scholarly journals Seasonal characteristics of chemical and dynamical transports into the extratropical upper troposphere/lower stratosphere

2018 ◽  
Author(s):  
Yoichi Inai ◽  
Ryo Fujita ◽  
Toshinobu Machida ◽  
Hidekazu Matsueda ◽  
Yousuke Sawa ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Lower Troposphere ◽  
Air Masses ◽  
Upper Troposphere ◽  
Weather Forecasts ◽  
Chemical Tracers ◽  
Spatiotemporal Distributions ◽  
Seasonal Characteristics ◽  
Exchange Processes ◽  
Ch4 And N2o

Abstract. To investigate the seasonal characteristics of chemical tracer distributions in the extratropical upper troposphere and lower stratosphere (ExUTLS) as well as stratosphere–troposphere exchange processes, mixing fractions of air masses originating in the stratosphere, tropical troposphere, mid-latitude lower troposphere (LT), and high-latitude LT in the ExUTLS are estimated using 90-day backward trajectories calculated with European Centre For Medium-Range Weather Forecasts (ECMWF) ERA-Interim data as the meteorological input. Time-series of chemical tracers obtained from ground-based and airborne observations are incorporated into the estimated mixing fractions, thus reconstructing spatiotemporal distributions of chemical tracers in the ExUTLS. The reconstructed tracer distributions are analysed with the mixing fractions and the stratospheric age of air (AoA) estimated using a 10-year backward trajectory. The reconstructed distributions of CO and CO2 in the ExUTLS are affected primarily by tropospheric air masses because of the short chemical lifetime of the former and large seasonal variations in the troposphere of the latter. Distributions of CH4, N2O, and SF6 are controlled primarily by seasonally varying air masses transported from the stratosphere. For CH4 and N2O distributions, air masses transported via the deep branch of the Brewer–Dobson circulation are particularly important. This interpretation is qualitatively and quantitatively supported by the estimated spatiotemporal distributions of AoA.

scholarly journals Seasonal characteristics of trace gas transport into the extratropical upper troposphere and lower stratosphere

2019 ◽  
Vol 19 (10) ◽  
pp. 7073-7103 ◽  
Author(s):  
Yoichi Inai ◽  
Ryo Fujita ◽  
Toshinobu Machida ◽  
Hidekazu Matsueda ◽  
Yousuke Sawa ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Trace Gases ◽  
Source Region ◽  
Lower Troposphere ◽  
Trace Gas ◽  
Air Masses ◽  
Backward Trajectories ◽  
Upper Troposphere ◽  
Passive Behavior ◽  
Seasonal Characteristics

Abstract. To investigate the seasonal characteristics of trace gas distributions in the extratropical upper troposphere and lower stratosphere (ExUTLS) as well as stratosphere–troposphere exchange processes, origin fractions of air masses originating in the stratosphere, tropical troposphere, midlatitude lower troposphere (LT), and high-latitude LT in the ExUTLS are estimated using 10-year backward trajectories calculated with European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim data as the meteorological input. Time series of trace gases obtained from ground-based and airborne observations are incorporated into the trajectories, thus reconstructing spatiotemporal distributions of trace gases in the ExUTLS. The reconstructed tracer distributions are analyzed with the origin fractions and the stratospheric age of air (AoA) estimated using the backward trajectories. The reconstructed distributions of SF6 and CO2 in the ExUTLS are linearly correlated with those of AoA because of their chemically passive behavior and quasi-stable increasing trends in the troposphere. Distributions of CH4, N2O, and CO are controlled primarily by chemical decay along the transport path from the source region via the stratosphere and subsequent mixing of such stratospheric air masses with tropospheric air masses in the ExUTLS.

scholarly journals The impact of organic pollutants from Indonesian peatland fires on the tropospheric and lower stratospheric composition

2021 ◽  
Vol 21 (14) ◽  
pp. 11257-11288
Author(s):  
Simon Rosanka ◽  
Bruno Franco ◽  
Lieven Clarisse ◽  
Pierre-François Coheur ◽  
Andrea Pozzer ◽  
...  
Keyword(s):  
Biomass Burning ◽  
El Niño ◽  
Lower Stratosphere ◽  
El Nino ◽  
Lower Troposphere ◽  
Atmospheric Composition ◽  
Voc Emissions ◽  
Upper Troposphere ◽  
Upward Transport ◽  
The Impact

Abstract. The particularly strong dry season in Indonesia in 2015, caused by an exceptionally strong El Niño, led to severe peatland fires resulting in high volatile organic compound (VOC) biomass burning emissions. At the same time, the developing Asian monsoon anticyclone (ASMA) and the general upward transport in the Intertropical Convergence Zone (ITCZ) efficiently transported the resulting primary and secondary pollutants to the upper troposphere and lower stratosphere (UTLS). In this study, we assess the importance of these VOC emissions for the composition of the lower troposphere and the UTLS and investigate the effect of in-cloud oxygenated VOC (OVOC) oxidation during such a strong pollution event. This is achieved by performing multiple chemistry simulations using the global atmospheric model ECHAM/MESSy (EMAC). By comparing modelled columns of the biomass burning marker hydrogen cyanide (HCN) and carbon monoxide (CO) to spaceborne measurements from the Infrared Atmospheric Sounding Interferometer (IASI), we find that EMAC properly captures the exceptional strength of the Indonesian fires. In the lower troposphere, the increase in VOC levels is higher in Indonesia compared to other biomass burning regions. This has a direct impact on the oxidation capacity, resulting in the largest regional reduction in the hydroxyl radical (OH) and nitrogen oxides (NOx). While an increase in ozone (O3) is predicted close to the peatland fires, simulated O3 decreases in eastern Indonesia due to particularly high phenol concentrations. In the ASMA and the ITCZ, the upward transport leads to elevated VOC concentrations in the lower stratosphere, which results in the reduction of OH and NOx and the increase in the hydroperoxyl radical (HO2). In addition, the degradation of VOC emissions from the Indonesian fires becomes a major source of lower stratospheric nitrate radicals (NO3), which increase by up to 20 %. Enhanced phenol levels in the upper troposphere result in a 20 % increase in the contribution of phenoxy radicals to the chemical destruction of O3, which is predicted to be as large as 40 % of the total chemical O3 loss in the UTLS. In the months following the fires, this loss propagates into the lower stratosphere and potentially contributes to the variability of lower stratospheric O3 observed by satellite retrievals. The Indonesian peatland fires regularly occur during El Niño years, and the largest perturbations of radical concentrations in the lower stratosphere are predicted for particularly strong El Niño years. By activating the detailed in-cloud OVOC oxidation scheme Jülich Aqueous-phase Mechanism of Organic Chemistry (JAMOC), we find that the predicted changes are dampened. Global models that neglect in-cloud OVOC oxidation tend to overestimate the impact of such extreme pollution events on the atmospheric composition.

scholarly journals In situ detection of electrified aerosols in the upper troposphere and in the stratosphere

2013 ◽  
Vol 13 (3) ◽  
pp. 7061-7079 ◽  
Author(s):  
J.-B. Renard ◽  
S. N. Tripathi ◽  
M. Michael ◽  
A. Rawal ◽  
G. Berthet ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Lower Troposphere ◽  
Stratospheric Aerosol ◽  
Balloon Flight ◽  
Model Calculations ◽  
Upper Troposphere ◽  
Charged Aerosols ◽  
In Situ Detection ◽  
Aerosol Counter

Abstract. Electrified aerosols have been observed in the lower troposphere and in the mesosphere, but have never been detected in the stratosphere and upper troposphere. We present measurements of aerosols during a balloon flight to an altitude of ~24 km. The measurements were performed with an improved version of the STAC aerosol counter dedicated to the search for charged aerosols. It is found that most of the aerosols are charged in the upper troposphere for altitudes below 10 km and in the stratosphere for altitudes above 20 km. On the contrary, the aerosols seem to be uncharged between 10 km and 20 km. Model calculations are used to quantify the electrification of the aerosols with a stratospheric aerosol-ion model. The percentages of charged aerosols obtained with model calculations are in excellent agreement with the observations below 10 km and above 20 km. On the other hand, the model cannot reproduce the absence of detected electrification in the lower stratosphere, such that a distinct unknown process in this altitude range inhibits electrification. The presence of sporadic transient layers of electrified aerosol in the upper troposphere and in the stratosphere could have significant implications for sprite formation.

scholarly journals Stratosphere–Troposphere Exchange and O3 Decline in the Lower Stratosphere over Irene SHADOZ Site, South Africa

2020 ◽  
Author(s):  
Thumeka Mkololo ◽  
Nkanyiso Mbatha ◽  
Sivakumar Venkataraman ◽  
Nelson Begue ◽  
Gerrie Coetzee ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Potential Vorticity ◽  
Lower Stratosphere ◽  
Polar Vortex ◽  
Air Masses ◽  
Upper Troposphere ◽  
Average Decrease ◽  
Ozone Trends ◽  
K 12 ◽  
Troposphere Ozone

This study aims to investigate the Stratosphere-Troposphere Exchange (STE) events and ozone trends over Irene (25.5°S, 28.1°E). Twelve years of ozonesondes data (2000–2007, 2012–2015) from Irene station operating in the framework of the Southern Hemisphere Additional Ozonesodes (SHADOZ) was used to study the troposphere (0–16 km) and stratosphere (17– 28 km) ozone (O3) vertical profiles. Ozone profiles were grouped into three categories (2000–2003, 2004–2007 and 2012–2015) and average composites were calculated for each category. Fifteen O3 enhancement events were identified over the study period. These events were observed in all seasons (one event in summer, four events in autumn, five events in winter and five events in spring), however, they predominantly occur in winter and spring. The STE events presented here are observed to be influenced by the Southern Hemisphere polar vortex. During the STE events, the advected potential vorticity maps assimilated using Modélisation Isentrope du transport Méso–échelle de l’Ozone Stratosphérique par Advection (MIMOSA) model for the 350 K (~12–13 km) isentropic level indicated a transport of high latitude air masses which seems to be responsible for the reduction of the O3 mole fractions at the lower stratosphere over Irene which takes place at the same time with the enhancement of ozone in the upper troposphere. In general, the stratosphere is dominated by higher Modern Retrospective Analysis for Research Application (MERRA-2) potential vorticity (PV) values compared to the troposphere. However, during the STE events, higher PV values from the stratosphere were observed to intrude the troposphere. Ozone decline was observed from 12 km to 24 km with highest decline occurring from 14 km to 18 km. An average decrease of 6.0 and 9.1% was calculated from 12 to 24 km in 2004–2007 and 2012–2015 respectively. The observed decline occurred in the upper troposphere and lower stratosphere with winter and spring showing more decline compared with summer and autumn.

scholarly journals Methane (CH<sub>4</sub>) and nitrous oxide (N<sub>2</sub>O) from ground-based FTIR at Addis Ababa: observations, error analysis and comparison with satellite data

2019 ◽  
Author(s):  
Temesgen Yirdaw Berhe ◽  
Gizaw Mengistu Tsidu ◽  
Thomas Blumenstock ◽  
Frank Hase ◽  
Gabriele P. Stiller
Keyword(s):  
Nitrous Oxide ◽  
Spectral Resolution ◽  
Lower Stratosphere ◽  
Addis Ababa ◽  
Negative Bias ◽  
Positive Bias ◽  
Altitude Range ◽  
Upper Troposphere ◽  
Maximum Value ◽  
Ch4 And N2o

Abstract. A ground based high spectral resolution Fourier transform infrared (FTIR) spectrometer has been operational at Addis Ababa (9.0° N, 38.76° E, 2443 m a.s.l.) since May 2009 to obtain information on the total column abundances and vertical distribution of various constituents in the atmosphere. The retrieval strategy and the results on information content and corresponding full error budget evaluation for methane and nitrous oxide retrievals are presented. They reveal the high quality of FTIR measurements at Addis Ababa. The FTIR products of CH4 and N2O have been compared to coincident volume mixing ratio (VMR) measurements obtained from the reduced spectral resolution (Institute of Meteorology and Climate Research) IMK/IAA MIPAS satellite instrument (Version V5R_CH4_224 and V5R_N2O_224), the Microwave Limb Sounder on board of the Aura satellite (Aura/MLS) (MLS v3.3 of N2O and CH4 derived from MLS v3.3 products of CO, N2O and H2O) and the Atmospheric Infrared Sounder (AIRS). From comparison of FTIR CH4 and IMK/IAA MIPAS V5R_CH4_224, a statistically significant bias between −4.8 and +4.6 % in altitude ranges of the upper troposphere and lower stratosphere (15–27 km) are determined. The largest negative bias in FTIR CH4 is found in the altitude range of 11–19 km with a maximum difference of −0.08 ppmv (−4.8 %) at around 15 km, a positive bias of less than 0.14 ppmv (9 %) is found in the altitude range of 21 to 27 km with a maximum value at around 27 km with respect to AIRS. On the other hand, comparison of CH4 from ground based FTIR and MLS-derived CH4 (version 3.3) indicate existence of a significant positive bias of 2.3 % to 11 % in the altitude range of 20 to 27 km and a negative bias −1.7 % at 17 km. In the case of N2O derived from FTIR and MIPAS V5R_N2O_224 comparison, a significant positive bias of less than 15 % in the altitude range 22–27 km with a maximum value at around 25 km and a negative bias of −7 % have been found at 17 km. A positive bias of less than 18.6 % in FTIR N2O for the altitude below 27 km is noted when compared to MLS v3.3 N2O. Precision of ground based FTIR CH4 and N2O in the upper troposphere and lower stratosphere over Addis Ababa are better than 7.2 % and 9 %, respectively which are comparable to the bias obtained from the comparisons.

scholarly journals Performance of the Vaisala RS80A/H and RS90 Humicap Sensors and the Meteolabor “Snow White” Chilled-Mirror Hygrometer in Paramaribo, Suriname

2006 ◽  
Vol 23 (11) ◽  
pp. 1506-1518 ◽  
Author(s):  
Gé Verver ◽  
Masatomo Fujiwara ◽  
Pier Dolmans ◽  
Cor Becker ◽  
Paul Fortuin ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Time Lag ◽  
Lower Troposphere ◽  
Upper Troposphere ◽  
Weather Forecasts ◽  
Snow White ◽  
Study Results ◽  
The Tropics ◽  
Humidity Profiles ◽  
Dry Bias

Abstract In climate research there is a strong need for accurate observations of water vapor in the upper atmosphere. Radiosoundings provide relative humidity profiles but the accuracy of many routine instruments is notoriously inadequate in the cold upper troposphere. In this study results from a soundings program executed in Paramaribo, Suriname (5.8°N, 55.2°W), are presented. The aim of this program was to compare the performance of different humidity sensors in the upper troposphere in the Tropics and to test different bias corrections suggested in the literature. The payload of each sounding consisted of a chilled-mirror “Snow White” sensor from Meteolabor AG, which was used as a reference, and two additional sensors from Vaisala, that is, either the RS80A, the RS80H, or the RS90. In total 37 separate soundings were made. For the RS80A a clear, dry bias of between −4% and −8% RH is found in the lower troposphere compared to the Snow White observation, confirming the findings in previous studies. A mean dry bias was found in the upper troposphere, which could be effectively corrected. The RS80H sensor shows a significant wet bias of 2%–5% in RH in the middle and upper troposphere, which has not been reported before. Comparing observations with RS80H sensors of different ages gives no indication of sensor aging or sensor contamination. It is therefore concluded that the plastic cover introduced by Vaisala to avoid sensor contamination is effective. Finally, the RS90 sensor yields a small but significant wet bias of 2%–3% below 7-km altitude. The time-lag error correction from Miloshevich et al. was applied to the Vaisala data, which resulted in an increased variability in the relative humidity profile above 9- (RS80A), 8- (RS80H), and 11-km (RS90) altitude, respectively, which is in better agreement with the Snow White data. The averaged Snow White profile is compared with the average profiles of relative humidity from the European Centre for Medium-Range Weather Forecasts (ECMWF). No significant bias is found in either the analyses or the forecasts. The correlation coefficient for the Snow White and ECMWF data between 200 and 800 hPa was 0.66 for the 36-h forecast and 0.77 for the analysis.

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 Ground-based water vapor raman lidar measurements up to the upper troposphere and lower stratosphere for long-term monitoring

2012 ◽  
Vol 5 (1) ◽  
pp. 17-36 ◽  
Author(s):  
T. Leblanc ◽  
I. S. McDermid ◽  
T. D. Walsh
Keyword(s):  
Water Vapor ◽  
Lower Stratosphere ◽  
Lower Troposphere ◽  
Atmospheric Composition ◽  
Raman Lidar ◽  
Upper Troposphere ◽  
Lidar Measurements ◽  
Development Data ◽  
Instrumental Development

Abstract. Recognizing the importance of water vapor in the upper troposphere and lower stratosphere (UTLS) and the scarcity of high-quality, long-term measurements, JPL began the development of a powerful Raman lidar in 2005 to try to meet these needs. This development was endorsed by the Network for the Detection of Atmospheric Composition Change (NDACC) and the validation program for the EOS-Aura satellite. In this paper we review the stages in the instrumental development, data acquisition and analysis, profile retrieval and calibration procedures of the lidar, as well as selected results from three validation campaigns: MOHAVE (Measurements of Humidity in the Atmosphere and Validation Experiments), MOHAVE-II, and MOHAVE 2009. In particular, one critical result from this latest campaign is the very good agreement (well below the reported uncertainties) observed between the lidar and the Cryogenic Frost-Point Hygrometer in the entire lidar range 3–20 km, with a mean bias not exceeding 2% (lidar dry) in the lower troposphere, and 3% (lidar moist) in the UTLS. Ultimately the lidar has demonstrated capability to measure water vapor profiles from ∼1 km above the ground to the lower stratosphere with a precision of 10% or better near 13 km and below, and an estimated accuracy of 5%. Since 2005, nearly 1000 profiles have been routinely measured, and since 2009, the profiles have typically reached 14 km for one-hour integration times and 1.5 km vertical resolution, and can reach 21 km for 6-h integration times using degraded vertical resolutions. These performance figures show that, with our present target of routinely running our lidar two hours per night, 4 nights per week, we can achieve measurements with a precision in the UTLS equivalent to that achieved if launching one CFH per month.

scholarly journals Air mass origins influencing TTL chemical composition over West Africa during 2006 summer monsoon

2010 ◽  
Vol 10 (22) ◽  
pp. 10753-10770 ◽  
Author(s):  
K. S. Law ◽  
F. Fierli ◽  
F. Cairo ◽  
H. Schlager ◽  
S. Borrmann ◽  
...  
Keyword(s):  
West Africa ◽  
Summer Monsoon ◽  
Large Scale ◽  
Lower Stratosphere ◽  
Deep Convection ◽  
Lower Troposphere ◽  
Trace Gas ◽  
Air Mass ◽  
Back Trajectories ◽  
Air Masses

Abstract. Trace gas and aerosol data collected in the tropical tropopause layer (TTL) between 12–18.5 km by the M55 Geophysica aircraft as part of the SCOUT-AMMA campaign over West Africa during the summer monsoon in August 2006 have been analysed in terms of their air mass origins. Analysis of domain filling back trajectories arriving over West Africa, and in the specific region of the flights, showed that the M55 flights were generally representative of air masses arriving over West Africa during the first 2 weeks of August, 2006. Air originating from the mid-latitude lower stratosphere was under-sampled (in the mid-upper TTL) whilst air masses uplifted from central Africa (into the lower TTL) were over-sampled in the latter part of the campaign. Signatures of recent (previous 10 days) origins were superimposed on the large-scale westward flow over West Africa. In the lower TTL, air masses were impacted by recent local deep convection over Africa at the level of main convective outflow (350 K, 200 hPa) and on certain days up to 370 K (100 hPa). Estimates of the fraction of air masses influenced by local convection vary from 10 to 50% depending on the method applied and from day to day during the campaign. The analysis shows that flights on 7, 8 and 11 August were more influenced by local convection than on 4 and 13 August allowing separation of trace gas and aerosol measurements into "convective" and "non-convective" flights. Strong signatures, particularly in species with short lifetimes (relative to CO2) like CO, NO and fine-mode aerosols were seen during flights most influenced by convection up to 350–365 K. Observed profiles were also constantly perturbed by uplift (as high as 39%) of air masses from the mid to lower troposphere over Asia, India, and oceanic regions resulting in import of clean oceanic (e.g. O3-poor) or polluted air masses from Asia (high O3, CO, CO2) into West Africa. Thus, recent uplift of CO2 over Asia may contribute to the observed positive CO2 gradients in the TTL over West Africa. This suggests a more significant fraction of younger air masses in the TTL and needs to taken into consideration in derivations of mean age of air. Transport of air masses from the mid-latitude lower stratosphere had an impact from the mid-TTL upwards (20–40% above 370 K) during the campaign period importing air masses with high O3 and NOy. Ozone profiles show a less pronounced lower TTL minimum than observed previously by regular ozonesondes at other tropical locations. Concentrations are less than 100 ppbv in the lower TTL and vertical gradients less steep than in the upper TTL. The air mass origin analysis and simulations of in-situ net photochemical O3 production, initialised with observations, suggest that the lower TTL is significantly impacted by uplift of O3 precursors (over Africa and Asia) leading to positive production rates (up to 2 ppbv per day) in the lower and mid TTL even at moderate NOx levels. Photochemical O3 production increases with higher NOx and H2O in air masses with O3 less than 150 ppbv.

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