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 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.

scholarly journals Vertical profiles of sub-3 nm particles over the boreal forest

2019 ◽  
Vol 19 (6) ◽  
pp. 4127-4138 ◽  
Author(s):  
Katri Leino ◽  
Janne Lampilahti ◽  
Pyry Poutanen ◽  
Riikka Väänänen ◽  
Antti Manninen ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Boreal Forest ◽  
Forest Canopy ◽  
Meteorological Data ◽  
Vertical Mixing ◽  
Lower Troposphere ◽  
Ground Level ◽  
Forest Site ◽  
Vertical Profiles ◽  
Boundary Layer Dynamics

Abstract. This work presents airborne observations of sub-3 nm particles in the lower troposphere and investigates new particle formation (NPF) within an evolving boundary layer (BL). We studied particle concentrations together with supporting gas and meteorological data inside the planetary BL over a boreal forest site in Hyytiälä, southern Finland. The analysed data were collected during three flight measurement campaigns: May–June 2015, August 2015 and April–May 2017, including 27 morning and 26 afternoon vertical profiles. As a platform for the instrumentation, we used a Cessna 172 aircraft. The analysed flight data were collected horizontally within a 30 km distance from SMEAR II in Hyytiälä and vertically from 100 m above ground level up to 2700 m. The number concentration of 1.5–3 nm particles was observed to be, on average, the highest near the forest canopy top and to decrease with increasing altitude during the mornings of NPF event days. This indicates that the precursor vapours emitted by the forest play a key role in NPF in Hyytiälä. During daytime, newly formed particles were observed to grow in size and the particle population became more homogenous within the well-mixed BL in the afternoon. During undefined days with respect to NPF, we also detected an increase in concentration of 1.5–3 nm particles in the morning but not their growth in size, which indicates an interrupted NPF process during these undefined days. Vertical mixing was typically stronger during the NPF event days than during the undefined or non-event days. The results shed light on the connection between boundary layer dynamics and NPF.

scholarly journals Comparison of lidar-derived PM<sub>10</sub> with regional modeling and ground-based observations in the frame of MEGAPOLI experiment

2011 ◽  
Vol 11 (20) ◽  
pp. 10705-10726 ◽  
Author(s):  
P. Royer ◽  
P. Chazette ◽  
K. Sartelet ◽  
Q. J. Zhang ◽  
M. Beekmann ◽  
...  
Keyword(s):  
Mixed Boundary ◽  
Ground Level ◽  
In Situ Measurements ◽  
Percentage Error ◽  
Atmospheric Conditions ◽  
Transport Models ◽  
Near Surface ◽  
Lidar Measurements ◽  
Surface Measurements

Abstract. An innovative approach using mobile lidar measurements was implemented to test the performances of chemistry-transport models in simulating mass concentrations (PM10) predicted by chemistry-transport models. A ground-based mobile lidar (GBML) was deployed around Paris onboard a van during the MEGAPOLI (Megacities: Emissions, urban, regional and Global Atmospheric POLlution and climate effects, and Integrated tools for assessment and mitigation) summer experiment in July 2009. The measurements performed with this Rayleigh-Mie lidar are converted into PM10 profiles using optical-to-mass relationships previously established from in situ measurements performed around Paris for urban and peri-urban aerosols. The method is described here and applied to the 10 measurements days (MD). MD of 1, 15, 16 and 26 July 2009, corresponding to different levels of pollution and atmospheric conditions, are analyzed here in more details. Lidar-derived PM10 are compared with results of simulations from POLYPHEMUS and CHIMERE chemistry-transport models (CTM) and with ground-based observations from the AIRPARIF network. GBML-derived and AIRPARIF in situ measurements have been found to be in good agreement with a mean Root Mean Square Error RMSE (and a Mean Absolute Percentage Error MAPE) of 7.2 μg m−3 (26.0%) and 8.8 μg m−3 (25.2%) with relationships assuming peri-urban and urban-type particles, respectively. The comparisons between CTMs and lidar at ~200 m height have shown that CTMs tend to underestimate wet PM10 concentrations as revealed by the mean wet PM10 observed during the 10 MD of 22.4, 20.0 and 17.5 μg m−3 for lidar with peri-urban relationship, and POLYPHEMUS and CHIMERE models, respectively. This leads to a RMSE (and a MAPE) of 6.4 μg m−3 (29.6%) and 6.4 μg m−3 (27.6%) when considering POLYPHEMUS and CHIMERE CTMs, respectively. Wet integrated PM10 computed (between the ground and 1 km above the ground level) from lidar, POLYPHEMUS and CHIMERE results have been compared and have shown similar results with a RMSE (and MAPE) of 6.3 mg m−2 (30.1%) and 5.2 mg m−2 (22.3%) with POLYPHEMUS and CHIMERE when comparing with lidar-derived PM10 with periurban relationship. The values are of the same order of magnitude than other comparisons realized in previous studies. The discrepancies observed between models and measured PM10 can be explained by difficulties to accurately model the background conditions, the positions and strengths of the plume, the vertical turbulent diffusion (as well as the limited vertical model resolutions) and chemical processes as the formation of secondary aerosols. The major advantage of using vertically resolved lidar observations in addition to surface concentrations is to overcome the problem of limited spatial representativity of surface measurements. Even for the case of a well-mixed boundary layer, vertical mixing is not complete, especially in the surface layer and near source regions. Also a bad estimation of the mixing layer height would introduce errors in simulated surface concentrations, which can be detected using lidar measurements. In addition, horizontal spatial representativity is larger for altitude integrated measurements than for surface measurements, because horizontal inhomogeneities occurring near surface sources are dampened.

scholarly journals Vertical profiles of sub-3 nm particles over the boreal forest

2018 ◽  
Author(s):  
Katri Leino ◽  
Janne Lampilahti ◽  
Pyry Poutanen ◽  
Riikka Väänänen ◽  
Antti Manninen ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Forest Canopy ◽  
Meteorological Data ◽  
Vertical Mixing ◽  
Lower Troposphere ◽  
Ground Level ◽  
Forest Site ◽  
Vertical Profiles ◽  
Particle Population ◽  
Flight Measurement

Abstract. This work presents airborne observations of sub-3 nm particles in the lower troposphere and investigates new particle formation (NPF) within an evolving boundary layer (BL). We studied particle concentrations together with supporting gas and meteorological data inside the planetary BL over a boreal forest site in Hyytiälä, Southern Finland. The analysed data were collected during three flight measurement campaigns: May–June 2015, August 2015 and April–May 2017, including 27 morning and 26 afternoon vertical profiles. As a platform for the instrumentation, we used a Cessna 172 aircraft. The analysed flight data were collected horizontally within a 30-km distance from the SMEAR II station in Hyytiälä and vertically from 100 metres above ground level up to 2700 m. The number concentration of 1.5–3 nm particles was observed to be, on average, the highest near the forest canopy top and to decrease with an increasing altitude during the mornings of NPF event days. This indicates that the precursor vapours emitted by the forest play a key role in NPF in Hyytiälä. During daytime, newly-formed particles were observed to grow in size and the particle population became more homogenous within the well-mixed BL in the afternoon. During undefined days in respect to NPF, we also detected an increase in concentrations of 1.5–3 nm particles in the morning but not their growth in size, which indicates an interrupted NPF process during these undefined days. Vertical mixing was typically stronger during the NPF event days than during the undefined or non-event days.

scholarly journals Summertime total OH reactivity measurements from boreal forest during HUMPPA-COPEC 2010

2012 ◽  
Vol 12 (17) ◽  
pp. 8257-8270 ◽  
Author(s):  
A. C. Nölscher ◽  
J. Williams ◽  
V. Sinha ◽  
T. Custer ◽  
W. Song ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Forest Canopy ◽  
Marked Change ◽  
Reactive Species ◽  
Organic Precursor ◽  
The Impact ◽  
First Time ◽  
Comparative Reactivity

Abstract. Ambient total OH reactivity was measured at the Finnish boreal forest station SMEAR II in Hyytiälä (Latitude 61°51' N; Longitude 24°17' E) in July and August 2010 using the Comparative Reactivity Method (CRM). The CRM – total OH reactivity method – is a direct, in-situ determination of the total loss rate of hydroxyl radicals (OH) caused by all reactive species in air. During the intensive field campaign HUMPPA-COPEC 2010 (Hyytiälä United Measurements of Photochemistry and Particles in Air – Comprehensive Organic Precursor Emission and Concentration study) the total OH reactivity was monitored both inside (18 m) and directly above the forest canopy (24 m) for the first time. The comparison between these two total OH reactivity measurements, absolute values and the temporal variation have been analyzed here. Stable boundary layer conditions during night and turbulent mixing in the daytime induced low and high short-term variability, respectively. The impact on total OH reactivity from biogenic emissions and associated photochemical products was measured under "normal" and "stressed" (i.e. prolonged high temperature) conditions. The advection of biomass burning emissions to the site caused a marked change in the total OH reactivity vertical profile. By comparing the OH reactivity contribution from individually measured compounds and the directly measured total OH reactivity, the size of any unaccounted for or "missing" sink can be deduced for various atmospheric influences. For "normal" boreal conditions a missing OH reactivity of 58%, whereas for "stressed" boreal conditions a missing OH reactivity of 89% was determined. Various sources of not quantified OH reactive species are proposed as possible explanation for the high missing OH reactivity.

scholarly journals Multi-lidar wind resource mapping in complex terrain

2019 ◽  
Author(s):  
Robert Menke ◽  
Nikola Vasiljević ◽  
Johannes Wagner ◽  
Steven P. Oncley ◽  
Jakob Mann
Keyword(s):  
Complex Terrain ◽  
Forest Canopy ◽  
Ground Level ◽  
Atmospheric Conditions ◽  
Surface Drag ◽  
Wind Speeds ◽  
Forest Distribution ◽  
Aerodynamic Roughness ◽  
Wind Resource ◽  
Wind Resources

Abstract. Scanning Doppler lidars have great potential for reducing uncertainty of wind resource estimation in complex terrain. Due to their scanning capabilities, they can measure at multiple locations over large areas. We demonstrate this ability using dual-Doppler lidar measurements of flow over two parallel ridges. The data have been collected using two pairs of long-range WindScanner systems operated in a dual-Doppler mode during the Perdigão 2017 measurement campaign. The lidars mapped the flow along the southwest and northeast ridges 80 m above ground level. By analyzing the collected data, we found that for different flow conditions on average wind speeds are 10 % higher over the southwest ridge compared to the northeast ridge. At the southwest ridge, the data shows, depending on the atmospheric conditions, a change of 20 % in wind speed along the ridge. For the measurement period, we have simulated the flow over the site using WRF-LES to compare how well the model can capture wind resources along the ridges. We used two model configurations. In the first configuration, surface drag is based purely on aerodynamic roughness whereas in the second configuration forest canopy drag is also considered. We found that simulated winds are underestimated in WRF-LES runs with forest drag due to an unrealistic forest distribution on the ridge tops. The correlation of simulated and observed winds is, however, improved when the forest parameterization is applied. WRF-LES results without forest drag overestimated the wind resources over the southwest and northeast ridges by 6.5 % and 4.5 % respectively. Overall, this study demonstrates the ability of scanning lidars to map wind resources in complex terrain.

scholarly journals Summertime total OH reactivity measurements from boreal forest during HUMPPA-COPEC 2010

2012 ◽  
Vol 12 (3) ◽  
pp. 7419-7452 ◽  
Author(s):  
A. C. Nölscher ◽  
J. Williams ◽  
V. Sinha ◽  
T. Custer ◽  
W. Song ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Forest Canopy ◽  
Marked Change ◽  
Reactive Species ◽  
Organic Precursor ◽  
The Impact ◽  
First Time ◽  
Comparative Reactivity

Abstract. Ambient total OH reactivity was measured at the Finnish boreal forest station SMEAR II in Hyytiälä (Latitude 61°51' N; Longitude 24°17' E) in July and August 2010 using the Comparative Reactivity Method (CRM). The CRM – total OH reactivity method – is a direct, in-situ determination of the total loss rate of hydroxyl radicals (OH) caused by all reactive species in air. During the intensive field campaign HUMPPA-COPEC 2010 (Hyytiälä United Measurements of Photochemistry and Particles in Air – Comprehensive Organic Precursor Emission and Concentration study) the total OH reactivity was monitored both inside (18 m) and directly above the forest canopy (24 m) for the first time. The comparison between these two total OH reactivity measurements, absolute values and the temporal variation have been analyzed here. Stable boundary layer conditions during night and turbulent mixing in the daytime induced low and high short-term variability, respectively. The impact on total OH reactivity from biogenic emissions and associated photochemical products was measured under "normal" and "stressed" (i.e. prolonged high temperature) conditions. The advection of biomass burning emissions to the site caused a marked change in the total OH reactivity vertical profile. By comparing the OH reactivity contribution from individually measured compounds and the directly measured total OH reactivity, the size of any unaccounted for or "missing" sink can be deduced for various atmospheric influences. For "normal" boreal conditions a missing OH reactivity of 58%, whereas for "stressed" boreal conditions a missing OH reactivity of 89% was determined. Various sources of not quantified OH reactive species are proposed as possible explanation for the high missing OH reactivity.

scholarly journals Snapshot of the Atlantic Forest canopy: surveying arboreal mammals in a biodiversity hotspot

2021 ◽  
Author(s):  
Mariane C. Kaizer ◽  
Thiago H.G. Alvim ◽  
Claudio L. Novaes ◽  
Allan D. Mcdevitt ◽  
Robert J. Young
Keyword(s):  
Atlantic Forest ◽  
Forest Canopy ◽  
Forest Cover ◽  
Mammalian Species ◽  
Ground Level ◽  
Camera Traps ◽  
Camera Trapping ◽  
Conservation Strategies ◽  
Arboreal Mammal ◽  
First Time

AbstractThe Atlantic Forest of South America supports some of the greatest terrestrial biodiversity on our planet but is now reduced to only a small extent of its original forest cover. It hosts a large number of endemic mammalian species but our knowledge on arboreal mammal ecology and conservation has been hindered by the challenges of observing arboreal species from ground level. Camera trapping has proven to be an effective tool in terrestrial mammal monitoring, but the technique has rarely been used for arboreal species. Here we generated data on the arboreal mammal community based on canopy camera trapping for the first time in the Atlantic Forest, focusing on Caparaó National Park, Brazil. We placed 24 infrared camera traps in the forest canopy distributed in seven areas within the Park, operating continuously from January 2017 to June 2019. In this time, they accumulated 4,736 camera-days and generated 2,256 sets of pictures and 30 second videos of vertebrates. Canopy camera traps were able to detect arboreal mammals spanning a wide variety of body sizes. The local mammal assemblage comprised of 15 identifiable species, including the critically endangered northern muriqui (Brachyteles hypoxanthus) and the buffy-headed marmoset (Callithrix flaviceps), and other rare, nocturnal and inconspicuous species. For the first time, we confirmed the occurrence of the thin-spined porcupine (Chaetomys subspinosus) in the Park. Species richness varied across sampling areas and forest types. Our findings demonstrate the potential of canopy camera trapping for future surveying efforts to better inform conservation strategies for mammals.

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