Research Highlights

Are Increases in Thunderstorm Activity in Southeast China Related to Air Pollution?
Mar 12, 2015       
Pollution aerosols are thought to have an invigorative effect on convective clouds by suppressing warm precipitation in moist and convectively unstable environments. As clouds develop to above the freezing level, mixed-phase clouds containing ice and supercooled water can grow further more readily and induce cloud electrification and thunderstorms during summertime. In southeastern China, the summer [...]

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Strongly Absorbing Aerosols Affect Retrievals of Cloud Optical Depth
Mar 12, 2015       
Surface-based and satellite remote sensing techniques have proven indispensable for learning more about cloud temporal and spatial variations. Comparisons between cloud properties retrieved from surface and spaceborne platforms are commonly done as a way of validating satellite retrievals. Observations made at the surface are often treated as the “ground-truth” with respect to satellite retrievals. Both [...]

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Filling Gaps Within Instrument Records
Mar 09, 2015       
The ARM SGP site in Lamont, Oklahoma, is home to one of the longest records of actively sensed cloud information anywhere on the planet. Despite the best efforts of the program, instruments occasionally misbehave or are taken down for maintenance, resulting in holes within this record. Utilizing the Active Remote Sensing of Clouds Value-Added Product [...]

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Quantifying the Importance of Cold Pool Mechanisms for Convection Triggering
Mar 09, 2015       
The organization of the subcloud layer into cold pools, areas of evaporatively cooled downdraft air spreading on the surface, is one of the key processes that help sustainin deep convection. It has long been known cold pools can spawn new convective cells by mechanically lifting air along their gust front. Such lifting could be the [...]

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Modeling Precipitating Cumulus Congestus Observed by the ARM Radar Suite During the MC3E Field Campaign
Mar 04, 2015       
Much of the uncertainty in climate model projections stems from the limited understanding of cloud and precipitation processes and the parameterization of these processes in global climate models (GCMs). Typically, results from cloud-resolving models (CRMs) or large-eddy simulation (LES) models serve as benchmarks for developing and tuning single-column models (SCMs), which, in turn, form the [...]

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Evaluation of Trigger Functions for Convective Parameterization Schemes
Mar 03, 2015       
In a convective parameterization scheme, the trigger function activates the onset of convection. Hence, an accurate trigger function is important to the correct simulation of convection in global climate models (GCMs). However, the formulation of trigger functions in many of convective schemes is ad hoc and convection is often activated too easily. The over-activation of [...]

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Even at High Humidity, Aerosols Stick Around: Slowly Evaporating Particles Refute Assumption
Feb 23, 2015       
Ubiquitous carbon-rich aerosol particles created by emissions from cars, trees, and other sources alter our climate and affect air quality. Until recently, the properties of these aerosols were hard to experimentally characterize, forcing computational models to rely on unsupported assumptions. For several years, scientists at Pacific Northwest National Laboratory (PNNL) have chipped away at these [...]

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Tall Clouds from Tiny Raindrops Grow
Feb 18, 2015       
Big clouds get bigger and small clouds shrink may seem like a simple statement, but the myriad mechanisms behind how clouds are born, grow, and die are surprisingly complex. These very mechanisms may be key to understanding future weather patterns and global climate change. In a study published in the Journal of Geophysical Research: Atmospheres, [...]

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Modeling Dust as Component Minerals in the Community Atmosphere Model
Feb 11, 2015       
Desert dust affects Earth’s radiation balance, cloud formation and biogeochemical trace nutrient cycling. Including mineralogy of dust in climate models is important to understand these effects. Researchers, including a Department of Energy scientist at Pacific Northwest National Laboratory, found that ability to correctly include the mineralogy of dust in climate models is hindered by its [...]

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A Novel Approach for Introducing 3D Cloud Spatial Structure Into 1D Radiative Transfer
Feb 06, 2015       
Subgrid-scale variability is one of the main reasons why parameterizations are needed in large-scale models. Similarly, subpixel-scale cloud heterogeneity also plagues satellite retrievals of cloud and aerosol properties. Cloud heterogeneity, to some extent, can be represented by the so-called Independent Column Appoximation, i.e., the gridbox or pixel can be divided into many non-interactive subcolumns and [...]

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Long-Term Measurements of Submicrometer Aerosol Chemistry at SGP Using an ACSM
Feb 05, 2015       
Aerosols are one of the greatest sources of uncertainty in radiative forcing climate model predictions. Co-located measurements of meteorology, radiation, and aerosols are needed to evaluate and improve treatments of aerosol processes in climate models. Measurements characterizing the chemical and physical properties of aerosols are particularly important for understanding sources and processes of aerosols in [...]

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A New Approach for Representing Ice Particles in Weather and Climate Model
Feb 02, 2015       
Proper representation of cloud microphysical and precipitation processes is critical for the simulation of weather and climate. Despite decades of advancement, the representation of cloud and precipitation particles in weather and climate models still has many uncertainties. This is due to an incomplete understanding of the important physical processes as well as the inherent complexity [...]

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Multiday Production of SOA in Urban and Forest Outflow
Jan 30, 2015       
Secondary organic aerosol (SOA) production in urban and biogenic outflow was investigated using the explicit gas-phase chemical mechanism generator GECKO-A (Lee-Taylor et al. 2015). Urban outflow simulations show several-fold increases in SOA mass continuing for multiple days, whereas forest outflow simulations showed only modest SOA mass increases, and no long-term growth. The multiday SOA production [...]

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Finding the Causes for Consistently Low Biased Stratiform Rainfall in Models
Jan 29, 2015       
The amount of convective relative to stratiform rainfall in a mesoscale convective system is important because it significantly impacts the distribution of heating and moistening. This study, the second of a two-part study, compares output from ten cloud-resolving model (CRM) and four limited area model (LAM) simulations of active monsoonal tropical convection during the Tropical [...]

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Overly Intense Convective Updrafts Exposed as a Significant Contributor to Model Biases
Jan 29, 2015       
Mesoscale simulations run at cloud-resolving scales often fail to reproduce observed cloud and precipitation structures of convective systems and their dependence on large-scale environmental conditions. This is an important issue because these types of simulations are increasingly used in satellite retrievals and improving representation of convective systems in general circulation models. In this first of [...]

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Sensitivity of Arctic Mixed-Phase Stratocumulus to Surface-Layer and Cloud-Top Moisture Sources
Jan 09, 2015       
Arctic mixed-phase stratocumulus cloud systems (AMPS) play an important role in determining the structure of the Arctic atmospheric boundary layer and magnitudes of surface energy budget terms, due to the presence of radiatively important supercooled cloud liquid water. AMPS occur in significantly different environments than subtropical stratocumuli. For example, AMPS are observed above both stable [...]

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