scholarly journals Tropical cooling in the case of stratospheric sudden warming in January 2009: focus on the tropical tropopause layer

2011 ◽  
Vol 11 (1) ◽  
pp. 2263-2296 ◽  
Author(s):  
K. Yoshida ◽  
K. Yamazaki
Keyword(s):  
Source Region ◽  
Temperature Drop ◽  
Eastern Africa ◽  
Stratospheric Sudden Warming ◽  
Tropical Tropopause Layer ◽  
Cooling Period ◽  
Wave Forcing ◽  
Tropical Tropopause ◽  
Vertical Heat Flux ◽  
The Tropics

Abstract. Temperature changes in the tropics, especially in the tropical tropopause layer, are investigated at the time of a major stratospheric sudden warming (SSW) event that started on about 16 January 2009. During the SSW, the temperature in the tropical upper stratosphere declined and the cold anomaly propagated downward, while the tropics between 150 and 100 hPa started to cool from 18 January, prior to a temperature drop at 70 hPa. We performed thermodynamical and dynamical analyses with ERA-Interim data. During the SSW event, the tropical stratosphere was cooled by upwelling, and the upwelling was induced by wave forcing in the northern extratropical stratosphere. However, the stratospheric wave forcing generated only weak upwelling in the tropics below 100 hPa. During the cooling period at around 18 January, tropical ascent was the main contributor to cooling of the tropics between 150 and 100 hPa. Subsequently, vertical convergence of the vertical heat flux, which is closely tied to the convection structure, resulted in a gradual decrease in temperature within the tropical uppermost troposphere. Waves that had same source region with the upward-propagating waves that caused the SSW event, propagated from Alaska to the tropics of Eastern South America and Eastern Africa at around 100 hPa, and dissipated in these areas; the associated wave forcing drove the tropical ascent between 150 and 100 hPa.

scholarly journals Tropical cooling in the case of stratospheric sudden warming in January 2009: focus on the tropical tropopause layer

2011 ◽  
Vol 11 (13) ◽  
pp. 6325-6336 ◽  
Author(s):  
K. Yoshida ◽  
K. Yamazaki
Keyword(s):  
Source Region ◽  
Temperature Drop ◽  
Eastern Africa ◽  
Stratospheric Sudden Warming ◽  
Tropical Tropopause Layer ◽  
Cooling Period ◽  
Wave Forcing ◽  
Tropical Tropopause ◽  
Vertical Heat Flux ◽  
The Tropics

Abstract. Temperature changes in the tropics, especially in the tropical tropopause layer, are investigated at the time of a major stratospheric sudden warming (SSW) event that started on about 16 January 2009. During the SSW, the temperature in the tropical upper stratosphere declined and the cold anomaly propagated downward, while the tropics between 150 and 100 hPa started to cool from 18 January, prior to a temperature drop at 70 hPa. We performed thermodynamical and dynamical analyses with ERA-Interim data. During the SSW event, the tropical stratosphere was cooled by upwelling, and the upwelling was induced by wave forcing in the northern extratropical stratosphere. However, the stratospheric wave forcing generated only weak upwelling in the tropics below 100 hPa. During the cooling period at around 18 January, tropical ascent was the main contributor to cooling of the tropics between 150 and 100 hPa. Subsequently, vertical convergence of the vertical heat flux, which is closely tied to the convection structure, resulted in a gradual decrease in temperature within the tropical uppermost troposphere. Waves that had same source region with the upward-propagating waves that caused the SSW event, propagated from Alaska to the tropics of eastern South America and eastern Africa at around 100 hPa, and dissipated in these areas; the associated wave forcing drove the tropical ascent between 150 and 100 hPa.

scholarly journals Impact of land convection on troposphere-stratosphere exchange in the tropics

2007 ◽  
Vol 7 (2) ◽  
pp. 3269-3300 ◽  
Author(s):  
P. Ricaud ◽  
B. Barret ◽  
J.-L. Attié ◽  
E. Le Flochmoën ◽  
E. Motte ◽  
...  
Keyword(s):  
Transport Model ◽  
Source Region ◽  
Tropical Rainfall Measuring Mission ◽  
Convective Transport ◽  
Chemical Transport Model ◽  
Tropical Tropopause Layer ◽  
Evergreen Forests ◽  
Tropical Tropopause ◽  
Longitudinal Gradients ◽  
The Tropics

Abstract. The mechanism of troposphere-stratosphere exchange in the tropics was investigated from space-borne observations of the horizontal distributions of nitrous oxide (N2O), methane (CH4) and carbon monoxide (CO) at 17 km in March-April-May by the ODIN/Sub-Millimeter Radiometer (SMR), the Upper Atmosphere Research Satellite (UARS)/Halogen Occultation Experiment (HALOE) and the TERRA/Measurements Of Pollution In The Troposphere (MOPITT) instruments in 2002–2004, completed by recent observations of the AURA/Microwave Limb Sounder (MLS) instrument during the same season in 2005. At the top of the Tropical Tropopause Layer (TTL), all gases show significant longitudinal gradients with maximum amounts primarily over Africa and, depending on the species, secondary more or less pronounced maxima above northern South America and South-East Asia. The Maritime continent in the Western Pacific never appears as a source region for the stratosphere. The large longitudinal gradient at latitudes where the circulation is essentially zonal, and the co-location of the maximum tropospheric trace gases concentrations with the overshooting features reported by the Tropical Rainfall Measuring Mission (TRMM) satellite precipitation radar, strongly supports that rapid uplift over land convective regions is the dominating process of troposphere-stratosphere exchange. Calculations carried out with the MOCAGE-Climat chemical transport model well capture the location of the maximum gas concentration in the TTL but of lesser amplitude. Although there are obvious misrepresentations of some of the sources in the model, i.e. CH4 emissions by evergreen forests, the main reason for discrepancy appears to be the underestimation of the maximum altitude reached by land convective transport in MOCAGE.

scholarly journals Tracer measurements in the tropical tropopause layer during the AMMA/SCOUT-O3 aircraft campaign

2010 ◽  
Vol 10 (8) ◽  
pp. 3615-3627 ◽  
Author(s):  
C. D. Homan ◽  
C. M. Volk ◽  
A. C. Kuhn ◽  
A. Werner ◽  
J. Baehr ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Deep Convection ◽  
Transport Processes ◽  
Gradual Transition ◽  
Tropical Tropopause Layer ◽  
Mixing Ratios ◽  
Tropical Tropopause ◽  
Multidisciplinary Analysis ◽  
The Tropics

Abstract. We present airborne in situ measurements made during the AMMA (African Monsoon Multidisciplinary Analysis)/SCOUT-O3 campaign between 31 July and 17 August 2006 on board the M55 Geophysica aircraft, based in Ouagadougou, Burkina Faso. CO2 and N2O were measured with the High Altitude Gas Analyzer (HAGAR), CO was measured with the Cryogenically Operated Laser Diode (COLD) instrument, and O3 with the Fast Ozone ANalyzer (FOZAN). We analyse the data obtained during five local flights to study the dominant transport processes controlling the tropical tropopause layer (TTL, here ~350–375 K) and lower stratosphere above West-Africa: deep convection up to the level of main convective outflow, overshooting of deep convection, and horizontal inmixing across the subtropical tropopause. Besides, we examine the morphology of the stratospheric subtropical barrier. Except for the flight of 13 August, distinct minima in CO2 mixing ratios indicate convective outflow of boundary layer air in the TTL. The CO2 profiles show that the level of main convective outflow was mostly located at potential temperatures between 350 and 360 K, and for 11 August reached up to 370 K. While the CO2 minima indicate quite significant convective influence, the O3 profiles suggest that the observed convective signatures were mostly not fresh, but of older origin (several days or more). When compared with the mean O3 profile measured during a previous campaign over Darwin in November 2005, the O3 minimum at the main convective outflow level was less pronounced over Ouagadougou. Furthermore O3 mixing ratios were much higher throughout the whole TTL and, unlike over Darwin, rarely showed low values observed in the regional boundary layer. Signatures of irreversible mixing following overshooting of convective air were scarce in the tracer data. Some small signatures indicative of this process were found in CO2 profiles between 390 and 410 K during the flights of 4 and 8 August, and in CO data at 410 K on 7 August. However, the absence of expected corresponding signatures in other tracer data makes this evidence inconclusive, and overall there is little indication from the observations that overshooting convection has a profound impact on gas-phase tracer TTL composition during AMMA. We find the amount of photochemically aged air isentropically mixed into the TTL across the subtropical tropopause to be not significant. Using the N2O observations we estimate the fraction of aged extratropical stratospheric air in the TTL to be 0.0±0.1 up to 370 K during the local flights. Above the TTL this fraction increases to 0.3±0.1 at 390 K. The subtropical barrier, as indicated by the slope of the correlation between N2O and O3 between 415 and 490 K, does not appear as a sharp border between the tropics and extratropics, but rather as a gradual transition region between 10° N and 25° N where isentropic mixing between these two regions may occur.

scholarly journals The NASA Airborne Tropical Tropopause Experiment: High-Altitude Aircraft Measurements in the Tropical Western Pacific

2017 ◽  
Vol 98 (1) ◽  
pp. 129-143 ◽  
Author(s):  
Eric J. Jensen ◽  
Leonhard Pfister ◽  
David E. Jordan ◽  
Thaopaul V. Bui ◽  
Rei Ueyama ◽  
...  
Keyword(s):  
High Altitude ◽  
Active Species ◽  
Convective Transport ◽  
Western Pacific ◽  
Lower Altitude ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Cloud Properties ◽  
The Tropics ◽  
Global Hawk

Abstract The February–March 2014 deployment of the National Aeronautics and Space Administration (NASA) Airborne Tropical Tropopause Experiment (ATTREX) provided unique in situ measurements in the western Pacific tropical tropopause layer (TTL). Six flights were conducted from Guam with the long-range, high-altitude, unmanned Global Hawk aircraft. The ATTREX Global Hawk payload provided measurements of water vapor, meteorological conditions, cloud properties, tracer and chemical radical concentrations, and radiative fluxes. The campaign was partially coincident with the Convective Transport of Active Species in the Tropics (CONTRAST) and the Coordinated Airborne Studies in the Tropics (CAST) airborne campaigns based in Guam using lower-altitude aircraft (see companion articles in this issue). The ATTREX dataset is being used for investigations of TTL cloud, transport, dynamical, and chemical processes, as well as for evaluation and improvement of global-model representations of TTL processes. The ATTREX data are publicly available online (at https://espoarchive.nasa.gov/).

scholarly journals Correlation between equatorial Kelvin waves and the occurrence of extremely thin ice clouds at the tropical tropopause

2008 ◽  
Vol 8 (14) ◽  
pp. 4019-4026 ◽  
Author(s):  
F. Immler ◽  
K. Krüger ◽  
M. Fujiwara ◽  
G. Verver ◽  
M. Rex ◽  
...  
Keyword(s):  
Kelvin Waves ◽  
Clear Correlation ◽  
Temperature Structure ◽  
Kelvin Wave ◽  
Ice Clouds ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Water Vapour Concentration ◽  
Vapour Concentration ◽  
The Tropics

Abstract. A number of field-campaigns in the tropics have been conducted in recent years with two different LIDAR systems at Paramaribo (5.8° N, 55.2° W), Suriname. The lidars detect particles in the atmosphere with high vertical and temporal resolution and are capable of detecting extremely thin cloud layers which frequently occur in the tropical tropopause layer (TTL). Radiosonde as well as operational ECMWF analysis showed that equatorial Kelvin waves propagated in the TTL and greatly modulated its temperature structure. We found a clear correlation between the temperature anomalies introduced by these waves and the occurrence of thin cirrus in the TTL. In particular we found that extremely thin ice clouds form regularly where cold anomalies shift the tropopause to high altitudes. These findings suggest an influence of Kelvin wave activity on the dehydration in the TTL and thus on the global stratospheric water vapour concentration.

scholarly journals The role of tropical deep convective clouds on temperature, water vapor, and dehydration in the tropical tropopause layer (TTL)

2010 ◽  
Vol 10 (4) ◽  
pp. 8963-8994 ◽  
Author(s):  
J. H. Chae ◽  
D. L. Wu ◽  
W. G. Read ◽  
S. C. Sherwood
Keyword(s):  
Water Vapor ◽  
Relative Humidity ◽  
Temperature Drop ◽  
Critical Factor ◽  
Tropical Tropopause Layer ◽  
Convective Clouds ◽  
Tropical Tropopause ◽  
Dehydration Mechanism ◽  
Environmental Air ◽  
Cloud Tops

Abstract. Temperature and water vapor variations due to clouds in the TTL have been investigated using co-located MLS, CALISPO, and CloudSat data. Convective cooling occurs only up to cloud top heights, but there is warming above these heights in the TTL. Water vapor and ozone anomalies above cloud top heights support that the warming anomalies occur due to downward motion. Thicker clouds cause a greater magnitude of the temperature anomalies. Water vapor of the environment below cloud tops can either increase or decrease, depending on the cloud top height. The critical factor, which divides these different water vapor variations below cloud tops, is the relative humidity. Clouds hydrate the environment below 16 km, where the air after mixing between cloud and the environmental air does not reach saturation, but clouds dehydrate above 16 km, due to the supersaturation because of the larger temperature drop and the high initial relative humidity. Water vapor above cloud tops has negative anomalies compared to clear skies and suggests another dehydration mechanism.

Inorganic and organic bromine measurements around the extra-tropical tropopause: Insights into total stratospheric bromine

2020 ◽  
Author(s):  
Meike Rotermund ◽  
Ben Schreiner ◽  
Flora Kluge ◽  
Tilman Hüneke ◽  
Andreas Engel ◽  
...  
Keyword(s):  
Western Europe ◽  
Trace Gases ◽  
Lagrangian Model ◽  
Optical Absorption Spectroscopy ◽  
Air Mass ◽  
Tropical Tropopause Layer ◽  
Mixing Ratios ◽  
Tropical Tropopause ◽  
Extratropical Tropopause ◽  
The Tropics

<p>Bromine greatly influences the UT/LS ozone concentrations, however the transport of bromine across the tropical tropopause layer and in particular across the extratropical tropopause is not well quantified. Air-borne measurements of atmospheric trace gases such as organic and inorganic bromine along the tropopause are studied during the WISE (Wave-driven ISentropic Exchange) research campaign over the northern Atlantic and western Europe from September 13 - October 21, 2017. The remote sensing instrument mini-DOAS (Differential Optical Absorption Spectroscopy) is mounted on the HALO (High Altitude and LOng range) aircraft and measures BrO (O<sub>3</sub>, NO<sub>2</sub> among other trace gases). The novel scaling method is applied to infer the target gas BrO mixing ratios from slant column densities using in-situ O<sub>3</sub> measurements from the FAIRO instrument (operated by KIT) as the scaling gas. For each flight, the inferred mixing ratios are directly compared with CLaMS (Chemical Lagrangian Model of the Stratosphere) simulated curtains of the trace gases along the flight path. The partitioning coefficient of inorganic bromine from CLaMS and all relevant organic halogen species and air mass ages (SF<sub>6</sub>, CO<sub>2</sub>) from the GhOST-MS instrument (operated by UFra) are used to determine the total bromine budget along the UT/LS. A climatology of organic, inorganic and total bromine is constructed with respect to the extratropical tropopause as well as the air mass ages. This indicates the interplay of bromine transport across the extratropical tropopause and of the transport of air via the lower branch from the tropics as well as potential losses of inorganic bromine by uptake onto and sedimentation of ice particles.</p>

scholarly journals A global non-hydrostatic model study of a downward coupling through the tropical tropopause layer during a stratospheric sudden warming

2015 ◽  
Vol 15 (1) ◽  
pp. 297-304 ◽  
Author(s):  
N. Eguchi ◽  
K. Kodera ◽  
T. Nasuno
Keyword(s):  
Cumulus Parameterization ◽  
Cloud Formation ◽  
Boreal Winter ◽  
Convective Activity ◽  
Stratospheric Sudden Warming ◽  
Southwest Indian Ocean ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Model Study ◽  
Hydrostatic Model

Abstract. The dynamical coupling process between the stratosphere and troposphere in the tropical tropopause layer (TTL) during a~stratospheric sudden warming (SSW) in boreal winter was investigated using simulation data from a global non-hydrostatic model (NICAM) that does not use cumulus parameterization. The model reproduced well the observed tropical tropospheric changes during the SSW, including the enhancement of convective activity following the amplification of planetary waves. Deep convective activity was enhanced in the latitude zone 20–10° S, in particular over the southwest Pacific and southwest Indian Ocean. Although the upwelling in the TTL was correlated with that in the stratosphere, the temperature tendency in the TTL changed little due to a compensation by diabatic heating originating from cloud formation. This result suggests that the stratospheric meridional circulation affects cloud formation in the TTL.

scholarly journals Bromoform and dibromomethane in the tropics: a 3-D model study of chemistry and transport

2010 ◽  
Vol 10 (2) ◽  
pp. 719-735 ◽  
Author(s):  
R. Hossaini ◽  
M. P. Chipperfield ◽  
B. M. Monge-Sanz ◽  
N. A. D. Richards ◽  
E. Atlas ◽  
...  
Keyword(s):  
Transport Model ◽  
Three Dimensional ◽  
Vertical Motion ◽  
Chemical Transport Model ◽  
Heating Rates ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Modelling Studies ◽  
Vertical Winds ◽  
The Tropics

Abstract. We have developed a detailed chemical scheme for the degradation of the short-lived source gases bromoform (CHBr3) and dibromomethane (CH2Br2) and implemented it in the TOMCAT/SLIMCAT three-dimensional (3-D) chemical transport model (CTM). The CTM has been used to predict the distribution of the two source gases (SGs) and 11 of their organic product gases (PGs). These first global calculations of the organic PGs show that their abundance is small. The longest lived organic PGs are CBr2O and CHBrO, but their peak tropospheric abundance relative to the surface volume mixing ratio (vmr) of the SGs is less than 5%. We calculate their mean local tropospheric lifetimes in the tropics to be ~7 and ~2 days (due to photolysis), respectively. Therefore, the assumption in previous modelling studies that SG degradation leads immediately to inorganic bromine seems reasonable. We have compared observed tropical SG profiles from a number of aircraft campaigns with various model experiments. In the tropical tropopause layer (TTL) we find that the CTM run using p levels (TOMCAT) and vertical winds from analysed divergence overestimates the abundance of CH2Br2, and to a lesser extent CHBr3, although the data is sparse and comparisons are not conclusive. Better agreement in the TTL is obtained in the sensitivity run using θ levels (SLIMCAT) and vertical motion from diabatic heating rates. Trajectory estimates of residence times in the two model versions show slower vertical transport in the SLIMCAT θ-level version. In the p-level model even when we switch off convection we still find significant amounts of the SGs considered may reach the cold point tropopause; the stratospheric source gas injection (SGI) is only reduced by ~16% for CHBr3 and ~2% for CH2Br2 without convection. Overall, the relative importance of the SG pathway and the PG pathway for transport of bromine to the stratospheric overworld (θ>380 K) has been assessed. Assuming a 10-day washout lifetime of Bry in TOMCAT, we find the delivery of total Br from CHBr3 to be 0.72 pptv with ~53% of this coming from SGI. Similary, for CH2Br2 we find a total Br value of 1.69 pptv with ~94% coming from SGI. We infer that these species contribute ~2.4 pptv of inorganic bromine to the lower stratosphere with SGI being the dominant pathway. Slower transport to and through the TTL would decrease this estimate.

scholarly journals Bridging the gap between bromocarbon oceanic emissions and upper air concentrations

2012 ◽  
Vol 12 (2) ◽  
pp. 4477-4505 ◽  
Author(s):  
S. Tegtmeier ◽  
K. Krüger ◽  
B. Quack ◽  
I. Pisso ◽  
A. Stohl ◽  
...  
Keyword(s):  
Transport Model ◽  
Degradation Products ◽  
Source Region ◽  
Western Pacific ◽  
Emission Rates ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Oceanic Emissions ◽  
Atmospheric Concentrations ◽  
The Western Pacific

Abstract. Oceanic emissions of halogenated very short-lived substances (VSLS) are expected to contribute significantly to the stratospheric halogen loading and therefore to ozone depletion. Estimates of the amount of VSLS transported into the stratosphere are highly uncertain and based on sporadic observations around the tropical tropopause layer (TTL) and on modeling studies which use prescribed emission scenarios to reproduce observed atmospheric concentrations. Actual measurements of VSLS emissions at the ocean surface have not been linked to the stratospheric halogen loading until now. Here we use observations of oceanic VSLS emissions in the western Pacific and an atmospheric Lagrangian transport model to estimate the direct contribution of bromoform (CHBr3), and dibromomethane (CH2Br2) to the stratospheric bromine loading. Our emission-based estimates of VSLS profiles provide the first link between observed oceanic emissions and in situ TTL measurements. The emission-based and observed profiles of CHBr3 show good agreement, confirming the importance of the western Pacific as a source region. However, CH2Br2 emission-based estimates are considerable smaller than current upper air observations as a result of relatively low western Pacific emissions. We estimate the relative importance of the highly variable emission rates and the surface to stratosphere transport for the contribution of the two bromocarbons to the stratospheric bromine budget. Our results show that stratospheric entrainment of bromine in form of VSLS or their degradation products is highly variable and that this variability is primarily linked to the variability of the observed sea-to-air flux. Together, both bromocarbons contribute to the stratospheric bromine budget with 0.4 pptv on average and 2.3 pptv for cases of maximum emissions.

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