scholarly journals Characterizing tropospheric ozone and CO around Frankfurt between 1994–2012 based on MOZAIC-IAGOS aircraft measurements

2015 ◽  
Vol 15 (17) ◽  
pp. 23841-23891 ◽  
Author(s):  
H. Petetin ◽  
V. Thouret ◽  
A. Fontaine ◽  
B. Sauvage ◽  
G. Athier ◽  
...  

Abstract. In the framework of the MOZAIC-IAGOS program, ozone and carbon monoxide vertical profiles are available since 1994 and 2002, respectively. This study investigates the variability and trends of both species at several tropospheric layers above the Frankfurt and Munich airports where about 21 600 flights have been performed over the 1994–2012 period, which represents the densest dataset in the world (about 75 flights per month on average). Over that period, most mean ozone trends are positive but insignificant at a 95 % confidence level, except in winter where significant upward trends (around +0.38 ± 0.24 ppb yr−1) are found. Conversely, a significant increase of annual background ozone is highlighted, mostly during winter and autumn. Mean annual ozone trends increase with altitude, the largest increase being found in summer due to a noticeable decrease of highest ozone concentrations observed in the lower troposphere during the second half period. Over the 2002–2012 period, most mean CO trends are significantly negative, the decrease being higher in the lower troposphere compared to the mid- and upper troposphere with again, major differences in summer. Trends in the ozone seasonal cycle are also investigated, with a focus on the phase. Ozone maxima occur earlier and earlier with a shift around −10.6 ± 2.9 days decade−1 in the lower troposphere, in agreement with previous studies. The analysis of other ozone datasets in Europe (including surface stations and ozone soundings) confirms this trend, but highlights strong heterogeneities in the phase change. Interestingly, this shift is shown to decrease with altitude, with trends of −4.3 ± 2.4 and −2.0 ± 1.7 days decade−1 in the mid- and upper troposphere, respectively. The geographic origin of the air masses sampled by aircraft is analysed with FLEXPART backward simulations and suggests, together with trends and phase changes results, that an increase of the Asian contribution to ozone in the upper troposphere may compensate during summer the decrease of European and North American contributions associated to emission control over these two regions.

2019 ◽  
Vol 19 (10) ◽  
pp. 7073-7103 ◽  
Author(s):  
Yoichi Inai ◽  
Ryo Fujita ◽  
Toshinobu Machida ◽  
Hidekazu Matsueda ◽  
Yousuke Sawa ◽  
...  

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.


2013 ◽  
Vol 6 (5) ◽  
pp. 1413-1423 ◽  
Author(s):  
W. W. Verstraeten ◽  
K. F. Boersma ◽  
J. Zörner ◽  
M. A. F. Allaart ◽  
K. W. Bowman ◽  
...  

Abstract. In this analysis, Tropospheric Emission Spectrometer (TES) V004 nadir ozone (O3) profiles are validated with more than 4400 coinciding ozonesonde measurements taken across the world from the World Ozone and Ultraviolet Radiation Data Centre (WOUDC) during the period 2005–2010. The TES observation operator was applied to the sonde data to ensure a consistent comparison between TES and ozonesonde data, i.e. without the influence of the a priori O3 profile needed to regulate the retrieval. Generally, TES V004 O3 retrievals are biased high by 2–7 ppbv (7–15%) in the troposphere, consistent with validation results from earlier studies. Because of two degrees of freedom for signal in the troposphere, we can distinguish between upper and lower troposphere mean biases, respectively ranging from −0.4 to +13.3 ppbv for the upper troposphere and +3.9 to +6.0 ppbv for the lower troposphere. Focusing on the 464 hPa retrieval level, broadly representative of the free tropospheric O3, we find differences in the TES biases for the tropics (+3 ppbv, +7%), sub-tropics (+5 ppbv, +11%), and northern (+7 ppbv, +13%) and southern mid-latitudes (+4 ppbv, +10%). The relatively long-term record (6 yr) of TES–ozonesonde comparisons allowed us to quantify temporal variations in TES biases at 464 hPa. We find that there are no discernable biases in each of these latitudinal bands; temporal variations in the bias are typically within the uncertainty of the difference between TES and ozonesondes. Establishing these bias patterns is important in order to make meaningful use of TES O3 data in applications such as model evaluation, trend analysis, or data assimilation.


Author(s):  
Thumeka Mkololo ◽  
Nkanyiso Mbatha ◽  
Sivakumar Venkataraman ◽  
Nelson Begue ◽  
Gerrie Coetzee ◽  
...  

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.


2018 ◽  
Author(s):  
Ryan S. Williams ◽  
Michaela I. Hegglin ◽  
Brian J. Kerridge ◽  
Patrick Jöckel ◽  
Barry G. Latter ◽  
...  

Abstract. The stratospheric contribution to tropospheric ozone (O3) has been a subject of much debate in recent decades, but is known to have an important influence. Recent improvements in diagnostic and modelling tools provide new evidence that the stratosphere has a much larger influence than previously thought. This study aims to characterise the seasonal and geographical distribution of tropospheric ozone, its variability and changes, and provide quantification of the stratospheric influence on these measures. To this end, we evaluate hindcast specified dynamics chemistry-climate model (CCM) simulations from the ECHAM/MESSy Atmospheric Chemistry (EMAC) model and the Canadian Middle Atmosphere Model (CMAM), as contributed to the IGAC/SPARC Chemistry Climate Model Initiative (CCMI) activity, together with satellite observations from the Ozone Monitoring Instrument (OMI) and ozonesonde profile measurements from the World Ozone and Ultraviolet Radiation Data Centre (WOUDC) over a period of concurrent data availability (2005–2010). An overall positive, seasonally dependent bias in 1000–450 hPa (~ 0–5.5 km) subcolumn ozone is found for EMAC, ranging from 2–8 Dobson Units (DU), whereas CMAM is found to be in closer agreement with the observations, although with substantial seasonal and regional variation in the sign and magnitude of the bias (~ −4 to +4 DU). Although the application of OMI averaging kernels (AKs) improves agreement with model estimates from both EMAC and CMAM as expected, comparisons with ozonesondes indicate a positive ozone bias in the lower stratosphere in CMAM, together with an underestimation of photochemical ozone production (negative bias) in the troposphere. Model variability is found to be more similar in magnitude to that implied from ozonesondes, in comparison with OMI which has significantly larger variability. Noting the overall consistency of the CCMs, the influence of the model chemistry schemes and internal dynamics is discussed in relation to the inter-model differences found. In particular, it is shown that CMAM simulates a faster and shallower Brewer-Dobson Circulation (BDC) relative to both EMAC and observational estimates, which has implications for the distribution and magnitude of the downward flux of stratospheric ozone, over the most recent climatological period (1980–2010). Nonetheless, it is shown that the stratospheric influence on tropospheric ozone is larger than previously thought and is estimated to exceed 50 % in the wintertime extratropics, even in the lower troposphere. Finally, long term changes in the CCM ozone tracers are calculated for different seasons between 1980–89 and 2001–10. An overall statistically significant increase in tropospheric ozone is found across much of the world, but particularly in the Northern Hemisphere and in the middle to upper troposphere, where the increase is on the order of 4–6 ppbv (5–10 %). Our model study implies that attribution from stratosphere-troposphere exchange (STE) to such ozone changes ranges from 25–30 % at the surface to as much as 50–80 % in the upper troposphere-lower stratosphere (UTLS) across many regions of the world. These findings highlight the importance of a well-resolved stratosphere in simulations of tropospheric ozone and its implications for the radiative forcing, air quality and oxidation capacity of the troposphere.


2011 ◽  
Vol 11 (11) ◽  
pp. 31115-31136 ◽  
Author(s):  
M. T. Montgomery ◽  
R. K. Smith

Abstract. Analyses of thermodynamic data gathered from airborne dropwindsondes during the Tropical Cyclone Structure (2008) experiment are presented for the disturbance that became Typhoon Nuri. Although previous work has suggested that Nuri formed within the protective recirculating "pouch" region of a westward-propagating wave-like disturbance and implicated rotating deep convective clouds in driving the inflow to spin up the tangential circulation of the system-scale flow, the nature of the thermodynamic environment that supported the genesis remains a topic of debate. During the genesis phase, vertical profiles of virtual potential temperature show little variability between soundings on a particular day and the system-average soundings likewise show a negligible change. There is a tendency also for the lower and middle troposphere to moisten. However, the data show that on the scale of the recirculating region of the disturbance, there was no noticeable reduction of virtual temperature in the lower troposphere, but a small warming (less than 1 K) in the upper troposphere. Vertical profiles of pseudo-equivalent potential temperature, θe, during the genesis show a modestly decreasing deficit of θe in the vertical between the surface and a height of minimum θe (between 3 and 4 km), from 17.5 K to 15.2 K. The findings reported here are consistent with that found for developing disturbances observed in the Pre-Depression Investigation of Cloud Systems in the Tropics (PREDICT) experiment in 2010. Some implications of the findings are discussed.


2003 ◽  
Vol 3 (2) ◽  
pp. 459-468 ◽  
Author(s):  
M. Traub ◽  
H. Fischer ◽  
M. de Reus ◽  
R. Kormann ◽  
H. Heland ◽  
...  

Abstract. During the Mediterranean Intensive Oxidant Study (MINOS) in August 2001 a total of 14 measurement flights were performed with the DLR Falcon jet aircraft from Heraklion, Crete. One objective of this campaign was to investigate the role of long-range transport of pollutants into the Mediterranean area. An analysis of 5-day back trajectories indicates that in the lower troposphere (0-4 km) air masses originated from eastern and western Europe, in the mid-troposphere (4-8 km) from the North Atlantic Ocean region and in the upper troposphere (8-14 km) from North Atlantic Ocean/North America (NANA) as well as South Asia. We allocated all back trajectories to clusters based on their ending height and source region. The mixing ratios of ozone, nitrogen oxide, total reactive oxidized nitrogen (NOy), formaldehyde, methanol, acetonitrile, acetone, peroxyacetyl nitrate (PAN), carbon dioxide, carbon monoxide and methane measured along the flight tracks are examined in relation to the different cluster trajectories. In the lower troposphere the mean trace gas mixing ratios of the eastern Europe cluster trajectories were significantly higher than those from western Europe. In the upper troposphere air from the NANA region seems to be influenced by the stratosphere, in addition, air masses were transported from South Asia, being influenced by strong convection in the Indian monsoon.


2018 ◽  
Author(s):  
Yoichi Inai ◽  
Ryo Fujita ◽  
Toshinobu Machida ◽  
Hidekazu Matsueda ◽  
Yousuke Sawa ◽  
...  

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.


2003 ◽  
Vol 3 (1) ◽  
pp. 107-134 ◽  
Author(s):  
M. Traub ◽  
H. Fischer ◽  
M. de Reus ◽  
R. Kormann ◽  
J. Heland ◽  
...  

Abstract. During the Mediterranean Intensive Oxidant Study (MINOS) in August 2001 a total of 14 measurement flights were performed with the DLR Falcon aircraft from Heraklion, Crete. One objective of this campaign was to investigate the role of long-range transport of pollutants into the Mediterranean area. An analysis of 5-day back trajectories indicates that in the lower troposphere (0–4 km) air masses originated from eastern and western Europe, in the mid-troposphere (4–8 km) from the Atlantic Ocean region and in the upper troposphere (8–14 km) from North Artlantic Ocean/North America  (NAONA) as well as South Asia. We allocated all back trajectories to clusters based on their ending height and source region. The mixing ratios of ozone, nitrogen oxide, total reactive oxidized nitrogen (NOy), formaldehyde, methanol, acetonitrile, acetone, peroxyacetyl nitrate (PAN), carbon dioxide, carbon monoxide and methane measured along the flight tracks are examined in relation to the different cluster trajectories. In the lower troposphere the mean gas mixing ratios of the eastern Europe cluster trajectories were significantly higher than that from western Europe. Considering 2-day instead of 5-day trajectories the relative differences between the concentrations of these two clusters increased. In the upper troposphere relatively high concentrations of  O3 and NOy, combined with low CO of the NAONA trajectories indicate mixing with stratospheric air masses.


2017 ◽  
Author(s):  
Naveen Chandra ◽  
Sachiko Hayashida ◽  
Tazu Saeki ◽  
Prabir K. Patra

Abstract. Methane (CH4) is one of the most important short-lived climate forcer (SLCFs) according to the United Nations Environment Programme as well as it plays also a critical role in air pollution chemistry in the troposphere. With the availability of satellite observations from space, variabilities in CH4 have been captured for most parts of the global land with major emissions. The satellite observations however do not allow us to derive emission information straightforwardly, unlike in-situ measurements near the source region, without separating the role of transport and chemistry in the columnar dry-air mole fractions of methane (XCH4), which involves the CH4 densities at all altitudes along the solar light path. Observations of enhanced XCH4 are often linked to the local/regional emissions by simple correlation, without separating transport and chemistry contributions to XCH4 variability. Here, we present the analysis of XCH4 variability over different inland and surrounding cleaner oceanic regions of India using GHGs Observation SATellite (GOSAT). We also use the JAMSTEC's state-of-the-art atmospheric chemistry-transport model (ACTM) for simulating the observed XCH4 concentrations by varying surface emissions. The model-observation comparisons help us to elucidate the synoptic and seasonal variabilities in XCH4 in relation with coupled monsoon meteorology and surface fluxes. Distinct seasonal variations of XCH4 have been observed over the regions lying in the northern (north of 15° N) and southern part (south of 15° N) of India, corresponding to the peak during southwest (SW) monsoon (July–September) and early autumn season (October–December), respectively. The detailed study of all possible governing factors (transport, emission and chemistry) responsible for XCH4 seasonal cycle suggests that distinct XCH4 seasonal cycle over northern and southern regions of India is not only governed by the heterogeneous distributions of surface emissions, but also distribution of CH4 in the upper tropospheric layer. We have observed different contributions from lower troposphere (~1000–600 hPa), affected mainly by surface emissions, and transport dominated upper atmosphere (~600–0 hPa) in the XCH4 seasonal cycle. Over most of northern part of the Indian regions, up to 40 % of the peak during the SW monsoon season is attributed to the lower troposphere, while ~ 60 % to uplifted high-CH4 air masses in the upper atmosphere. In contrast, XCH4 enhancement over the semi-arid western India is mainly (~ 88 %) attributed to the upper atmosphere. The ratios of contribution changed over the southern peninsula and cleaner oceanic region; up to 60 % of seasonal cycle of XCH4 is contributed by lower tropospheric region. These differences arise due to the complex atmospheric transport mechanisms, caused by the seasonally varying monsoon. The CH4 enriched air masses uplifted from high emission region by the SW monsoon circulation and deep cumulus convection, and then confined by anticyclonic wind in the upper troposphere (~ 200 hPa), cause the strong contribution of the upper troposphere in the peak of XCH4 over most of the regions lying in the northern part of India. Based on this analysis, we suggest that a link between surface emissions and higher levels of XCH4 is not always valid over Asian monsoon regions, although there is often a fair correlation between surface emissions and XCH4.


2012 ◽  
Vol 12 (9) ◽  
pp. 4001-4009 ◽  
Author(s):  
M. T. Montgomery ◽  
R. K. Smith

Abstract. Analyses of thermodynamic data gathered from airborne dropwindsondes during the Tropical Cyclone Structure (2008) experiment are presented for the disturbance that became Typhoon Nuri. Although previous work has suggested that Nuri formed within the protective recirculating "pouch" region of a westward propagating wave-like disturbance and implicated rotating deep convective clouds in driving the inflow to spin up the tangential circulation of the system-scale flow, the nature of the thermodynamic environment that supported the genesis remains a topic of debate. During the genesis phase, vertical profiles of virtual potential temperature show little variability between soundings on a particular day and the system-average soundings likewise show a negligible change. There is a tendency also for the lower and middle troposphere to moisten. However, the data show that, on the scale of the recirculating region of the disturbance, there was no noticeable reduction of virtual temperature in the lower troposphere, but a small warming (less than 1 K) in the upper troposphere. Vertical profiles of pseudo-equivalent potential temperature, θe, during the genesis show a modestly decreasing deficit of θe in the vertical between the surface and the height of minimum θe (between 3 and 4 km), from 17.5 K to 15.2 K. The findings reported here are consistent with those found for developing disturbances observed in the Pre-Depression Investigation of Cloud Systems in the Tropics (PREDICT) experiment in 2010. Some implications of the findings are discussed.


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