Age and gravitational separation of the stratospheric  air over Indonesia

Abstract. The gravitational separation of major atmospheric components, in addition to the age of air, would provide additional useful information about stratospheric circulation. However, observations of the age of air and gravitational separation are still geographically sparse, especially in the tropics. In order to address this issue, air samples were collected over Biak, Indonesia in February 2015 using four large plastic balloons, each loaded with two compact cryogenic samplers. With a vertical resolution of better than 2 km, air samples from seven different altitudes were analyzed for CO2 and SF6 mole fractions, δ15N of N2, δ18O of O2, and δ(Ar∕N2) to examine the vertically dependent age and gravitational separation of air in the tropical tropopause layer (TTL) and the equatorial stratosphere. By comparing their measured mole fractions with aircraft observations in the upper tropical troposphere, we have found that CO2 and SF6 ages increase gradually with increasing altitude from the TTL to 22 km, and then rapidly from there up to 29 km. The CO2 and SF6 ages agree well with each other in the TTL and in the lower stratosphere, but show a significant difference above 24 km. The average values of δ15N of N2, δ18O of O2, and δ(Ar∕N2) all show a small but distinct upward decrease due to the gravitational separation effect. Simulations with a two-dimensional atmospheric transport model indicate that the gravitational separation effect decreases as tropical upwelling is enhanced. From the model calculations with enhanced eddy mixing, it is also found that the upward increase in air age is magnified by horizontal mixing. These model simulations also show that the gravitational separation effect remains relatively constant in the lower stratosphere. The results of this study strongly suggest that the gravitational separation, combined with the age of air, can be used to diagnose air transport processes in the stratosphere.

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Age and gravitational separation of the stratospheric air over Indonesia

10.5194/acp-2017-583 ◽

2017 ◽

Cited By ~ 1

Author(s):

Satoshi Sugawara ◽

Shigeyuki Ishidoya ◽

Shuji Aoki ◽

Shinji Morimoto ◽

Takakiyo Nakazawa ◽

...

Keyword(s):

Lower Stratosphere ◽

Transport Model ◽

Atmospheric Transport ◽

Transport Processes ◽

Model Calculations ◽

Separation Effect ◽

Air Samples ◽

Tropical Tropopause Layer ◽

Tropical Tropopause ◽

Significant Difference

Abstract. Stratospheric air samples were collected over Biak, Indonesia in February 2015 using four large plastic balloons, each loaded with two compact cryogenic samplers. With a vertical resolution of better than 2 km, air samples from seven different altitudes were analyzed for CO2 and SF6 mole fractions, δ15N of N2, δ18O of O2, and δ(Ar/N2), to examine vertically dependent age and gravitational separation of air in the Tropical Tropopause Layer (TTL) and the equatorial stratosphere. By comparing their measured mole fractions with aircraft observation in the upper tropical troposphere, we have found that CO2 and SF6 age increases gradually with increasing altitude from the TTL to 22 km, and then rapidly from there up to 25 km. The CO2 and SF6 age agrees well with each other in the TTL and in the lower stratosphere, but shows a significant difference above 24 km. The average values of δ15N of N2, δ18O of O2, and δ(Ar/N2) all show small but distinct upward decrease due to the gravitational separation effect. Simulations with a two-dimensional atmospheric transport model indicate that the gravitational separation effect decreases as tropical upwelling is enhanced. From the model calculations with enhanced eddy mixing, it is also found that the upward increase in air age is magnified by horizontal mixing. These model simulations also show that the gravitational separation effect remains relatively constant in the lower stratosphere. The results of this study strongly suggest that the gravitational separation, combined with the age of air, can be used to diagnose air transport processes in the stratosphere.

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The impact of overshooting deep convection on local transport and mixing in the tropical upper troposphere/lower stratosphere (UTLS)

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-6467-2015 ◽

2015 ◽

Vol 15 (11) ◽

pp. 6467-6486 ◽

Cited By ~ 21

Author(s):

W. Frey ◽

R. Schofield ◽

P. Hoor ◽

D. Kunkel ◽

F. Ravegnani ◽

...

Keyword(s):

Lower Stratosphere ◽

Deep Convection ◽

Horizontal Resolution ◽

Transport Processes ◽

Convective System ◽

Upper Troposphere ◽

Tropical Tropopause Layer ◽

Tropical Tropopause ◽

Transport And Mixing ◽

The Impact

Abstract. In this study we examine the simulated downward transport and mixing of stratospheric air into the upper tropical troposphere as observed on a research flight during the SCOUT-O3 campaign in connection with a deep convective system. We use the Advanced Research Weather and Research Forecasting (WRF-ARW) model with a horizontal resolution of 333 m to examine this downward transport. The simulation reproduces the deep convective system, its timing and overshooting altitudes reasonably well compared to radar and aircraft observations. Passive tracers initialised at pre-storm times indicate the downward transport of air from the stratosphere to the upper troposphere as well as upward transport from the boundary layer into the cloud anvils and overshooting tops. For example, a passive ozone tracer (i.e. a tracer not undergoing chemical processing) shows an enhancement in the upper troposphere of up to about 30 ppbv locally in the cloud, while the in situ measurements show an increase of 50 ppbv. However, the passive carbon monoxide tracer exhibits an increase, while the observations show a decrease of about 10 ppbv, indicative of an erroneous model representation of the transport processes in the tropical tropopause layer. Furthermore, it could point to insufficient entrainment and detrainment in the model. The simulation shows a general moistening of air in the lower stratosphere, but it also exhibits local dehydration features. Here we use the model to explain the processes causing the transport and also expose areas of inconsistencies between the model and observations.

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Transport of short-lived halocarbons to the stratosphere over the Pacific Ocean

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-1163-2020 ◽

2020 ◽

Vol 20 (2) ◽

pp. 1163-1181

Author(s):

Michal T. Filus ◽

Elliot L. Atlas ◽

Maria A. Navarro ◽

Elena Meneguz ◽

David Thomson ◽

...

Keyword(s):

Boundary Layer ◽

Lower Stratosphere ◽

Atmospheric Transport ◽

Convective Transport ◽

Transport Processes ◽

Lagrangian Model ◽

Convection Scheme ◽

Model Calculations ◽

Upper Troposphere ◽

Tropical Troposphere

Abstract. The effectiveness of transport of short-lived halocarbons to the upper troposphere and lower stratosphere remains an important uncertainty in quantifying the supply of ozone-depleting substances to the stratosphere. In early 2014, a major field campaign in Guam in the western Pacific, involving UK and US research aircraft, sampled the tropical troposphere and lower stratosphere. The resulting measurements of CH3I, CHBr3 and CH2Br2 are compared here with calculations from a Lagrangian model. This methodology benefits from an updated convection scheme that improves simulation of the effect of deep convective motions on particle distribution within the tropical troposphere. We find that the observed CH3I, CHBr3 and CH2Br2 mixing ratios in the tropical tropopause layer (TTL) are consistent with those in the boundary layer when the new convection scheme is used to account for convective transport. More specifically, comparisons between modelled estimates and observations of short-lived CH3I indicate that the updated convection scheme is realistic up to the lower TTL but is less good at reproducing the small number of extreme convective events in the upper TTL. This study consolidates our understanding of the transport of short-lived halocarbons to the upper troposphere and lower stratosphere by using improved model calculations to confirm consistency between observations in the boundary layer, observations in the TTL and atmospheric transport processes. Our results support recent estimates of the contribution of short-lived bromocarbons to the stratospheric bromine budget.

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Regionally Resolved Diagnostic of Transport: A Simplified Forward Model for CO2

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-16-0367.1 ◽

2017 ◽

Vol 74 (8) ◽

pp. 2689-2700 ◽

Cited By ~ 2

Author(s):

Paul Konopka ◽

Felix Ploeger ◽

Mengchu Tao ◽

Martin Riese

Keyword(s):

Transport Model ◽

Lower Boundary ◽

Transport Processes ◽

Diagnostic Tools ◽

Transport Models ◽

Lower Boundary Condition ◽

Tropical Tropopause Layer ◽

Tropical Tropopause ◽

Combined Use ◽

Complex Chemistry

Abstract Simply diagnostic tools are useful for understanding transport processes in complex chemistry transport models (CTMs). For this purpose, a combined use of the airmass origin fractions (AOFs) and regionally resolved mean ages (RMAs) is presented. This approach merges the concept of the origin of air with the well-known theory of the mean age of air (AoA) for different regions covering the whole Earth. The authors show how the AoA calculated relative to Earth’s surface can be decomposed into regionally resolved components (i.e., into RMAs). Using both AOFs and RMAs, the authors discuss differences in the seasonality of transport from the Northern and Southern Hemispheres into the tropical tropopause layer (TTL), the asymmetries of the interhemispheric exchange, and differences in relation to the continental or oceanic origin of air. Furthermore, a simplified transport model for a chemically passive species (tracer) is formulated that has some potential to approximate the full transport within a CTM. This analytic approach uses the AOFs as well as the RMAs as parameters to propagate a tracer prescribed on Earth’s surface (lower boundary condition). This method is exactly valid for sources that change linearly with time in each of the considered regions. The authors analyze how well this approach approximates the propagation of CO2 from the planetary boundary layer (PBL) into the whole atmosphere. The CO2 values in the PBL are specified by the CarbonTracker dataset. The authors discuss how this approach can be used for inverse modeling of CO2.

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The impact of overshooting deep convection on local transport and mixing in the tropical upper troposphere/lower stratosphere (UTLS)

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-1041-2015 ◽

2015 ◽

Vol 15 (1) ◽

pp. 1041-1091 ◽

Cited By ~ 1

Author(s):

W. Frey ◽

R. Schofield ◽

P. Hoor ◽

D. Kunkel ◽

F. Ravegnani ◽

...

Keyword(s):

Lower Stratosphere ◽

Deep Convection ◽

Horizontal Resolution ◽

Transport Processes ◽

Convective System ◽

Upper Troposphere ◽

Tropical Tropopause Layer ◽

Tropical Tropopause ◽

Transport And Mixing ◽

The Impact

Abstract. In this study we examine the simulated downward transport and mixing of stratospheric air into the upper tropical troposphere as observed on a research flight during the SCOUT-O3 campaign in connection to a deep convective system. We use the Advanced Research Weather and Research Forecasting (WRF-ARW) model with a horizontal resolution of 333 m to examine this downward transport. The simulation reproduces the deep convective system, its timing and overshooting altitudes reasonably well compared to radar and aircraft observations. Passive tracers initialised at pre-storm times indicate the downward transport of air from the stratosphere to the upper troposphere as well as upward transport from the boundary layer into the cloud anvils and overshooting tops. For example, a passive ozone tracer (i.e. a tracer not undergoing chemical processing) shows an enhancement in the upper troposphere of up to about 30 ppbv locally in the cloud, while the in situ measurements show an increase of 50 ppbv. However, the passive carbon monoxide tracer exhibits an increase, while the observations show a decrease of about 10 ppbv, indicative of an erroneous model representation of the transport processes in the tropical tropopause layer. Furthermore, it could point to insufficient entrainment and detrainment in the model. The simulation shows a general moistening of air in the lower stratosphere but it also exhibits local dehydration features. Here we use the model to explain the processes causing the transport and also expose areas of inconsistencies between the model and observations.

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Transport of short-lived halocarbons to the stratosphere over the Pacific Ocean

10.5194/acp-2018-640 ◽

2018 ◽

Author(s):

Michal T. Filus ◽

Elliot L. Atlas ◽

Maria A. Navarro ◽

Elena Meneguz ◽

David Thomson ◽

...

Keyword(s):

Boundary Layer ◽

Lower Stratosphere ◽

Atmospheric Transport ◽

Convective Transport ◽

Transport Processes ◽

Lagrangian Model ◽

Convection Scheme ◽

Model Calculations ◽

Upper Troposphere ◽

Tropical Troposphere

Abstract. The effectiveness of transport of short-lived halocarbons to the upper troposphere and lower stratosphere remains an important unknown in quantifying the supply of ozone-depleting substances to the stratosphere. In early 2014, a major field campaign in Guam in the West Pacific, involving UK and US research aircraft, sampled the tropical troposphere and lower stratosphere. The resulting measurements of CH3I, CHBr3 and CH2Br2 are compared here with calculations from a Lagrangian model. This methodology benefits from an updated convection scheme which improves simulation of the effect of deep convective motions on particle distribution within the tropical troposphere. We find that the observed CH3I, CHBr3 and CH2Br2 mixing ratios in the Tropical Tropopause Layer (TTL) are consistent with those in the boundary layer when the new convection scheme is used to account for convective transport. Particularly, comparisons between modelled estimates and observations of shortest-lived CH3I indicates that the NAME convection scheme is realistic up to the lower TTL but less good at reproducing the small number of extreme convective events in the upper TTL. This study consolidates our understanding of the transport of short-lived halocarbons to the upper troposphere and lower stratosphere by using improved model calculations to confirm consistency between observations in the boundary layer, observations in the TTL, and atmospheric transport processes. Our results support recent estimates of the contribution of short-lived bromocarbons to the stratospheric bromine budget.

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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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Modeling the transport of very short-lived substances into the tropical upper troposphere and lower stratosphere

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-9-18511-2009 ◽

2009 ◽

Vol 9 (5) ◽

pp. 18511-18543 ◽

Cited By ~ 2

Author(s):

J. Aschmann ◽

B. M. Sinnhuber ◽

E. L. Atlas ◽

S. M. Schauffler

Keyword(s):

Large Scale ◽

Lower Stratosphere ◽

Transport Model ◽

Three Dimensional ◽

Chemical Transport Model ◽

Heating Rates ◽

Model Calculations ◽

Upper Troposphere ◽

Mass Fluxes ◽

Tropical Upper Troposphere

Abstract. The transport of very short-lived substances into the tropical upper troposphere and lower stratosphere is investigated by a three-dimensional chemical transport model using archived convective updraft mass fluxes (or detrainment rates) from the European Centre for Medium-Range Weather Forecast's ERA-Interim reanalysis. Large-scale vertical velocities are calculated from diabatic heating rates. With this approach we explicitly model the large scale subsidence in the tropical troposphere with convection taking place in fast and isolated updraft events. The model calculations agree generally well with observations of bromoform and methyl iodide from aircraft campaigns and with ozone and water vapor from sonde and satellite observations. Using a simplified treatment of dehydration and bromine product gas washout we give a range of 1.6 to 3 ppt for the contribution of bromoform to stratospheric bromine, assuming a uniform source in the boundary layer of 1 ppt. We show that the most effective region for VSLS transport into the stratosphere is the West Pacific, accounting for about 55% of the bromine from bromoform transported into the stratosphere under the supposition of a uniformly distributed source.

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Effect of tropical cyclones on the tropical tropopause parameters observed using COSMIC GPS RO data

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-10239-2015 ◽

2015 ◽

Vol 15 (18) ◽

pp. 10239-10249 ◽

Cited By ~ 10

Author(s):

S. Ravindra Babu ◽

M. Venkat Ratnam ◽

G. Basha ◽

B. V. Krishnamurthy ◽

B. Venkateswararao

Keyword(s):

Tropical Cyclones ◽

Lower Stratosphere ◽

Thermal Structure ◽

Radial Distance ◽

Lapse Rate ◽

Tropical Tropopause Layer ◽

Water Vapour Transport ◽

Tropical Tropopause ◽

High Vertical Resolution ◽

Cold Point

Abstract. Tropical cyclones (TCs) are deep convective synoptic-scale systems that play an important role in modifying the thermal structure, tropical tropopause parameters and hence also modify stratosphere–troposphere exchange (STE) processes. In the present study, high vertical resolution and high accuracy measurements from COSMIC Global Positioning System (GPS) radio occultation (RO) measurements are used to investigate and quantify the effect of tropical cyclones that occurred over Bay of Bengal and Arabian Sea in the last decade on the tropical tropopause parameters. The tropopause parameters include cold-point tropopause altitude (CPH) and temperature (CPT), lapse-rate tropopause altitude (LRH) and temperature (LRT) and the thickness of the tropical tropopause layer (TTL), that is defined as the layer between convective outflow level (COH) and CPH, obtained from GPS RO data. From all the TC events, we generate the mean cyclone-centred composite structure for the tropopause parameters and removed it from the climatological mean obtained from averaging the GPS RO data from 2002 to 2013. Since the TCs include eye, eye walls and deep convective bands, we obtained the tropopause parameters based on radial distance from the cyclone eye. In general, decrease in the CPH in the eye is noticed as expected. However, as the distance from the cyclone eye increases by 300, 400, and 500 km, an enhancement in CPH (CPT) and LRH (LRT) is observed. Lowering of CPH (0.6 km) and LRH (0.4 km) values with coldest CPT and LRT (2–3 K) within a 500 km radius of the TC centre is noticed. Higher (2 km) COH leading to the lowering of TTL thickness (2–3 km) is clearly observed. There are multiple tropopause structures in the profiles of temperature obtained within 100 km from the centre of the TC. These changes in the tropopause parameters are expected to influence the water vapour transport from the troposphere to the lower stratosphere, and ozone from the lower stratosphere to the upper troposphere, hence influencing STE processes.

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Impact of tropical tropopause layer cooling trend on extreme deep convection in Asian-African sector

10.5194/egusphere-egu21-9359 ◽

2021 ◽

Author(s):

Kunihiko Kodera ◽

Nawo Eguchi ◽

Rei Ueyama ◽

Beatriz Funatsu ◽

Marco Gaetani ◽

...

Keyword(s):

Lower Stratosphere ◽

Essential Feature ◽

Deep Convection ◽

Boreal Summer ◽

Surface Precipitation ◽

Tropical Tropopause Layer ◽

Tropical Tropopause ◽

Extreme Precipitation Events ◽

Cooling Trend ◽

Sahel Region

<p>Previous studies have suggested that the recent increase in tropical extreme deep convection, in particular over Asia and Africa during the boreal summer, has occurred in association with a cooling in the tropical lower stratosphere. The present study is focused on the Sahel region of West Africa, where an increased occurrence of extreme precipitation events has been reported over recent decades. The results show that the changes since the 1980s involve a cooling trend in the tropical lower stratosphere and tropopause layer, combined with a warming in the troposphere. This feature is similar to that which might result from increased greenhouse gas levels. It is suggested that the decrease in the vertical temperature gradient in the tropical tropopause region enhances extreme deep convection where penetrating convection is frequent, whereas tropospheric warming suppresses the shallower convection. The essential feature of the recent changes over the tropics is therefore the depth of convection, rather than the total amount of surface precipitation. This could enhance cooling in the lower stratosphere through decrease in ozone concentration.</p><p>&#160;</p>

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