scholarly journals Variability in upwelling across the tropical tropopause and correlations with tracers in the lower stratosphere

2012 ◽  
Vol 12 (7) ◽  
pp. 18817-18851 ◽  
Author(s):  
M. Abalos ◽  
W. J. Randel ◽  
E. Serrano
Keyword(s):  
Time Series ◽  
Temporal Variability ◽  
Seasonal Cycle ◽  
Strong Influence ◽  
Lower Stratosphere ◽  
Momentum Balance ◽  
Annual Cycles ◽  
Tropical Tropopause ◽  
Vertical Gradients ◽  
Good Agreement

Abstract. Temporal variability of the upwelling near the tropical tropopause on daily to annual timescales is investigated using three different estimates computed from the ERA-Interim reanalysis. These include upwelling archived by the reanalysis, plus estimates derived from thermodynamic and momentum balance calculations. Substantial variability in upwelling is observed on both seasonal and sub-seasonal time scales, and the three estimates show reasonably good agreement. Tropical upwelling should exert strong influence on temperatures and on tracers with large vertical gradients in the lower stratosphere. We test this behavior by comparing the calculated upwelling estimates with observed temperatures in the tropical lower stratosphere, and with measurements of ozone and carbon monoxide (CO) from the Aura Microwave Limb Sounder (MLS) satellite instrument. Time series of temperature, ozone and CO are well correlated in the tropical lower stratosphere, and we quantify the influence of tropical upwelling on this joint variability. Strong coherent annual cycles observed in each quantity are found to reflect the seasonal cycle in upwelling. Statistically significant correlations between upwelling, temperatures and tracers are also found for sub-seasonal timescales, demonstrating the importance of upwelling in forcing transient variability in the lower tropical stratosphere.

scholarly journals Variability in upwelling across the tropical tropopause and correlations with tracers in the lower stratosphere

2012 ◽  
Vol 12 (23) ◽  
pp. 11505-11517 ◽  
Author(s):  
M. Abalos ◽  
W. J. Randel ◽  
E. Serrano
Keyword(s):  
Time Series ◽  
Temporal Variability ◽  
Seasonal Cycle ◽  
Strong Influence ◽  
Lower Stratosphere ◽  
Momentum Balance ◽  
Annual Cycles ◽  
Tropical Tropopause ◽  
Vertical Gradients ◽  
Good Agreement

Abstract. Temporal variability of the upwelling near the tropical tropopause on daily to annual timescales is investigated using three different estimates computed from the ERA-Interim reanalysis. These include upwelling archived by the reanalysis, plus estimates derived from thermodynamic and momentum balance calculations. Substantial variability in upwelling is observed on both seasonal and sub-seasonal timescales, and the three estimates show reasonably good agreement. Tropical upwelling should exert strong influence on temperatures and on tracers with large vertical gradients in the lower stratosphere. We test this behavior by comparing the calculated upwelling estimates with observed temperatures in the tropical lower stratosphere, and with measurements of ozone and carbon monoxide (CO) from the Aura Microwave Limb Sounder (MLS) satellite instrument. Time series of temperature, ozone and CO are well correlated in the tropical lower stratosphere, and we quantify the influence of tropical upwelling on this joint variability. Strong coherent annual cycles observed in each quantity are found to reflect the seasonal cycle in upwelling. Statistically significant correlations between upwelling, temperatures and tracers are also found for sub-seasonal timescales, demonstrating the importance of upwelling in forcing transient variability in the lower tropical stratosphere.

A Large Annual Cycle in Ozone above the Tropical Tropopause Linked to the Brewer–Dobson Circulation

2007 ◽  
Vol 64 (12) ◽  
pp. 4479-4488 ◽  
Author(s):  
William J. Randel ◽  
Mijeong Park ◽  
Fei Wu ◽  
Nathaniel Livesey
Keyword(s):  
Annual Cycle ◽  
Seasonal Cycle ◽  
Annual Variation ◽  
Lower Stratosphere ◽  
Vertical Gradient ◽  
Relative Amplitude ◽  
Vertical Layer ◽  
Satellite Measurements ◽  
Tropical Tropopause ◽  
Vertical Gradients

Abstract Near-equatorial ozone observations from balloon and satellite measurements reveal a large annual cycle in ozone above the tropical tropopause. The relative amplitude of the annual cycle is large in a narrow vertical layer between ∼16 and 19 km, with approximately a factor of 2 change in ozone between the minimum (during NH winter) and maximum (during NH summer). The annual cycle in ozone occurs over the same altitude region, and is approximately in phase with the well-known annual variation in tropical temperature. This study shows that the large annual variation in ozone occurs primarily because of variations in vertical transport associated with mean upwelling in the lower stratosphere (the Brewer–Dobson circulation); the maximum relative amplitude peak in the lower stratosphere is collocated with the strongest background vertical gradients in ozone. A similar large seasonal cycle is observed in carbon monoxide (CO) above the tropical tropopause, which is approximately out of phase with ozone (associated with an oppositely signed vertical gradient). The observed ozone and CO variations can be used to constrain estimates of the seasonal cycle in tropical upwelling.

Dynamical Balances and Tropical Stratospheric Upwelling

2008 ◽  
Vol 65 (11) ◽  
pp. 3584-3595 ◽  
Author(s):  
William J. Randel ◽  
Rolando Garcia ◽  
Fei Wu
Keyword(s):  
Seasonal Cycle ◽  
Significant Contribution ◽  
Lower Stratosphere ◽  
Reanalysis Data ◽  
Planetary Waves ◽  
Momentum Balance ◽  
Flux Divergence ◽  
Large Component ◽  
Tropical Tropopause ◽  
The Tropics

Abstract The dynamical balances associated with upwelling in the tropical lower stratosphere are investigated based on climatological 40-yr ECMWF Re-Analysis (ERA-40) and NCEP–NCAR reanalysis data. Zonal mean upwelling is calculated from momentum balance and continuity (“downward control”), and these estimates in the deep tropics are found to be in reasonable agreement with stratospheric upwelling calculated from thermodynamic balance (and also with vertical velocity obtained from ERA-40). The detailed momentum balances associated with the dynamical upwelling are investigated, particularly the contributions to climatological Eliassen–Palm (EP) flux divergence in the subtropics. Results show that the equatorward extension of extratropical waves (baroclinic eddies and, in the NH, quasi-stationary planetary waves) contribute a large component of the subtropical wave driving at 100 hPa. Additionally, there is a significant contribution to subtropical forcing from equatorial planetary waves, which exhibit a strong seasonal cycle (a reversal in phase) in response to latitudinal migration of tropical convection. The observed balances suggest that the strong annual cycle in upwelling across the tropical tropopause is forced by subtropical horizontal eddy momentum flux convergence associated with waves originating in both the tropics and extratropics.

scholarly journals Quantifying tracer transport in the tropical lower stratosphere using WACCM

2013 ◽  
Vol 13 (5) ◽  
pp. 13245-13283 ◽  
Author(s):  
M. Abalos ◽  
W. J. Randel ◽  
D. E. Kinnison ◽  
E. Serrano
Keyword(s):  
Lower Stratosphere ◽  
Climate Model ◽  
Latitudinal Gradients ◽  
Explicit Calculation ◽  
Boreal Summer ◽  
Tracer Transport ◽  
Annual Cycles ◽  
Tropical Tropopause ◽  
Eddy Transport ◽  
Isentropic Coordinates

Abstract. The zonal mean transport of ozone and carbon monoxide (CO) near the tropical tropopause is investigated using the Whole-Atmosphere Community Climate Model version 4 (WACCM4). The variability in temperature, ozone and CO in the model shows good agreement with satellite and balloon observations. Modeled temperature and tracers exhibit large and closely coupled annual cycles in the tropical lower stratosphere, as in the observations. The thermodynamic and tracer budgets in the model are analyzed based on the Transformed Eulerian Mean (TEM) framework on log-pressure coordinates and also using the isentropic formulation. Results show that the coupled seasonal cycles are mainly forced by tropical upwelling over altitudes with large vertical tracer gradients, in agreement with previous observational studies. The model also allows explicit calculation of eddy transport terms, which make an important contribution to ozone tendencies in the tropical lower stratosphere. The character of the eddy fluxes changes with altitude. At higher levels (~2 km above the cold point tropopause), isentropic eddy transport occurs during winter and spring in each hemisphere in the sub-tropics, associated with transient Rossby waves acting on strong background latitudinal gradients. At lower altitudes, close to the tropical tropopause, there is a maximum in horizontal eddy transport during boreal summer associated with the Asian monsoon anticyclone. Sub-seasonal variability in ozone and CO, tied to fluctuations in temperature, is primarily driven by transient tropical upwelling. In isentropic coordinates, the overall tracer budgets are similar to the log-pressure results, highlighting cross-isentropic mean advection as the main term in the balance. However, in isentropic coordinates the tracer variability is largely reduced on both seasonal and sub-seasonal timescales, because the tracer and temperature fluctuations are highly correlated (as a response to upwelling).

Dynamical Forcing of Subseasonal Variability in the Tropical Brewer–Dobson Circulation

2014 ◽  
Vol 71 (9) ◽  
pp. 3439-3453 ◽  
Author(s):  
Marta Abalos ◽  
William J. Randel ◽  
Encarna Serrano
Keyword(s):  
Lower Stratosphere ◽  
Momentum Balance ◽  
Strongly Correlated ◽  
Temperature Changes ◽  
Upper Troposphere ◽  
Weather Forecasts ◽  
Wave Forcing ◽  
Tropical Tropopause ◽  
Subseasonal Variability ◽  
Medium Range

Abstract Upwelling across the tropical tropopause exhibits strong subseasonal variability superimposed on the well-known annual cycle, and these variations directly affect temperature and tracers in the tropical lower stratosphere. In this work, the dynamical forcing of tropical upwelling on subseasonal time scales is investigated using the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Re-Analysis (ERA-Interim) for 1979–2011. Momentum balance diagnostics reveal that transience in lower-stratospheric upwelling is linked to the effects of extratropical wave forcing, with centers of action in the extratropical winter stratosphere and in the subtropical upper troposphere of both hemispheres. The time-dependent forcing in these regions induces a remote coupled response in the zonal mean wind and the meridional circulation (with associated temperature changes), which drives upwelling variability in the tropical stratosphere. This behavior is observed in the reanalysis, consistent with theory. Dynamical patterns reflect distinctive forcing of the shallow versus deep branches of the Brewer–Dobson circulation; the shallow branch is most strongly correlated with wave forcing in the subtropical upper troposphere and lower stratosphere, while the deep branch is mainly influenced by high-latitude planetary waves.

scholarly journals TransCom model simulations of CH<sub>4</sub> and related species: linking transport, surface flux and chemical loss with CH<sub>4</sub> variability in the troposphere and lower stratosphere

2011 ◽  
Vol 11 (24) ◽  
pp. 12813-12837 ◽  
Author(s):  
P. K. Patra ◽  
S. Houweling ◽  
M. Krol ◽  
P. Bousquet ◽  
D. Belikov ◽  
...  
Keyword(s):  
Time Series ◽  
Sulfur Hexafluoride ◽  
Lower Stratosphere ◽  
Transport Model ◽  
Distribution Model ◽  
Emission Scenarios ◽  
Model Simulations ◽  
Upper Troposphere ◽  
Exchange Time ◽  
Vertical Gradients

Abstract. A chemistry-transport model (CTM) intercomparison experiment (TransCom-CH4) has been designed to investigate the roles of surface emissions, transport and chemical loss in simulating the global methane distribution. Model simulations were conducted using twelve models and four model variants and results were archived for the period of 1990–2007. All but one model transports were driven by reanalysis products from 3 different meteorological agencies. The transport and removal of CH4 in six different emission scenarios were simulated, with net global emissions of 513 ± 9 and 514 ± 14 Tg CH4 yr−1 for the 1990s and 2000s, respectively. Additionally, sulfur hexafluoride (SF6) was simulated to check the interhemispheric transport, radon (222Rn) to check the subgrid scale transport, and methyl chloroform (CH3CCl3) to check the chemical removal by the tropospheric hydroxyl radical (OH). The results are compared to monthly or annual mean time series of CH4, SF6 and CH3CCl3 measurements from 8 selected background sites, and to satellite observations of CH4 in the upper troposphere and stratosphere. Most models adequately capture the vertical gradients in the stratosphere, the average long-term trends, seasonal cycles, interannual variations (IAVs) and interhemispheric (IH) gradients at the surface sites for SF6, CH3CCl3 and CH4. The vertical gradients of all tracers between the surface and the upper troposphere are consistent within the models, revealing vertical transport differences between models. An average IH exchange time of 1.39 ± 0.18 yr is derived from SF6 time series. Sensitivity simulations suggest that the estimated trends in exchange time, over the period of 1996–2007, are caused by a change of SF6 emissions towards the tropics. Using six sets of emission scenarios, we show that the decadal average CH4 growth rate likely reached equilibrium in the early 2000s due to the flattening of anthropogenic emission growth since the late 1990s. Up to 60% of the IAVs in the observed CH4 concentrations can be explained by accounting for the IAVs in emissions, from biomass burning and wetlands, as well as meteorology in the forward models. The modeled CH4 budget is shown to depend strongly on the troposphere-stratosphere exchange rate and thus on the model's vertical grid structure and circulation in the lower stratosphere. The 15-model median CH4 and CH3CCl3 atmospheric lifetimes are estimated to be 9.99 ± 0.08 and 4.61 ± 0.13 yr, respectively, with little IAV due to transport and temperature.

scholarly journals Quantifying tracer transport in the tropical lower stratosphere using WACCM

2013 ◽  
Vol 13 (21) ◽  
pp. 10591-10607 ◽  
Author(s):  
M. Abalos ◽  
W. J. Randel ◽  
D. E. Kinnison ◽  
E. Serrano
Keyword(s):  
Lower Stratosphere ◽  
Climate Model ◽  
Latitudinal Gradients ◽  
Explicit Calculation ◽  
Boreal Summer ◽  
Tracer Transport ◽  
Annual Cycles ◽  
Tropical Tropopause ◽  
Eddy Transport ◽  
Isentropic Coordinates

Abstract. The zonal mean transport of ozone and carbon monoxide (CO) near the tropical tropopause is investigated using the Whole-Atmosphere Community Climate Model version 4 (WACCM4). The variability in temperature, ozone and CO in the model shows good agreement with satellite and balloon observations. Modeled temperature and tracers exhibit large and closely coupled annual cycles in the tropical lower stratosphere, as in the observations. The thermodynamic and tracer budgets in the model are analyzed based on the Transformed Eulerian Mean (TEM) framework on log-pressure coordinates and also using the isentropic formulation. Results show that the coupled seasonal cycles are mainly forced by tropical upwelling over altitudes with large vertical tracer gradients, in agreement with previous observational studies. The model also allows explicit calculation of eddy transport terms, which make an important contribution to ozone tendencies in the tropical lower stratosphere. The character of the eddy fluxes changes with altitude. At higher levels (~2 km above the cold point tropopause), isentropic eddy transport occurs during winter and spring in each hemisphere in the sub-tropics, associated with transient Rossby waves acting on strong background latitudinal gradients. At lower altitudes, close to the tropical tropopause, there is a maximum in horizontal eddy transport during boreal summer associated with the Asian monsoon anticyclone. Sub-seasonal variability in ozone and CO, tied to fluctuations in temperature, is primarily driven by transient tropical upwelling. In isentropic coordinates, the overall tracer budgets are similar to the log-pressure results, highlighting cross-isentropic advection as the main term in the time-mean balance, with large seasonality above the tropopause. However, in isentropic coordinates the tracer variability is largely reduced on both seasonal and sub-seasonal timescales, because tracer fluctuations are highly correlated with temperature (as a response to upwelling).

scholarly journals Carbon monoxide as a tracer for tropical troposphere to stratosphere transport in the Chemical Lagrangian Model of the Stratosphere (CLaMS)

2011 ◽  
Vol 4 (2) ◽  
pp. 1185-1211 ◽  
Author(s):  
R. Pommrich ◽  
R. Müller ◽  
J.-U. Grooß ◽  
P. Konopka ◽  
G. Günther ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Lagrangian Model ◽  
Mixing Ratio ◽  
Forecast System ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Tropical Troposphere ◽  
The Tropics ◽  
The Impact ◽  
Good Agreement

Abstract. Variations in the mixing ratio of trace gases of tropospheric origin entering the stratosphere in the tropics are of interest for assessing both troposphere to stratosphere transport fluxes in the tropics and the impact on the composition of the tropical lower stratosphere of quasi-horizontal in-mixing into the tropical tropopause layer from the mid-latitude stratosphere. Here, we present a simplified chemistry scheme for the Chemical Lagrangian Model of the Stratosphere (CLaMS) for the simulation, at comparatively low numerical cost, of CO, ozone, and long-lived trace substances (CH4, N2O, CCl3F, and CO2) in the lower tropical stratosphere. The boundary conditions at the ground are represented for the long-lived trace substances CH4, N2O, CCl3F, and CO2 based on ground-based measurements. The boundary condition for CO in the free troposphere is deduced from MOPITT measurements. We find that the zonally averaged tropical CO anomaly patterns simulated by this model version of CLaMS are in good agreement with observations. The introduction of a new scheme in the ECMWF integrated forecast system (Tompkins et al., 2007) for the ice supersaturation after September 2006, results in a somewhat less good agreement between observed and simulated CO patterns in the tropical lower stratosphere after this date.

scholarly journals VARIASI TRACE GASES SELAMA 10 TAHUN DAN PENCAMPURAN DI SEKITAR LAPISAN TROPOPAUSE DI INDONESIA BERBASIS SATELIT (TRACE GASES VARIATION FOR 10 YEARS AND MIXING AROUND THE TROPOPAUSE LAYERS IN INDONESIA BASED ON SATELLITE)

2018 ◽  
Vol 14 (2) ◽  
pp. 83
Author(s):  
Novita Ambarsari ◽  
Ninong Komala ◽  
Fanny Aditya Putri
Keyword(s):  
Time Series ◽  
Cross Section ◽  
Lower Stratosphere ◽  
Trace Gases ◽  
Radiation Budget ◽  
Vertical Profiles ◽  
Upper Troposphere ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Budget Analysis

Measurement of trace gases (CO, O3, CH3Cl, HCl, H2O, and HNO3) and temperatures around upper troposphere/lower stratosphere (UT/LS) or rather around Tropical Tropopause Layer (TTL) in Indonesia by using Microwave Limb Sounder (MLS) instrument board on Satellite AURA for 2005-2014 period to make variations of these gases over the 10 years around TTL allows to be studied more deeply. TTL becomes the main route entry of chemical compounds and aerosols originating in the troposphere into the stratosphere. The composition of minor gases in the TTL is very important because it affects the global radiation budget. Analysis of vertical profiles of these gases in the TTL was done to determine the suitability of the concept of TTL which starts from the upper troposphere to the lower stratosphere. Other method are the time series diagram of the altitude (height versus time series cross section) which shows the annual and interannual variations in vertical profiles of these gases in the TTL and the possible influence of the dynamics of the atmosphere. The results showed correlation of these gases with ozone showed most of the air in the stratosphere is experiencing mixing in the TTL. In addition, changes in concentration and temperature values in the TTL have been calculated using the trends of each parameter and it is known that the parameters of HCl, CH3Cl, and temperature show respective decreases of -0.036 ppmv, -0.024 ppmv, and -0.456 K. As for other parameters such as ozone, CO, H2O, and HNO3 showed an increase of respectively 0.0036 ppmv, 0.0096 ppmv, 0.108 ppmv, and 0.06 ppmv. AbstrakPengukuran trace gases (CO, O3, CH3Cl, HCl, H2O, HNO3) dan temperatur di sekitar lapisan troposfer atas/stratosfer bawah (UT/LS) atau tepatnya di sekitar Tropical Tropopause Layer (TTL) di Indonesia menggunakan instrumen Microwave Limb Sounder (MLS) pada Satelit AURA periode 2005-2014 menjadikan variasi gas-gas tersebut selama 10 tahun di sekitar TTL memungkinkan untuk dikaji lebih dalam. TTL menjadi jalur utama masuknya senyawa-senyawa kimia dan aerosol yang bersumber di troposfer ke stratosfer. Komposisi gas-gas minor di TTL sangat penting karena mempengaruhi budget radiasi global. Analisis profil vertikal gas-gas tersebut di TTL dilakukan untuk mengetahui kesesuaian konsep TTL yang dimulai dari lapisan troposfer atas hingga ke stratosfer bawah. Metode lainnya adalah dengan diagram time series terhadap ketinggian (time series versus height cross section) yang menunjukkan variasi tahunan maupun antar tahunan profil vertikal gas-gas tersebut di TTL serta kemungkinan adanya pengaruh dari proses dinamika atmosfer. Hasil penelitian menunjukkan korelasi gas-gas tersebut dengan ozon menunjukkan adanya sebagian udara di stratosfer yang mengalami pencampuran di wilayah TTL. Selain itu, perubahan nilai konsentrasi dan temperatur di TTL telah dihitung menggunakan trend masing-masing parameter dan diketahui bahwa parameter HCl, CH3Cl, dan temperatur menunjukkan penurunan masing-masing sebesar  -0,036 ppmv, -0,024 ppmv, dan -0,456 K. Adapun parameter lain seperti ozon, CO, H2O, dan HNO3 menunjukkan adanya peningkatan masing-masing sebesar 0,0036 ppmv, 0,0096 ppmv, 0,108 ppmv, dan 0,06 ppmv.  

scholarly journals The high Arctic in extreme winters: vortex, temperature, and MLS and ACE-FTS trace gas evolution

2008 ◽  
Vol 8 (3) ◽  
pp. 505-522 ◽  
Author(s):  
G. L. Manney ◽  
W. H. Daffer ◽  
K. B. Strawbridge ◽  
K. A. Walker ◽  
C. D. Boone ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Lower Stratosphere ◽  
High Arctic ◽  
Trace Gas ◽  
Satellite Measurements ◽  
Broadband Emission ◽  
Gas Measurements ◽  
Chemistry Experiment ◽  
Very High ◽  
Good Agreement

Abstract. The first three Arctic winters of the ACE mission represented two extremes of winter variability: Stratospheric sudden warmings (SSWs) in 2004 and 2006 were among the strongest, most prolonged on record; 2005 was a record cold winter. Canadian Arctic Atmospheric Chemistry Experiment (ACE) Validation Campaigns were conducted at Eureka (80° N, 86° W) during each of these winters. New satellite measurements from ACE-Fourier Transform Spectrometer (ACE-FTS), Sounding of the Atmosphere using Broadband Emission Radiometry (SABER), and Aura Microwave Limb Sounder (MLS), along with meteorological analyses and Eureka lidar temperatures, are used to detail the meteorology in these winters, to demonstrate its influence on transport, and to provide a context for interpretation of ACE-FTS and validation campaign observations. During the 2004 and 2006 SSWs, the vortex broke down throughout the stratosphere, reformed quickly in the upper stratosphere, and remained weak in the middle and lower stratosphere. The stratopause reformed at very high altitude, near 75 km. ACE measurements covered both vortex and extra-vortex conditions in each winter, except in late-February through mid-March 2004 and 2006, when the strong, pole-centered vortex that reformed after the SSWs resulted in ACE sampling only inside the vortex in the middle through upper stratosphere. The 2004 and 2006 Eureka campaigns were during the recovery from the SSWs, with the redeveloping vortex over Eureka. 2005 was the coldest winter on record in the lower stratosphere, but with an early final warming in mid-March. The vortex was over Eureka at the start of the 2005 campaign, but moved away as it broke up. Disparate temperature profile structure and vortex evolution resulted in much lower (higher) temperatures in the upper (lower) stratosphere in 2004 and 2006 than in 2005. Satellite temperatures agree well with lidar data up to 50–60 km, and ACE-FTS, MLS and SABER show good agreement in high-latitude temperatures throughout the winters. Consistent with a strong, cold upper stratospheric vortex and enhanced radiative cooling after the SSWs, MLS and ACE-FTS trace gas measurements show strongly enhanced descent in the upper stratospheric vortex in late January through March 2006 compared to that in 2005.

Sign in / Sign up

Export Citation Format

Share Document