scholarly journals MIPAS measurements of upper tropospheric C<sub>2</sub>H<sub>6</sub> and O<sub>3</sub> during the southern hemispheric biomass burning season in 2003

2007 ◽  
Vol 7 (22) ◽  
pp. 5861-5872 ◽  
Author(s):  
T. von Clarmann ◽  
N. Glatthor ◽  
M. E. Koukouli ◽  
G. P. Stiller ◽  
B. Funke ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Biomass Burning ◽  
Michelson Interferometer ◽  
Measured Signal ◽  
South American ◽  
African Savanna ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
Savanna Fires ◽  
Spectrally Resolved

Abstract. Under cloud free conditions, the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) provides measurements of spectrally resolved limb radiances down to the upper troposphere. These are used to infer global distributions of mixing ratios of atmospheric constituents in the upper troposphere and the stratosphere. From 21 October to 12 November 2003, MIPAS observed enhanced amounts of upper tropospheric C2H6 (up to about 400 pptv) and ozone (up to about 80 ppbv). The absolute values of C2H6, however, may be systematically low by about 30% due to uncertainties of the spectroscopic data used. By means of trajectory calculations, the enhancements observed in the southern hemisphere are, at least partly, attributed to a biomass burning plume, which covers wide parts of the Southern hemisphere, from South America, the Atlantic Ocean, Africa, the Indian Ocean to Australia. The chemical composition of the part of the plume-like pollution belt associated with South American fires, where rainforest burning is predominant appears different from the part of the plume associated with southern African savanna burning. In particular, African savanna fires lead to a larger ozone enhancement than equatorial American fires. In this analysis, MIPAS observations of high ozone were disregarded where low CFC-11 (below 245 pptv) was observed, because this hints at a stratospheric component in the measured signal. Different type of vegetation burning (flaming versus smouldering combustion) has been identified as a candidate explanation for the different plume compositions.

scholarly journals MIPAS measurements of upper tropospheric C<sub>2</sub>H<sub>6</sub> and O<sub>3</sub> during the Southern hemispheric biomass burning season in 2003

2007 ◽  
Vol 7 (4) ◽  
pp. 12067-12095 ◽  
Author(s):  
T. von Clarmann ◽  
N. Glatthor ◽  
G. P. Stiller ◽  
U. Grabowski ◽  
M. Höpfner ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Biomass Burning ◽  
Michelson Interferometer ◽  
South American ◽  
African Savanna ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
Savanna Fires ◽  
The Indian Ocean ◽  
Spectrally Resolved

Abstract. Under cloud free conditions, the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) provides measurements of spectrally resolved limb radiances down to the upper troposphere. These are used to infer global distributions of mixing ratios of atmospheric constituents in the upper troposphere and the stratosphere. From 21 October to 14 November 2003, MIPAS observed enhanced amounts of upper tropospheric C2H6 (up to about 400 pptv, depending on spectroscopic data chosen) and ozone (up to about 80 ppbv). By means of trajectory calculations, the enhancements observed in the Southern hemisphere are, at least partly, attributed to a biomass burning plume, which covers wide parts of the Southern hemisphere, from South America, the Atlantic ocean, Africa, the Indian Ocean to Australia. The chemical composition of the part of the plume-like pollution belt associated with South American rainforest burning appears different from the part associated with Southern African savanna burning. In particular, African savanna fires lead to a larger ozone enhancement than South American rainforest fires.

scholarly journals Global distributions of acetone in the upper troposphere from MIPAS spectra

2012 ◽  
Vol 12 (2) ◽  
pp. 757-768 ◽  
Author(s):  
D. P. Moore ◽  
J. J. Remedios ◽  
A. M. Waterfall
Keyword(s):  
North America ◽  
Southern Hemisphere ◽  
Biomass Burning ◽  
Michelson Interferometer ◽  
Transport Processes ◽  
Hemispheric Differences ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
Atmospheric Sounding ◽  
European Values

Abstract. This study reports the first global measurements of acetone (C3H6O) in the upper troposphere (UT). Profiles were obtained between 9 km and 15 km from measurements made by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) onboard Envisat in August 2003. Errors per profile are lower than 40 % between 180 hPa and 350 hPa. We report strong hemispheric differences in the acetone volume mixing ratios (VMRs), with average concentrations highest in the Northern Hemisphere (NH) mid-latitude UT, between 1000 pptv and 1600 pptv with maxima up to 2300 pptv. Our results show a strong enhancement of acetone relative to CO, particularly over Europe (7 pptv ppbv−1), confirming aircraft studies. Ten-day backward trajectories from these high European values show strong contributions from air flows over North America (56 %) and 25 % from Southernmost Asia. Enhanced acetone is also observed over Greenland, Siberia and biomass burning regions of Africa. Zonal distributions show that acetone VMRs decrease rapidly with increasing altitude (decreasing pressure), particularly in the NH. Poleward of 45° S, acetone VMRs remain fairly consistent with average VMRs between 400 pptv and 500 pptv. In 5-day averages at 9 km, NH VMRs poleward of 45° N are consistently higher than Southern Hemisphere observations poleward of 45° S, by between 750 pptv and 1100 pptv. The results show a clear influence of mid-latitude and transport processes on the acetone summertime distribution.

scholarly journals Acetylene C<sub>2</sub>H<sub> 2</sub> retrievals from MIPAS data and regions of enhanced upper tropospheric concentrations in August 2003

2011 ◽  
Vol 11 (19) ◽  
pp. 10243-10257 ◽  
Author(s):  
R. J. Parker ◽  
J. J. Remedios ◽  
D. P. Moore ◽  
V. P. Kanawade
Keyword(s):  
Biomass Burning ◽  
Cross Sections ◽  
Asian Monsoon ◽  
Michelson Interferometer ◽  
Convective Transport ◽  
Random Errors ◽  
Transport Pathways ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
Fast Processing

Abstract. Acetylene (C2H2) volume mixing ratios (VMRs) have been successfully retrieved from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) Level 1B radiances during August 2003, providing the first global map of such data and ratios to CO in the literature. The data presented here contain most information between 300 hPa and 100 hPa with systematic errors less than 10% at the upper levels. Random errors per point are less than 15% at lower levels and are closer to 30% at 100 hPa. Global distributions of the C2H2 and C2H2/CO ratio confirm significant features associated with both the Asian monsoon anticyclone and biomass burning for this important hydrocarbon in a characteristic summer month (August 2003), showing tight correlations regionally, particularly at lower to medium values, but globally emphasising the differences between sources and lifetimes of CO and C2H2. The correlations are seen to be particularly disturbed in the regions of highest C2H2 concentrations, indicating variability in the surface emissions or fast processing. A strong isolation of C2H2 within the Asian monsoon anticyclone is observed, evidencing convective transport into the upper troposphere, horizontal advection within the anticyclone at 200 hPa, distinct gradients at the westward edge of the vortex and formation of a secondary dynamical feature from the eastward extension of the anticyclone outflow over the Asian Pacific. Ratios of C2H2/CO are consistent with the evidence from the cross-sections that the C2H2 is uplifted rapidly in convection. Observations are presented of enhanced C2H2 associated with the injection from biomass burning into the upper troposphere and the outflow from Africa at 200 hPa into both the Atlantic and Indian Oceans. In the biomass burning regions, C2H2 and CO are well correlated, but the uplift is less marked and peaks at lower altitudes compared to the strong effects observed in the Asian monsoon anticyclone. Ratios of C2H2/CO clearly decay along transport pathways for the outflow, indicating photochemical ageing of the plumes. Overall, the data show the distinctive nature of C2H2 distributions, confirm in greater detail than previously possible features of hydrocarbon enhancements in the upper troposphere and highlight the future use of MIPAS hydrocarbon data for testing model transport and OH decay regimes in the middle to upper troposphere.

scholarly journals Acetylene C<sub>2</sub>H<sub>2</sub> retrievals from MIPAS data and regions of enhanced upper tropospheric concentrations in August 2003

2010 ◽  
Vol 10 (12) ◽  
pp. 29735-29771 ◽  
Author(s):  
R. J. Parker ◽  
J. J. Remedios ◽  
D. P. Moore ◽  
V. P. Kanawade
Keyword(s):  
Biomass Burning ◽  
Asian Monsoon ◽  
Convective Transport ◽  
Random Errors ◽  
Lower Altitude ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
Asian Pacific ◽  
The Tropics ◽  
Lower Correlation

Abstract. Acetylene (C2H2) volume mixing ratios (VMRs) have been successfully retrieved from MIPAS Level 1B radiances during August 2003. The data presented here contain most information between 300 hPa and 100 hPa based on the averaging kernels, with information also at lower altitude levels (up to 500 hPa) albeit with some influence from the 300 hPa level. In our C2H2 retrievals, data at altitude levels above 100 hPa must be treated with caution. Systematic errors are less than 10% at the upper levels but can reach higher levels at 300 hPa in the tropics due to water vapour influences. Random errors per point are less than 15% at lower pressure levels and are closer to 30% at 100 hPa. Global distributions of both the absolute C2H2 and ratios to MOPITT 150 hPa retrievals of carbon monoxide (CO) confirm some significant features for this important hydrocarbon in a characteristic summer month (August 2003), showing tight correlations regionally but globally emphasising the differences between sources and lifetimes of CO and C2H2. The ratios to CO are estimated to be accurate to approximately 10%. A strong isolation of C2H2 within the Asian monsoon anticyclone is observed, evidencing convective transport into the upper troposphere, horizontal advection within the anticyclone at 200 hPa, distinct but measurable gradients at the westward edge of the vortex and formation of a secondary dynamical feature over the Asian Pacific. The data for C2H2 strongly support evidence for a strong isolated core to the anticyclone with distinct gradients surrounding this core. Within this region, there is a relatively lower correlation of C2H2 and CO suggesting difference in injection ratios or more likely due to expected chemical processing. A second strong feature to the global distributions is observed in the enhancement and outflow of biomass burning from Africa at 200 hPa, both north-westward and eastward from 10° S. The easterly flow shows high C2H2 ratios to CO which have significantly decayed before reaching Australia. In the biomass burning regions, C2H2 and CO are relatively tightly correlated. C2H2 enhancements are observed to penetrate to lower altitudes in the African biomass outflow in this month compared to uplift observed in the Asian monsoon anticyclone region. Overall, the data show the distinctive nature of C2H2 distributions, confirm in greater detail than previously possible features of hydrocarbon enhancements in the upper troposphere and highlight the future use of MIPAS hydrocarbon data for testing model transport and OH decay regimes in the middle to upper troposphere.

scholarly journals Hydrogen cyanide in the upper troposphere: GEM-AQ simulation and comparison with ACE-FTS observations

2009 ◽  
Vol 9 (1) ◽  
pp. 2165-2194 ◽  
Author(s):  
A. Lupu ◽  
J. W. Kaminski ◽  
L. Neary ◽  
J. C. McConnell ◽  
K. Toyota ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Atmospheric Chemistry ◽  
Hydrogen Cyanide ◽  
Weather Forecasting ◽  
Boreal Summer ◽  
Air Quality Model ◽  
Quality Model ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
The Tropics

Abstract. We investigate the spatial and temporal distribution of hydrogen cyanide (HCN) in the upper troposphere through numerical simulations and comparison with observations from a space-based instrument. To perform the simulations, we used the Global Environmental Multiscale Air Quality model (GEM-AQ), which is based on the three-dimensional global multiscale model developed by the Meteorological Service of Canada for operational weather forecasting. The model was run for the period 2004–2006 on a 1.5°×1.5° global grid with 28 hybrid vertical levels from the surface up to 10 hPa. Objective analysis data from the Canadian Meteorological Centre were used to update the meteorological fields every 24 h. Fire emission fluxes of gas species were generated by using year-specific inventories of carbon emissions with 8-day temporal resolution from the Global Fire Emission Database (GFED) version 2. The model output is compared with HCN profiles measured by the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) instrument onboard the Canadian SCISAT-1 satellite. High values of up to a few ppbv are observed in the tropics in the Southern Hemisphere; the enhancement in HCN volume mixing ratios in the upper troposphere is most prominent in October. Low upper-tropospheric mixing ratios of less than 100 pptv are mostly recorded at middle and high latitudes in the Southern Hemisphere in May–July. Mixing ratios in Northern Hemisphere peak in the boreal summer. The amplitude of the seasonal variation is less pronounced than in the Southern Hemisphere. Our model results show that in the upper troposphere GEM-AQ performs well globally for all seasons, except at Northern high and middle latitudes in summer, where the model has a large negative bias, and in the tropics in winter and spring, where it exhibits large positive bias. This may reflect inaccurate emissions or possible inaccuracies in the emission profile. The model is able to explain most of the observed variability in the upper troposphere HCN field, including the interannual variations in the observed mixing ratio. The estimated average global emission equals 1.3 Tg N yr−1. The average atmospheric burden is 0.53 Tg N, and the corresponding lifetime is 4.9 months.

scholarly journals Climatology and comparison of ozone from ENVISAT/GOMOS and SHADOZ/balloon-sonde observations in the southern tropics

2010 ◽  
Vol 10 (1) ◽  
pp. 1457-1481
Author(s):  
N. Mze ◽  
A. Hauchecorne ◽  
H. Bencherif ◽  
F. Dalaudier ◽  
J.-L. Bertaux
Keyword(s):  
Southern Hemisphere ◽  
Satisfactory Agreement ◽  
Positive Bias ◽  
Altitude Range ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
Stellar Occultation ◽  
Monthly Distribution

Abstract. In this paper, the stellar occultation instrument GOMOS is compared with ozonesondes from the SHADOZ network. We only used nighttime O3 profiles and a requirement selection at 8 Southern Hemisphere stations. 7 years of GOMOS datasets (GOPR 6.0cf and IPF 5.0) and 11 years of balloon-sondes are used in this study. A monthly distribution of GOMOS O3 mixing ratios is performed in the upper-troposphere and in the stratosphere (15–50 km). A comparison with SHADOZ is done in the altitude range from 15 km to 30 km. In the 21–30 km altitude range, a satisfactory agreement is observed between GOMOS and SHADOZ although some differences are observed depending on the station. The range for monthly differences is generally decreasing with increasing height and is within ±15%. It is found that the agreement between GOMOS and SHADOZ degrades below ~20 km. The median differences are nearly within ±5% particularly above 23 km. But a large positive bias is found below 21 km compared to SHADOZ.

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 Reactive nitrogen, ozone and ozone production in the Arctic troposphere and the impact of stratosphere-troposphere exchange

2011 ◽  
Vol 11 (24) ◽  
pp. 13181-13199 ◽  
Author(s):  
Q. Liang ◽  
J. M. Rodriguez ◽  
A. R. Douglass ◽  
J. H. Crawford ◽  
J. R. Olson ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Stratospheric Ozone ◽  
Arctic Region ◽  
Ozone Production ◽  
The Arctic ◽  
Subsequent Formation ◽  
Air Masses ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
The Impact

Abstract. We use aircraft observations obtained during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) mission to examine the distributions and source attributions of O3 and NOy in the Arctic and sub-Arctic region. Using a number of marker tracers, we distinguish various air masses from the background troposphere and examine their contributions to NOx, O3, and O3 production in the Arctic troposphere. The background Arctic troposphere has a mean O3 of ~60 ppbv and NOx of ~25 pptv throughout spring and summer with CO decreasing from ~145 ppbv in spring to ~100 ppbv in summer. These observed mixing ratios are not notably different from the values measured during the 1988 ABLE-3A and the 2002 TOPSE field campaigns despite the significant changes in emissions and stratospheric ozone layer in the past two decades that influence Arctic tropospheric composition. Air masses associated with stratosphere-troposphere exchange are present throughout the mid and upper troposphere during spring and summer. These air masses, with mean O3 concentrations of 140–160 ppbv, are significant direct sources of O3 in the Arctic troposphere. In addition, air of stratospheric origin displays net O3 formation in the Arctic due to its sustainable, high NOx (75 pptv in spring and 110 pptv in summer) and NOy (~800 pptv in spring and ~1100 pptv in summer). The air masses influenced by the stratosphere sampled during ARCTAS-B also show conversion of HNO3 to PAN. This active production of PAN is the result of increased degradation of ethane in the stratosphere-troposphere mixed air mass to form CH3CHO, followed by subsequent formation of PAN under high NOx conditions. These findings imply that an adequate representation of stratospheric NOy input, in addition to stratospheric O3 influx, is essential to accurately simulate tropospheric Arctic O3, NOx and PAN in chemistry transport models. Plumes influenced by recent anthropogenic and biomass burning emissions observed during ARCTAS show highly elevated levels of hydrocarbons and NOy (mostly in the form of NOx and PAN), but do not contain O3 higher than that in the Arctic tropospheric background except some aged biomass burning plumes sampled during spring. Convection and/or lightning influences are negligible sources of O3 in the Arctic troposphere but can have significant impacts in the upper troposphere in the continental sub-Arctic during summer.

scholarly journals Climatology and comparison of ozone from ENVISAT/GOMOS and SHADOZ/balloon-sonde observations in the southern tropics

2010 ◽  
Vol 10 (16) ◽  
pp. 8025-8035 ◽  
Author(s):  
N. Mze ◽  
A. Hauchecorne ◽  
H. Bencherif ◽  
F. Dalaudier ◽  
J.-L. Bertaux
Keyword(s):  
Southern Hemisphere ◽  
Satisfactory Agreement ◽  
Positive Bias ◽  
Altitude Range ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
Stellar Occultation ◽  
Monthly Distribution ◽  
Made In

Abstract. In this paper, the stellar occultation instrument GOMOS is compared with ozonesondes from the SHADOZ network. We only used nighttime O3 profiles and selected 8 Southern Hemisphere stations. 7 years of GOMOS datasets (GOPR 6.0cf and IPF 5.0) and 11 years of balloon-sondes are used in this study. A monthly distribution of GOMOS O3 mixing ratios was performed in the upper-troposphere and in the stratosphere (15–50 km). A comparison with SHADOZ was made in the altitude range between 15 km and 30 km. In the 21–30 km altitude range, a satisfactory agreement was observed between GOMOS and SHADOZ, although some differences were observed depending on the station. The range for monthly differences generally decreases with increasing height and is within ±15%. It was found that the agreement between GOMOS and SHADOZ declines below ~20 km. The median differences are almost within ±5%, particularly above 23 km. But a large positive bias was found below 21 km, in comparison to SHADOZ.

scholarly journals Reactive nitrogen, ozone and ozone production in the Arctic troposphere and the impact of stratosphere-troposphere exchange

2011 ◽  
Vol 11 (4) ◽  
pp. 10721-10767 ◽  
Author(s):  
Q. Liang ◽  
J. M. Rodriguez ◽  
A. R. Douglass ◽  
J. H. Crawford ◽  
E. Apel ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Arctic Region ◽  
Tropospheric Chemistry ◽  
Ozone Production ◽  
The Arctic ◽  
Source Attribution ◽  
Air Masses ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
The Impact

Abstract. We analyze the aircraft observations obtained during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellite (ARCTAS) mission together with the GEOS-5 CO simulation to examine O3 and NOy in the Arctic and sub-Arctic region and their source attribution. Using a number of marker tracers and their probability density distributions, we distinguish various air masses from the background troposphere and examine their contribution to NOx, O3, and O3 production in the Arctic troposphere. The background Arctic troposphere has mean O3 of ~60 ppbv and NOx of ~25 pptv throughout spring and summer with CO decreases from ~145 ppbv in spring to ~100 ppbv in summer. These observed CO, NOx and O3 mixing ratios are not notably different from the values measured during the 1988 ABLE-3A and the 2002 TOPSE field campaigns despite the significant changes in the past two decades in processes that could have changed the Arctic tropospheric composition. Air masses associated with stratosphere-troposphere exchange are present throughout the mid and upper troposphere during spring and summer. These air masses with mean O3 concentration of 140–160 ppbv are the most important direct sources of O3 in the Arctic troposphere. In addition, air of stratospheric origin is the only notable driver of net O3 formation in the Arctic due to its sustainable high NOx (75 pptv in spring and 110 pptv in summer) and NOy (~800 pptv in spring and ~1100 pptv in summer) levels. The ARCTAS measurements present observational evidence suggesting significant conversion of nitrogen from HNO3 to NOx and then to PAN (a net formation of ~120 pptv PAN) in summer when air of stratospheric origin is mixed with tropospheric background during stratosphere-to-troposphere transport. These findings imply that an adequate representation of stratospheric O3 and NOy input are essential in accurately simulating O3 and NOx photochemistry as well as the atmospheric budget of PAN in tropospheric chemistry transport models of the Arctic. Anthropogenic and biomass burning pollution plumes observed during ARCTAS show highly elevated hydrocarbons and NOy (mostly in the form of NOx and PAN), but do not contribute significantly to O3 in the Arctic troposphere except in some of the aged biomass burning plumes sampled during spring. Convection and/or lightning influences are negligible sources of O3 in the Arctic troposphere but can have significant impacts in the upper troposphere in the continental sub-Arctic during summer.

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