Research Highlights

First Observations of Tracking Clouds Using Scanning ARM Cloud Radars
Oct 05, 2014       
Scanning cloud radars provide new opportunities to map clouds and their evolution. Specifically, these radars observe cloud particles well in advance of large droplet formation, while also capturing the clouds at spatial and temporal scales sufficient for continuous tracking algorithms. To better demonstrate the capabilities of the new Scanning ARM Cloud Radars (SACR) at the [...]

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Validation of CERES-MODIS Cloud Retrievals Using the Azores Data
Sep 26, 2014       
Marine boundary layer (MBL) cloud properties derived for the National Aeronautics and Space Administration (NASA) Clouds and the Earth's Radiant Energy System (CERES) Project using Terra and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) data are compared with observations taken at the ARM Mobile Facility at the Azores (AMF-Azores) site from June 2009 through December 2010. [...]

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Diurnal Variation of MBL Cloud Properties over the Azores
Sep 26, 2014       
For the single-layered marine boundary layer (MBL) cloud microphysical properties, Dong, Xi, and Wu (2014) provided the diurnal variations of cloud liquid water path (LWP) and liquid water content (LWC). However, they only presented the daytime LWP, LWC, cloud-droplet effective radius (re), number concentration (Nd), and cloud optical depth (τ), as well as surface measured [...]

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Effects of Sea Spray on the Thermodynamics of the Hurricane Boundary Layer
Sep 24, 2014       
The effects of sea spray on surface fluxes under strong winds is usually attributed to surface layer dynamics in the vicinity of the ocean surface. We propose that the main effects of sea spray on surface fluxes and intensity of hurricanes are related to the microphysical effects of spray drops penetrating deep convective clouds in [...]

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A New Theory of Time-dependent Freezing and Its Application to Investigation of Formation of Hail
Sep 24, 2014       
A new theory of wet growth of hail takes into account the inhomogeneities of surface temperature and of liquid film over the surface of the particle and parameterizes effects of non-sphericity of hail particles on their growth by accretion (Figure 1a). The time-dependent process of raindrop freezing as well as freezing of accreted water by [...]

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Turn Trash Into Treasure: Continental Warm Cloud Properties Derived from Unexploited Solar Background Signals
Sep 20, 2014       
Low-altitude boundary layer clouds strongly influence global climate through their impact on Earth’s radiation and hydrological cycle. Therefore, long-term global measurements are crucial for providing direct observational constraints to improve our knowledge of cloud and precipitation formation, and to better represent these clouds in weather and climate models. At the Atmospheric Radiation Measurement [...]

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Growing More Effective Ways to Measure Climate Change
Sep 17, 2014       
Life on earth depends on the movement of carbon dioxide through the environment. Plants take it in through photosynthesis, people and animals breath it out, the burning of fossils fuels sends it back into the atmosphere. According to the U.S. Environmental Protection Agency, in 2012, carbon dioxide accounted for about 82% of all greenhouse gas [...]

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Deciphering Raindrop Collisions with Dual-polarization Radar
Sep 01, 2014       
As raindrops descend to the surface, they undergo a variety of collisions with one another. These collisions can lead to coalescence of the drops into a larger one, breakup of the colliding drops into small fragments, or can be inconsequential. These processes affect the evolution of the drop size distribution (DSD), ultimately influencing the potential [...]

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Clouds, Aerosol, and Precipitation in the Marine Boundary Layer: an ARM Mobile Facility Deployment
Aug 26, 2014       
The Clouds, Aerosol, and Precipitation in the Marine Boundary Layer (CAP-MBL) deployment at Graciosa Island in the Azores generated a 21-month (April 2009-December 2010) comprehensive data set documenting clouds, aerosols and precipitation using the Atmospheric Radiation Measurement (ARM) Mobile Facility (AMF). The scientific aim of the deployment is to gain improved understanding of the interactions [...]

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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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