scholarly journals Radiative Impacts of the 2011 Abrupt Drops in Water Vapor and Ozone in the Tropical Tropopause Layer

2016 ◽  
Vol 29 (2) ◽  
pp. 595-612 ◽  
Author(s):  
Daniel M. Gilford ◽  
Susan Solomon ◽  
Robert W. Portmann
Keyword(s):  
Water Vapor ◽  
Radiative Forcing ◽  
Tropical Tropopause Layer ◽  
Stratospheric Water Vapor ◽  
Tropical Tropopause ◽  
Radiative Impacts ◽  
Radiative Impact ◽  
Rf Values ◽  
Mean Structure ◽  
Large Water

Abstract An abrupt drop in tropical tropopause layer (TTL) water vapor, similar to that observed in 2000, recently occurred in 2011, and was concurrent with reductions in TTL temperature and ozone. Previous studies have indicated that such large water vapor variability can have significant radiative impacts. This study uses Aura Microwave Limb Sounder observations, the Stratospheric Water Vapor and Ozone Satellite Homogenized dataset, and two radiative transfer models to examine the radiative effects of the observed changes in TTL water vapor and ozone on TTL temperatures and global radiative forcing (RF). The analyses herein suggest that quasi-isentropic poleward propagation of TTL water vapor reductions results in a zonal-mean structure with “wings” of extratropical water vapor reductions, which account for about half of the 2011 abrupt drop global radiative impact. RF values associated with the mean water vapor concentrations differences between 2012/13 and 2010/11 are between −0.01 and −0.09 W m−2, depending upon the altitude above which perturbations are considered. TTL water vapor and ozone variability during this period jointly lead to a transient radiative cooling of ~0.25–0.5 K in layers below the tropopause. The 2011 abrupt drop also prolonged the reduction in stratospheric water vapor that followed the 2000 abrupt drop, providing a longer-term radiative forcing of climate. Water vapor concentrations from 2005 to 2013 are lower than those from 1990 to 1999, resulting in a RF between these periods of about −0.045 W m−2, approximately 12% as large as, but of opposite sign to, the concurrent estimated CO2 forcing.

scholarly journals Modeling upper tropospheric and lower stratospheric water vapor anomalies

2013 ◽  
Vol 13 (4) ◽  
pp. 9653-9679 ◽  
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.

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

2015 ◽  
Vol 15 (6) ◽  
pp. 3517-3526 ◽  
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.

scholarly journals The relationship between tropospheric wave forcing and tropical lower stratospheric water vapor

2006 ◽  
Vol 6 (5) ◽  
pp. 9563-9581 ◽  
Author(s):  
S. Dhomse ◽  
M. Weber ◽  
J. Burrows
Keyword(s):  
Heat Flux ◽  
Water Vapor ◽  
Planetary Wave ◽  
Wave Activity ◽  
Data Sets ◽  
Tropical Tropopause Layer ◽  
Stratospheric Water Vapor ◽  
Tropical Tropopause ◽  
Eddy Heat Flux ◽  
Sudden Decrease

Abstract. The compact relationship between stratospheric temperatures (as well as ozone) and tropospheric generated planetary wave activity have been widely discussed. Higher wave activity leads to a strengthening of the Brewer-Dobson (BD) circulation, which results in warmer/colder temperatures in the polar/tropical stratosphere. The influence of this wave activity on stratospheric water vapor (WV) is not yet well explored primarily due to lack of high quality long term data sets. Using WV data from HALOE and SAGE II, an anti-correlation between planetary wave driving (here expressed by the mid-latitude eddy heat flux at 50 hPa added from both hemispheres) and tropical lower stratospheric (TLS) WV has been found. This appears to be the most direct manifestation of the inter-annual variability of the known relationship between ascending motion in the tropical stratosphere (due to rising branch of the BD circulation) and the amount of the WV entering into the stratosphere from the tropical tropopause layer. A decrease in planetary wave activity in the mid-nineties is probably responsible for the increasing trends in stratospheric WV until late 1990s. After 2000 a sudden decrease in lower stratospheric WV has been reported and was observed by different satellite instruments such as HALOE, SAGE II and POAM III indicating that the lower stratosphere has become drier since then. This is consistent with a sudden rise in the combined mid-latitude eddy heat flux with nearly equal contribution from both hemispheres. The low water vapor and enhanced strength of the Brewer-Dobson circulation has persisted until now. It is estimated that the strengthening of the BD circulation after 2000 contributed to a 0.7 K cooling in the TLS.

scholarly journals Contribution of different processes to changes in tropical lower-stratospheric water vapor in chemistry–climate models

2017 ◽  
Vol 17 (13) ◽  
pp. 8031-8044 ◽  
Author(s):  
Kevin M. Smalley ◽  
Andrew E. Dessler ◽  
Slimane Bekki ◽  
Makoto Deushi ◽  
Marion Marchand ◽  
...  
Keyword(s):  
Water Vapor ◽  
Regression Model ◽  
21St Century ◽  
Climate Models ◽  
Quasi Biennial Oscillation ◽  
Tropical Tropopause Layer ◽  
Stratospheric Water Vapor ◽  
Tropical Tropopause ◽  
The Impact

Abstract. Variations in tropical lower-stratospheric humidity influence both the chemistry and climate of the atmosphere. We analyze tropical lower-stratospheric water vapor in 21st century simulations from 12 state-of-the-art chemistry–climate models (CCMs), using a linear regression model to determine the factors driving the trends and variability. Within CCMs, warming of the troposphere primarily drives the long-term trend in stratospheric humidity. This is partially offset in most CCMs by an increase in the strength of the Brewer–Dobson circulation, which tends to cool the tropical tropopause layer (TTL). We also apply the regression model to individual decades from the 21st century CCM runs and compare them to a regression of a decade of observations. Many of the CCMs, but not all, compare well with these observations, lending credibility to their predictions. One notable deficiency is that most CCMs underestimate the impact of the quasi-biennial oscillation on lower-stratospheric water vapor. Our analysis provides a new and potentially superior way to evaluate model trends in lower-stratospheric humidity.

scholarly journals Coordinated Upper-Troposphere-to-Stratosphere Balloon Experiment in Biak

2018 ◽  
Vol 99 (6) ◽  
pp. 1213-1230 ◽  
Author(s):  
F. Hasebe ◽  
S. Aoki ◽  
S. Morimoto ◽  
Y. Inai ◽  
T. Nakazawa ◽  
...  
Keyword(s):  
Water Vapor ◽  
Climate Models ◽  
Turnover Time ◽  
Tape Recorder ◽  
Climate Forcing ◽  
Upper Troposphere ◽  
Tropical Tropopause Layer ◽  
Stratospheric Water Vapor ◽  
Tropical Tropopause ◽  
Balloon Experiment

AbstractThe stratospheric response to climate forcing, such as an increase in greenhouse gases, is often unpredictable because of interactions between radiation, dynamics, and chemistry. Climate models are unsuccessful in simulating the realistic distribution of stratospheric water vapor. The long-term trend of the stratospheric age of air (AoA), a measure that characterizes the stratospheric turnover time, remains inconsistent between diagnoses in climate models and estimates from tracer observations. For these reasons, observations designed specifically to distinguish the effects of individual contributing processes are required. Here, we report on the Coordinated Upper-Troposphere-to-Stratosphere Balloon Experiment in Biak (CUBE/Biak), an observation campaign organized in Indonesia. Being inside the “tropical pipe” makes it possible to study the dehydration in the tropical tropopause layer and the gradual ascent in the stratosphere while minimizing the effects of multiple circulation pathways and wave mixing. Cryogenic sampling of minor constituents and major isotopes was conducted simultaneously with radiosonde observations of water vapor, ozone, aerosols, and cloud particles. The water vapor “tape recorder,” gravitational separation, and isotopocules are being studied in conjunction with tracers that are accumulated in the atmosphere as dynamical and chemical measures of elapsed time since stratospheric air entry. The observational estimates concerning the AoA and water vapor tape recorder are compared with those derived from trajectory calculations.

scholarly journals Modeling upper tropospheric and lower stratospheric water vapor anomalies

2013 ◽  
Vol 13 (15) ◽  
pp. 7783-7793 ◽  
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 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 due to 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 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 in 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.

scholarly journals The Tropical Tropopause Layer 1960–2100

2009 ◽  
Vol 9 (5) ◽  
pp. 1621-1637 ◽  
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.

scholarly journals The Tropical Tropopause Layer 1960–2100

2008 ◽  
Vol 8 (1) ◽  
pp. 1367-1413 ◽  
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.

scholarly journals Effect of deep convection on the tropical tropopause layer composition over the southwest Indian Ocean during austral summer

2020 ◽  
Vol 20 (17) ◽  
pp. 10565-10586
Author(s):  
Stephanie Evan ◽  
Jerome Brioude ◽  
Karen Rosenlof ◽  
Sean M. Davis ◽  
Holger Vömel ◽  
...  
Keyword(s):  
Water Vapor ◽  
Indian Ocean ◽  
Tropical Cyclones ◽  
Austral Summer ◽  
Lagrangian Model ◽  
Southwest Indian Ocean ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Tropopause Region ◽  
The Impact

Abstract. Balloon-borne measurements of cryogenic frost-point hygrometer (CFH) water vapor, ozone and temperature and water vapor lidar measurements from the Maïdo Observatory on Réunion Island in the southwest Indian Ocean (SWIO) were used to study tropical cyclones' influence on tropical tropopause layer (TTL) composition. The balloon launches were specifically planned using a Lagrangian model and Meteosat-7 infrared images to sample the convective outflow from tropical storm (TS) Corentin on 25 January 2016 and tropical cyclone (TC) Enawo on 3 March 2017. Comparing the CFH profile to Aura's Microwave Limb Sounder's (MLS) monthly climatologies, water vapor anomalies were identified. Positive anomalies of water vapor and temperature, and negative anomalies of ozone between 12 and 15 km in altitude (247 to 121 hPa), originated from convectively active regions of TS Corentin and TC Enawo 1 d before the planned balloon launches according to the Lagrangian trajectories. Near the tropopause region, air masses on 25 January 2016 were anomalously dry around 100 hPa and were traced back to TS Corentin's active convective region where cirrus clouds and deep convective clouds may have dried the layer. An anomalously wet layer around 68 hPa was traced back to the southeast Indian Ocean where a monthly water vapor anomaly of 0.5 ppmv was observed. In contrast, no water vapor anomaly was found near or above the tropopause region on 3 March 2017 over Maïdo as the tropopause region was not downwind of TC Enawo. This study compares and contrasts the impact of two tropical cyclones on the humidification of the TTL over the SWIO. It also demonstrates the need for accurate balloon-borne measurements of water vapor, ozone and aerosols in regions where TTL in situ observations are sparse.

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

2015 ◽  
Vol 28 (16) ◽  
pp. 6516-6535 ◽  
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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