Aircraft vertical profiling of variation of CO2over a Canadian Boreal Forest Site: a role of advection in the changes in the atmospheric boundary layer CO2content

Tellus B ◽  
2007 ◽  
Vol 59 (2) ◽  
Author(s):  
Alexander Shashkov ◽  
Kaz Higuchi ◽  
Douglas Chan
Keyword(s):  
Boundary Layer ◽  
Boreal Forest ◽  
Atmospheric Boundary Layer ◽  
Forest Site ◽  
Vertical Profiling ◽  
Canadian Boreal Forest

scholarly journals Particle concentration and flux dynamics in the atmospheric boundary layer as the indicator of formation mechanism

2011 ◽  
Vol 11 (12) ◽  
pp. 5591-5601 ◽  
Author(s):  
J. Lauros ◽  
A. Sogachev ◽  
S. Smolander ◽  
H. Vuollekoski ◽  
S.-L. Sihto ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Formation Mechanism ◽  
Turbulent Transport ◽  
Particle Formation ◽  
Formation Mechanisms ◽  
Forest Site ◽  
Aerosol Formation ◽  
Flux Dynamics ◽  
Layer Deposition

Abstract. We carried out column model simulations to study particle fluxes and deposition and to evaluate different particle formation mechanisms at a boreal forest site in Finland. We show that kinetic nucleation of sulphuric acid cannot be responsible for new particle formation alone as the simulated vertical profile of particle number concentration does not correspond to observations. Instead organic induced nucleation leads to good agreement confirming the relevance of the aerosol formation mechanism including organic compounds emitted by the biosphere. The simulation of aerosol concentration within the atmospheric boundary layer during nucleation event days shows a highly dynamical picture, where particle formation is coupled with chemistry and turbulent transport. We have demonstrated the suitability of our turbulent mixing scheme in reproducing the most important characteristics of particle dynamics within the boundary layer. Deposition and particle flux simulations show that deposition affects noticeably only the smallest particles in the lowest part of the atmospheric boundary layer.

scholarly journals Entropy production by evapotranspiration and its geographic variation

2008 ◽  
Vol 3 (Special Issue No. 1) ◽  
pp. S89-S94 ◽  
Author(s):  
A. Kleidon
Keyword(s):  
Boundary Layer ◽  
Relative Humidity ◽  
Atmospheric Boundary Layer ◽  
Entropy Production ◽  
Land Surface ◽  
Model Simulation ◽  
Hydrologic Cycle ◽  
Climate System Model ◽  
Biotic Effects

The hydrologic cycle is a system far from thermodynamic equilibrium that is characterized by its rate of entropy production in the climatological mean steady state. Over land, the hydrologic cycle is strongly affected by the presence of terrestrial vegetation. In order to investigate the role of the biota in the hydrologic cycle, it is critical to investigate the consequences of biotic effects from this thermodynamic perspective. Here I quantify entropy production by evapotranspiration with a climate system model of intermediate complexity and estimate its sensitivity to vegetation cover. For present-day conditions, the global mean entropy production of evaporation is 8.4 mW/m<sup>2</sup>/K, which is about 1/3 of the estimated entropy production of the whole hydrologic cycle. On average, ocean surfaces generally produce more than twice as much entropy as land surfaces. On land, high rates of entropy production of up to 16 mW/m<sup>2</sup>/K are found in regions of high evapotranspiration, although relative humidity of the atmospheric boundary layer is also an important factor. With an additional model simulation of a “Desert” simulation, where the effects of vegetation on land surface functioning is removed, I estimate the sensitivity of these entropy production rates to the presence of vegetation. Land averaged evapotranspiration decreases from 2.4 to 1.4 mm/d, while entropy production is reduced comparatively less from 4.2 to 3.1 mW/m<sup>2</sup>/K. This is related to the reduction in relative humidity of the atmospheric boundary layer as a compensatory effect, and points out the importance of a more complete treatment of entropy production calculations to investigate the role of biotic effects on Earth system functioning.

scholarly journals The role of advective transport mechanism in continental-scale transport of fungal plant epidemics

2020 ◽  
Author(s):  
Nolan Elauria ◽  
Taeah Truong ◽  
Kush Upadhyay ◽  
Oleg Kogan
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Plant Pathogen ◽  
Transport Mechanism ◽  
Short Range ◽  
Free Troposphere ◽  
Advective Transport ◽  
Transport Channel ◽  
Continental Scale

AbstractIn examining the continental-scale plant pathogen spread, we focus on the competition between the short-range stochastic hopping within the atmospheric boundary layer, and the laminar advection by the currents in the free troposphere. The latter is typically ignored, since it is assumed that the population of spores which have reached the troposphere is small, and the fraction of the remaining spores that survived the subsequent journey is negligible due to ultraviolet light and frigid temperatures. However, we claim that it is in fact a crucial mechanism for continental-scale spread. We argue that free tropospheric currents can not be ignored, even as the probability for spores to reach them and to survive within them approaches zero. In other words, models that neglect tropospheric advection are fragile – their predictions change qualitatively if this alternative transport channel becomes accessible – even when the rate at which spores actually make use of this transport channel approaches zero.

scholarly journals Vertical characterization of Highly Oxygenated Molecules (HOMs) below and above a boreal forest canopy

2017 ◽  
Author(s):  
Qiaozhi Zha ◽  
Chao Yan ◽  
Heikki Junninen ◽  
Matthieu Riva ◽  
Juho Aalto ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Boreal Forest ◽  
Forest Canopy ◽  
Mixed Boundary ◽  
Ground Level ◽  
Atmospheric Conditions ◽  
Research Attention ◽  
Significant Research ◽  
First Time

Abstract. While the role of highly oxygenated molecules (HOMs) in new particle formation (NPF) and secondary organic aerosol (SOA) formation is not in dispute, the interplay between HOM chemistry and atmospheric conditions continues to draw significant research attention. During the Influence of Biosphere-Atmosphere Interactions on the Reactive Nitrogen budget (IBAIRN) campaign, profile measurements of neutral HOM molecules below and above the forest canopy were performed for the first time in the boreal forest SMEAR II station during September 2016. The HOM concentrations and composition distributions below and above the canopy were similar, supporting a well-mixed boundary layer approximation during daytime. However, much lower HOM concentration were frequently observed at ground level due to the formation of a shallow decoupled layer below the canopy attached to the forest floor. Near ground HOMs were influenced by the changes in the precursors and oxidants, and enhancement of the loss on surfaces in this layer, while the HOMs above the canopy top were not significantly affected. Our findings also illustrate that near-ground HOM measurements conducted in strong stably stratified conditions might only be representative of a small fraction of the entire nocturnal boundary layer. This might, in turn, influence the growth of newly formed particles and SOA formation below the canopy where a large majority of measurements are typically conducted.

scholarly journals Observations of total RONO<sub>2</sub> over the boreal forest: NO<sub>x</sub> sinks and HNO<sub>3</sub> sources

2013 ◽  
Vol 13 (9) ◽  
pp. 4543-4562 ◽  
Author(s):  
E. C. Browne ◽  
K.-E. Min ◽  
P. J. Wooldridge ◽  
E. Apel ◽  
D. R. Blake ◽  
...  
Keyword(s):  
Nitrogen Oxides ◽  
Boreal Forest ◽  
Organic Nitrates ◽  
Primary Role ◽  
Atmospheric Lifetime ◽  
Isoprene Nitrates ◽  
Ultimate Fate ◽  
Canadian Boreal Forest ◽  
Hydrolysis Of

Abstract. In contrast with the textbook view of remote chemistry where HNO3 formation is the primary sink of nitrogen oxides, recent theoretical analyses show that formation of RONO2 (ΣANs) from isoprene and other terpene precursors is the primary net chemical loss of nitrogen oxides over the remote continents where the concentration of nitrogen oxides is low. This then increases the prominence of questions concerning the chemical lifetime and ultimate fate of ΣANs. We present observations of nitrogen oxides and organic molecules collected over the Canadian boreal forest during the summer which show that ΣANs account for ~20% of total oxidized nitrogen and that their instantaneous production rate is larger than that of HNO3. This confirms the primary role of reactions producing ΣANs as a control over the lifetime of NOx (NOx = NO + NO2) in remote, continental environments. However, HNO3 is generally present in larger concentrations than ΣANs indicating that the atmospheric lifetime of ΣANs is shorter than the HNO3 lifetime. We investigate a range of proposed loss mechanisms that would explain the inferred lifetime of ΣANs finding that in combination with deposition, two processes are consistent with the observations: (1) rapid ozonolysis of isoprene nitrates where at least ~40% of the ozonolysis products release NOx from the carbon backbone and/or (2) hydrolysis of particulate organic nitrates with HNO3 as a product. Implications of these ideas for our understanding of NOx and NOy budget in remote and rural locations are discussed.

scholarly journals Vertical characterization of highly oxygenated molecules (HOMs) below and above a boreal forest canopy

2018 ◽  
Vol 18 (23) ◽  
pp. 17437-17450 ◽  
Author(s):  
Qiaozhi Zha ◽  
Chao Yan ◽  
Heikki Junninen ◽  
Matthieu Riva ◽  
Nina Sarnela ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Boreal Forest ◽  
Forest Canopy ◽  
Mixed Boundary ◽  
Ground Level ◽  
Atmospheric Conditions ◽  
Research Attention ◽  
Significant Research ◽  
First Time

Abstract. While the role of highly oxygenated molecules (HOMs) in new particle formation (NPF) and secondary organic aerosol (SOA) formation is not in dispute, the interplay between HOM chemistry and atmospheric conditions continues to draw significant research attention. During the Influence of Biosphere-Atmosphere Interactions on the Reactive Nitrogen budget (IBAIRN) campaign in September 2016, profile measurements of neutral HOMs below and above the forest canopy were performed for the first time at the boreal forest SMEAR II station. The HOM concentrations and composition distributions below and above the canopy were similar during daytime, supporting a well-mixed boundary layer approximation. However, much lower nighttime HOM concentrations were frequently observed at ground level, which was likely due to the formation of a shallow decoupled layer below the canopy. Near the ground HOMs were influenced by the changes in the precursors and oxidants and enhancement of the loss on surfaces in this layer, while the HOMs above the canopy top were not significantly affected. Our findings clearly illustrate that near-ground HOM measurements conducted under stably stratified conditions at this site might only be representative of a small fraction of the entire nocturnal boundary layer. This could, in turn, influence the growth of newly formed particles and SOA formation below the canopy where the large majority of measurements are typically conducted.

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