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High atop the Greenland Ice Sheet, cloudy skies portend warmer temperatures and higher winds. These clouds alter the surface energy budget, diminish the strong near-surface atmospheric stability, and precipitate ice crystal to the surface. Together these processes comprise the focus of the Integrated Characterization of Energy, Clouds, Atmospheric state, and Precipitation at Summit [...]
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Researchers, including DOE scientists working at Pacific Northwest National Laboratory, used two field campaigns to understand the distribution and mixing state of carbonaceous aerosols in California. Research for the Nexus of Air Quality and Climate Change (CalNex) campaign sampled aerosols over southern California to understand the role of particle composition on air quality and climate [...]
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Stratiform mixed-phase clouds have been shown to commonly occur and impact the surface energy budget at high latitudes (e.g., de Boer et al. 2009, Shupe et al. 2006), and cloud-induced changes to the surface energy budget have been hypothesized to contribute in modulation of sea-ice extent (Kay et al. 2008). An area of research [...]
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Reanalysis data have been widely used in various climate-related studies; for example, they serve as “surrogate observations” where there are either no observations or only sparse observations, or as boundary conditions for regional climate modeling. Evaluation of cloud properties in reanalysis also directly sheds light on the deficiencies of relevant parameterizations in climate models [...]
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Different turbulent entrainment-mixing processes (e.g., homogeneous and inhomogeneous) in clouds give rise to distinct cloud properties, and thus accurate representation of these processes is critical for improving in large scale-models; however, scientists still lack such a parameterization that spans the spectrum of entrainment-mixing processes. Department of Energy scientists at Brookhaven National Laboratory and collaborators tried [...]
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Despite their widely recognized importance, aerosol indirect effects are still full of uncertainty, even controversy for some aspects. One reason for the uncertainty/controversy is that aerosol effects are often intertwined with changes in cloud dynamics such as vertical velocity, and separation of aerosol indirect effects from dynamical effects poses a confounding challenge, especially in observations. [...]
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The rate at which cloud engulfs dry air (entrainment rate) has proven to be one of the strongest controls on the climate sensitivity of climate models; it is also one of the least understood problems in convection parameterization. Studies on the dependence of entrainment rate on dry air sources and on the probability density [...]
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French scientists suggest heating of the Earth’s surface plays a major role in semi-arid regions compared to the tropics.
In the western part of North Africa, just south of the Sahara, year-to-year failure of rainfall over the past several decades led to one of the most severe droughts the last century witnessed. In a new paper [...]
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Using high-resolution model simulations, two scientists from Pacific Northwest National Laboratory uncovered the relative importance of unique conditions that lead to tropical rainstorm clouds using a novel mathematical approach. Among four key environmental factors, they found that the presence of moisture and vertical wind velocity events, about one hour before the cloud forms, are the [...]
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Dead grass, extreme heat, little to no rainfall. For two years, starting in the summer of 2005, a severe drought brought the states of Oklahoma and Texas to their knees. The drought cost the state of Texas $4.1 billion in losses and two million acres burned in wildfires.
Finally, in May of 2007, a series [...]
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Researchers at Pacific Northwest National Laboratory designed an update to a frequently used computer model that represents the impact of small, puffy, fair-weather clouds on the amount of sunshine reaching Earth’s surface. The new method includes variations in temperature and humidity near the surface and their role in forming these small clouds. Their method offers [...]
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This paper addresses a fundamental question of the relationship between two single-scattering albedo spectra for water droplets (and ice crystals) at weakly absorbing wavelengths. The single-scattering albedo in atmospheric radiative transfer is the ratio of the scattering coefficient to the total extinction coefficient. It is equal to unity if all extinction is due [...]
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Every day, the incomplete combustion of fossil fuels, biofuels, and biomass forms black carbon particles in the atmosphere. Once deposited in the Arctic, these black carbon particles darken the surface of snow and ice, increasing the amount of the sun’s energy converted to heat rather than reflected back to space. At a larger scale, sunlight [...]
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Scientists have long known that global climate models struggle to accurately simulate tropical storms and the clouds they produce in different kinds of meteorological states. Research has shown that tropical weather patterns can be classified into eight such states, including two monsoon states (active monsoon and break monsoon). Additional research comparing a range of global [...]
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Absorption and emission of infrared radiation by water high in the atmosphere helps cool the Earth and fuels the updrafts and downdrafts that can lead to cloud formation. Until recently, technology limitations prevented scientists from collecting data in one of the most important subsections of the infrared scale, the far-infrared. Lacking such data, global climate [...]
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Aerosols—tiny airborne particles from sources like pollution or desert dust—can increase the brightness of clouds, changing how much of the sun’s energy is reflected or radiated back to space compared to how much is trapped in the atmosphere. Some current climate change estimates are based on models that combine or aggregate aerosol and cloud observations [...]
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Scientists refer to clouds containing both ice and supercooled water as “mixed-phase” clouds. In the Arctic, these clouds occur frequently during all seasons and can persist for many days at a time. This persistence is remarkable given the inherent instability of ice-liquid mixtures. How is this possible?
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On local to global scales, newly formed particles contribute significantly to the concentration of atmospheric particles. In general, particles influence climate by affecting the balance of atmospheric radiation, both directly through scattering and absorbing incoming solar radiation and indirectly through impacts on cloud properties and lifetimes. However, the process of particle formation has long puzzled [...]
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Previous work by Romps (2010) found large entrainment rates of ~100% per kilometer for deep convection using a new technique for large-eddy simulations (LES) called “Eulerian direct measurement”. These results were confirmed by Dawe and Austin (2011) using a related approach. These techniques, however, are unable to pinpoint the reasons for the high [...]
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