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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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Raw moments from the scanning ARM precipitation radars (SAPRs) are subject to a number of instrument and atmospheric phenomena that must be retrieved and corrected for. The Corrected Moments in Antenna Coordinates (CMAC) value-added product contains both raw data and fields that have been processed to:
correct for velocity aliasing
unfold and generate a cross-polarimetric phase [...]
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Precipitation rates from cloud systems can give a fundamental insight into in-cloud processes. While rain gauges and disdrometers can give information at a single point, remote sensors such as radars can provide rainfall information over a defined area.
The Quantitative Precipitation Experiment (QPE) value-added product (VAP) contains precipitation rates gathered by the C-band scanning ARM precipitation [...]
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Editor's note: Dr. Larry Berg is the lead scientist for the Two-Column Aerosol Project.
We are back on Cape Cod for the second TCAP intensive operations period, which we abbreviate as IOP. The weather conditions have been challenging (more on that later), but we have managed to get in a number of good research flights [...]
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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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The images in this post are graphic and could very well be those of me on a boat. Eight years ago, as a first-year graduate student, I was participating in a week-long oceanographic research cruise just off the coast of southern California. A severe case of seasickness rendered me so nauseous and incapable of work [...]
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The eighth biennial Gordon Research Conference (GRC) on Radiation and Climate will be held at Colby-Sawyer College in New Hampshire, July 7-12, 2013. The GRC will be preceded by a second, associated Gordon Research Seminar (GRS) for early-career scientists on July 6-7, 2013. Graduate students and early-career scientists will have the opportunity to present their [...]
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Early this January, ARM's second mobile facility completed its first extended marine operation. Curious workers at the Los Angeles shipping dock watched as engineers using cranes unloaded the scientific instruments from a cargo ship after finishing eight round trips between Los Angeles, California, and Honolulu, Hawaii.
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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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The Shortwave Array Spectroradiometer-Hemispheric (SASHE) is a ground-based instrument that measures both direct and diffuse shortwave irradiance. SASHE provides hyperspectral measurements from about 350 nm to 1700 nm at a wavelength resolution from 1 to several nanometers.
The SASHE Aerosol Optical Depth (SASHE AOD) VAP processes the files created by the SASHE Langley VAP [...]
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A Langley plot is a regression of log (signal) versus airmass. Under appropriate conditions, the Langley regression yields values that represent the response of an instrument in absence of atmosphere (i.e., at the top of atmosphere), and these values are ultimately useful for instrument calibration. The existing LANGLEY VAP (available through special request from the [...]
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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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Guest post and photos by Chad Baldi, Project Engineer, ProSensing Inc.
Three of us from ProSensing recently made a trip to Manus Island in Papua New Guinea to perform some upgrades to two ARM radars. We made a few interesting discoveries.
In 2011, the ARM zenith cloud radar Ka-band antenna was replaced, and the old antenna [...]
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Temperature is one of the most fundamental atmospheric state variables and is crucial to the understanding of many meteorological processes. The Raman lidars at the ARM Climate Research Facility Southern Great Plains (SGP) and Tropical Western Pacific (TWP) Darwin sites are currently the only ARM active remote sensing instruments capable of profiling temperature through much [...]
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Aerosol optical depth (AOD) measures total aerosol burden in the atmosphere. The spectral dependence of AOD, typically described by the Angstrom exponent, is also an indicator of particle size. Small Angstrom exponent values (near zero) indicate presence of large particles, and vice versa.
The AOD value-added product (VAP) provides both the wavelength-dependent values of AOD and [...]
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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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