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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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Researchers at Pacific Northwest National Laboratory, in collaboration with colleagues at NASA Ames Research Center, developed a next-generation assessment of tiny airborne particle-understanding capability, the Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research, or 4STAR. Their new model demonstrates the potential for the new airborne instrument to obtain the most important climate-related properties of tiny particles suspended [...]
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Anthropogenic aerosols contribute to the global mean radiative forcing. Uncertainties associated with these aerosol radiative forcings are the largest contributor to the overall uncertainty in anthropogenic radiative forcing of climate. Assessments of how regional emission changes will influence aerosol radiative forcing are required from both a scientific and policy perspective.
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Despite recent advances made in climate modeling, large systematic biases are still present in the models’ simulated mean state of climate. However, fully understanding the cause of these systematic biases is difficult because of the complexity of the climate system. Scientists at Lawrence Livermore National Laboratory (LLNL) have used the U.S. Department of Energy (DOE)-funded [...]
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Department of Energy scientists at Pacific Northwest National Laboratory capitalized on the multiple sensors available at ARM's Tropical Western Pacific Darwin site to understand how and when mid-level clouds form in the tropics. Low and high clouds get most of the attention—because they are easier to detect. The researchers found that the timing and temperature [...]
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