scholarly journals Distribution and influence of convection in the tropical tropopause region

2002 ◽  
Vol 107 (D10) ◽  
pp. ACL 6-1-ACL 6-12 ◽  
Author(s):  
A. Gettelman ◽  
M. L. Salby ◽  
F. Sassi
Keyword(s):  
Tropical Tropopause ◽  
Tropopause Region

scholarly journals Effect of deep convection on the tropical tropopause layer composition over the southwest Indian Ocean during austral summer

2020 ◽  
Vol 20 (17) ◽  
pp. 10565-10586
Author(s):  
Stephanie Evan ◽  
Jerome Brioude ◽  
Karen Rosenlof ◽  
Sean M. Davis ◽  
Holger Vömel ◽  
...  
Keyword(s):  
Water Vapor ◽  
Indian Ocean ◽  
Tropical Cyclones ◽  
Austral Summer ◽  
Lagrangian Model ◽  
Southwest Indian Ocean ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Tropopause Region ◽  
The Impact

Abstract. Balloon-borne measurements of cryogenic frost-point hygrometer (CFH) water vapor, ozone and temperature and water vapor lidar measurements from the Maïdo Observatory on Réunion Island in the southwest Indian Ocean (SWIO) were used to study tropical cyclones' influence on tropical tropopause layer (TTL) composition. The balloon launches were specifically planned using a Lagrangian model and Meteosat-7 infrared images to sample the convective outflow from tropical storm (TS) Corentin on 25 January 2016 and tropical cyclone (TC) Enawo on 3 March 2017. Comparing the CFH profile to Aura's Microwave Limb Sounder's (MLS) monthly climatologies, water vapor anomalies were identified. Positive anomalies of water vapor and temperature, and negative anomalies of ozone between 12 and 15 km in altitude (247 to 121 hPa), originated from convectively active regions of TS Corentin and TC Enawo 1 d before the planned balloon launches according to the Lagrangian trajectories. Near the tropopause region, air masses on 25 January 2016 were anomalously dry around 100 hPa and were traced back to TS Corentin's active convective region where cirrus clouds and deep convective clouds may have dried the layer. An anomalously wet layer around 68 hPa was traced back to the southeast Indian Ocean where a monthly water vapor anomaly of 0.5 ppmv was observed. In contrast, no water vapor anomaly was found near or above the tropopause region on 3 March 2017 over Maïdo as the tropopause region was not downwind of TC Enawo. This study compares and contrasts the impact of two tropical cyclones on the humidification of the TTL over the SWIO. It also demonstrates the need for accurate balloon-borne measurements of water vapor, ozone and aerosols in regions where TTL in situ observations are sparse.

scholarly journals Modeling the stratospheric warming following the Mt. Pinatubo eruption: uncertainties in aerosol extinctions

2013 ◽  
Vol 13 (22) ◽  
pp. 11221-11234 ◽  
Author(s):  
F. Arfeuille ◽  
B. P. Luo ◽  
P. Heckendorn ◽  
D. Weisenstein ◽  
J. X. Sheng ◽  
...  
Keyword(s):  
General Circulation ◽  
Climate Model ◽  
Circulation Model ◽  
Temperature Record ◽  
Data Sets ◽  
Stratospheric Warming ◽  
Data Set ◽  
Tropical Tropopause ◽  
Pinatubo Eruption ◽  
Tropopause Region

Abstract. In terms of atmospheric impact, the volcanic eruption of Mt. Pinatubo (1991) is the best characterized large eruption on record. We investigate here the model-derived stratospheric warming following the Pinatubo eruption as derived from SAGE II extinction data including recent improvements in the processing algorithm. This method, termed SAGE_4λ, makes use of the four wavelengths (385, 452, 525 and 1024 nm) of the SAGE II data when available, and uses a data-filling procedure in the opacity-induced "gap" regions. Using SAGE_4λ, we derived aerosol size distributions that properly reproduce extinction coefficients also at much longer wavelengths. This provides a good basis for calculating the absorption of terrestrial infrared radiation and the resulting stratospheric heating. However, we also show that the use of this data set in a global chemistry–climate model (CCM) still leads to stronger aerosol-induced stratospheric heating than observed, with temperatures partly even higher than the already too high values found by many models in recent general circulation model (GCM) and CCM intercomparisons. This suggests that the overestimation of the stratospheric warming after the Pinatubo eruption may not be ascribed to an insufficient observational database but instead to using outdated data sets, to deficiencies in the implementation of the forcing data, or to radiative or dynamical model artifacts. Conversely, the SAGE_4λ approach reduces the infrared absorption in the tropical tropopause region, resulting in a significantly better agreement with the post-volcanic temperature record at these altitudes.

scholarly journals Tropical temperature variability and Kelvin-wave activity in the UTLS from GPS RO measurements

2017 ◽  
Vol 17 (2) ◽  
pp. 793-806 ◽  
Author(s):  
Barbara Scherllin-Pirscher ◽  
William J. Randel ◽  
Joowan Kim
Keyword(s):  
Large Scale ◽  
Deep Convection ◽  
Wave Activity ◽  
Kelvin Waves ◽  
Temperature Variability ◽  
Stationary Waves ◽  
Kelvin Wave ◽  
Quasi Biennial Oscillation ◽  
Tropical Tropopause ◽  
Tropopause Region

Abstract. Tropical temperature variability over 10–30 km and associated Kelvin-wave activity are investigated using GPS radio occultation (RO) data from January 2002 to December 2014. RO data are a powerful tool for quantifying tropical temperature oscillations with short vertical wavelengths due to their high vertical resolution and high accuracy and precision. Gridded temperatures from GPS RO show the strongest variability in the tropical tropopause region (on average 3 K2). Large-scale zonal variability is dominated by transient sub-seasonal waves (2 K2), and about half of sub-seasonal variance is explained by eastward-traveling Kelvin waves with periods of 4 to 30 days (1 K2). Quasi-stationary waves associated with the annual cycle and interannual variability contribute about a third (1 K2) to total resolved zonal variance. Sub-seasonal waves, including Kelvin waves, are highly transient in time. Above 20 km, Kelvin waves are strongly modulated by the quasi-biennial oscillation (QBO) in stratospheric zonal winds, with enhanced wave activity during the westerly shear phase of the QBO. In the tropical tropopause region, however, peaks of Kelvin-wave activity are irregularly distributed in time. Several peaks coincide with maxima of zonal variance in tropospheric deep convection, but other episodes are not evidently related. Further investigations of convective forcing and atmospheric background conditions are needed to better understand variability near the tropopause.

scholarly journals A reassessment of the discrepancies in the annual variation of <i>δ</i>D-H<sub>2</sub>O in the tropical lower stratosphere between the MIPAS and ACE-FTS satellite data sets

2020 ◽  
Vol 13 (1) ◽  
pp. 287-308
Author(s):  
Stefan Lossow ◽  
Charlotta Högberg ◽  
Farahnaz Khosrawi ◽  
Gabriele P. Stiller ◽  
Ralf Bauer ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Annual Variation ◽  
Lower Stratosphere ◽  
Michelson Interferometer ◽  
Tape Recorder ◽  
Data Sets ◽  
Altitude Effect ◽  
Data Set ◽  
Tropical Tropopause ◽  
Tropopause Region

Abstract. The annual variation of δD in the tropical lower stratosphere is a critical indicator for the relative importance of different processes contributing to the transport of water vapour through the cold tropical tropopause region into the stratosphere. Distinct observational discrepancies of the δD annual variation were visible in the works of Steinwagner et al. (2010) and Randel et al. (2012). Steinwagner et al. (2010) analysed MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) observations retrieved with the IMK/IAA (Institut für Meteorologie und Klimaforschung in Karlsruhe, Germany, in collaboration with the Instituto de Astrofísica de Andalucía in Granada, Spain) processor, while Randel et al. (2012) focused on ACE-FTS (Atmospheric Chemistry Experiment Fourier Transform Spectrometer) observations. Here we reassess the discrepancies based on newer MIPAS (IMK/IAA) and ACE-FTS data sets, also showing for completeness results from SMR (Sub-Millimetre Radiometer) observations and a ECHAM/MESSy (European Centre for Medium-Range Weather Forecasts Hamburg and Modular Earth Submodel System) Atmospheric Chemistry (EMAC) simulation (Eichinger et al., 2015b). Similar to the old analyses, the MIPAS data set yields a pronounced annual variation (maximum about 75 ‰), while that derived from the ACE-FTS data set is rather weak (maximum about 25 ‰). While all data sets exhibit the phase progression typical for the tape recorder, the annual maximum in the ACE-FTS data set precedes that in the MIPAS data set by 2 to 3 months. We critically consider several possible reasons for the observed discrepancies, focusing primarily on the MIPAS data set. We show that the δD annual variation in the MIPAS data up to an altitude of 40 hPa is substantially impacted by a “start altitude effect”, i.e. dependency between the lowermost altitude where MIPAS retrievals are possible and retrieved data at higher altitudes. In itself this effect does not explain the differences with the ACE-FTS data. In addition, there is a mismatch in the vertical resolution of the MIPAS HDO and H2O data (being consistently better for HDO), which actually results in an artificial tape-recorder-like signal in δD. Considering these MIPAS characteristics largely removes any discrepancies between the MIPAS and ACE-FTS data sets and shows that the MIPAS data are consistent with a δD tape recorder signal with an amplitude of about 25 ‰ in the lowermost stratosphere.

scholarly journals Seasonality and extent of extratropical TST derived from in-situ CO measurements during SPURT

2004 ◽  
Vol 4 (5) ◽  
pp. 1427-1442 ◽  
Author(s):  
P. Hoor ◽  
C. Gurk ◽  
D. Brunner ◽  
M. I. Hegglin ◽  
H. Wernli ◽  
...  
Keyword(s):  
Potential Temperature ◽  
Mixing Layer ◽  
Trace Gas ◽  
Tropical Tropopause ◽  
Tropopause Region ◽  
Gas Measurements ◽  
Transport And Mixing ◽  
Extratropical Tropopause ◽  
Background Air

Abstract. We present airborne in-situ trace gas measurements which were performed on eight campaigns between November 2001 and July 2003 during the SPURT-project (SPURenstofftransport in der Tropopausenregion, trace gas transport in the tropopause region). The measurements on a quasi regular basis allowed an overview of the seasonal variations of the trace gas distribution in the tropopause region over Europe from 35°-75°N to investigate the influence of transport and mixing across the extratropical tropopause on the lowermost stratosphere. From the correlation of CO and O3 irreversible mixing of tropospheric air into the lowermost stratosphere is identified. The CO distribution indicates that transport and subsequent mixing of tropospheric air across the extratropical tropopause predominantly affects a layer, which closely follows the shape of the local tropopause. In addition, the seasonal cycle of CO2 illustrates the strong coupling of that layer to the extratropical troposphere. Both, horizontal gradients of CO on isentropes as well as the CO-O3-distribution in the lowermost stratosphere reveal that the influence of quasi-horizontal transport and subsequent mixing weakens with distance from the local tropopause. The mixing layer extends to about 25 K in potential temperature above the local tropopause exhibiting only a weak seasonality. However, at large distances from the tropopause a significant influence of tropospheric air is still evident. The relation between N2O and CO2 indicates that a significant contribution of air originating from the tropical tropopause contributes to the background air in the extratropical lowermost stratosphere.

scholarly journals Measurements of NO, NO<sub>y</sub>, N<sub>2</sub>O, and O<sub>3</sub> during SPURT: implications for transport and chemistry in the lowermost stratosphere

2005 ◽  
Vol 5 (5) ◽  
pp. 8649-8688 ◽  
Author(s):  
M. I. Hegglin ◽  
D. Brunner ◽  
Th. Peter ◽  
P. Hoor ◽  
H. Fischer ◽  
...  
Keyword(s):  
Atmospheric Transport ◽  
Potential Temperature ◽  
Transport Processes ◽  
Ozone Production ◽  
Data Set ◽  
Latitude Range ◽  
Mixing Ratios ◽  
Tropical Tropopause ◽  
Tropopause Region ◽  
Extratropical Tropopause

Abstract. We present measurements of NO, NOy, O3, and N2O within the lowermost stratosphere (LMS) over Europe obtained during the SPURT project. The measurements cover each of the four seasons during two years between November 2001 and July 2003, and probe the entire altitude and latitude range of the LMS: from 5° N to 85° N equivalent latitude, and from 290 to 375 K potential temperature. The measurements represent a comprehensive data set of these tracers and reveal atmospheric transport processes that influence tracer distributions in the LMS. Mean mixing ratios of stratospheric tracers in equivalent latitude-potential temperature coordinates show a clear seasonal cycle related to the Brewer-Dobson circulation with highest values in spring and lowest values in autumn. Vertical profiles show strong gradients at the extratropical tropopause suggesting that vertical (cross-isentropic) mixing is reduced above the tropopause. Mixing along isentropes is also strongly reduced since pronounced meridional gradients are found on potential temperature surfaces in the LMS. Concurrent large gradients in PV in the vertical and in the meridional direction horizontally suggest the presence of a transport and mixing barrier. Well above the tropopause distinguished seasonal cycles were found in the correlation slopes ΔO3/ΔN2O and ΔNOy/ΔN2O. Smallest slopes found during spring indicate chemically aged stratospheric air originating from high altitudes and latitudes. The slopes are larger in summer and autumn suggesting that a substantial fraction of air takes a 'short-cut' from the tropical tropopause region into the extratropical LMS. The comparison of measured NO with critical NO values at which net ozone production changes from negative to positive implies a net ozone production up to 20 K above the local tropopause in winter, increasing during spring and summer to up to 50 K in autumn. Above this height NO values favor ozone destruction.

scholarly journals Uncertainties in modelling the stratospheric warming following Mt. Pinatubo eruption

2013 ◽  
Vol 13 (2) ◽  
pp. 4601-4635 ◽  
Author(s):  
F. Arfeuille ◽  
B. P. Luo ◽  
P. Heckendorn ◽  
D. Weisenstein ◽  
J. X. Sheng ◽  
...  
Keyword(s):  
General Circulation ◽  
Climate Model ◽  
Circulation Model ◽  
Temperature Record ◽  
Size Distributions ◽  
Stratospheric Warming ◽  
Extinction Data ◽  
Tropical Tropopause ◽  
Pinatubo Eruption ◽  
Tropopause Region

Abstract. In terms of atmospheric impact, the volcanic eruption of Mt. Pinatubo (1991) is the best characterized large eruption on record. We investigate here the stratospheric warming following the Pinatubo eruption derived from SAGE II extinction data including most recent improvements in the processing algorithm and a data filling procedure in the opacity-induced "gap" regions. From these data, which cover wavelengths of 1.024 micrometer and shorter, we derived aerosol size distributions which properly reproduce extinction coefficients at much longer wavelength. This provides a good basis for calculating the absorption of terrestrial infrared radiation and the resulting stratospheric heating. However, we also show that the use of this dataset in the global chemistry-climate model (CCM) SOCOL leads to exaggerated aerosol-induced stratospheric heating compared to observations, even partly larger than the already too high values found by many models in recent general circulation model (GCM) and CCM intercomparisons. This suggests that the overestimation of the stratospheric warming after the Pinatubo eruption arises from deficiencies in the model radiation codes rather than an insufficient observational data basis. Conversely, our approach reduces the infrared absorption in the tropical tropopause region, in better agreement with the post-volcanic temperature record at these altitudes.

Volcanic aerosol heating in the tropical tropopause region and associated water vapour changes

2021 ◽  
Author(s):  
Clarissa Kroll ◽  
Hauke Schmidt ◽  
Claudia Timmreck
Keyword(s):  
Water Vapour ◽  
Volcanic Eruptions ◽  
Aerosol Layer ◽  
Volcanic Aerosol ◽  
Surface Warming ◽  
Tropical Tropopause ◽  
Tropopause Region ◽  
Cold Point ◽  
The Impact

&lt;p&gt;Large volcanic eruptions affect the distribution of atmospheric water vapour, for instance through cooling of the surface, warming of the lowermost stratosphere, and increasing the upwelling in the tropical tropopause region.&lt;/p&gt;&lt;p&gt;To better understand the volcanic impact on the tropical tropopause region and associated changes in the water vapour distribution in the stratosphere we employ a combination of short term convection-resolving global simulations with ICON and long term low resolution ensemble simulations with the MPI-ESM1.2-LR EVAens&lt;strong&gt;, &lt;/strong&gt;both with prescribed volcanic forcing. With the EVAens a long term statistical analysis of the water vapour trends during the build-up and decay of a volcanic aerosol layer is made possible. The impact of the heating in the cold point regions is studied for five different eruption magnitudes. Stratospheric water vapour changes are analyzed in simulations with synthetic and observation based aerosol profiles showing that the distance of the aerosol profile from the cold point region can be more important for the water vapour entry into the stratosphere than the emitted amount of sulfur.&lt;/p&gt;&lt;p&gt;Whereas the EVAens is ideal to investigate the slow ascent of water vapour into the stratosphere the 10 km high resolution simulations with ICON allow insights into the convective changes after volcanic eruptions going beyond the limitations parameterizations usually impose on the model data.&lt;/p&gt;

scholarly journals Seven years of IASI ozone retrievals from FORLI: validation with independent total column and vertical profile measurements

2016 ◽  
Vol 9 (9) ◽  
pp. 4327-4353 ◽  
Author(s):  
Anne Boynard ◽  
Daniel Hurtmans ◽  
Mariliza E. Koukouli ◽  
Florence Goutail ◽  
Jérôme Bureau ◽  
...  
Keyword(s):  
Global Scale ◽  
Vertical Profiles ◽  
High Latitudes ◽  
Limited Information ◽  
Brightness Temperatures ◽  
Tropical Tropopause ◽  
Global Comparison ◽  
Tropopause Region ◽  
Independent Observations ◽  
Retrieval Software

Abstract. This paper presents an extensive intercomparison and validation for the ozone (O3) product measured by the two Infrared Atmospheric Sounding Interferometers (IASIs) launched on board the MetOp-A and MetOp-B satellites in 2006 and in 2012 respectively. IASI O3 total columns and vertical profiles obtained from Fast Optimal Retrievals on Layers for IASI (FORLI) v20140922 software (running up until recently) are validated against independent observations during the period 2008–2014 on a global scale. On average for the period 2013–2014, IASI-A and IASI-B total ozone columns (TOCs) retrieved using FORLI are consistent, with IASI-B providing slightly lower values with a global difference of only 0.2 ± 0.8 %. The comparison between IASI-A and IASI-B O3 vertical profiles shows differences within ± 2 % over the entire altitude range. Global validation results for 7 years of IASI TOCs from FORLI against the Global Ozone Monitoring Experiment-2 (GOME-2) launched on board MetOp-A and Brewer–Dobson data show that, on average, IASI overestimates the ultraviolet (UV) data by 5–6 % with the largest differences found in the southern high latitudes. The comparison with UV–visible SAOZ (Système d'Analyse par Observation Zénithale) measurements shows a mean bias between IASI and SAOZ TOCs of 2–4 % in the midlatitudes and tropics and 7 % at the polar circle. Part of the discrepancies found at high latitudes can be attributed to the limited information content in the observations due to low brightness temperatures. The comparison with ozonesonde vertical profiles (limited to 30 km) shows that on average IASI with FORLI processing underestimates O3 by  ∼  5–15 % in the troposphere while it overestimates O3 by ∼  10–40 % in the stratosphere, depending on the latitude. The largest relative differences are found in the tropical tropopause region; this can be explained by the low O3 amounts leading to large relative errors. In this study, we also evaluate an updated version of FORLI-O3 retrieval software (v20151001), using look-up tables recalculated to cover a larger spectral range using the latest HITRAN spectroscopic database (HITRAN 2012) and implementing numerical corrections. The assessment of the new O3 product with the same set of observations as that used for the validation exercise shows a correction of ∼  4 % for the TOC positive bias when compared to the UV ground-based and satellite observations, bringing the overall global comparison to ∼  1–2 % on average. This improvement is mainly associated with a decrease in the retrieved O3 concentration in the middle stratosphere (above 30 hPa/25 km) as shown by the comparison with ozonesonde data.

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