Research Highlights

The Spectroscopic Foundation of Radiative Forcing of Climate by Carbon Dioxide
Jul 21, 2016       
We explored the state-of-the-science of how rising atmospheric CO2 concentrations warm the climate system through radiative forcing caused by spectroscopic absorption features. We found that uncertainties in the absorption line parameters and understanding of the shape of CO2 lines, both of which are important for CO2 radiative forcing, are much smaller than the actual forcing.

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Field Testing the Next-Generation of Radiosondes
Jul 21, 2016       
During 3-8 June 2014, an intercomparison study of Vaisala radiosondes RS92 (the current ARM instrumentation) and RS41 (next generation) was undertaken at the ARM SGP site. The results indicate that the sounding measurements generally agree well within manufactured-defined uncertainties with notable exceptions when exiting liquid cloud layers where evaporative cooling impacts are mitigated for the [...]

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Trace Gas Removal by Deep Convective Storms
Jul 20, 2016       
Deep convective storms have a large impact on the climate by sending atmospheric trace gases high into the atmosphere where they participate in particle formation and ozone formation that affect the amount of sunlight, or radiative energy, that passes through the atmosphere to Earth’s surface. Understanding how storms, or convective systems, transport trace-gas concentrations to [...]

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Observing the Amazon: the Role of Time and Place in Cloud Measurements
Jul 20, 2016       
Research led by Department of Energy scientists at Pacific Northwest National Laboratory laid the groundwork for future explorations of the Green Ocean Amazon, GOAmazon, 2014/15 field campaign data sets by documenting the variability in space and time of deep convection around the field campaign surface sites distributed upwind and downwind of Manaus, Brazil. Understanding the [...]

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Capturing Biogenic Volatile Organic Compounds in a Coupled-Model System Compared to Observation
Jul 20, 2016       
Current climate models still have large uncertainties in estimating biogenic (naturally emitted) trace gases, which can significantly affect atmospheric chemistry and secondary aerosol formation that ultimately influence the capacity of aerosol particles to affect Earth’s energy balance (aerosol radiative forcing) and air quality. These uncertainties result from many factors, including uncertainties in land-surface processes (exchanges [...]

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Hiding in Plain Sight: a Less-Explored Secret of Secondary Organic Aerosols
Jul 19, 2016       
More than 50% of the fine atmospheric aerosol particle mass is often comprised of organic aerosols, most of which are secondary organic aerosols (SOA), formed by atmospheric oxidation of organic gases. Recent measurements suggest that a major fraction of SOA has volatility that is orders of magnitude lower than previously assumed. It is important to [...]

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Getting Cloud Ice from Pollution
Jul 19, 2016       
Atmospheric soot (black carbon) particles absorb solar energy to warm the atmosphere—yet high in the atmosphere they may instigate cloud ice formation. But when these particles mix with other aerosols and compounds in the atmosphere, their ice-forming (ice-nucleating) ability suffers, thus altering the properties of pure ice clouds (cirrus), vital for their impact to moderate [...]

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Three Dimensions Are Better Than Two, When It Comes to Representing Aerosols
Jul 19, 2016       
A research team led by scientists at Pacific Northwest National Laboratory developed a novel three-dimensional particle representation for aerosol modeling. This new add-on solves for particle size, the amount of black carbon in the particle, and the ability of the particle to draw moisture, or hygroscopicity. All three attributes are needed to accurately estimate how [...]

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ARM Azores Observations Help Identify Deficiencies in Climate Model Simulations of Low Clouds
Jul 16, 2016       
The correctness of low-cloud representation in climate models is crucial to climate change projections and needs to be comprehensively evaluated.

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Pollution from a Megacity in the Amazon: the Case of Manaus, Brazil
Jul 12, 2016       
This special journal issue outlines the Observations and Modeling of the Green Ocean Amazon (GoAmazon2014/5) Experiment. The field campaign research sought to quantify how aerosol and cloud life cycles in a clean background in the tropics are influenced by pollutant outflow from a large tropical city. The team used ground-based research sites and aircraft measurement [...]

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Two-Column Aerosol Project: Impact of Elevated Particle Layers on Particle Optical Depth
Jul 11, 2016       
A group of DOE-funded scientists on an ARM field campaign discovered elevated levels of aerosols even on Cape Cod's cloud-free days—and these aerosols have a large impact on the amount of sunlight reaching the surface. The year-long study included measurements to examine the chemical composition of the particles, the way they reflect or scatter light, [...]

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Fall Speeds of Cirrus Crystals Faster Than Expected
Jul 11, 2016       
The fall speeds of high cirrus cloud crystals depend upon crystal mass, for which no direct measurements exist. Based on new measurements of crystal images, calculated mass yields fall speeds as a function of maximum particle dimension that are, surprisingly, roughly twice as large as derived in the most commonly used past studies.

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Sub-micrometre Particulate Matter Is Primarily in Liquid Form over Amazon Rain Forest
Jul 07, 2016       
A team of scientists, including U.S. Department of Energy-funded researchers, found that particles with diameters smaller than 1 μm are primarily in liquid form over the tropical rainforest of central Amazonia, where the relative humidity is greater than 80% more than 70% to 80% of the time during the dry and wet seasons. These findings are [...]

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Urban Emissions Significantly Enhance SOA Production at a Rural Site in the NE US
Jun 12, 2016       
During our study, we observed that aerosol concentration and composition at a rural site in the Northeastern U.S. were influenced strongly by upwind urban emissions. A possible reason is that anthropogenic pollutants advected from urban areas interacted with biogenic emissions in the rural region and led to a substantial enhancement of secondary organic aerosol production.

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Chamber Studies Uncover New Pathways for Atmospheric Aerosol Growth
May 31, 2016       
The first few hours following the formation of a new atmospheric aerosol particle are a competition between the growth of the particle due to the condensation of low volatility “sticky” gases and the loss of the particle by collisions with other aerosol particles. New observations from the Cosmics Leaving Outdoor Droplets (CLOUD) chamber at CERN [...]

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Spiraling Through a Storm
May 26, 2016       
A multi-sensor effort that blends observations from UND Citation aircraft spirals and ground-based ARM scanning precipitation and cloud radars to investigate the signatures associated with riming and aggregation processes.

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On the Impacts of Different Definitions of Maximum Dimension for Nonspherical Cloud Particles
May 25, 2016       
Knowledge of ice crystal particle size distributions (PSDs) is critical for development of microphysical parameterization schemes for numerical models and remote-sensing retrieval algorithms. Two-dimensional in situ images captured by cloud-imaging probes on aircraft are widely used to derive PSDs in term of maximum particle dimension (Dmax). However, inconsistencies in the definition of Dmax used in [...]

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Isoprene Photochemistry over the Amazon Rainforest
May 24, 2016       
Isoprene is a biogenic volatile organic compound that, when oxidized by sunlight, heavily influences atmospheric chemistry over forested areas. Using field measurements from the ground and the air, this paper tracked the fate of isoprene over the central Amazon for eight weeks during the wet season. The main research site, 70 kilometers downwind of the [...]

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Regime Dependence of Cloud Water Variability Observed at the ARM Sites
May 11, 2016       
Observations from ARM sites across the world have improved our understanding of how the amount of water in clouds varies at small scales. Based on these observations, a new way of describing how cloud water varies with cloud regime has been developed for use in global weather and climate models.

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Microphysical Piggybacking: Understanding the Coupling Between Cloud Dynamics and Microphysics
May 08, 2016       
A novel modeling approach was developed to clearly document the impact of cloud microphysics (i.e., the model representation of growth and fallout of cloud and precipitation particles) on cloud simulations. A traditional approach is to perform parallel simulations with different microphysics schemes or scheme parameters. In such parallel simulations, clearly separating physical impacts from merely [...]

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