scholarly journals CarbonTracker-CH<sub>4</sub>: an assimilation system for estimating emissions of atmospheric methane

2014 ◽  
Vol 14 (16) ◽  
pp. 8269-8293 ◽  
Author(s):  
L. Bruhwiler ◽  
E. Dlugokencky ◽  
K. Masarie ◽  
M. Ishizawa ◽  
A. Andrews ◽  
...  
Keyword(s):  
North America ◽  
The Arctic ◽  
Anthropogenic Emissions ◽  
Atmospheric Methane ◽  
High Northern Latitude ◽  
Annual Variability ◽  
Northern Latitudes ◽  
Small Uncertainty ◽  
The Tropics ◽  
Assimilation System

Abstract. We describe an assimilation system for atmospheric methane (CH4), CarbonTracker-CH4, and demonstrate the diagnostic value of global or zonally averaged CH4 abundances for evaluating the results. We show that CarbonTracker-CH4 is able to simulate the observed zonal average mole fractions and capture inter-annual variability in emissions quite well at high northern latitudes (53–90° N). In contrast, CarbonTracker-CH4 is less successful in the tropics where there are few observations and therefore misses significant variability and is more influenced by prior flux estimates. CarbonTracker-CH4 estimates of total fluxes at high northern latitudes are about 81 ± 7 Tg CH4 yr−1, about 12 Tg CH4 yr−1 (13%) lower than prior estimates, a result that is consistent with other atmospheric inversions. Emissions from European wetlands are decreased by 30%, a result consistent with previous work by Bergamaschi et al. (2005); however, unlike their results, emissions from wetlands in boreal Eurasia are increased relative to the prior estimate. Although CarbonTracker-CH4 does not estimate an increasing trend in emissions from high northern latitudes for 2000 through 2010, significant inter-annual variability in high northern latitude fluxes is recovered. Exceptionally warm growing season temperatures in the Arctic occurred in 2007, a year that was also anonymously wet. Estimated emissions from natural sources were greater than the decadal average by 4.4 ± 3.8 Tg CH4 yr−1 in 2007. CarbonTracker-CH4 estimates for temperate latitudes are only slightly increased over prior estimates, but about 10 Tg CH4 yr−1 is redistributed from Asia to North America. This difference exceeds the estimated uncertainty for North America (±3.5 Tg CH4 yr−1). We used time invariant prior flux estimates, so for the period from 2000 to 2006, when the growth rate of global atmospheric CH4 was very small, the assimilation does not produce increases in natural or anthropogenic emissions in contrast to bottom-up emission data sets. After 2006, when atmospheric CH4 began its recent increases, CarbonTracker-CH4 allocates some of the increases to anthropogenic emissions at temperate latitudes, and some to tropical wetland emissions. For temperate North America the prior flux increases by about 4 Tg CH4 yr−1 during winter when biogenic emissions are small. Examination of the residuals at some North American observation sites suggests that increased gas and oil exploration may play a role since sites near fossil fuel production are particularly hard for the inversion to fit and the prior flux estimates at these sites are apparently lower and lower over time than what the atmospheric measurements imply. The tropics are not currently well resolved by CarbonTracker-CH4 due to sparse observational coverage and a short assimilation window. However, there is a small uncertainty reduction and posterior emissions are about 18% higher than prior estimates. Most of this increase is allocated to tropical South America rather than being distributed among the global tropics. Our estimates for this source region are about 32 ± 4 Tg CH4 yr−1, in good agreement with the analysis of Melack et al. (2004) who obtained 29 Tg CH4 yr−1 for the most productive region, the Amazon Basin.

scholarly journals CarbonTracker-CH<sub>4</sub>: an assimilation system for estimating emissions of atmospheric methane

2014 ◽  
Vol 14 (2) ◽  
pp. 2175-2233 ◽  
Author(s):  
L. M. Bruhwiler ◽  
E. Dlugokencky ◽  
K. Masarie ◽  
M. Ishizawa ◽  
A. Andrews ◽  
...  
Keyword(s):  
North America ◽  
Diagnostic Value ◽  
Anthropogenic Emissions ◽  
Atmospheric Methane ◽  
High Northern Latitude ◽  
Annual Variability ◽  
Northern Latitudes ◽  
Small Uncertainty ◽  
Prior Estimate ◽  
Assimilation System

Abstract. We describe an assimilation system for atmospheric methane (CH4), CarbonTracker-CH4, and demonstrate the diagnostic value of global or zonally averaged CH4 abundances for evaluating the results. We show that CarbonTracker-CH4 is able to simulate the observed zonal average mole fractions and capture inter-annual variability in emissions quite well at high northern latitudes (53–90° N). CarbonTracker-CH4 estimates of total fluxes at high northern latitudes are about 81 Tg CH4 yr−1, about 12 Tg CH4 yr−1 (13%) lower than prior estimates, a result that is consistent with other atmospheric inversions. Emissions from European wetlands are decreased by 30%, a result consistent with previous; however, emissions from wetlands in Boreal Eurasia are increased relative to the prior estimate. Although CarbonTracker-CH4 does not estimate increases in emissions from high northern latitudes for 2000 through 2010, significant inter-annual variability in high northern latitude fluxes is recovered. During the exceptionally warm Arctic summer of 2007, estimated emissions were greater than the decadal average by 4.4 Tg CH4 yr−1. In 2008, temperatures returned to more normal values over Arctic North America while they stayed above normal over Arctic Eurasia. CarbonTracker-CH4 estimates were 2.4 Tg CH4 yr−1 higher than the decadal average, and the anomalous emissions occurred over Arctic Eurasia, suggesting that the data allow discrimination between these two source regions. Also, the emission estimates respond to climate variability without having the system constrained by climate parameters. CarbonTracker-CH4 estimates for temperate latitudes are only slightly increased over prior estimates, but about 10 Tg CH4 yr−1 is redistributed from Asia to North America. We used time invariant prior flux estimates, so for the period from 2000 to 2006, when the growth rate of global atmospheric CH4 was very small, the assimilation does not produce increases in natural or anthropogenic emissions in contrast to bottom-up emission datasets. After 2006, when atmospheric CH4 began its recent increases, CarbonTracker-CH4 allocates some of the increases to anthropogenic emissions at temperate latitudes, and some to tropical wetland emissions. For temperate North America the prior flux increases by about 4 Tg CH4 yr−1 during winter when biogenic emissions are small. Examination of the residuals at some North American observation sites suggests that increased gas and oil exploration may play a role since sites near fossil fuel production are particularly hard for the inversion to fit. The tropics are not currently well resolved by CarbonTracker-CH4 due to sparse observational coverage and a short assimilation window. However, there is a small uncertainty reduction and posterior emissions are about 18% higher than prior estimates. Most of this increase is allocated to tropical South America rather than being distributed among the global tropics.

scholarly journals Mid-upper tropospheric methane retrieval from IASI and its validation

2013 ◽  
Vol 6 (2) ◽  
pp. 2501-2531 ◽  
Author(s):  
X. Xiong ◽  
C. Barnet ◽  
E. S. Maddy ◽  
A. Gambacorta ◽  
T. S. King ◽  
...  
Keyword(s):  
The Arctic ◽  
Aircraft Measurements ◽  
Atmospheric Methane ◽  
Infrared Sensors ◽  
High Northern Latitude ◽  
Observation Network ◽  
The Pacific ◽  
Data Stewardship ◽  
The Tropics ◽  
Cross Track

Abstract. Mid-upper tropospheric atmospheric methane (CH4), as an operational product at NOAA's (National Oceanic and Atmospheric Administration) Comprehensive Large Array-data Stewardship System (CLASS), has been retrieved from the Infrared Atmospheric Sounding Interferometer (IASI) since 2008. This paper provides a description of the retrieval method and the validation using 596 CH4 vertical profiles from aircraft measurements by the HIAPER Pole-to-Pole Observations (HIPPO) program over the Pacific Ocean. The degree of freedom of the CH4 retrieval is mostly less than 1.5, and it decreases under cloudy conditions. The most sensitivity layer is between 100–600 hPa in the tropics, 200–750 hPa in the mid to high latitude. Validation is accomplished using aircraft measurements (convolved by applying the averaging kernels) collocated with all the retrieved profiles within 200 km and in the same day, and the results show that, on average, the largest error of CH4 occurs at 300–500 hPa, and the bias in the trapezoid of 374–477 hPa is −1.74% with residual standard deviation of 1.20%. The retrieval error is relatively larger in the high northern latitude regions and/or under cloudy conditions. The main reasons for this negative bias might be due to the uncertainty in the spectroscopy near methane Q-branch and/or the empirical bias correction, plus cloud-contamination in the cloud-cleared radiances. It is expected for NOAA to generate the CH4 product for 20+ yr using similar algorithm from three similar thermal infrared sensors, i.e. Atmospheric Infrared Sounder (AIRS), IASI and the Cross-track Infrared Sounder (CrIS). Such a unique product will provide a supplementary to current ground-based observation network, particularly in the Arctic, for monitoring the CH4 cycle, its transport and trend associated with climate change.

scholarly journals Source attribution of Arctic black carbon constrained by aircraft and surface measurements

2017 ◽  
Vol 17 (19) ◽  
pp. 11971-11989 ◽  
Author(s):  
Jun-Wei Xu ◽  
Randall V. Martin ◽  
Andrew Morrow ◽  
Sangeeta Sharma ◽  
Lin Huang ◽  
...  
Keyword(s):  
North America ◽  
Biomass Burning ◽  
Western Siberia ◽  
Transport Model ◽  
Chemical Transport ◽  
The Arctic ◽  
Anthropogenic Emissions ◽  
Chemical Transport Model ◽  
Northern Asia ◽  
Airborne Measurements

Abstract. Black carbon (BC) contributes to Arctic warming, yet sources of Arctic BC and their geographic contributions remain uncertain. We interpret a series of recent airborne (NETCARE 2015; PAMARCMiP 2009 and 2011 campaigns) and ground-based measurements (at Alert, Barrow and Ny-Ålesund) from multiple methods (thermal, laser incandescence and light absorption) with the GEOS-Chem global chemical transport model and its adjoint to attribute the sources of Arctic BC. This is the first comparison with a chemical transport model of refractory BC (rBC) measurements at Alert. The springtime airborne measurements performed by the NETCARE campaign in 2015 and the PAMARCMiP campaigns in 2009 and 2011 offer BC vertical profiles extending to above 6 km across the Arctic and include profiles above Arctic ground monitoring stations. Our simulations with the addition of seasonally varying domestic heating and of gas flaring emissions are consistent with ground-based measurements of BC concentrations at Alert and Barrow in winter and spring (rRMSE  < 13 %) and with airborne measurements of the BC vertical profile across the Arctic (rRMSE  = 17 %) except for an underestimation in the middle troposphere (500–700 hPa).Sensitivity simulations suggest that anthropogenic emissions in eastern and southern Asia have the largest effect on the Arctic BC column burden both in spring (56 %) and annually (37 %), with the largest contribution in the middle troposphere (400–700 hPa). Anthropogenic emissions from northern Asia contribute considerable BC (27 % in spring and 43 % annually) to the lower troposphere (below 900 hPa). Biomass burning contributes 20 % to the Arctic BC column annually.At the Arctic surface, anthropogenic emissions from northern Asia (40–45 %) and eastern and southern Asia (20–40 %) are the largest BC contributors in winter and spring, followed by Europe (16–36 %). Biomass burning from North America is the most important contributor to all stations in summer, especially at Barrow.Our adjoint simulations indicate pronounced spatial heterogeneity in the contribution of emissions to the Arctic BC column concentrations, with noteworthy contributions from emissions in eastern China (15 %) and western Siberia (6.5 %). Although uncertain, gas flaring emissions from oilfields in western Siberia could have a striking impact (13 %) on Arctic BC loadings in January, comparable to the total influence of continental Europe and North America (6.5 % each in January). Emissions from as far as the Indo-Gangetic Plain could have a substantial influence (6.3 % annually) on Arctic BC as well.

scholarly journals Accelerating methane growth rate from 2010 to 2017: leading contributions from the tropics and East Asia

2020 ◽  
Author(s):  
Yi Yin ◽  
Frederic Chevallier ◽  
Philippe Ciais ◽  
Philippe Bousquet ◽  
Marielle Saunois ◽  
...  
Keyword(s):  
Growth Rate ◽  
Carbon Monoxide ◽  
Satellite Observations ◽  
Anthropogenic Emissions ◽  
Atmospheric Methane ◽  
Sources And Sinks ◽  
Ch4 Emissions ◽  
Significant Acceleration ◽  
Oxidation Chain ◽  
The Tropics

Abstract. After stagnating in the early 2000s, the atmospheric methane growth rate has been positive since 2007 with a significant acceleration starting in 2014. While causes for previous growth rate variations are still not well determined, this recent increase can be studied with dense surface and satellite observations. Here, we use an ensemble of six multi-tracer atmospheric inversions that have the capacity to assimilate the major tracers in the methane oxidation chain – namely methane, formaldehyde, and carbon monoxide – to simultaneously optimize both the methane sources and sinks at each model grid. We show that the recent surge of the atmospheric growth rate between 2010–2013 and 2014–2017 is most likely explained by an increase of global CH4 emissions by 17.5 ± 1.5 Tg yr−1 (mean ± 1σ), while variations in CH4 sinks remained small. The inferred emission increase is consistently supported by both surface and satellite observations, with leading contributions from the tropics wetlands (~ 35 %) and anthropogenic emissions in China (~ 20 %). Such a high consecutive atmospheric growth rate has not been observed since the 1980s and corresponds to unprecedented global total CH4 emissions.

scholarly journals Space-borne observation of methane from atmospheric infrared sounder version 6: validation and implications for data analysis

2015 ◽  
Vol 8 (8) ◽  
pp. 8563-8597 ◽  
Author(s):  
X. Xiong ◽  
F. Weng ◽  
Q. Liu ◽  
E. Olsen
Keyword(s):  
Data Analysis ◽  
Cloud Amount ◽  
Retrieval Algorithm ◽  
Atmospheric Methane ◽  
Atmospheric Infrared Sounder ◽  
Northern Latitudes ◽  
Standard Product ◽  
The Mean ◽  
The Tropics ◽  
Recent Version

Abstract. Atmospheric Methane (CH4) is generated as a standard product in recent version of the hyperspectral Atmospheric Infrared Sounder (AIRS-V6) aboard NASA's Aqua satellite at the NASA Goddard Earth Sciences Data and Information Services Center (NASA/GES/DISC). Significant improvements in AIRS-V6 was expected but without a thorough validation. This paper first introduced the improvements of CH4 retrieval in AIRS-V6 and some characterizations, then presented the results of validation using ~ 1000 aircraft profiles from several campaigns spread over a couple of years and in different regions. It was found the mean biases of AIRS CH4 at layers 343–441 and 441–575 hPa are −0.76 and −0.05 % and the RMS errors are 1.56 and 1.16 %, respectively. Further analysis demonstrates that the errors in the spring and in the high northern latitudes are larger than in other seasons or regions. The error is correlated with Degree of Freedoms (DOFs), particularly in the tropics or in the summer, and cloud amount, suggesting that the "observed" spatiotemporal variation of CH4 by AIRS is imbedded with some artificial impact from the retrieval sensitivity in addition to its variation in reality, so the variation of information content in the retrievals needs to be taken into account in data analysis of the retrieval products. Some additional filtering (i.e. rejection of profiles with obvious oscillation as well as those deviating greatly from the norm) for quality control is recommended for the users to better utilize AIRS-V6 CH4, and their implementation in the future versions of the AIRS retrieval algorithm is under consideration.

scholarly journals The Influence of Stratospheric Vortex Displacements and Splits on Surface Climate

2013 ◽  
Vol 26 (8) ◽  
pp. 2668-2682 ◽  
Author(s):  
Daniel M. Mitchell ◽  
Lesley J. Gray ◽  
James Anstey ◽  
Mark P. Baldwin ◽  
Andrew J. Charlton-Perez
Keyword(s):  
North America ◽  
Time Scales ◽  
Polar Vortex ◽  
Reanalysis Data ◽  
The Arctic ◽  
Positive Temperature ◽  
Cold Air ◽  
Weather Patterns ◽  
Northern Latitudes ◽  
Stratospheric Variability

Abstract A strong link exists between stratospheric variability and anomalous weather patterns at the earth’s surface. Specifically, during extreme variability of the Arctic polar vortex termed a “weak vortex event,” anomalies can descend from the upper stratosphere to the surface on time scales of weeks. Subsequently the outbreak of cold-air events have been noted in high northern latitudes, as well as a quadrupole pattern in surface temperature over the Atlantic and western European sectors, but it is currently not understood why certain events descend to the surface while others do not. This study compares a new classification technique of weak vortex events, based on the distribution of potential vorticity, with that of an existing technique and demonstrates that the subdivision of such events into vortex displacements and vortex splits has important implications for tropospheric weather patterns on weekly to monthly time scales. Using reanalysis data it is found that vortex splitting events are correlated with surface weather and lead to positive temperature anomalies over eastern North America of more than 1.5 K, and negative anomalies over Eurasia of up to −3 K. Associated with this is an increase in high-latitude blocking in both the Atlantic and Pacific sectors and a decrease in European blocking. The corresponding signals are weaker during displacement events, although ultimately they are shown to be related to cold-air outbreaks over North America. Because of the importance of stratosphere–troposphere coupling for seasonal climate predictability, identifying the type of stratospheric variability in order to capture the correct surface response will be necessary.

scholarly journals Anthropogenic emissions during Arctas-A: mean transport characteristics and regional case studies

2011 ◽  
Vol 11 (16) ◽  
pp. 8677-8701 ◽  
Author(s):  
D. L. Harrigan ◽  
H. E. Fuelberg ◽  
I. J. Simpson ◽  
D. R. Blake ◽  
G. R. Carmichael ◽  
...  
Keyword(s):  
North America ◽  
Wrf Model ◽  
Middle Latitude ◽  
Horizontal Resolution ◽  
Atmospheric Composition ◽  
The Arctic ◽  
Anthropogenic Emissions ◽  
International Polar Year ◽  
Trajectory Calculations ◽  
Arctic Haze

Abstract. The National Aeronautics and Space Administration (NASA) conducted the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) mission during 2008 as a part of the International Polar Year (IPY). The purpose of ARCTAS was to study the factors responsible for changes in the Arctic's atmospheric composition and climate. A major emphasis was to investigate Arctic haze, which is most pronounced during winter and early spring. This study focuses on the spring phase of ARCTAS (ARCTAS-A) that was based in Alaska during April 2008. Although anthropogenic emissions historically have been associated with Arctic haze, biomass burning emissions dominated the ARCTAS-A period and have been the focus of many ARCTAS related studies. This study determines mean transport characteristics of anthropogenic emissions during ARCTAS-A. Trajectories are initiated each day from three significant regions of anthropogenic emissions (Asia, North America, and Europe). The fifteen day forward trajectories are calculated using data from the Weather Research and Forecasting (WRF) model at 45 km horizontal resolution. The trajectory calculations indicate: origins of emissions that reach the Arctic (defined as north of 70° N) within fifteen days, pathways of these emissions, Arctic entry locations, and altitudes at which the trajectories enter the Arctic. Three cases during the ARCTAS-A period (one for each of the regions above) are examined using backward trajectories and chemical fingerprinting based on in situ data sampled from the NASA DC-8. The fingerprinting utilizes volatile organic compounds that represent pure anthropogenic tracers, Asian anthropogenic pollution, incomplete combustion, and natural gas emissions. We determine flight legs containing anthropogenic emissions and the pathways travelled by these emissions. Results show that the DC-8 sampled anthropogenic emissions from Asia, North America, and Europe during the spring phase of ARCTAS. The pathways travelled by these emissions agree with our derived transport characteristics and previous studies of Arctic transport. Meteorological analysis and trajectory calculations indicate that middle latitude cyclones and their associated warm conveyor belts play an important role in lofting the surface based emissions to their sampling altitude in all three cases.

scholarly journals Source contributions to Northern Hemisphere CO and black carbon during spring and summer 2008 from POLARCAT and START08/preHIPPO observations and MOZART-4

2011 ◽  
Vol 11 (2) ◽  
pp. 5935-5983 ◽  
Author(s):  
S. Tilmes ◽  
L. K. Emmons ◽  
K. S. Law ◽  
G. Ancellet ◽  
H. Schlager ◽  
...  
Keyword(s):  
Black Carbon ◽  
Northern Hemisphere ◽  
Southeast Asian ◽  
The Arctic ◽  
Anthropogenic Emissions ◽  
High Latitudes ◽  
Fire Emissions ◽  
Source Regions ◽  
Fire Plumes ◽  
Northern Latitudes

Abstract. Anthropogenic pollution and wildfires are main producers of carbon monoxide (CO) and black carbon (BC) in the Northern Hemisphere. High concentrations of these compounds are transported into the Arctic troposphere, influencing the ecosystem in high northern latitudes and the global climate. The global chemical transport model MOZART-4 is used to quantify the seasonal evolution of the contribution of CO and BC from different source regions in spring and summer 2008 by tagging their emissions. Aircraft observations from the POLARCAT experiments, in particular NASA ARCTAS, NOAA ARCPAC, POLARCAT-France, DLR GRACE and YAK-AEROSIB, as well as the NSF START08/preHIPPO experiments during Spring-Summer 2008 are combined to quantify the representation of simulated tracer characteristics in anthropogenic and fire plumes. In general, the model reproduces CO and BC well. Based on aircraft measurements and FLEXPART back-trajectories, the altitude contribution of emissions coming from different source regions is well captured in the model. Uncertainties of the MOZART-4 model are identified by comparing the data with model results on the flight tracks and using MOPITT satellite observations. Anthropogenic emissions are underestimated by about 10% in high northern latitudes in spring, and shortcomings exist in simulating fire plumes. The remote impact of East-Siberian fire emissions is underestimated for spring, whereas the impact of Southeast Asian fire emissions to mid-latitude CO values is overestimated by the model. In summer, mid-latitude CO values agree well between model and observations, whereas summer high latitude East-Siberian fire emissions in the model are overestimated by 20% in comparison to observations in the region. On the other hand, CO concentrations are underestimated by about 30% over Alaska and Canada at altitudes above 4 km. BC values are overestimated by the model at altitudes above 4 km in summer. Based on MOZART-4, with tagged CO and BC tracers, anthropogenic emissions of Asia, Europe and the US have the largest contribution to the CO and BC in mid- and high latitudes in spring and summer. Southeast Asian, Chinese and Indian fires have a large impact on CO pollution in spring in low latitudes with a maximum between 20° and 30°, whereas Siberian fires contribute largely to the pollution in high latitudes, up to 10% in spring and up to 30% in summer. The largest contributions to BC values in high latitudes are from anthropogenic emissions (about 70%). CO and BC have larger mass loadings in April than in July, as a result of photochemistry and dynamics.

scholarly journals Accelerating methane growth rate from 2010 to 2017: leading contributions from the tropics and East Asia

2021 ◽  
Vol 21 (16) ◽  
pp. 12631-12647
Author(s):  
Yi Yin ◽  
Frederic Chevallier ◽  
Philippe Ciais ◽  
Philippe Bousquet ◽  
Marielle Saunois ◽  
...  
Keyword(s):  
Growth Rate ◽  
Satellite Observations ◽  
Anthropogenic Emissions ◽  
Atmospheric Methane ◽  
Tropical Wetlands ◽  
Sources And Sinks ◽  
Ch4 Emissions ◽  
Significant Acceleration ◽  
Oxidation Chain ◽  
The Tropics

Abstract. After stagnating in the early 2000s, the atmospheric methane growth rate has been positive since 2007 with a significant acceleration starting in 2014. While the causes for previous growth rate variations are still not well determined, this recent increase can be studied with dense surface and satellite observations. Here, we use an ensemble of six multi-species atmospheric inversions that have the capacity to assimilate observations of the main species in the methane oxidation chain – namely, methane, formaldehyde, and carbon monoxide – to simultaneously optimize both the methane sources and sinks at each model grid. We show that the surge of the atmospheric growth rate between 2010–2013 and 2014–2017 is most likely explained by an increase of global CH4 emissions by 17.5±1.5 Tg yr−1 (mean ± 1σ), while variations in the hydroxyl radicals (OH) remained small. The inferred emission increase is consistently supported by both surface and satellite observations, with leading contributions from the tropical wetlands (∼ 35 %) and anthropogenic emissions in China (∼ 20 %). Such a high consecutive atmospheric growth rate has not been observed since the 1980s and corresponds to unprecedented global total CH4 emissions.

scholarly journals Transport of anthropogenic emissions during ARCTAS-A: a climatology and regional case studies

2011 ◽  
Vol 11 (2) ◽  
pp. 5435-5491 ◽  
Author(s):  
D. L. Harrigan ◽  
H. E. Fuelberg ◽  
I. J. Simpson ◽  
D. R. Blake ◽  
G. R. Carmichael ◽  
...  
Keyword(s):  
North America ◽  
Wrf Model ◽  
Anthropogenic Pollution ◽  
Middle Latitude ◽  
Horizontal Resolution ◽  
Atmospheric Composition ◽  
The Arctic ◽  
Anthropogenic Emissions ◽  
International Polar Year ◽  
Arctic Haze

Abstract. The National Aeronautics and Space Administration (NASA) conducted the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) mission during 2008 as a part of the International Polar Year (IPY). The purpose of ARCTAS was to study the factors responsible for changes in the Arctic's atmospheric composition and climate. A major emphasis was to investigate Arctic haze, which is most pronounced during winter and early spring. This study focuses on the spring phase of ARCTAS (ARCTAS-A) that was based in Alaska during April 2008. Although anthropogenic emissions historically have been associated with Arctic haze, biomass burning dominated the ARCTAS-A period and has been the focus of many ARCTAS related studies. This study determines the common pathways for anthropogenic emissions during ARCTAS-A. Trajectories (air parcels) are released each day from three historically significant regions of anthropogenic emissions (Asia, North America, and Europe). These fifteen day forward trajectories are calculated using data from the Weather Research and Forecasting (WRF) model at 45 km horizontal resolution. The trajectories then are examined to determine: origins of emissions that reach the Arctic (defined as north of 70° N) within fifteen days, pathways of the emissions reaching the Arctic, Arctic entry locations, and altitudes at which the trajectories enter the Arctic. These results serve as regional "climatologies" for the ARCTAS-A period. Three cases during the ARCTAS-A period (one for each of the regions above) are examined using backward trajectories and chemical fingerprinting based on in situ data sampled from the NASA DC-8. The fingerprinting utilizes volatile organic compounds that represent pure anthropogenic tracers, Asian anthropogenic pollution, incomplete combustion, and natural gas emissions. We determine flight legs containing anthropogenic emissions and the pathways travelled by these emissions. Results show that the DC-8 sampled anthropogenic emissions from Asia, North America, and Europe during the spring phase of ARCTAS. The pathways travelled by these emissions agree with our derived "climatologies" and previous studies of Arctic transport. Meteorological analysis and trajectory calculations indicate that middle latitude cyclones and their associated warm conveyor belts play an important role in lofting the surface based emissions to their sampling altitude in all three cases.

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