scholarly journals Diagnosing the transition layer in the extra-tropical lowermost stratosphere using MLS O<sub>3</sub> and MOPITT CO analyses

2012 ◽  
Vol 12 (8) ◽  
pp. 22023-22057
Author(s):  
J. Barré ◽  
L. El Amraoui ◽  
P. Ricaud ◽  
J.-L. Attié ◽  
W. A. Lahoz ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Transition Layer ◽  
Transport Model ◽  
Global Scale ◽  
Model Resolution ◽  
Mixing Processes ◽  
Chemistry Transport Model ◽  
Coarse Model

Abstract. The behavior of the Extra-tropical Transition Layer (ExTL) in the lowermost stratosphere is investigated using a Chemistry Transport Model (CTM) and analyses derived from assimilation of MLS (Microwave Limb Sounder) O3 and MOPITT (Measurements Of Pollution In The Troposphere) CO data. We use O3-CO correlations to quantify the effect of the assimilation on the height and depth of the ExTL. We firstly focus on a Stratosphere-Troposphere Exchange (STE) case study which occurred on 15 August 2007 over the British Isles (50° N, 10° W). We also extend the study at the global scale for the month of August 2007. For the STE case study, MOPITT CO analyses have the capability to sharpen the ExTL distribution whereas MLS O3 analyses provide a tropospheric expansion of the ExTL distribution with its maximum close to the thermal tropopause. When MLS O3 and MOPITT CO analyses are used together, the ExTL shows more realistic results and matches the thermal tropopause. At global scale, MOPITT CO analyses still show a sharper chemical transition between stratosphere and troposphere than the free model run. MLS O3 analyses move the ExTL toward the troposphere and broaden it. When MLS O3 analyses and MOPITT CO analyses are used together the ExTL matches the thermal tropopause poleward of 50°. This study shows that data assimilation can help overcome the shortcomings associated with a relatively coarse model resolution. The ExTL spread is larger in the Northern Hemisphere than the Southern Hemisphere suggesting that mixing processes are more active in the UTLS in the Northern Hemisphere than in the Southern Hemisphere. This work opens perspectives for studying the seasonal variations of the ExTL at extra-tropical latitudes.

scholarly journals Diagnosing the transition layer at extratropical latitudes using MLS O<sub>3</sub> and MOPITT CO analyses

2013 ◽  
Vol 13 (14) ◽  
pp. 7225-7240 ◽  
Author(s):  
J. Barré ◽  
L. El Amraoui ◽  
P. Ricaud ◽  
W. A. Lahoz ◽  
J.-L. Attié ◽  
...  
Keyword(s):  
Data Assimilation ◽  
Transition Region ◽  
Transition Layer ◽  
Transport Model ◽  
Global Scale ◽  
British Isles ◽  
Chemistry Transport Model ◽  
Free Model ◽  
The Relationship

Abstract. The behavior of the extratropical transition layer (ExTL) is investigated using a chemistry transport model (CTM) and analyses derived from assimilation of MLS (Microwave Limb Sounder) O3 and MOPITT (Measurements Of Pollution In The Troposphere) CO data. We firstly focus on a stratosphere–troposphere exchange (STE) case study that occurred on 15 August 2007 over the British Isles (50° N, 10° W). We evaluate the effect of data assimilation on the O3–CO correlations. It is shown that data assimilation disrupts the relationship in the transition region. When MLS O3 is assimilated, CO and O3 values are not consistent between each other, leading to unphysical correlations at the STE location. When MLS O3 and MOPITT CO assimilated fields are taken into account in the diagnostics the relationship happens to be more physical. We then use O3–CO correlations to quantify the effect of data assimilation on the height and depth of the ExTL. When the free-model run O3 and CO fields are used in the diagnostics, the ExTL distribution is found 1.1 km above the thermal tropopause and is 2.6 km wide (2σ). MOPITT CO analyses only slightly sharpen (by −0.02 km) and lower (by −0.2 km) the ExTL distribution. MLS O3 analyses provide an expansion (by +0.9 km) of the ExTL distribution, suggesting a more intense O3 mixing. However, the MLS O3 analyses ExTL distribution shows a maximum close to the thermal tropopause and a mean location closer to the thermal tropopause (+0.45 km). When MLS O3 and MOPITT CO analyses are used together, the ExTL shows a mean location that is the closest to the thermal tropopause (+0.16 km). We also extend the study at the global scale on 15 August 2007 and for the month of August 2007. MOPITT CO analyses still show a narrower chemical transition between stratosphere and troposphere than the free-model run. MLS O3 analyses move the ExTL toward the troposphere and broaden it. When MLS O3 analyses and MOPITT CO analyses are used together, the ExTL matches the thermal tropopause poleward of 50°.

scholarly journals Can bomb-peak tritium persist in the transition zone? A case study from the German island of Langeoog

2018 ◽  
Vol 54 ◽  
pp. 00022
Author(s):  
V.E.A. Post ◽  
G.J. Houben
Keyword(s):  
Transition Zone ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Half Life ◽  
Tritium Concentration ◽  
Nuclear Bomb ◽  
Hydrogeological Studies

Tritium has been used as a tracer in hydrogeological studies to date young groundwater. It was released in massive amounts to the atmosphere by nuclear bomb testing in the 1950’s and early 1960’s. Its activity in the atmosphere peaked around 1963-1964 and has been steadily falling since then due to its half-life of 12.32 years. On the northern hemisphere, where the atmospheric tritium concentration reached much higher levels than on the southern hemisphere, elevated tritium activities in groundwater persist, and thus can still be used to identify groundwater that has recharged during the post-bomb era.

scholarly journals The influence of biogenic emissions on upper-tropospheric methanol as revealed from space

2007 ◽  
Vol 7 (24) ◽  
pp. 6119-6129 ◽  
Author(s):  
G. Dufour ◽  
S. Szopa ◽  
D. A. Hauglustaine ◽  
C. D. Boone ◽  
C. P. Rinsland ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Biomass Burning ◽  
Transport Model ◽  
Tropospheric Chemistry ◽  
Biogenic Emissions ◽  
Chemistry Transport Model ◽  
Mixing Ratios ◽  
Oxygenated Compounds ◽  
Global Space ◽  
The Impact

Abstract. The distribution and budget of oxygenated organic compounds in the atmosphere and their impact on tropospheric chemistry are still poorly constrained. Near-global space-borne measurements of seasonally resolved upper tropospheric profiles of methanol (CH3OH) by the ACE Fourier transform spectrometer provide a unique opportunity to evaluate our understanding of this important oxygenated organic species. ACE-FTS observations from March 2004 to August 2005 period are presented. These observations reveal the pervasive imprint of surface sources on upper tropospheric methanol: mixing ratios observed in the mid and high latitudes of the Northern Hemisphere reflect the seasonal cycle of the biogenic emissions whereas the methanol cycle observed in the southern tropics is highly influenced by biomass burning emissions. The comparison with distributions simulated by the state-of-the-art global chemistry transport model, LMDz-INCA, suggests that: (i) the background methanol (high southern latitudes) is correctly represented by the model considering the measurement uncertainties; (ii) the current emissions from the continental biosphere are underestimated during spring and summer in the Northern Hemisphere leading to an underestimation of modelled upper tropospheric methanol; (iii) the seasonal variation of upper tropospheric methanol is shifted to the fall in the model suggesting either an insufficient destruction of CH3OH (due to too weak chemistry and/or deposition) in fall and winter months or an unfaithful representation of transport; (iv) the impact of tropical biomass burning emissions on upper tropospheric methanol is rather well reproduced by the model. This study illustrates the potential of these first global profile observations of oxygenated compounds in the upper troposphere to improve our understanding of their global distribution, fate and budget.

Variability of PM pollution in the light of emission changes and meteorological variability: a case study for Styria, Austria

2020 ◽  
Author(s):  
Christian A. Schmidt ◽  
Peter Huszár ◽  
Monika Mayer ◽  
Johannes Fritzer ◽  
Harald E. Rieder
Keyword(s):  
Air Pollution ◽  
Emission Reduction ◽  
Transport Model ◽  
Special Importance ◽  
Chemistry Transport Model ◽  
The Alps ◽  
Industrial Regions ◽  
Emission Changes ◽  
Local Emissions

&lt;p&gt;Despite ambitious efforts to abate surface air pollution, the air quality thresholds for PM10 and PM2.5 are regularly exceeded in the state of Styria. PM target levels are most frequently exceeded in industrial regions and urban cores of the forelands preceeding the alps. Besides local emissions, ambient meteorology and particularly stagnation are of special importance for PM pollution. Here we assess local and regional changes in PM pollution following emission reduction measures, while simultaneously considering effects of meteorological variability. We further supplement our observational study with a set of high-resolution chemistry-transport-model (CTM) simulations to assess future changes in the PM burden in Styria.&lt;/p&gt;

scholarly journals Interannual variability of tropospheric composition: the influence of changes in emissions, meteorology and clouds

2010 ◽  
Vol 10 (5) ◽  
pp. 2491-2506 ◽  
Author(s):  
A. Voulgarakis ◽  
N. H. Savage ◽  
O. Wild ◽  
P. Braesicke ◽  
P. J. Young ◽  
...  
Keyword(s):  
Interannual Variability ◽  
Biomass Burning ◽  
Strong Influence ◽  
Transport Model ◽  
Global Scale ◽  
Meteorological Conditions ◽  
Shortwave Radiation ◽  
Chemistry Transport Model ◽  
Attribution Analysis ◽  
Emission Changes

Abstract. We have run a chemistry transport model (CTM) to systematically examine the drivers of interannual variability of tropospheric composition during 1996–2000. This period was characterised by anomalous meteorological conditions associated with the strong El Niño of 1997–1998 and intense wildfires, which produced a large amount of pollution. On a global scale, changing meteorology (winds, temperatures, humidity and clouds) is found to be the most important factor driving interannual variability of NO2 and ozone on the timescales considered. Changes in stratosphere-troposphere exchange, which are largely driven by meteorological variability, are found to play a particularly important role in driving ozone changes. The strong influence of emissions on NO2 and ozone interannual variability is largely confined to areas where intense biomass burning events occur. For CO, interannual variability is almost solely driven by emission changes, while for OH meteorology dominates, with the radiative influence of clouds being a very strong contributor. Through a simple attribution analysis for 1996–2000 we conclude that changing cloudiness drives 25% of the interannual variability of OH over Europe by affecting shortwave radiation. Over Indonesia this figure is as high as 71%. Changes in cloudiness contribute a small but non-negligible amount (up to 6%) to the interannual variability of ozone over Europe and Indonesia. This suggests that future assessments of trends in tropospheric oxidizing capacity should account for interannual variability in cloudiness, a factor neglected in many previous studies.

scholarly journals Refinement of land use data for emission calculations in the CHIMERE chemistry-transport model: A case study for the Nizhny Novgorod region .

2021 ◽  
Vol 3 ◽  
pp. 150-161
Author(s):  
D.V. Borisov ◽  
◽  
I.U. Shalygina ◽  
Keyword(s):  
Land Use ◽  
Transport Model ◽  
Monitoring And Evaluation ◽  
Emission Data ◽  
Chemistry Transport Model ◽  
Model Calculations ◽  
Pollutant Concentrations ◽  
Real Distribution ◽  
Nizhny Novgorod Region

Refinement of land use data for emission calculations in the CHIMERE chemistry-transport model: A case study for the Nizhny Novgorod region / Borisov D.V., Shalygina I.U. // Hydrometeorological Research and Forecasting, 2021, no. 3 (381), pp. 150-161. The quality of calculating the concentration of pollutants in the chemistry-transport model largely depends on the reliability of used emission data. The possibility of updating the EMEP (European Monitoring and Evaluation Program) emission data using OpenStreetMap geodata for the CHIMERE chemistry-transport model calculations is discussed on the example of the Nizhny Novgorod region. The GlobCover land-use data refinement procedure based on OpenStreetMap information provides a 3.3% increase in the urban area and a more accurate configuration of the emission field as compared to the real distribution of sources of atmospheric emissions. Experimental CHIMERE chemistry-transport model calculations of pollutant concentrations based on the initial and updated emission fields demonstrated the efficiency of the proposed approach. Keywords: emissions, EMEP, land use, OpenStreetMap, CHIMERE chemistry-transport model, air quality

scholarly journals Global upper-tropospheric formaldehyde: seasonal cycles observed by the ACE-FTS satellite instrument

2009 ◽  
Vol 9 (1) ◽  
pp. 1051-1095 ◽  
Author(s):  
G. Dufour ◽  
S. Szopa ◽  
M. P. Barkley ◽  
C. D. Boone ◽  
A. Perrin ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Biomass Burning ◽  
Growing Season ◽  
Global Scale ◽  
Tropospheric Chemistry ◽  
Data Set ◽  
Mixing Ratios ◽  
Good Reproduction ◽  
Summer Maximum

Abstract. Seasonally-resolved upper tropospheric profiles of formaldehyde (HCHO) observed by the ACE Fourier transform spectrometer (ACE-FTS) on a near-global scale are presented for the time period from March 2004 to November 2006. Large upper tropospheric HCHO mixing ratios (>150 pptv) are observed during the growing season of the terrestrial biosphere in the Northern Hemisphere and during the biomass burning season in the Southern Hemisphere. The total errors estimated for the retrieved mixing ratios range from 30 to 40% in the upper troposphere and increase in the lower stratosphere. The sampled HCHO concentrations are in satisfactory agreement with previous aircraft and satellite observations with a negative bias (<25%) within observation errors. An overview of the seasonal cycle of the upper tropospheric HCHO is given for different latitudes. A maximum is observed during summer, i.e. during the growing season, in the northern mid- and high latitudes. The influence of biomass burning is visible in HCHO upper tropospheric concentrations during the September-to-October period in the southern tropics and subtropics. Comparisons with two state-of-the-art models (GEOS-Chem and LMDz-INCA) show that the models fail to reproduce the seasonal variations observed in the southern tropics and subtropics but they capture well the variations observed in the Northern Hemisphere (correlation >0.9). Both models underestimate the summer maximum over Europe and Russia and differences in the emissions used for North America result in a good reproduction of the summer maximum by GEOS-Chem but in an underestimate by LMDz-INCA. Globally, GEOS-Chem reproduces well the observations on average over one year but has some difficulties in reproducing the spatial variability of the observations. LMDz-INCA shows significant bias in the Southern Hemisphere, likely related to an underestimation of methane, but better reproduces the temporal and spatial variations. The differences between the models underline the large uncertainties that remain in the emissions of HCHO precursors. Observations of the HCHO upper tropospheric profile provided by the ACE-FTS represent a unique data set for investigating and improving our current understanding of the formaldehyde budget and upper tropospheric chemistry.

scholarly journals An Evaluation of the CHIMERE Chemistry Transport Model to Simulate Dust Outbreaks across the Northern Hemisphere in March 2014

Atmosphere ◽  
2017 ◽  
Vol 8 (12) ◽  
pp. 251 ◽  
Author(s):  
Bertrand Bessagnet ◽  
Laurent Menut ◽  
Augustin Colette ◽  
Florian Couvidat ◽  
Mo Dan ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Transport Model ◽  
Chemistry Transport Model
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