scholarly journals Lagrangian simulations of the transport of young air masses to the top of the Asian monsoon anticyclone and into the tropical pipe

2018 ◽  
Author(s):  
Bärbel Vogel ◽  
Rolf Müller ◽  
Gebhard Günther ◽  
Reinhold Spang ◽  
Sreeharsha Hanumanthu ◽  
...  
Keyword(s):  
Asian Monsoon ◽  
Lagrangian Model ◽  
Backward Trajectory ◽  
Air Mass ◽  
Air Masses ◽  
3 Dimensional ◽  
Trajectory Calculations ◽  
Trace Back ◽  
Air Mass Origin ◽  
Artificial Tracers

Abstract. We have performed backward trajectory calculations and simulations with the 3-dimensional Chemical Lagrangian Model of the Stratosphere (CLaMS) for two succeeding monsoon seasons using artificial tracers of air mass origin. With these tracers we trace back the origin of young air masses (age 

scholarly journals Long-term real-time chemical characterization of submicron aerosols at Montsec (southern Pyrenees, 1570 m a.s.l.)

2015 ◽  
Vol 15 (6) ◽  
pp. 2935-2951 ◽  
Author(s):  
A. Ripoll ◽  
M. C. Minguillón ◽  
J. Pey ◽  
J. L. Jimenez ◽  
D. A. Day ◽  
...  
Keyword(s):  
Real Time ◽  
Long Range ◽  
Chemical Characterization ◽  
Western Mediterranean ◽  
Continuous Increase ◽  
Air Mass ◽  
Air Masses ◽  
Diurnal Cycles ◽  
Western Mediterranean Basin ◽  
Air Mass Origin

Abstract. Real-time measurements of inorganic (sulfate, nitrate, ammonium, chloride and black carbon (BC)) and organic submicron aerosols (particles with an aerodynamic diameter of less than 1 μm) from a continental background site (Montsec, MSC, 1570 m a.s.l.) in the western Mediterranean Basin (WMB) were conducted for 10 months (July 2011–April 2012). An aerosol chemical speciation monitor (ACSM) was co-located with other online and offline PM1 measurements. Analyses of the hourly, diurnal, and seasonal variations are presented here, for the first time, for this region. Seasonal trends in PM1 components are attributed to variations in evolution of the planetary boundary layer (PBL) height, air mass origin, and meteorological conditions. In summer, the higher temperature and solar radiation increases convection, enhancing the growth of the PBL and the transport of anthropogenic pollutants towards high altitude sites. Furthermore, the regional recirculation of air masses over the WMB creates a continuous increase in the background concentrations of PM1 components and causes the formation of reservoir layers at relatively high altitudes. The combination of all these atmospheric processes results in a high variability of PM1 components, with poorly defined daily patterns, except for the organic aerosols (OA). OA was mostly composed (up to 90%) of oxygenated organic aerosol (OOA), split in two types: semivolatile (SV-OOA) and low-volatility (LV-OOA), the rest being hydrocarbon-like OA (HOA). The marked diurnal cycles of OA components regardless of the air mass origin indicates that they are not only associated with anthropogenic and long-range-transported secondary OA (SOA) but also with recently produced biogenic SOA. Very different conditions drive the aerosol phenomenology in winter at MSC. The thermal inversions and the lower vertical development of the PBL leave MSC in the free troposphere most of the day, being affected by PBL air masses only after midday, when the mountain breezes transport emissions from the adjacent valleys and plains to the top of the mountain. This results in clear diurnal patterns of both organic and inorganic concentrations. OA was also mainly composed (71%) of OOA, with contributions from HOA (5%) and biomass burning OA (BBOA; 24%). Moreover, in winter sporadic long-range transport from mainland Europe is observed. The results obtained in the present study highlight the importance of SOA formation processes at a remote site such as MSC, especially in summer. Additional research is needed to characterize the sources and processes of SOA formation at remote sites.

scholarly journals Water vapor increase in the lower stratosphere of the Northern Hemisphere due to the Asian monsoon anticyclone observed during the TACTS/ESMVal campaigns

2018 ◽  
Vol 18 (4) ◽  
pp. 2973-2983 ◽  
Author(s):  
Christian Rolf ◽  
Bärbel Vogel ◽  
Peter Hoor ◽  
Armin Afchine ◽  
Gebhard Günther ◽  
...  
Keyword(s):  
Water Vapor ◽  
Northern Hemisphere ◽  
Asian Monsoon ◽  
Eastern China ◽  
Potential Temperature ◽  
Monsoon Region ◽  
Asian Monsoon Region ◽  
Air Mass ◽  
Air Masses ◽  
The Impact

Abstract. The impact of air masses originating in Asia and influenced by the Asian monsoon anticyclone on the Northern Hemisphere stratosphere is investigated based on in situ measurements. A statistically significant increase in water vapor (H2O) of about 0.5 ppmv (11 %) and methane (CH4) of up to 20 ppbv (1.2 %) in the extratropical stratosphere above a potential temperature of 380 K was detected between August and September 2012 during the HALO aircraft missions Transport and Composition in the UT/LMS (TACTS) and Earth System Model Validation (ESMVal). We investigate the origin of the increased water vapor and methane using the three-dimensional Chemical Lagrangian Model of the Stratosphere (CLaMS). We assign the source of the moist air masses in the Asian region (northern and southern India, eastern China, southeast Asia, and the tropical Pacific) based on tracers of air mass origin used in CLaMS. The water vapor increase is correlated with an increase of the simulated Asian monsoon air mass contribution from about 10 % in August to about 20 % in September, which corresponds to a doubling of the influence from the Asian monsoon region. Additionally, back trajectories starting at the aircraft flight paths are used to differentiate transport from the Asian monsoon anticyclone and other source regions by calculating the Lagrangian cold point (LCP). The geographic location of the LCPs, which indicates the region where the set point of water vapor mixing ratio along these trajectories occurs, can be predominantly attributed to the Asian monsoon region.

scholarly journals Large-scale upper tropospheric pollution observed by MIPAS HCN and C<sub>2</sub>H<sub>6</sub> global distributions

2009 ◽  
Vol 9 (24) ◽  
pp. 9619-9634 ◽  
Author(s):  
N. Glatthor ◽  
T. von Clarmann ◽  
G. P. Stiller ◽  
B. Funke ◽  
M. E. Koukouli ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Industrial Pollution ◽  
Large Scale ◽  
Fossil Fuels ◽  
Emission Spectra ◽  
Significant Feature ◽  
Backward Trajectory ◽  
Air Masses ◽  
Mixing Ratios ◽  
Trajectory Calculations

Abstract. We present global upper tropospheric HCN and C2H6 amounts derived from MIPAS/ENVISAT limb emission spectra. HCN and C2H6 are retrieved in the spectral regions 715.5–782.7 cm−1 and 811.5–835.7 cm−1, respectively. The datasets consist of 54 days between September 2003 and March 2004. This period covers the peak and decline of the southern hemispheric biomass burning period and some months thereafter. HCN is a nearly unambiguous tracer of biomass burning with an assumed tropospheric lifetime of several months. Indeed, the most significant feature in the MIPAS HCN dataset is an upper tropospheric plume of enhanced values caused by southern hemispheric biomass burning, which in September and October 2003 extended from tropical South America over Africa, Australia to the Southern Pacific. The spatial extent of this plume agrees well with the MOPITT CO distribution of September 2003. Further there is good agreement with the shapes and mixing ratios of the southern hemispheric HCN and C2H6 fields measured by the ACE experiment between September and November 2005. The MIPAS HCN plume extended from the lowermost observation height of 8 km up to about 16 km altitude, with maximum values of 500–600 pptv in October 2003. It was still clearly visible in December 2003, but had strongly decreased by March 2004, confirming the assumed tropospheric lifetime. The main sources of C2H6 are production and transmission of fossil fuels, followed by biofuel use and biomass burning. The C2H6 distribution also clearly reflected the southern hemispheric biomass burning plume and its seasonal variation, with maximum amounts of 600–700 pptv. Generally there was good spatial overlap between the southern hemispheric distributions of both pollution tracers, except for the region between Peru and the mid-Pacific. Here C2H6was considerably enhanced, whereas the HCN amounts were low. Backward trajectory calculations suggested that industrial pollution was responsible for the elevated C2H6 concentration in these particular air masses. Except for the Asian monsoon anticyclone in September 2003, there were only comparably small regions of enhanced HCN in the Northern Hemisphere. However, C2H6 showed an equally strong northern hemispheric signal between the equator and low midlatitudes, persisting over the whole observation period. Backward trajectory calculations for air masses from this region also point to industrial sources of this pollution. Generally, C2H6/HCN ratios between 1 and 1.5 indicate biomass burning and ratios larger than 1.5 industrial pollution. However, in March 2004 ratios of up to 2 were also found in some regions of the former southern biomass burning plume.

scholarly journals Variability of aerosol, gaseous pollutants and meteorological characteristics associated with changes in air mass origin at the SW Atlantic coast of Iberia

2012 ◽  
Vol 12 (8) ◽  
pp. 3761-3782 ◽  
Author(s):  
J.-M. Diesch ◽  
F. Drewnick ◽  
S. R. Zorn ◽  
S.-L. von der Weiden-Reinmüller ◽  
M. Martinez ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Gas Phase ◽  
Organic Aerosol ◽  
Research Station ◽  
Air Mass ◽  
Air Masses ◽  
Air Mass Types ◽  
Marine Air ◽  
The Impact ◽  
Air Mass Origin

Abstract. Measurements of the ambient aerosol were performed at the Southern coast of Spain, within the framework of the DOMINO (Diel Oxidant Mechanisms In relation to Nitrogen Oxides) project. The field campaign took place from 20 November until 9 December 2008 at the atmospheric research station "El Arenosillo" (37°5'47.76" N, 6°44'6.94" W). As the monitoring station is located at the interface between a natural park, industrial cities (Huelva, Seville) and the Atlantic Ocean, a variety of physical and chemical parameters of aerosols and gas phase could be characterized in dependency on the origin of air masses. Backwards trajectories were examined and compared with local meteorology to classify characteristic air mass types for several source regions. Aerosol number and mass as well as polycyclic aromatic hydrocarbons and black carbon concentrations were measured in PM1 and size distributions were registered covering a size range from 7 nm up to 32 μm. The chemical composition of the non-refractory submicron aerosol (NR-PM1) was measured by means of an Aerosol Mass Spectrometer (Aerodyne HR-ToF-AMS). Gas phase analyzers monitored various trace gases (O3, SO2, NO, NO2, CO2) and a weather station provided meteorological parameters. Lowest average submicron particle mass and number concentrations were found in air masses arriving from the Atlantic Ocean with values around 2 μg m−3 and 1000 cm−3. These mass concentrations were about two to four times lower than the values recorded in air masses of continental and urban origins. For some species PM1-fractions in marine air were significantly larger than in air masses originating from Huelva, a closely located city with extensive industrial activities. The largest fraction of sulfate (54%) was detected in marine air masses and was to a high degree not neutralized. In addition, small concentrations of methanesulfonic acid (MSA), a product of biogenic dimethyl sulfate (DMS) emissions, could be identified in the particle phase. In all air masses passing the continent the organic aerosol fraction dominated the total NR-PM1. For this reason, using Positive Matrix Factorization (PMF) four organic aerosol (OA) classes that can be associated with various aerosol sources and components were identified: a highly-oxygenated OA is the major component (43% OA) while semi-volatile OA accounts for 23%. A hydrocarbon-like OA mainly resulting from industries, traffic and shipping emissions as well as particles from wood burning emissions also contribute to total OA and depend on the air mass origin. A significant variability of ozone was observed that depends on the impact of different air mass types and solar radiation.

scholarly journals Physical aerosol properties and their relation to air mass origin at Monte Cimone (Italy) during the first MINATROC campaign

2005 ◽  
Vol 5 (8) ◽  
pp. 2203-2226 ◽  
Author(s):  
R. Van Dingenen ◽  
J.-P. Putaud ◽  
S. Martins-Dos Santos ◽  
F. Raes
Keyword(s):  
Boundary Layer ◽  
Black Carbon ◽  
Water Soluble ◽  
Size Distributions ◽  
Soluble Organic Matter ◽  
Air Mass ◽  
Air Masses ◽  
Hygroscopic Properties ◽  
Hygroscopic Particles ◽  
Air Mass Origin

Abstract. Aerosol physical properties were measured at the Monte Cimone Observatory (Italy) from 1 June till 6 July 2000. The measurement site is located in the transition zone between the continental boundary layer and the free troposphere (FT), at the border between the Mediterranean area and Central Europe, and is exposed to a variety of air masses. Sub-μm number size distributions, aerosol hygroscopicity near 90% RH, refractory size distribution at 270°C and equivalent black carbon mass were continuously measured. Number size distributions and hygroscopic properties indicate that the site is exposed to aged continental air masses, however during daytime it is also affected by upslope winds. The mixing of this transported polluted boundary layer air masses with relatively clean FT air leads to frequent nucleation events around local noon. Night-time size distributions, including fine and coarse fractions for each air mass episode, have been parameterized by a 3-modal lognormal distribution. Number and volume concentrations in the sub-μm modes are strongly affected by the air mass origin, with highest levels in NW-European air masses, versus very clean, free tropospheric air coming from the N-European sector. During a brief but distinct dust episode, the coarse mode is clearly enhanced. The observed hygroscopic behavior of the aerosol is consistent with the chemical composition described by Putaud et al. (2004), but no closure between known chemical composition and measured hygroscopicity could be made because the hygroscopic properties of the water-soluble organic matter (WSOM) are not known. The data suggest that WSOM is slightly-to-moderately hygroscopic (hygroscopic growth factor GF at 90% relative humidity between 1.05 and 1.51), and that this property may well depend on the air mass origin and history. External mixing of aerosol particles is observed in all air masses through the occurrence of two hygroscopicity modes (average GF of 1.22 and 1.37, respectively). However, the presence of "less" hygroscopic particles has mostly such a low occurrence rate that the average growth factor distribution for each air mass sector actually appears as a single mode. This is not the case for the dust episode, where the external mixing between less hygroscopic and more hygroscopic particles is very prominent, and indicating clearly the occurrence of a dust accumulation mode, extending down to 50 nm particles, along with an anthropogenic pollution mode. The presented physical measurements finally allow us to provide a partitioning of the sub-μm aerosol in four non-overlapping fractions (soluble/volatile, non-soluble/volatile, refractory/non-black carbon, black carbon) which can be associated with separate groups of chemical compounds determined with chemical-analytical techniques (ions, non-water soluble organic matter, dust, elemental carbon). All air masses except the free-tropospheric N-European and Dust episodes show a similar composition within the uncertainty of the data (53%, 37%, 5% and 5% respectively for the four defined fractions). Compared to these sectors, the dust episode shows a clearly enhanced refractory-non-BC fraction (17%), attributed to dust in the accumulation mode, whereas for the very clean N-EUR sector, the total refractory fraction is 25%, of which 13% non-BC and 12% BC.

scholarly journals Long-term real-time chemical characterization of submicron aerosols at Montsec (Southern Pyrenees, 1570 m a.s.l.)

2014 ◽  
Vol 14 (21) ◽  
pp. 28809-28844 ◽  
Author(s):  
A. Ripoll ◽  
M. C. Minguillón ◽  
J. Pey ◽  
J. L. Jimenez ◽  
D. A. Day ◽  
...  
Keyword(s):  
Real Time ◽  
Long Range ◽  
Chemical Characterization ◽  
Western Mediterranean ◽  
Continuous Increase ◽  
Air Mass ◽  
Air Masses ◽  
Diurnal Patterns ◽  
Western Mediterranean Basin ◽  
Air Mass Origin

Abstract. Real-time measurements of inorganic (sulfate, nitrate, ammonium, chloride and black carbon (BC)) and organic submicron aerosols from a continental background site (Montsec, MSC, 1570 m a.s.l.) in the Western Mediterranean Basin (WMB) were conducted for 10 months (July 2011–April 2012). An Aerosol Chemical Speciation Monitor (ACSM) was co-located with other on-line and off-line PM1 measurements. Analyses of the hourly, diurnal, and seasonal variations are presented here, for the first time for this region. Seasonal trends in PM1 components are attributed to variations in: evolution of the planetary boundary layer (PBL) height, air mass origin, and meteorological conditions. In summer, the higher temperature and solar radiation increases convection, enhancing the growth of the PBL and the transport of anthropogenic pollutants towards high altitude sites. Furthermore, the regional recirculation of air masses over the WMB creates a continuous increase in the background concentrations of PM1 components and causes the formation of reserve strata at relatively high altitudes. Sporadically, MSC is affected by air masses from North Africa. The combination of all these atmospheric processes at local, regional and continental scales results in a high variability of PM1 components, with poorly defined daily patterns, except for the organic aerosols (OA). OA was mostly oxygenated organic aerosol (OOA), with two different types: semi-volatile (SV-OOA) and low-volatile (LV-OOA), and both showed marked diurnal cycles regardless of the air mass origin, especially SV-OOA. This different diurnal variation compared to inorganic aerosols suggested that OA components at MSC are not only associated with anthropogenic and long-range-transported secondary OA (SOA), but also with recently-produced biogenic SOA. Very different conditions drive the aerosol phenomenology in winter at MSC. The thermal inversions and the lower vertical development of the PBL leave MSC in the free troposphere most of the day, being affected by PBL air masses only after midday, when the mountain breezes transport emissions from the adjacent valleys and plains to the top of the mountain. This results in clear diurnal patterns of both organic and inorganic concentrations. Moreover, in winter sporadic long-range transport from mainland Europe is observed and leads to less marked diurnal patterns. The results obtained in the present study highlight the importance of SOA formation processes at a remote site such as MSC, especially in summer. Additional research is needed to characterize the sources of SOA at remote sites.

scholarly journals A Lagrangian model of air-mass photochemistry and mixing using a trajectory ensemble: the Cambridge Tropospheric Trajectory model of Chemistry And Transport (CiTTyCAT) version 4.2

2011 ◽  
Vol 4 (3) ◽  
pp. 2469-2544 ◽  
Author(s):  
T. A. M. Pugh ◽  
M. Cain ◽  
J. Methven ◽  
O. Wild ◽  
S. R. Arnold ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Lagrangian Model ◽  
Small Scale ◽  
Analysis Model ◽  
Air Mass ◽  
Air Masses ◽  
Trajectory Model ◽  
Boundary Layer Height ◽  
Community Model ◽  
First Time

Abstract. A Lagrangian model of photochemistry and mixing is described (CiTTyCAT, stemming from the Cambridge Tropospheric Trajectory model of Chemistry And Transport), which is suitable for transport and chemistry studies throughout the troposphere. Over the last five years, the model has been developed in parallel at several different institutions and here those developments have been incorporated into one "community" model and documented for the first time. The key photochemical developments include a new scheme for biogenic volatile organic compounds and updated emissions schemes. The key physical development is to evolve composition following an ensemble of trajectories within neighbouring air-masses, including a simple scheme for mixing between them via an evolving "background profile", both within the boundary layer and free troposphere. The model runs along trajectories pre-calculated using winds and temperature from meteorological analyses. In addition, boundary layer height and precipitation rates, output from the analysis model, are interpolated to trajectory points and used as inputs to the mixing and wet deposition schemes. The model is most suitable in regimes when the effects of small-scale turbulent mixing are slow relative to advection by the resolved winds so that coherent air-masses form with distinct composition and strong gradients between them. Such air-masses can persist for many days while stretching, folding and thinning. Lagrangian models offer a useful framework for picking apart the processes of air-mass evolution over inter-continental distances, without being hindered by the numerical diffusion inherent to global Eulerian models. The model, including different box and trajectory modes, is described and some output for each of the modes is presented for evaluation. The model is available for download from a Subversion-controlled repository by contacting the corresponding authors.

scholarly journals Aerosol particle measurements at three stationary sites in the megacity of Paris during summer 2009: meteorology and air mass origin dominate aerosol particle composition and size distribution

2013 ◽  
Vol 13 (2) ◽  
pp. 933-959 ◽  
Author(s):  
F. Freutel ◽  
J. Schneider ◽  
F. Drewnick ◽  
S.-L. von der Weiden-Reinmüller ◽  
M. Crippa ◽  
...  
Keyword(s):  
Particle Size ◽  
Black Carbon ◽  
Aerosol Particle ◽  
Organic Aerosol ◽  
Air Mass ◽  
Air Masses ◽  
Aerosol Mass ◽  
The Impact ◽  
Air Mass Origin ◽  
Mass Concentrations

Abstract. During July 2009, a one-month measurement campaign was performed in the megacity of Paris. Amongst other measurement platforms, three stationary sites distributed over an area of 40 km in diameter in the greater Paris region enabled a detailed characterization of the aerosol particle and gas phase. Simulation results from the FLEXPART dispersion model were used to distinguish between different types of air masses sampled. It was found that the origin of air masses had a large influence on measured mass concentrations of the secondary species particulate sulphate, nitrate, ammonium, and oxygenated organic aerosol measured with the Aerodyne aerosol mass spectrometer in the submicron particle size range: particularly high concentrations of these species (about 4 μg m−3, 2 μg m−3, 2 μg m−3, and 7 μg m−3, respectively) were measured when aged material was advected from continental Europe, while for air masses originating from the Atlantic, much lower mass concentrations of these species were observed (about 1 μg m−3, 0.2 μg m−3, 0.4 μg m−3, and 1–3 μg m−3, respectively). For the primary emission tracers hydrocarbon-like organic aerosol, black carbon, and NOx it was found that apart from diurnal source strength variations and proximity to emission sources, local meteorology had the largest influence on measured concentrations, with higher wind speeds leading to larger dilution and therefore smaller measured concentrations. Also the shape of particle size distributions was affected by wind speed and air mass origin. Quasi-Lagrangian measurements performed under connected flow conditions between the three stationary sites were used to estimate the influence of the Paris emission plume onto its surroundings, which was found to be rather small. Rough estimates for the impact of the Paris emission plume on the suburban areas can be inferred from these measurements: Volume mixing ratios of 1–14 ppb of NOx, and upper limits for mass concentrations of about 1.5 μg m−3 of black carbon and of about 3 μg m−3 of hydrocarbon-like organic aerosol can be deduced which originate from both, local emissions and the overall Paris emission plume. The secondary aerosol particle phase species were found to be not significantly influenced by the Paris megacity, indicating their regional origin. The submicron aerosol mass concentrations of particulate sulphate, nitrate, and ammonium measured during time periods when air masses were advected from eastern central Europe were found to be similar to what has been found from other measurement campaigns in Paris and south-central France for this type of air mass origin, indicating that the results presented here are also more generally valid.

scholarly journals Source classification of upper tropospheric pollution by MIPAS HCN and C<sub>2</sub>H<sub>6</sub> global distributions

2009 ◽  
Vol 9 (4) ◽  
pp. 16197-16232 ◽  
Author(s):  
N. Glatthor ◽  
T. von Clarmann ◽  
G. P. Stiller ◽  
B. Funke ◽  
M. E. Koukouli ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Industrial Pollution ◽  
Fossil Fuels ◽  
Emission Spectra ◽  
Significant Feature ◽  
Backward Trajectory ◽  
Air Masses ◽  
Mixing Ratios ◽  
Trajectory Calculations ◽  
Good Agreement

Abstract. We present global upper tropospheric HCN and C2H6 amounts derived from MIPAS/ENVISAT limb emission spectra. HCN and C2H6 are retrieved in the spectral regions 715.5–782.7 cm−1 and 811.5–835.7 cm−1, respectively. The datasets we present consist of 54 days between September 2003 and March 2004. This period covers the peak and decline of the southern hemispheric biomass burning period and some months thereafter. HCN is a nearly unambiguous tracer of biomass burning with an assumed tropospheric lifetime of several months. Indeed, the most significant feature in the MIPAS HCN dataset is an upper tropospheric plume of enhanced values caused by southern hemispheric biomass burning, which in September and October 2003 extended from tropical South America over Africa, Australia to the Southern Pacific. The spatial extent of this plume agrees well with the MOPITT CO distribution of September 2003. Further there is good agreement with the shapes and mixing ratios of the southern hemispheric HCN and C2H6 fields measured by the ACE experiment between September and November 2005. The MIPAS HCN plume extended from the lowermost observation height (8 km) up to about 16 km altitude, with maximum values of 500–600 pptv in October 2003. It was still clearly visible in December 2003, but had strongly decreased by March 2004, confirming the assumed tropospheric lifetime. The main sources of C2H6 are production and transmission of fossil fuels, followed by biofuel use and biomass burning. The C2H6 distribution also clearly reflected the southern hemispheric biomass burning plume and its seasonal variation, with maximum amounts of 600–700 pptv. Generally there was good agreement between the southern hemispheric distributions of both pollution tracers, except for the region between Peru and the mid-Pacific. Here C2H6 was considerably enhanced, whereas the HCN amounts were low. Backward trajectory calculations suggested that industrial pollution was responsible for the elevated C2H6 in these particular air masses. Except for the Asian monsoon anticyclone in September 2003, there were only comparably small regions of enhanced HCN in the Northern Hemisphere. However, C2H6 showed an equally strong northern hemispheric signal between the equator and low midlatitudes, persisting over the whole observation period. Backward trajectory calculations for air masses from this region also pointed to industrial sources of this pollution. Generally, C2H6/HCN ratios between 1 and 1.5 indicate biomass burning and ratios larger than 1.5 industrial pollution. However, in March 2004 ratios of up to 2 were also found in some regions of the former southern biomass burning plume.

scholarly journals A Lagrangian model of air-mass photochemistry and mixing using a trajectory ensemble: the Cambridge Tropospheric Trajectory model of Chemistry And Transport (CiTTyCAT) version 4.2

2012 ◽  
Vol 5 (1) ◽  
pp. 193-221 ◽  
Author(s):  
T. A. M. Pugh ◽  
M. Cain ◽  
J. Methven ◽  
O. Wild ◽  
S. R. Arnold ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Lagrangian Model ◽  
Small Scale ◽  
Analysis Model ◽  
Air Mass ◽  
Air Masses ◽  
Trajectory Model ◽  
Boundary Layer Height ◽  
Community Model ◽  
First Time

Abstract. A Lagrangian model of photochemistry and mixing is described (CiTTyCAT, stemming from the Cambridge Tropospheric Trajectory model of Chemistry And Transport), which is suitable for transport and chemistry studies throughout the troposphere. Over the last five years, the model has been developed in parallel at several different institutions and here those developments have been incorporated into one "community" model and documented for the first time. The key photochemical developments include a new scheme for biogenic volatile organic compounds and updated emissions schemes. The key physical development is to evolve composition following an ensemble of trajectories within neighbouring air-masses, including a simple scheme for mixing between them via an evolving "background profile", both within the boundary layer and free troposphere. The model runs along trajectories pre-calculated using winds and temperature from meteorological analyses. In addition, boundary layer height and precipitation rates, output from the analysis model, are interpolated to trajectory points and used as inputs to the mixing and wet deposition schemes. The model is most suitable in regimes when the effects of small-scale turbulent mixing are slow relative to advection by the resolved winds so that coherent air-masses form with distinct composition and strong gradients between them. Such air-masses can persist for many days while stretching, folding and thinning. Lagrangian models offer a useful framework for picking apart the processes of air-mass evolution over inter-continental distances, without being hindered by the numerical diffusion inherent to global Eulerian models. The model, including different box and trajectory modes, is described and some output for each of the modes is presented for evaluation. The model is available for download from a Subversion-controlled repository by contacting the corresponding authors.

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