric cooling at the tropical tropopause. Stratospheric water vapor at 100 hPa increases by up to 0.5–1 ppmv by 2100. This is less than implied directly by the temperature and methane increases, highlighting the correlation of tropopause temperatures with stratospheric water vapor, but also the complex nature of TTL transport.

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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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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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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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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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Revisiting the factors that drive interannual variability in stratospheric entry water vapour

10.5194/egusphere-egu2020-5231 ◽

2020 ◽

Author(s):

Shlomi Ziskin Ziv ◽

Chaim I. Garfinkel

Keyword(s):

Water Vapor ◽

Interannual Variability ◽

Large Scale ◽

Trace Gases ◽

Transport Processes ◽

Tropospheric Temperature ◽

Stratospheric Water Vapor ◽

Cold Point ◽

Stratospheric Trace Gases

Understanding the sinks, sources and transport processes of stratospheric trace gases can improve our prediction of mid to long term climate change. In this study we consider the processes that lead to variability in stratospheric water vapor. We perform a Multiple Linear Regression(MLR) on the SWOOSH combined anomaly filled water vapor product with ENSO, QBO, BDC, mid-tropospheric temperature, and CH4 as predictors, in an attempt to find the factors that most succinctly explain observed water vapor variability. We also consider the fraction of entry water vapor variability that can be accounted for by variations of the cold point temperature as an upper bound on how much water vapor variability is predictable from large scale processes. Several periods in which the MLR fails to account for interannual variability are treated as case studies in order to better understand variability in entry water not governed by these large scale processes.

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