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 Spectrum of Wave Forcing Associated with the Annual Cycle of Upwelling at the Tropical Tropopause

2016 ◽  
Vol 73 (2) ◽  
pp. 855-868 ◽  
Author(s):  
Joowan Kim ◽  
William J. Randel ◽  
Thomas Birner ◽  
Marta Abalos
Keyword(s):  
Annual Cycle ◽  
Lower Stratosphere ◽  
Mass Conservation ◽  
Upper Troposphere ◽  
Wave Forcing ◽  
Planetary Scale ◽  
Tropical Tropopause ◽  
Zonal Wavenumber ◽  
Wavenumber Spectrum ◽  
Transformed Eulerian Mean

Abstract The zonal wavenumber spectrum of atmospheric wave forcing in the lower stratosphere is examined to understand the annual cycle of upwelling at the tropical tropopause. Tropopause upwelling is derived based on the wave forcing computed from ERA-Interim using the momentum and mass conservation equations in the transformed Eulerian-mean framework. The calculated upwelling agrees well with other upwelling estimates and successfully captures the annual cycle, with a maximum during Northern Hemisphere (NH) winter. The spectrum of wave forcing reveals that the zonal wavenumber-3 component drives a large portion of the annual cycle in upwelling. The wave activity flux (Eliassen–Palm flux) shows that the associated waves originate from the NH extratropics and the Southern Hemisphere tropics during December–February, with both regions contributing significant wavenumber-3 fluxes. These wave fluxes are nearly absent during June–August. Wavenumbers 1 and 2 and synoptic-scale waves have a notable contribution to tropopause upwelling but have little influence on the annual cycle, except the wavenumber-4 component. The quasigeostrophic refractive index suggests that the NH extratropical wavenumber-3 component can enhance tropopause upwelling because these planetary-scale waves are largely trapped in the vertical, while being refracted toward the subtropical upper troposphere and lower stratosphere. Regression analysis based on interannual variability suggests that the wavenumber-3 waves are related to tropical convection and wave breaking along the subtropical jet in the NH extratropics.

scholarly journals The stratospheric Brewer–Dobson circulation inferred from age of air in the ERA5 reanalysis

2021 ◽  
Author(s):  
Felix Ploeger ◽  
Mohamadou Diallo ◽  
Edward Charlesworth ◽  
Paul Konopka ◽  
Bernard Legras ◽  
...  
Keyword(s):  
Diabatic Heating ◽  
Climate Models ◽  
Lower Stratosphere ◽  
Transport Model ◽  
Residual Circulation ◽  
Heating Rates ◽  
Weather Forecasts ◽  
Trend Pattern ◽  
Transit Times ◽  
Medium Range

Abstract. This paper investigates the global stratospheric Brewer–Dobson circulation (BDC) in the ERA5 meteorological reanalysis from the European Centre for Medium-Range Weather Forecasts (ECMWF). The analysis is based on simulations of stratospheric mean age of air, including the full age spectrum, with the Lagrangian transport model CLaMS, driven by winds and total diabatic heating rates from the reanalysis. ERA5-based results are compared to those of the preceding ERA–Interim reanalysis. Our results show a significantly slower BDC for ERA5 than for ERA–Interim, manifesting in weaker diabatic heating rates and larger age of air. In the tropical lower stratosphere, heating rates are 30–40 % weaker in ERA5, likely correcting a known bias in ERA–Interim. Above, ERA5 age of air appears slightly high-biased and the BDC slightly slow compared to tracer observations. The age trend in ERA5 over 1989–2018 is negative throughout the stratosphere, as climate models predict in response to global warming. However, the age decrease is not linear over the period but exhibits steplike changes which could be caused by muti-annual variability or changes in the assimilation system. Over the 2002–2012 period, ERA5 age shows a similar hemispheric dipole trend pattern as ERA–Interim, with age increasing in the NH and decreasing in the SH. Shifts in the age spectrum peak and residual circulation transit times indicate that reanalysis differences in age are likely caused by differences in the residual circulation. In particular, the shallow BDC branch accelerates similarly in both reanalyses while the deep branch accelerates in ERA5 and decelerates in ERA–Interim.

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

2015 ◽  
Vol 15 (11) ◽  
pp. 6467-6486 ◽  
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.

Dehydration of the upper troposphere and lower stratosphere by subvisible cirrus clouds near the tropical tropopause

1996 ◽  
Vol 23 (8) ◽  
pp. 825-828 ◽  
Author(s):  
Eric J. Jensen ◽  
Owen B. Toon ◽  
Leonard Pfister ◽  
Henry B. Selkirk
Keyword(s):  
Lower Stratosphere ◽  
Cirrus Clouds ◽  
Upper Troposphere ◽  
Tropical Tropopause

scholarly journals Physical Process Contributions to the Development of a Super Explosive Cyclone Over the Gulf Stream

2021 ◽  
Vol 9 ◽  
Author(s):  
Shuqin Zhang ◽  
Chunlei Liu ◽  
Jianjun Xu ◽  
Shaojing Zhang ◽  
Ruoying Tang ◽  
...  
Keyword(s):  
Gulf Stream ◽  
Diabatic Heating ◽  
Rapid Development ◽  
Cyclonic Vorticity ◽  
Upper Troposphere ◽  
Explosive Cyclone ◽  
Weather Forecasts ◽  
Vorticity Advection ◽  
Medium Range ◽  
Water Vapor Convergence

Contributions of different physical processes to the development of a super explosive cyclone (SEC) migrating over the Gulf Stream with the maximum deepening rate of 3.45 Bergeron were investigated using the ERA5 atmospheric reanalysis from European Centre for Medium-Range Weather Forecasts (ECMWF). The evolution of the SEC resembled the Shapiro-Keyser model. The moisture transported to the bent-back front by easterlies from Gulf Stream favored precipitation and enhanced the latent heat release. The bent-back front and warm front were dominated by the water vapor convergence in the mid-low troposphere, the cyclonic-vorticity advection in the mid-upper troposphere and the divergence in the upper troposphere. These factors favored the rapid development of the SEC, but their contributions showed significant differences during the explosive-developing stage. The diagnostic results based on the Zwack-Okossi equation suggested that the early explosive development of the SEC was mainly forced by the diabatic heating in the mid-low troposphere. From the early explosive-developing moment to maximum-deepening-rate moment, the diabatic heating, warm-air advection and cyclonic-vorticity advection were all enhanced significantly, their combination forced the most explosive development, and the diabatic heating had the biggest contribution, followed by the warm-air advection and cyclonic-vorticity advection, which is different from the previous studies of ECs over the Northwestern Atlantic. The cross section of these factors suggested that during the rapid development, the cyclonic-vorticity advection was distributed and enhanced significantly in the mid-low troposphere, the warm-air advection was strengthened significantly in the mid-low and upper troposphere, and the diabatic heating was distributed in the middle troposphere.

scholarly journals Anomalous temperature changes in the UTLS region prior to the 2008 Nura Earthquake

2021 ◽  
Vol 333 ◽  
pp. 02013
Author(s):  
Leonid Sverdlik
Keyword(s):  
Seismic Event ◽  
Lower Stratosphere ◽  
Temperature Anomaly ◽  
Tien Shan ◽  
Anomalous Temperature ◽  
Epicentral Area ◽  
Temperature Changes ◽  
Upper Troposphere ◽  
Temporal And Spatial ◽  
Temperature Time

The paper presents results of retrospective analysis of satellite temperature time series above the epicentral area of the destructive Nura earthquake of M=6.7, occurred in a seismically active Tien-Shan region on October 5, 2008. An algorithm based on the use of a modified STA/LTA criterion has been developed for the purpose of selection and identification of perturbations associated with seismic activity. It has been established that an explicit mesoscale temperature anomaly in the upper troposphere and lower stratosphere (UTLS) was observed during the period from October 1 to 3, 2008. Temporal and spatial distributions of the temperature perturbations consistently appeared at various UTLS levels suggest probable association with seismic event preparation.

scholarly journals Mid-winter lower stratosphere temperatures in the Antarctic vortex: comparison between observations and ECMWF operational model.

2006 ◽  
Vol 6 (4) ◽  
pp. 7697-7714
Author(s):  
M. C. Parrondo ◽  
M. Yela ◽  
M. Gil ◽  
P. von der Gathen ◽  
H. Ochoa
Keyword(s):  
Ozone Depletion ◽  
Lower Stratosphere ◽  
Transport Model ◽  
Temperature Fields ◽  
Temperature Profiles ◽  
Temperature Dependent ◽  
Operational Model ◽  
Weather Forecasts ◽  
Medium Range ◽  
The Antarctic

Abstract. Radiosonde temperature profiles from Belgrano (78° S) and other Antarctic stations have been compared with European Centre for Medium-Range Weather Forecasts (ECMWF) data during the winter of 2003. Results show a bias in the operational model which is height and temperature dependent, being too cold at layers peaking at 80 and 25–30 hPa, and hence resulting in an overestimation of the predicted potential PSC areas. Here we show the results of the comparison by considering the possibility of a bias in the sondes at extremely low temperatures and discuss the potential implications that this bias might have on the ozone depletion computed by Climate Transport Model based on ECMWF temperature fields.

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.

scholarly journals Nonstationary Synchronization of Equatorial QBO with SAO in Observations and a Model

2009 ◽  
Vol 66 (6) ◽  
pp. 1654-1664 ◽  
Author(s):  
Le Kuai ◽  
Run-Lie Shia ◽  
Xun Jiang ◽  
Ka-Kit Tung ◽  
Yuk L. Yung
Keyword(s):  
Angular Momentum ◽  
Solar Cycle ◽  
Natural Period ◽  
Quasi Biennial Oscillation ◽  
Integer Multiple ◽  
Weather Forecasts ◽  
Wave Forcing ◽  
Medium Range ◽  
Biennial Oscillation ◽  
Semiannual Oscillation

Abstract It has often been suggested that the period of the quasi-biennial oscillation (QBO) has a tendency to synchronize with the semiannual oscillation (SAO). Apparently the synchronization is better the higher up the observation extends. Using 45 yr of the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) data of the equatorial stratosphere up to the stratopause, the authors confirm that this synchronization is not just a tendency but a robust phenomenon in the upper stratosphere. A QBO period starts when a westerly SAO (w-SAO) descends from the stratopause to 7 hPa and initiates the westerly phase of the QBO (w-QBO) below. It ends when another w-SAO, a few SAO periods later, descends again to 7 hPa to initiate the next w-QBO. The fact that it is the westerly but not the easterly SAO (e-SAO) that initiates the QBO is also explained by the general easterly bias of the angular momentum in the equatorial stratosphere so that the e-SAO does not create a zero-wind line, unlike the w-SAO. The currently observed average QBO period of 28 months, which is not an integer multiple of SAO periods, is a result of intermittent jumps of the QBO period from four SAO to five SAO periods. The same behavior is also found in the Two and a Half Dimensional Interactive Isentropic Research (THINAIR) model. It is found that the nonstationary behavior in both the observation and model is caused not by the 11-yr solar-cycle forcing but by the incompatibility of the QBO’s natural period (determined by its wave forcing) and the “quantized” period determined by the SAO. The wave forcing parameter for the QBO period in the current climate probably lies between four SAO and five SAO periods. If the wave forcing for the QBO is tuned so that its natural period is compatible with the SAO period above (e.g., at 24 or 30 months), nonstationary behavior disappears.

scholarly journals Upper-troposphere and lower-stratosphere water vapor retrievals from the 1400 and 1900 nm water vapor bands

2014 ◽  
Vol 7 (10) ◽  
pp. 10221-10248
Author(s):  
B. C. Kindel ◽  
P. Pilewskie ◽  
K. S. Schmidt ◽  
T. Thornberry ◽  
A. Rollins ◽  
...  
Keyword(s):  
Water Vapor ◽  
Near Infrared ◽  
Lower Stratosphere ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Atmospheric Transmission ◽  
Absorption Bands ◽  
Upper Troposphere ◽  
Tropical Tropopause ◽  
Value Of Water

Abstract. Measuring water vapor in the upper troposphere and lower stratosphere is difficult due to the low mixing ratios found there, typically only a few parts per million. Here we examine near infrared spectra acquired with the Solar Spectral Flux Radiometer during the first science phase of the NASA Airborne Tropical Tropopause EXperiment. From the 1400 and 1900 nm absorption bands, we infer water vapor amounts in the tropical tropopause layer and adjacent regions between 14 and 18 km altitude. We compare these measurements to solar transmittance spectra produced with the MODerate resolution atmospheric TRANsmission (MODTRAN) radiative transfer model, using in situ water vapor, temperature, and pressure profiles acquired concurrently with the SSFR spectra. Measured and modeled transmittance values agree within 0.002, with some larger differences in the 1900 nm band (up to 0.004). Integrated water vapor amounts along the absorption path lengths of 3 to 6 km varied from 1.26 × 10−4 to 4.59 × 10−4 g cm−2. A 0.002 difference in absorptance at 1367 nm results in a 3.35 × 10−5 g cm−2 change of integrated water vapor amount, 0.004 absorptance change at 1870 nm results in 5.5 × 10−5 g cm−2 of water vapor. These are 27% (1367 nm) and 44% (1870 nm) differences at the lowest measured value of water vapor (1.26 × 10−4 g cm−2) and 7% (1367 nm) and 12% (1870 nm) differences at the highest measured value of water vapor (4.59 × 10−4 g cm−2). A potential method for extending this type of measurement from aircraft flight altitude to the top of the atmosphere (TOA) is discussed.

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