Intrusion Of Masses Research Articles

Increased atmospheric dust deposition during the Neoglacial in a boreal peat bog from north-eastern Canada

Dust deposition in north-eastern Canada was estimated from the geochemical signature of a boreal peat bog from the James Bay lowlands. The rare earth elements and other lithogenic elements, as well as Nd isotopes were measured by Q-ICP-MS, ICP-OES and MC-ICP-MS, respectively along a 4.20m peat core covering the last 7000years. A principal component analysis performed on the geochemical dataset shows that REEs display the same chemical behavior as other lithogenic elements such as Al and Ti, which suggests that they are immobile in the peat column and can be used as tracers of dust deposition. After 4000calyrBP, peaks in dust deposition associated with greater variability in testate amoebae assemblages and plant macrofossil composition as well as a change in ɛNd values are observed. Between 7000 and 4100calyrBP, the ɛNd values varied from −36 to −29, while they gradually increased from 4100calyrBP until 1500calyrBP, suggesting proportionally less dust from local source(s) is deposited in favor of more regional source(s). From 1500calyrBP, ɛNd values remained relatively stable around −15 and −12. Most of the dust peaks correspond to documented cold and dry periods likely linked to intrusion of arctic air masses. A migration of the polar front might explain the more frequent intrusion of Arctic air masses in the region and the greater variability in the LG2 record over the last 4000years.

Ice core and climate reanalysis analogs to predict Antarctic and Southern Hemisphere climate changes

A primary goal of the SCAR (Scientific Committee for Antarctic Research) initiated AntClim21 (Antarctic Climate in the 21st Century) Scientific Research Programme is to develop analogs for understanding past, present and future climates for the Antarctic and Southern Hemisphere. In this contribution to AntClim21 we provide a framework for achieving this goal that includes: a description of basic climate parameters; comparison of existing climate reanalyses; and ice core sodium records as proxies for the frequencies of marine air mass intrusion spanning the past ∼2000 years. The resulting analog examples include: natural variability, a continuation of the current trend in Antarctic and Southern Ocean climate characterized by some regions of warming and some cooling at the surface of the Southern Ocean, Antarctic ozone healing, a generally warming climate and separate increases in the meridional and zonal winds. We emphasize changes in atmospheric circulation because the atmosphere rapidly transports heat, moisture, momentum, and pollutants, throughout the middle to high latitudes. In addition, atmospheric circulation interacts with temporal variations (synoptic to monthly scales, inter-annual, decadal, etc.) of sea ice extent and concentration. We also investigate associations between Antarctic atmospheric circulation features, notably the Amundsen Sea Low (ASL), and primary climate teleconnections including the SAM (Southern Annular Mode), ENSO (El Nino Southern Oscillation), the Pacific Decadal Oscillation (PDO), the AMO (Atlantic Multidecadal Oscillation), and solar irradiance variations.

Stratospheric intrusion into the troposphere during the tropical cyclone Nilam (2012)

This article discusses different plausible mechanisms to account for the intrusion of dry ozone‐rich stratospheric air into the troposphere during the passage of the tropical cyclone Nilam‐2012. The present study shows that the overshooting convection associated with Nilam is found to be the prime candidate for the generation of turbulence in the vicinity of tropopause (VOT). In addition, the presence of strong updraughts and downdraughts in the VOT weakened the stability of the tropopause which allowed the dry ozone‐rich stratospheric air to penetrate downwards to the troposphere. Significant modulation of the tropopause structure is observed which is found to be accompanied by structures linked with shear instability. Concurrent ozone measurements also indicate the intrusion of stratospheric air mass into the upper and middle troposphere.

Polychaete distribution on the southwestern Atlantic continental shelf

ABSTRACTDiversity and distribution of polychaetes on the southeastern Brazilian Shelf (SBS) adjacent to the city of Santos were studied. The study area is situated in the vicinity of Santos Bay with its estuarine complex and other small rivers along the coast. A total of 16,274 specimens belonging to 214 polychaete species were found at 21 sampling stations during two different periods. Two communities occur along the shelf and were related firstly to sediment characteristics. Prionospio dayi (Spionidae) was dominant in the inner shelf community that was characterized by well-sorted, very fine sand. The outer shelf community was found in muddy sediments with high organic matter content and was dominated by subsurface deposit feeders, like Petersenaspis capillata (Sternaspidae) and Leitoscoloplos kerguelensis (Orbiniidae), and by large carnivores such as Aglaophamus sp. (Nephtyidae) and Sigambra sp. (Pilargidae). A transition zone of mixed sediments presenting high diversity and richness was found between these communities. The characteristics of bottom water and food quality in the sediment were important to divide the inner shelf into two sub-areas. Nearshore sampling stations (A group) were more influenced by freshwater input, mainly during summer. This influence is not conspicuous at stations close to 30 m depth (B group). However the effect of South Atlantic Central Water mass (SACW) intrusion on the benthic system was observed on the inner shelf – B group during the summer. The summer intrusion of SACW onto the inner shelf may explain the higher quality of organic matter that resulted in an increase in polychaete abundance and richness.

Delineating ShallowS‐Wave Velocity Structure Using Multiple Ambient‐Noise Surface‐Wave Methods: An Example from Western Junggar, China

Abstract Aiming for a geophysical survey to around 1.5 km depth, we conduct a passive‐source surface‐wave survey along a 70‐km‐long line on the western side of the Junggar basin in northwest China. We use frequency–time analysis and spatial autocorrelation methods to extract surface‐wave dispersion curves from ambient‐noise data of station pairs, as well as ambient‐noise multichannel analysis of surface waves from multistations. Dispersion curves corresponding to the same positions obtained by these three methods independently are comparable, which shows the validity of using these methods. After inverting more than 400 dispersion curves and aligning their results together, we construct a 2D shear S ‐wave velocity image around 1.5 km deep and 60 km long. A less than 6% difference between the inverted S ‐wave velocity profile and the borehole data in situ shows the relatively high accuracy of our method. The 2D S ‐wave velocity image clearly delineates the main geologic structures, including transition of landform, intrusion of rock mass, and shape of bedrock beneath the survey line.

Cross-shelf exchanges between the Coral Sea and the Great Barrier Reef lagoon determined from a regional-scale numerical model

Analyses of the variability in a 3.5-year run of a hydrodynamic model developed for simulating the circulation of the Great Barrier Reef (GBR) are presented. Sea-surface temperature, salinity, currents and cross-shelf transports between the GBR lagoon and the deep ocean offshore are investigated and compare well to available observations. Water mass intrusions and flushing events are critical factors in determining the health of coral reef and continental shelf ecosystems. Results from tracer release experiments provide a synoptic view of the variability of residence times within the GBR and identify critical regions of shelf-ocean exchange. One such region of significant tracer contribution to the shelf is identified in the vicinity of the Pompey Reefs in an area characterised by increased frequency of upslope transported water. Another location of enhanced flux on to the shelf exists in the region bracketing Palm Passage, where the reef matrix is very open, and provides little obstacle to cross-shelf exchange. The Palm Passage location is the origin of a northwards plume of elevated concentration. The model circulation provides a robust and useful picture of the Great Barrier Reef, rendering the model suitable for providing input to biogeochemical and sediment models to simulate, at a broad scale, the ecosystem health, water quality, transport and fate of water and waterborne material, moving through catchments and into the GBR lagoon.

Effects of the STCC eddies on the Kuroshio based on the 20-year JCOPE2 reanalysis results

In this study, 20years of model reanalysis data are analyzed to study the effects of the subtropical countercurrent (STCC) eddies on the upstream Kuroshio, from east of Luzon to east of Taiwan. The effects are assessed from individual events to interannual time scales. The wind-driven Kuroshio is modified by the STCC eddies, with high spatiotemporal variations. The mass balance in the composite eddy events indicates that the strengthening and weakening of the Kuroshio transport are locally caused by the mass convergence and divergence produced by the eddies. The same analogy applies to the interannual time scale. In the eddy-rich years, the upstream Kuroshio is generally stronger because of wind forcing, yet the strengthening is nonuniform because of modification by the eddies. The larger number of warm eddies to the east of Taiwan and Luzon Island further strengthen the jet, whereas the larger number of cold eddies to the east of the Luzon Strait weaken the Kuroshio in the Luzon Strait. Drifter trajectories show larger Luzon Strait intrusion during the occurrence of cold eddies. The local weakening of the Kuroshio by cold eddies leads to a weaker potential vorticity jump, producing favorable conditions for the intrusion of a water mass into the South China Sea.

Recent recovery of surface wind speed after decadal decrease: a focus on South Korea

We investigate the multi-decadal variability of observed surface wind speed around South Korea. It is found that surface wind speed exhibits decreasing trend from mid-1950s until 2003, which is similar with the trends reported for other parts of the world. However, the decreasing trend ceases and becomes unclear since then. It is revealed that decreasing wind speed until 2003 is strongly associated with the decreasing trend of the spatial variance in both atmospheric pressure and air temperature across the East Asia for the same period. On the contrary, break of decreasing trend in surface wind speed since 2003 is associated with increasing spatial variance in surface temperature over the East Asia. Ground observation shows that surface wind speed and air temperature exhibit highly negative correlations for both summer and winter prior to 2003. However, since 2003, the correlations differ between seasons. We suggest that mechanisms behind the recent wind speed trend are different between summer and winter. This is on the basis of an interesting finding that air temperature has decreased while surface temperature has increased during winter months since 2003. We hypothesize that such contrasting temperature trends indicate more frequent movement of external cold air mass into the region since 2003. We also hypothesize that increasing summer wind speed is driven by intrusion of warm air mass into the region which is witnessed via increasing spatial variance in surface temperature across East Asia and the fact that both air and surface temperature rise together.

Three-dimensional finite element analysis on En mass intrusion and retraction of maxillary anterior teeth with J-hook headgear

To investigate the biomechanics of J-hook headgear in En mass intrusion and retraction of maxillary anterior teeth and provide guidance for clinical treatment. A three-dimensional finite element model of maxillary teeth, periodontium, straight wire appliance and maxillary bone was established in ANSYS 14.0. En mass retraction of anterior teeth with force of 1.5 N through J-hook headgear was stimulated. Force was applied mesial to lateral incisor in group A and distal to lateral incisor in group B. The force direction was 30° to the sagittal plane and 20° to 60° to the occlusal plane. Force direction to the occlusal plane was changed every 5° and 18 cases were calculated. Displacement of upper anterior teeth and stress distribution in the periodontium were analyzed. As the degrees of force direction to the occlusal plane increased, the moving pattern of upper anterior teeth changed from clockwise rotation (lingual movement with intrusion) to bodily retraction and intrusion, and counter- clockwise rotation (intrusion with labial movement). With the force direction of 35° to occlusal plane applied mesial to lateral incisor or force direction of 45° to the occlusal plane applied distal to lateral incisor, bodily movement of upper anterior teeth without rotation was achieved. Placement of J-hook mesial to lateral incisor enable orthodontists to maintain better en mass intrusion and retraction of upper anterior teeth. The direction of J-hook should be adjusted according to individual condition and treatment objective.

Distinct atmospheric patterns and associations with acute heat-induced mortality in five regions of England.

The main objective of this paper was to identify possible acute heat-induced summer mortality in five regions of England namely the Yorkshire and the Humber, West Midlands, North East, North West and South East regions and reveal associations with specific air flows. For this purpose, backward air mass trajectories corresponding to daily episodes of increased temperatures were produced and divided to clusters, in order to define atmospheric pathways associated with warm air mass intrusions. A statistically significant at 95 % confidence interval increase in daily total mortality (DTMORT) was observed during the selected episodes at all five regions and thus, heat-induced mortality was indicated. The calculated raise was more intense in the West Midlands, North West and South East regions, whereas the results in the North East and Yorkshire and the Humber regions were less evident. Large fractions of thermal episodes, elevated average temperature values and higher average DTMORT levels were primarily associated with the short-medium range South West (SW) and/or East-South East (E-SE) trajectory clusters, suggesting relations among heat-induced mortality and specific atmospheric circulations. Short-medium length of SW and E-SE airflows, calculated by an application of Haversine formula along the centroid trajectory of each cluster, implies the arrival of slow moving air masses. Atmospheric stagnation could enhance human thermal stress due to low wind speed.

Variability of fronts, fresh water input and chlorophyll in the Indian Ocean sector of the Southern Ocean

The aim of this study was to understand the variability in the fronts and water masses, and the effect of melt water on the concentration of chlorophyll (Chl a) in the Indian Ocean sector of the Southern Ocean using hydrographic data collected during the austral summer (February 2010 and 2011). The Southern Subtropical Front (SSTF) and Northern Sub Antarctic Front (SAF1) were found to be further south at 57°30′E than at 47–48°E. This southward shift of the fronts was consistent with the southward meandering (c. 2°) of the Antarctic Circumpolar Current (ACC) core from the western section to the eastern section, which could have been caused by the bottom topography. The intrusion of water masses also differed between the western and eastern transects of the study region as a result of the meandering of the ACC core. Fresh water layer thickness relative to the winter water in 2011 was more compared to that during 2010. This could have been due to the larger amount of sea ice that was present in the winter of 2010, which subsequently melted, resulting in the advection of melt water from the south and west of the study region. In situ observations and satellite data detected a high Chl a concentration (c. 0.38 mg m−3) south of the Northern Polar Front (PF1) in 2011, which was caused by this melt water.

Diel patterns of temperature, conductivity and dissolved oxygen in an Amazon floodplain lake: description of a friagem phenomenon

AIM: The aim of this work was to study the diel stratification parameters temperature, dissolved oxygen and conductivity, providing a more detailed description of a friagem event. METHODS: the mixing behavior of the limnetic water column in Lago Catalão, an Amazon floodplain lake flooded by two of the world’s largest rivers (Solimões and Negro), was studied through diel profiling of temperature, conductivity and dissolved oxygen, between 2006 and 2007. Measurements were made every four hours at 1m depth intervals to the lake bottom. RESULTS: The water column remained stratified during most of the year with the exception of one month with low water level, when nocturnal mixing occurred and one friagem event during high water (May 2007) when an isothermal temperature profile and an atypical orthograde oxygen profile were observed. CONCLUSIONS: The friagem event, a large drop in air temperatures due to the intrusion of a polar air mass in the Amazon, constitutes an important force in the dynamics of the water column, which produces a profound redistribution of dissolved gases and solutes in the system. This is the first time that the effects of the friagem on the mixing patterns in a lowland Amazon lake have been documented in detail. The decline in air temperature, observed during the friagem event destabilized the normally stratified water column, which can be associated with an environmental disturb.

Enhanced thermal stability of phosphate capped magnetite nanoparticles

We have studied the effect of phosphate capping on the high temperature thermal stability and magnetic properties of magnetite (Fe3O4) nanoparticles synthesized through a single-step co-precipitation method. The prepared magnetic nanoparticles are characterized using various techniques. When annealed in air, the phosphate capped nanoparticle undergoes a magnetic to non-magnetic phase transition at a temperature of 689 °C as compared to 580 °C in the uncoated nanoparticle of similar size. The observed high temperature phase stability of phosphate capped nanoparticle is attributed to the formation of a phosphocarbonaceous shell over the nanoparticles, which acts as a covalently attached protective layer and improves the thermal stability of the core material by increasing the activation energy. The phosphocarbonaceous shell prevents the intrusion of heat, oxygen, volatiles, and mass into the magnetic core. At higher temperatures, the coalescence of nanoparticles occurs along with the restructuring of the phosphocarbonaceous shell into a vitreous semisolid layer on the nanoparticles, which is confirmed from the small angle X-ray scattering, Fourier transform infra red spectroscopy, and transmission electron microscopy measurements. The probable mechanism for the enhancement of thermal stability of phosphocarbonaceous capped nanoparticles is discussed.

Variations of alkenone temperature in the Sea of Japan during the last 170 ka and its paleoceanographic implications

Two sediment cores, KCES1 and ODP797, which were recovered from the Sea of Japan (JS), were measured for alkenone-derived sea surface temperatures (\(U^{{\text{K}}^{\prime}}_{37} {\text{-SSTs}}\)). Our results revealed that the SSTs closely follow the glacial-interglacial cycles during the last 170 ka, except in the last glacial maximum (LGM), during which the SST was higher than in the Holocene. The anomalous high temperature in the LGM is considered as an effect of the intrusion of a low salinity water mass into the JS when the sea level was almost below 130 m. On the glacial-interglacial to orbital timescale, the \( U^{{\text{K}}^{\prime }}_{37} {\text{-SSTs}} \) record in the JS correlated well with the benthic foraminiferal δ18O record and solar insolation, which suggests the dominant control of solar insolation and its related sea ice development on the SST in the JS. On the sub-orbital/millennial timescale, reduced SST corresponds to an enhanced east asian winter monsoon (EAWM) during the last glacial period (MIS3 and MIS4), indicating the dominant control of sea ice expansion due to the enhanced EAWM on the SST in the JS. In contrast, during the last interglacial period (MIS5), the SST in the JS was controlled by variations in the east Asian summer monsoon. These results highlight the key role of solar insolation and associated glacial-interglacial conditions in the variations of the SST in the JS since the last 170 ka.

Greenland ice sheet melt from MODIS and associated atmospheric variability.

Daily June-July melt fraction variations over the Greenland ice sheet (GIS) derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) (2000–2013) are associated with atmospheric blocking forming an omega-shape ridge over the GIS at 500 hPa height. Blocking activity with a range of time scales, from synoptic waves breaking poleward (<5 days) to full-fledged blocks (≥5 days), brings warm subtropical air masses over the GIS controlling daily surface temperatures and melt. The temperature anomaly of these subtropical air mass intrusions is also important for melting. Based on the years with the greatest melt (2002 and 2012) during the MODIS era, the area-average temperature anomaly of 2 standard deviations above the 14 year June-July mean results in a melt fraction of 40% or more. Though the summer of 2007 had the most blocking days, atmospheric temperature anomalies were too small to instigate extreme melting.Key PointsShort-term atmospheric blocking over Greenland contributes to melt episodesAssociated temperature anomalies are equally important for the meltDuration and strength of blocking events contribute to surface melt intensity

Weapons of mass intrusion: the leveraging of ambush marketing strategies

Purpose – The study presented in this article aims to examine the impact of the leveraging of three distinct ambush marketing strategies that are under-researched in the literature: Promotion, Event, and Broadcast. Design/methodology/approach – An experiment was conducted where the type of ambush strategy was manipulated (i.e. Promotion, Event, Broadcast, no ambush) as well as the market dominance of the sponsor (i.e. dominant or non-dominant) and the congruence level between the event and the sponsor (i.e. high or low congruence). Findings – Ambush strategies' impacts differ widely. The Broadcast strategy is the most harmful to the identification of the actual sponsor; the Event strategy favors the identification of the pseudo-sponsor as the sponsor, while the Promotion strategy is both harmful to the actual sponsor and beneficial for the pseudo-sponsor. Furthermore, although dominant brands benefit more from their sponsorships, they are more affected by an ambush than non-dominant brands. Research limitations/implications – Only one sponsor and one pseudo-sponsor were considered at a time. In addition, digital media were not investigated as vectors of ambush marketing. Further research where multiple sponsors and pseudo-sponsors are leveraging their associations to an event, using both off and on-line media, needs to be undertaken. Practical implications – Against the Promotion strategy sponsors need to create not only strong but also unique associations with the event. The Event strategy can be circumvented with preemptive smaller scale events. Exclusive access to the program broadcast for event sponsors can protect against pseudo-sponsors. Originality/value – This study is the first to provide empirical evidence regarding the impact of the Promotion, Event, and Broadcast strategies. Previous studies had focused almost exclusively on another strategy: the airing of commercials by pseudo-sponsors during event broadcast against which most sponsors are now effectively protected.

Elastic lidar measurements of summer nocturnal low level jet events over Baltimore, Maryland

Elastic lidar (532 nm) measurements were carried out by the Atmospheric Lidar Group at the University of Maryland, Baltimore County (UMBC, 39.25° N, 76.70° W) during meteorological conditions that favored the formation of the nocturnal low level jet (NLLJ) over the United States Mid-Atlantic region. The lidar timeseries from three case studies showed the intrusion of the NLLJ air mass into the nocturnal boundary layer (NBL) and the subsequent displacement of aerosols that were used for tracing atmospheric motion. Three distinctive regions were identified in the timeseries: 1) a wedging zone within the residual layer, that was heavily laden with aerosols, at the onset of the NLLJ, 2) a lofted layer of particulates above the “clean” jet core, and 3) a region where the lofted layer collapsed that was conterminous with the diminishing NLLJ below, and characterized by downward mixing analogous to turbulent wake regions. The National Oceanic and Atmospheric Administration’s (NOAA) Rapid Update Cycle (RUC, grid 252) model was used to analyze the horizontal extent and vertical structure of the NLLJ and to compare with observations acquired during these events. A conceptual model is proposed to highlight the role of the NLLJ, during similar weather patterns, in the regional transport of pollutants and their impact on poor air quality episodes in the Mid-Atlantic United States.

Immune dysfunction and cognitive deficit in stress and physiological aging (Part I): Pathogenesis and risk factors

The concept of stressful cognitive dysfunction, which is under consideration in this review, allows picking out several therapeutic targets. The brain, immune and endocrine systems being the principal adaptive systems in the body permanently share information both in the form of neural impulses and soluble mediators. The CNS differs from other organs due to several peculiarities that affect local immune surveillance. The brain cells secluded from the blood flow by a specialized blood-brain-barrier (BBB) can endogenously express pro- and anti-inflammatory cytokines without the intervention of the immune system. In normal brain the cytokine signaling rather contributes to exclusive brain function (e.g. long-term potentiation, synaptic plasticity, adult neurogenesis) than serves as immune communicator. The stress of different origin increases the serum cytokine levels and disrupts BBB. As a result peripheral cytokines penetrate into the brain where they begin to perform new functions. Mass intrusion of biologically active peptides having a lot of specific targets alters the brain work that we can observe both in humans and in animal experiments. In addition owing to BBB disruption dendritic cells and T cells also penetrate into the brain where they take up a perivascular position. The changes observed in stressed subject may accumulate during repeated episodes of stress forming a picture typical of the aging brain. Moreover long-term stress as well as physiological aging result in hormonal and immunological disturbances including hypothalamic-pituitary-adrenal axis depletion, regulatory T-cell accumulation and dehydroepiandrosterone decrease.

Immune dysfunction and cognitive deficit in stress and physiological aging. Part II: New approaches to cognitive disorder prevention and treatment

Long-term stress as well as physiological aging result in similar immunological and hormonal disturbances including hypothalamic-pituitary-adrenal) axis depletion, aberrant immune response (regulatory T-cells, Tregs, and T(h17)-lymphocyte accumulation) and decreased dehydroepian-drosterone synthesis both in the brain and in the adrenal glands. Since the main mechanisms of inflammation control, "prompt" (stress hormones) and "delayed" (Tregs), are broken, serum cytokine levels increase and become sufficient for blood-brain-barrier disruption. As a result peripheral cytokines penetrate into the brain where they begin to perform new functions. Structural and functional alterations of blood-brain-barrier as well as stress- (or age-) induced neuroinflammation promote influx of bone marrow derived dendritic cells and lymphocyte effectors into the brain parenchyma. Thereafter, mass intrusion ofpro-inflammatory mediators and immune cells having a lot of specific targets alters the brain work that we can observe both in humans and in animal experiments. The concept of stressful cognitive dysfunction, which is under consideration in this review, allows picking out several therapeutic targets: 1) reduction of excessive Treg accumulation; 2) supporting hypothalamic-pituitary-adrenal axis and inflammatory reaction attenuation; 3) recovery of dehydroepiandrosterone level; 4) improvement of blood-brain-barrier function.

ACE-FTS observations of pyrogenic trace species in boreal biomass burning plumes during BORTAS

Abstract. To further our understanding of the effects of biomass burning emissions on atmospheric composition, the BORTAS campaign (BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites) was conducted on 12 July to 3 August 2011 during the boreal forest fire season in Canada. The simultaneous aerial, ground and satellite measurement campaign sought to record instances of boreal biomass burning to measure the tropospheric volume mixing ratios (VMRs) of short- and long-lived trace molecular species from biomass burning emissions. The goal was to investigate the connection between the composition and the distribution of these pyrogenic outflows and their resulting perturbation to atmospheric chemistry, with particular focus on oxidant species to determine the overall impact on the oxidizing capacity of the free troposphere. Measurements of pyrogenic trace species in boreal biomass burning plumes were made by the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) onboard the Canadian Space Agency (CSA) SCISAT-1 satellite during the BORTAS campaign. Even though biomass burning emissions are typically confined to the boundary layer, outflows are often injected into the upper troposphere by isolated convection and fire-related convective processes, thus allowing space-borne instruments to measure these pyrogenic outflows. An extensive set of 14 molecules – CH3OH, C2H2, C2H6, C3H6O, CO, HCN, HCOOH, HNO3, H2CO, NO, NO2, OCS, O3, and PAN – have been analysed. Included in this analysis is the calculation of age-dependent sets of enhancement ratios for each of the species originating from fires in North America (Canada, Alaska) and Siberia for a period of up to 7 days. Ratio values for the shorter lived primary pyrogenic species decrease over time primarily due to oxidation by the OH radical as the plume ages and values for longer lived species such as HCN and C2H6 remain relatively unchanged. Increasing negative values are observed for the oxidant species, including O3, indicating a destruction process in the plume as it ages such that concentrations of the oxidant species have dropped below their off-plume values. Results from previous campaigns have indicated that values for the molar ratios of ΔO3 /ΔO obtained from the measurements of the pyrogenic outflow from boreal fires are highly variable and range from negative to positive, irrespective of plume age. This variability has been attributed to pollution effects where the pyrogenic outflows have mixed with either local urban NOx emissions or pyrogenic emissions from the long-range transport of older plumes, thus affecting the production of O3 within the plumes. The results from this study have identified another potential cause of the variability in O3 concentrations observed in the measurements of biomass burning emissions, where evidence of stratosphere–troposphere exchange due to the pyroconvective updrafts from fires has been identified. Perturbations caused by the lofted emissions in these fire-aided convective processes may result in the intrusion of stratospheric air masses into the free troposphere and subsequent mixing of stratospheric O3 into the pyrogenic outflows causing fluctuations in observed ΔO3/ΔCO molar ratios.