Research Highlights

Predicting Atmospheric Particle Population's Weight Gain
Aug 22, 2014       
Like people, particles in the atmosphere can gain weight, and it is not easy to predict how much and how quickly they do. The culprit is newly formed carbon-containing compounds in the atmosphere, also referred to as secondary organic aerosols (SOAs), which pile on pre-existing particles, resulting in a gain in mass. It is even [...]

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Checking Up on Tropical Sunlight
Aug 22, 2014       
Science is not settled on a bet or a hunch. Measurements and data support conclusions and provide clarity. Scientists at Pacific Northwest National Laboratory (PNNL) found that about 10 percent of the time two ground-based stations on a tropical island, though less than five miles apart, collect different incoming sunlight measurements based on which way [...]

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Parameterization of Vertical Velocity in Shallow Convections
Aug 17, 2014       
The parameterization of air vertical velocity within cumulus clouds in large-scale models has been a subject of active research. The mean vertical velocity in convective clouds is desired for several reasons. For example, it is needed to determine the cloud-top height. Traditionally, the neutral buoyancy level (NBL) is defined as the cloud top in most [...]

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Phase State and Physical Properties of Ambient and Lab Generated Aerosols: X-ray Microscopy
Aug 14, 2014       
Models of secondary organic aerosol (SOA) formation assume that the organic fraction is a liquid with condensed phase-diffusion rates fast enough to maintain equilibrium with the gas phase. However, numerous recent studies looking at particle bounce behavior, evaporation, thermal desorption, diffusion, physical manipulation, etc., have all shown that organic matter in aerosols can have higher [...]

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Location Matters: Origin of Ice Formation Influences Mixed-phase Stratiform Clouds
Aug 13, 2014       
Mixed-phase stratiform clouds are common features in the Arctic and midlatitude atmosphere. These thin clouds contain a mix of ice crystals and "supercooled" water droplets that, despite the freezing temperatures, remain in liquid form. Scientists aren't sure why these clouds can persist for long periods of time, even while steadily losing ice particles through precipitation. [...]

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Research Masters the Misunderstood Mixed-Phase Cloud
Aug 12, 2014       
They are ice, they are rain—and sometimes in-between. Mixed-phase clouds, ubiquitous in the Arctic, are an enigma for scientists trying to understand their role in affecting the climate. In a study led by Dr. Mikhail Ovchinnikov at Pacific Northwest National Laboratory, scientists found that unrealistic assumptions in previous modeling studies have misled predictions about key [...]

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Scientists Uncover Combustion Mechanism to Better Predict Warming by Wildfires
Aug 04, 2014       
Atmospheric particulate matter (PM) plays an important role in the Earth’s radiative balance by interacting directly with solar radiation, or indirectly by acting as cloud condensation or ice nuclei. PM can exhibit negative climate forcing by enhancing scattering of solar radiation. However, over the past two decades, it has been established that a portion of [...]

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The Anatomy and Physics of ZDR Columns
Jul 27, 2014       
Observations of deep convective storms using dual-polarization radars frequently reveal columnar regions of enhanced differential reflectivity (ZDR). These so-called "ZDR columns" often extend from low levels to several kilometers above the environmental 0 °C level and represent the lofting of supercooled liquid water by the storm's updraft. Despite several decades of remote sensing observations of [...]

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Aerosol-mediated Changes in Deep Convective Cloud Radiative Forcing over the SGP
Jul 24, 2014       
Studies have shown that aerosols can fuel cloud vertical development and lift cloud-top heights. Cloud anvils can also expand under the influence of aerosols. Such aerosol-mediated changes in cloud parameters can alter the cloud radiative forcing (CRF), which is often referred to as aerosol indirect forcing or the aerosol indirect effect. Among the aerosol-induced changes [...]

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Gas-Phase Dry Deposition as a Major Removal Mechanism for Secondary Organic Aerosols (SOA)
Jul 23, 2014       
Removal of secondary organic aerosols (SOA) from the atmosphere has been studied far less that its equal, production. In current regional and global chemistry models, rainout of SOA particles are their dominant loss. Here, we show the importance of a less direct pathway, in which large-scale evaporation of SOA particles occurs as a re-adjustment to [...]

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Ice Concentration Retrieval in Stratiform Mixed-Phase Clouds Using Cloud Radar Measurements
Jul 21, 2014       
The production of ice particles in clouds has significant impacts on their precipitation efficiency, lifetime, and radiative properties. Recent observations reveal that mixed-phase clouds, which contain both liquid droplets and ice particles, have a large global coverage and are the dominant cloud type over polar regions. The ice number concentrations (Ni) in these clouds are [...]

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