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 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 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 Aircraft validation of Aura Tropospheric Emission Spectrometer retrievals of HDO / H<sub>2</sub>O

2014 ◽  
Vol 7 (9) ◽  
pp. 3127-3138 ◽  
Author(s):  
R. L. Herman ◽  
J. E. Cherry ◽  
J. Young ◽  
J. M. Welker ◽  
D. Noone ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Water Vapor ◽  
Standard Deviation ◽  
Lower Troposphere ◽  
Temporal Variations ◽  
Observation Error ◽  
Free Troposphere ◽  
Data Set ◽  
Airborne Measurements

Abstract. The EOS (Earth Observing System) Aura Tropospheric Emission Spectrometer (TES) retrieves the atmospheric HDO / H2O ratio in the mid-to-lower troposphere as well as the planetary boundary layer. TES observations of water vapor and the HDO isotopologue have been compared with nearly coincident in situ airborne measurements for direct validation of the TES products. The field measurements were made with a commercially available Picarro L1115-i isotopic water analyzer on aircraft over the Alaskan interior boreal forest during the three summers of 2011 to 2013. TES special observations were utilized in these comparisons. The TES averaging kernels and a priori constraints have been applied to the in situ data, using version 5 (V005) of the TES data. TES calculated errors are compared with the standard deviation (1σ) of scan-to-scan variability to check consistency with the TES observation error. Spatial and temporal variations are assessed from the in situ aircraft measurements. It is found that the standard deviation of scan-to-scan variability of TES δD is ±34.1‰ in the boundary layer and ± 26.5‰ in the free troposphere. This scan-to-scan variability is consistent with the TES estimated error (observation error) of 10–18‰ after accounting for the atmospheric variations along the TES track of ±16‰ in the boundary layer, increasing to ±30‰ in the free troposphere observed by the aircraft in situ measurements. We estimate that TES V005 δD is biased high by an amount that decreases with pressure: approximately +123‰ at 1000 hPa, +98‰ in the boundary layer and +37‰ in the free troposphere. The uncertainty in this bias estimate is ±20‰. A correction for this bias has been applied to the TES HDO Lite Product data set. After bias correction, we show that TES has accurate sensitivity to water vapor isotopologues in the boundary layer.

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 HOLIMO II: a digital holographic instrument for ground-based in-situ observations of microphysical properties of mixed-phase clouds

2013 ◽  
Vol 6 (3) ◽  
pp. 4183-4221 ◽  
Author(s):  
J. Henneberger ◽  
J. P. Fugal ◽  
O. Stetzer ◽  
U. Lohmann
Keyword(s):  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Mixed Phase ◽  
Size Spectrum ◽  
Research Station ◽  
Resolution Limit ◽  
Microphysical Properties ◽  
Cloud Particles ◽  
Mixed Phase Clouds

Abstract. Measurements of the microphysical properties of mixed-phase clouds with high spatial resolution are important to understand the processes inside these clouds. This work describes the design and characterization of the newly developed ground-based field instrument HOLIMO II (HOLographic Imager for Microscopic Objects II). HOLIMO II uses digital in-line holography to in-situ image cloud particles in a well defined sample volume. By an automated algorithm, two-dimensional images of single cloud particles between 6 and 250 μm in diameter are obtained and the size spectrum, the concentration and water content of clouds are calculated. By testing the sizing algorithm with monosized beads a systematic overestimation near the resolution limit was found, which has been used to correct the measurements. Field measurements from the high altitude research station Jungfraujoch, Switzerland, are presented. The measured number size distributions are in good agreement with parallel measurements by a fog monitor (FM-100, DMT, Boulder USA). The field data shows that HOLIMO II is capable of measuring the number size distribution with a high spatial resolution and determines ice crystal shape, thus providing a method of quantifying variations in microphysical properties. A case study over a period of 8 h has been analyzed, exploring the transition from a liquid to a mixed-phase cloud, which is the longest observation of a cloud with a holographic device. During the measurement period, the cloud does not completely glaciate, contradicting earlier assumptions of the dominance of the Wegener–Bergeron–Findeisen (WBF) process.

scholarly journals The challenge of simulating the sensitivity of the Amazonian clouds microstructure to cloud condensation nuclei number concentrations

2019 ◽  
Author(s):  
Pascal Polonik ◽  
Christoph Knote ◽  
Tobias Zinner ◽  
Florian Ewald ◽  
Tobias Kölling ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Regional Scale ◽  
Cloud Droplet ◽  
Number Concentration ◽  
Effective Radius ◽  
Cloud Base ◽  
Condensation Nuclei ◽  
Aerosol Cloud ◽  
Microphysical Properties

Abstract. The realistic representation of cloud-aerosol interactions is of primary importance for accurate climate model projections. The investigation of these interactions in strongly contrasting clean and polluted atmospheric conditions in the Amazon area has been one of the motivations for several field observations, including the airborne Aerosol, Cloud, Precipitation, and Radiation Interactions and DynamIcs of CONvective cloud systems – Cloud Processes of the Main Precipitation Systems in Brazil: A Contribution to Cloud Resolving Modeling and to the GPM (Global Precipitation Measurement) (ACRIDICON-CHUVA) campaign based in Manaus, Brazil in September 2014. In this work we combine in situ and remotely sensed aerosol, cloud, and atmospheric radiation data collected during ACRIDICON-CHUVA with regional, online-coupled chemistry-transport simulations to evaluate the model’s ability to represent the indirect effects of biomass burning aerosol on cloud microphysical properties (droplet number concentration and effective radius). We found agreement between modeled and observed median cloud droplet number concentrations (CDNC) for low values of CDNC, i.e., low levels of pollution. In general, a linear relationship between modeled and observed CDNC with a slope of two was found, which means a systematic underestimation of modeled CDNC as compared to measurements. Variability in cloud condensation nuclei (CCN) number concentrations and cloud droplet effective radii (reff) was also underestimated by the model. Modeled effective radius profiles began to saturate around 500 CCN per cm3 at cloud base, indicating an upper limit for the model sensitivity well below CCN concentrations reached during the burning season in the Amazon Basin. Regional background aerosol concentrations were sufficiently high such that the additional CCN emitted from local fires did not cause a notable change in modelled cloud microphysical properties. In addition, we evaluate a parameterization of CDNC at cloud base using more readily available cloud microphysical properties, aimed at in situ observations and satellite retrievals. Our study casts doubt on the validity of regional scale modeling studies of the cloud albedo effect in convective situations for polluted situations where the number concentration of CCN is greater than 500 cm−3.

Survey of microphysical properties of marine boundary-layer clouds in the Western North Atlantic 

2021 ◽  
Author(s):  
Simon Kirschler ◽  
Christiane Voigt ◽  
Andrew S. Ackerman ◽  
Bruce Anderson ◽  
Gao Chen ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Water Content ◽  
North Atlantic ◽  
Radiation Budget ◽  
Late Winter ◽  
Western Atlantic ◽  
Low Level ◽  
Aerosol Cloud ◽  
Microphysical Properties ◽  
Cloud Properties

&lt;p&gt;Oceanic low level clouds strongly affect the atmospheric radiation budget. Uncertainties in their microphysical properties and cover currently limit the accuracy of climate predictions. Further, studies quantifying the relative importance of aerosol and dynamics on cloud properties in specific meteorological regimes are poorly constrained by observations in the Western North Atlantic boundary layer.&lt;/p&gt;&lt;p&gt;Low level clouds were measured during the Aerosol Cloud meTereology Interactions oVer the western ATlantic Experiment (ACTIVATE) campaign in winter and summer 2020. The two NASA LaRC research aircraft HU-25 Falcon and UC-12 B-200 King Air conducted 35 simultaneous flights to investigate aerosol-cloud interactions of maritime clouds and their impact on radiation. Number concentration, liquid water content, ice water content, and particle size distribution in the size range of 3 &amp;#181;m to 1460 &amp;#181;m in diameter were measured with the fast forward scattering cloud probe (FCDP) and 2-dimensional optical array imaging probe (2D-S) onboard the Falcon. Here, we present an overview of late winter (February-March) and late summer (August-September) oceanic cloud properties in the region 65&amp;#176;W to 80&amp;#176;W and 30&amp;#176;N to 40&amp;#176;N. We compare cloud properties in these two seasons and investigate their dependence on meteorological parameters and aerosol abundance. In a case study, we present cloud observations in a cold air outbreak event on 1 March 2020 with a specific focus on mixed-phase clouds.&lt;/p&gt;

Aircraft measurements of nitrous acid in excess of model predictions in the boundary layer and free troposphere

2020 ◽  
Author(s):  
Benjamin Schreiner ◽  
Klaus Pfeilsticker ◽  
Flora Kluge ◽  
Meike Rotermund ◽  
Andreas Zahn ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Optical Absorption Spectroscopy ◽  
Free Troposphere ◽  
Aerosol Composition ◽  
Transport And Transformation ◽  
Air Masses ◽  
Airborne Measurements ◽  
Photolysis Frequencies ◽  
Model Predictions

&lt;p&gt;Middle and long-term &amp;#160;photo-chemical effects of local and regional pollution are not well quantified and are an area of active study. NO&lt;sub&gt;x&lt;/sub&gt; (here defined as NO, NO&lt;sub&gt;2&lt;/sub&gt;, and HONO) is a regional pollutant, which influences atmospheric oxidation capacity and ozone formation. Airborne measurements of atmospheric trace gases from the HALO (High Altitude Long Range) aircraft, particularly of NO, NO&lt;sub&gt;2&lt;/sub&gt;, and HONO were performed as part of the EMeRGe (Effect of Megacities on the Transport and Transformation of Pollutants on the Regional to Global Scales) campaign over continental Europe and southeast Asia in July 2017 and April 2018, respectively. NO (and NO&lt;sub&gt;Y&lt;/sub&gt;), O&lt;sub&gt;3&lt;/sub&gt;, and the photolysis frequencies of NO&lt;sub&gt;2&lt;/sub&gt; and HONO were measured in-situ. NO&lt;sub&gt;2&lt;/sub&gt; and HONO were inferred from Limb measurements of the mini-DOAS (Differential Optical Absorption Spectroscopy) instrument, using the novel scaling method (H&amp;#252;neke et al., 2017). These measurements were compared with simulations of the MECO/EMAC models. In relatively polluted air-masses in the boundary layer and free troposphere, HONO measured in excess of model predictions (and previous measurements) suggests an in-situ formation and a significant source of OH as well as a pathway for re-noxification. Aerosol composition simultaneously measured &amp;#160;by the C-Tof-AMS instrument may reveal potential reaction mechanisms to explain the discrepancy.&amp;#160;&lt;/p&gt;

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