scholarly journals A numerical evaluation of global oceanic emissions of α-pinene and isoprene

2010 ◽  
Vol 10 (4) ◽  
pp. 2007-2015 ◽  
Author(s):  
G. Luo ◽  
F. Yu
Keyword(s):  
Numerical Evaluation ◽  
Input Data ◽  
Organic Aerosol ◽  
Aerosol Formation ◽  
Top Down ◽  
Mixing Processes ◽  
Bottom Up ◽  
Phytoplankton Communities ◽  
Oceanic Emissions

Abstract. A numerical evaluation of global oceanic emissions of α-pinene and isoprene based on both "bottom-up" and "top-down" methods is presented. We infer that the global "bottom-up" oceanic emissions of α-pinene and isoprene are 0.013 TgC yr−1 and 0.32 TgC yr−1, respectively. By constraining global chemistry model simulations with the shipborne measurement of Organics over the Ocean Modifying Particles in both Hemispheres summer cruise, we derived the global "top-down" oceanic α-pinene source of 29.5 TgC yr−1 and isoprene source of 11.6 TgC yr−1. Both the "bottom-up" and "top-down" values are subject to large uncertainties. The incomplete understanding of the in-situ phytoplankton communities and their range of emission potentials significantly impact the estimated global "bottom-up" oceanic emissions, while the estimated total amounts of the global "top-down" oceanic sources can be influenced by emission parameterizations, model and input data spatial resolutions, boundary layer mixing processes, and the treatments of chemical reactions. The global oceanic α-pinene source and its impact on organic aerosol formation is significant based on "top-down" method, but is negligible based on "bottom-up" approach. Our research highlights the importance of carrying out further research (especially measurements) to resolve the large offset in the derived oceanic organic emission based on two different approaches.

scholarly journals A numerical evaluation of global oceanic emissions of α-pinene and isoprene

2009 ◽  
Vol 9 (5) ◽  
pp. 20721-20738
Author(s):  
G. Luo ◽  
F. Yu
Keyword(s):  
Numerical Evaluation ◽  
Organic Aerosol ◽  
Aerosol Formation ◽  
Top Down ◽  
Bottom Up ◽  
Model Simulations ◽  
Oceanic Emissions

Abstract. A numerical evaluation of global oceanic emissions of α-pinene and isoprene based on both "bottom-up" and "top-down" methods is presented. As far as we know, this is the first quantification of global oceanic emission of α-pinene. We infer that the global "bottom-up" oceanic emissions of α-pinene and isoprene are 0.013 Tg C yr−1 and 0.32 Tg C yr−1, respectively. By constraining global chemistry model simulations with the shipboard measurement of Organics over the Ocean Modifying Particles in both Hemispheres summer cruise, we derived the global "top-down" oceanic α-pinene source of 35.1 Tg C yr−1 and isoprene source of 2.5 Tg C yr−1. The global oceanic α-pinene source and its impact on organic aerosol formation is significant based on "top-down" method, but is negligible based on "bottom-up" approach. Our research highlights the importance to carry out further research (especially measurements) to resolve the large offset in the derived oceanic organic emission based on two different approaches.

scholarly journals On-Site Participation for Proto-Architectural Assemblies Encompassing Technology and Human Improvisation: “Fish Trap” and “Orchid” Architectural Interventions

Complexity ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Peter Buš ◽  
Shi-Yen Wu ◽  
Ayça Tartar
Keyword(s):  
Computational Models ◽  
Design Strategy ◽  
Top Down ◽  
Bottom Up ◽  
Fish Trap ◽  
Human Needs ◽  
Qualitative Observation ◽  
Building System ◽  
Collaborative Improvisation

This research investigates the notion of builders’ on-site engagement to physically build architectural interventions based on their demands, spatial requirements, and collaborative improvisation enhanced with the principles of uniqueness and bespoke solutions which are previously explored in computational models. The paper compares and discusses two physical installations as proto-architectural assemblies testing two different designs and building approaches: the top-down predefined designers’ scenario contrary to bottom-up unpredictable improvisation. It encompasses a building strategy based on the discrete precut components assembled by builders themselves in situ. The paper evaluates both strategies in a qualitative observation and comparison defining advantages and limitations of the top-down design strategy in comparison with the decentralised bottom-up building system built by the builders themselves. As such, it outlines the position of a designer within the bottom-up building processes on-site. The paper argues that improvisation and builders’ direct engagement on-site lead to solutions that better reflect human needs and low-tech building principles incorporated can deliver unpredictable but convenient spatial scenarios.

scholarly journals Top-down and Bottom-up aerosol-cloud-closure: towards understanding sources of uncertainty in deriving cloud radiative flux

2017 ◽  
Author(s):  
Kevin J. Sanchez ◽  
Greg C. Roberts ◽  
Radiance Calmer ◽  
Keri Nicoll ◽  
Eyal Hashimshoni ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Radiative Flux ◽  
Research Station ◽  
Top Down ◽  
Bottom Up ◽  
Airborne Measurements ◽  
Aerosol Cloud ◽  
Microphysical Properties ◽  
Holistic Understanding

Abstract. Top-down and bottom-up aerosol-cloud-radiative flux closures were conducted at the Mace Head atmospheric research station in Galway, Ireland in August 2015. This study is part of the BACCHUS (Impact of Biogenic versus Anthropogenic emissions on Clouds and Climate: towards a Holistic UnderStanding) European collaborative project, with the goal of understanding key processes affecting aerosol-cloud-radiative flux closures to improve future climate predictions and develop sustainable policies for Europe. Instrument platforms include ground-based, unmanned aerial vehicles (UAV), and satellite measurements of aerosols, clouds and meteorological variables. The ground-based and airborne measurements of aerosol size distributions and cloud condensation nuclei (CCN) concentration were used to initiate a 1D microphysical aerosol-cloud parcel model (ACPM). UAVs were equipped for a specific science mission, with an optical particle counter for aerosol distribution profiles, a cloud sensor to measure cloud extinction, or a 5-hole probe for 3D wind vectors. UAV cloud measurements are rare and have only become possible in recent years through the miniaturization of instrumentation. These are the first UAV measurements at Mace Head. ACPM simulations are compared to in-situ cloud extinction measurements from UAVs to quantify closure in terms of cloud radiative flux. Two out of seven cases exhibit sub-adiabatic vertical temperature profiles within the cloud, which suggests that entrainment processes affect cloud microphysical properties and lead to an overestimate of simulated cloud radiative flux. Including an entrainment parameterization and explicitly calculating the entrainment fraction in the ACPM simulations both improved cloud-top radiative closure. Entrainment reduced the difference between simulated and observation-derived cloud-top radiative flux (δRF) by between 30 W m−2 and 40 W m−2. After accounting for entrainment, satellite-derived cloud droplet number concentrations (CDNC) were within 30 % of simulated CDNC. In cases with a well-mixed boundary layer, δRF is less than 25 W m−2 after accounting for cloud-top entrainment, compared to less than 50 W m−2 when entrainment is not taken into account. In cases with a decoupled boundary layer, cloud microphysical properties are inconsistent with ground-based aerosol measurements, as expected, and δRF is as high as 88 W m−2, even after accounting for cloud-top entrainment. This work demonstrates the need to take in-situ measurements of aerosol properties for cases where the boundary layer is decoupled as well as consider cloud-top entrainment to accurately model stratocumulus cloud radiative flux.

scholarly journals Top-down and bottom-up aerosol–cloud closure: towards understanding sources of uncertainty in deriving cloud shortwave radiative flux

2017 ◽  
Vol 17 (16) ◽  
pp. 9797-9814 ◽  
Author(s):  
Kevin J. Sanchez ◽  
Gregory C. Roberts ◽  
Radiance Calmer ◽  
Keri Nicoll ◽  
Eyal Hashimshoni ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Radiative Flux ◽  
Research Station ◽  
Top Down ◽  
Bottom Up ◽  
Airborne Measurements ◽  
Aerosol Cloud ◽  
Microphysical Properties ◽  
Holistic Understanding

Abstract. Top-down and bottom-up aerosol–cloud shortwave radiative flux closures were conducted at the Mace Head Atmospheric Research Station in Galway, Ireland, in August 2015. This study is part of the BACCHUS (Impact of Biogenic versus Anthropogenic emissions on Clouds and Climate: towards a Holistic UnderStanding) European collaborative project, with the goal of understanding key processes affecting aerosol–cloud shortwave radiative flux closures to improve future climate predictions and develop sustainable policies for Europe. Instrument platforms include ground-based unmanned aerial vehicles (UAVs)1 and satellite measurements of aerosols, clouds and meteorological variables. The ground-based and airborne measurements of aerosol size distributions and cloud condensation nuclei (CCN) concentration were used to initiate a 1-D microphysical aerosol–cloud parcel model (ACPM). UAVs were equipped for a specific science mission, with an optical particle counter for aerosol distribution profiles, a cloud sensor to measure cloud extinction or a five-hole probe for 3-D wind vectors. UAV cloud measurements are rare and have only become possible in recent years through the miniaturization of instrumentation. These are the first UAV measurements at Mace Head. ACPM simulations are compared to in situ cloud extinction measurements from UAVs to quantify closure in terms of cloud shortwave radiative flux. Two out of seven cases exhibit sub-adiabatic vertical temperature profiles within the cloud, which suggests that entrainment processes affect cloud microphysical properties and lead to an overestimate of simulated cloud shortwave radiative flux. Including an entrainment parameterization and explicitly calculating the entrainment fraction in the ACPM simulations both improved cloud-top radiative closure. Entrainment reduced the difference between simulated and observation-derived cloud-top shortwave radiative flux (δRF) by between 25 and 60 W m−2. After accounting for entrainment, satellite-derived cloud droplet number concentrations (CDNCs) were within 30 % of simulated CDNC. In cases with a well-mixed boundary layer, δRF is no greater than 20 W m−2 after accounting for cloud-top entrainment and up to 50 W m−2 when entrainment is not taken into account. In cases with a decoupled boundary layer, cloud microphysical properties are inconsistent with ground-based aerosol measurements, as expected, and δRF is as high as 88 W m−2, even high (> 30 W m−2) after accounting for cloud-top entrainment. This work demonstrates the need to take in situ measurements of aerosol properties for cases where the boundary layer is decoupled as well as consider cloud-top entrainment to accurately model stratocumulus cloud radiative flux. 1The regulatory term for UAV is remotely piloted aircraft (RPA).

scholarly journals Sources and Characteristics of Summertime Organic Aerosol in the Colorado Front Range: Perspective from Measurements and WRF-Chem Modeling

2018 ◽  
Author(s):  
Roya Bahreini ◽  
Ravan Ahmadov ◽  
Stu A. McKeen ◽  
Kennedy T. Vu ◽  
Justin H. Dingle ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Organic Aerosol ◽  
Colorado Front Range ◽  
Weather Research And Forecasting ◽  
Front Range ◽  
Top Down ◽  
Mixing Ratios ◽  
Oil And Natural Gas ◽  
The Mean

Abstract. Evolution of organic aerosol (OA) and their precursors in the boundary layer of Colorado Front Range during the Front Range Air Pollution and Photochemistry Éxperiment (FRAPPÉ, July–August 2014) was analyzed by in-situ measurements and chemical transport modeling. Measurements indicated significant production of secondary OA (SOA), with enhancement ratio of OA with respect to carbon monoxide (CO) reaching 0.068 ± 0.004 μg m−3 ppbv−1. At background mixing ratios of CO, up to ~ 2 μg m−3 background OA was observed, suggesting significant non-combustion contribution to OA in the Front Range. The mean concentration of OA in plumes with a high influence of oil and natural gas (O&G) emissions was ~ 40 % higher than in urban-influenced plumes. Positive matrix factorization confirmed a dominant contribution of secondary, oxygenated OA (OOA) in the boundary layer instead of fresh, hydrocarbon-like OA (HOA). Combinations of primary OA (POA) volatility assumptions, aging of semi-volatile species, and different emission estimates from the O&G sector were used in the Weather Research and Forecasting model, coupled with Chemistry (WRF-Chem) simulation scenarios. The assumption of semi-volatile POA resulted in greater than a factor of 10 lower POA concentrations compared to PMF-resolved HOA. Including a top-down modified O&G emissions resulted in substantially better agreements in modeled ethane, toluene, hydroxyl radical, and ozone compared to measurements in the high O&G-influenced plumes. By including emissions from the O&G sector using the top-down approach, it was estimated that the O&G sector contributed to

PEPTIDE NANOFILAMENTS USED FOR REPLICA-MOLDING: A COMBINATION OF "BOTTOM-UP" AND "TOP-DOWN"

2007 ◽  
Vol 14 (02) ◽  
pp. 301-307 ◽  
Author(s):  
YUZHAO TANG ◽  
XIAODONG ZHANG ◽  
JIELIN SUN ◽  
JUN HU ◽  
FENG ZHANG ◽  
...  
Keyword(s):  
Nanometer Scale ◽  
Top Down ◽  
Bottom Up ◽  
Polymeric Surfaces ◽  
Replica Molding ◽  
Force Microscopy ◽  
Self Assembling ◽  
Atomic Force ◽  
New Applications

A novel nanofabrication method that combines both "bottom-up" (template-assisted peptide self-assembling) and "top-down" (replica molding) techniques is introduced. A designer peptide, GAV-9 (NH2-VGGAVVAGV-CONH2), can epitaxially self-assemble into nanofilaments on the surface of mica, which is further used as the diversified masters for the application of replica molding. With in situ atomic force microscopy monitoring, several typical masters are fabricated by peptide self-assembling on the surface of mica. These masters can be easily molded into hard poly(dimethylsiloxane) surfaces, and then further replica-molded into polyurethane surfaces. The polymeric surfaces with regular 1D and 2D patterns on the nanometer scale are expected to have new applications in nanostructure's fabrication.

scholarly journals Bottom-Up and Top-Down Controls of Litter Decomposition Rates and N Dynamics in Arid Steppes.

2021 ◽  
Author(s):  
Maria-Victoria Piazza ◽  
Gaston R. Oñatibia ◽  
Martin R. Aguiar
Keyword(s):  
Litter Decomposition ◽  
Environmental Conditions ◽  
Ex Situ ◽  
Top Down ◽  
Decomposition Rates ◽  
N Dynamics ◽  
Bottom Up ◽  
Litter Traits ◽  
Grass Litter

Abstract AimsArid ecosystem soil processes are strongly bottom-up controlled by resource scarcity. However, grazing intensification can induce changes through multiple pathways and spatio-temporal scales. For example, by changing litter quality and site environmental conditions. Our purpuse was to understand the relative importance of top-down and bottom-up controls of litter decomposition and N dynamics in the Patagonian grass-shrub steppes.MethodsWe performed three litterbag decomposition experiments to evaluate: i) the interactive effects of litter traits and site environmental conditions (grazed vs. exclosure communities) (reciprocal transplants in situ), ii) the net effect of litter traits in a common garden (ex situ), and iii) the net effect of site environmental conditions using a foreign common litter substrate (in situ). The study was performed on three pairs of sites with areas under a long-term exclosure (> 25 years) or under year-round sheep grazing. Local litter included main community species composition and was sorted by grass and shrubs material. ResultsGrazing exclusion did not significantly alter litter decomposition, either through changes in grass litter traits that control decomposition or through changes in the site environmental conditions. Nevertheless, N released during litter decomposition was 286% higher in exclosures than in grazing commumnities. The difference was associated to changes in the grass litter chemical quality. The effects were maintained when we integrated results from the entire litter community. ConclusionOur study suggests that decomposition rates in arid steppes are mainly bottom-up determined, but top-down controls shaping grass litter traits importantly alter the flux of N during decomposition.

Sign in / Sign up

Export Citation Format

Share Document