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 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.

Water-vapor Measurements in the Lower Stratosphere

1974 ◽  
Vol 52 (8) ◽  
pp. 1527-1531 ◽  
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.

scholarly journals Simulation of stratospheric water vapor and trends using three reanalyses

2012 ◽  
Vol 12 (14) ◽  
pp. 6475-6487 ◽  
Author(s):  
M. R. Schoeberl ◽  
A. E. Dessler ◽  
T. Wang
Keyword(s):  
Water Vapor ◽  
Calculation Model ◽  
Vapor Concentration ◽  
The West ◽  
West Pacific ◽  
Stratospheric Water Vapor ◽  
Middle Latitudes ◽  
The Pacific ◽  
Northern High Latitude ◽  
Cold Point

Abstract. The domain-filling, forward trajectory calculation model developed by Schoeberl and Dessler (2011) is extended to the 1979–2010 period. We compare results from NASA's MERRA, NCEP's CFSR, and ECMWF's ERAi reanalyses with HALOE, MLS, and balloon observations. The CFSR based simulation produces a wetter stratosphere than MERRA, and ERAi produces a drier stratosphere than MERRA. We find that ERAi 100 hPa temperatures are cold biased compared to Singapore sondes and MERRA, which explains the ERAi result, and the CFSR grid does not resolve the cold point tropopause, which explains its relatively higher water vapor concentration. The pattern of dehydration locations is also different among the three reanalyses. ERAi dehydration pattern stretches across the Pacific while CFSR and MERRA concentrate dehydration activity in the West Pacific. CSFR and ERAi also show less dehydration activity in the West Pacific Southern Hemisphere than MERRA. The trajectory models' lower northern high latitude stratosphere tends to be dry because too little methane-derived water descends from the middle stratosphere. Using the MLS tropical tape recorder signal, we find that MERRA vertical ascent is 15% too weak while ERAi is 30% too strong. The trajectory model reproduces the observed reduction in the amplitude of the 100-hPa annual cycle in zonal mean water vapor as it propagates to middle latitudes. Finally, consistent with the observations, the models show less than 0.2 ppm decade−1 trend in water vapor both at mid-latitudes and in the tropics.

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 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 In situ observations of “cold trap" dehydration in the western tropical Pacific

2006 ◽  
Vol 6 (4) ◽  
pp. 6903-6931
Author(s):  
F. Hasebe ◽  
M. Fujiwara ◽  
N. Nishi ◽  
M. Shiotani ◽  
H. Vömel ◽  
...  
Keyword(s):  
Water Vapor ◽  
Trajectory Analysis ◽  
Cold Trap ◽  
Temperature History ◽  
Vapor Concentration ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
History Of ◽  
In Situ Observations

Abstract. Water vapor sonde observations were conducted at Bandung, Indonesia (6.90 S, 107.60 E) and Tarawa, Kiribati (1.35 N, 172.91 E) in December 2003 to examine the efficiency of the "cold trap'' dehydration in the tropical tropopause layer (TTL). Trajectory analysis based on bundles of trajectories suggest that the modification of air parcels' identity due to irreversible mixing by the branching-out and merging-in of nearby trajectories is found to be an important factor, in addition to the routes air parcels are supposed to follow, for interpreting the water vapor concentrations observed by radiosondes in the TTL. Clear correspondence between the observed water vapor concentration and the estimated temperature history of air parcels is found showing that dry air parcels are exposed to low temperatures while humid air parcels do not experience cold conditions during advection, in support of the "cold trap'' hypothesis. It is suggested that the observed air parcel retained the water vapor by roughly twice as much as the minimum saturation mixing ratio after its passage through the "cold trap,'' although appreciable uncertainties remain.

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 In situ observations of dehydrated air parcels advected horizontally in the Tropical Tropopause Layer of the western Pacific

2007 ◽  
Vol 7 (3) ◽  
pp. 803-813 ◽  
Author(s):  
F. Hasebe ◽  
M. Fujiwara ◽  
N. Nishi ◽  
M. Shiotani ◽  
H. Vömel ◽  
...  
Keyword(s):  
Water Vapor ◽  
Temperature History ◽  
Vapor Concentration ◽  
Tropical Tropopause Layer ◽  
Horizontal Advection ◽  
Tropical Tropopause ◽  
History Of ◽  
In Situ Observations ◽  
The Western Pacific

Abstract. Water vapor observations by chilled-mirror hygrometers were conducted at Bandung, Indonesia (6.90° S, 107.60° E) and Tarawa, Kiribati (1.35° N, 172.91° E) in December 2003 to examine the efficiency of dehydration during horizontal advection in the tropical tropopause layer (TTL). Trajectory analyses based on bundles of isentropic trajectories suggest that the modification of air parcels' identity due to irreversible mixing by the branching-out and merging-in of nearby trajectories is found to be an important factor, in addition to the routes air parcels follow, for interpreting the water vapor concentrations observed by chilled-mirror frostpoint hygrometers in the TTL. Clear correspondence between the observed water vapor concentration and the estimated temperature history of air parcels is found showing that drier air parcels were exposed to lower temperatures than were more humid ones during advection. Although the number of observations is quite limited, the water content in the observed air parcels on many occasions was more than that expected from the minimum saturation mixing ratio during horizontal advection prior to sonde observations.

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