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Processes of convection and clouds are usually parameterized in traditional general circulation models (GCMs), which contribute to uncertainties in predicting climate. Recently the Multiscale Modeling Framework (MMF), also called ``superparameterization'', was proposed to resolve these processes at their native scales by embedding a cloud resolving model (CRM) at each grid column of a GCM. [...]
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We have developed a simple, semi-empirical algorithm for finding cloud optical depth from surface-based broadband solar irradiance measurements. The algorithm consists of a one-line equation and is therefore very easy to apply. In a previous paper (Barnard and Long, 2004), the method was applied to warm, liquid water clouds. Here we describe [...]
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A crucial factor to improve our ability to forecast future climate change and short-range weather is a better representation of convection and clouds in large-scale models. This requires a better understanding of the statistical properties of clouds and deep convective storms, as well as the variability of these properties as a function of different temporal, [...]
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Radiative heating by clouds is an important component of the total diabatic heating of the atmosphere. Although the radiative effects of clouds on the Earth’s energy budget are most readily observable by examining top-of-atmosphere (TOA) and surface fluxes, their direct effect on the atmospheric circulation is through the redistribution of energy vertically in the [...]
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From large-scale global climate models (GCMs) down to small-scale large eddy simulation (LES), numerical models most commonly employ simple treatments of radiative transfer, where radiation streams upward and downward through the atmosphere. While computationally attractive, this simplification neglects horizontal radiation transport and associated effects such as cloud shadowing and cooling of lateral cloud boundaries. [...]
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Satellites monitor the aerosol loading (or pollution level) in the atmosphere by measuring the amount of reflected sunlight. However, nearby broken clouds bounce sunlight around, making aerosols seem brighter than they really are. This, in turn "fools" satellites into thinking that the atmosphere is more polluted (has larger aerosol loading) than it really is. For [...]
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The sensitivity of calculated aerosol direct radiative forcing to input parameters has been examined to determine the consequences of uncertainties in these input parameters on calculated radiative forcing and to identify areas where measurements might be most profitably improved. Input parameters incorporate aerosol optical properties: optical depth τ, single scattering albedo (the fraction of light [...]
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Ending its mission with a final flight on April 30, 2008, the Indirect and Semi-Direct Aerosol Campaign (ISDAC) flew a total of 103 research hours, completing 27 science flights primarily in the region around the ACRF North Slope of Alaska site in Barrow. These flights included several golden cases where both cloud and aerosol measurements [...]
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The phase composition and microphysical structure of clouds define the manner in which they modulate atmospheric radiation and contribute to the hydrologic cycle. Issues regarding cloud phase partitioning and transformation come to bear directly in mixed-phase clouds, and have been difficult to address within current modeling frameworks. Ground-based, remote-sensing observations of mixed-phase [...]
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Water vapor is the most abundant and the most highly variable greenhouse gas in the atmosphere. This temporal and spatial variability has a strong effect on the radiative fluxes at the surface and at the top of the atmosphere and on the radiative heating rates at all layers of the atmosphere. In addition, the [...]
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Clouds and aerosols are linked and have important roles in Earth’s climate. Among other effects, they reflect and absorb solar radiation thus reducing the amount reaching the surface. Clouds wouldn’t actually exist if a subset of aerosols called cloud condensation nuclei (CCN) was not available to provide a surface for water to condense or freeze [...]
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Cirrus consists almost exclusively of nonspherical ice crystals with various shapes and sizes (e.g., bullet rosettes, columns, plates, aggregates, and irregular crystals). Therefore, knowledge of the single-scattering properties (e.g., phase function, asymmetry parameter g and single-scattering albedo ωo) of non-spherical ice crystals is required because the general circulation models (GCMs) and remote sensing studies used [...]
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The global amount of atmospheric aerosol has increased substantially since the beginning of the industrialized era. Aerosol particles directly affect solar radiation by both reflecting and absorbing light. However, aerosol also can affect sunlight in an indirect manner by causing changes in cloud properties through the subset of particles that act as cloud condensation [...]
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While fair-weather clouds (FWC) are small in size, they are ubiquitous, occurring over large areas of continents and in the trade wind regions over the oceans. These clouds play an important role in the Earth’s climate by reflecting the sun’s energy away from the planet. FWC are smaller than the grid spacing used in [...]
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In order to better understand and predict shortwave radiation in realistic cloudy atmospheres, we need to specify the three-dimensional (3D) distribution of cloud liquid water. Also, statistical cloud retrievals that include 3D radiative transfer need to be trained on a large number of 3D cloud fields. Realistic cloud fields and spatial distributions of [...]
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An improved convective triggering mechanism developed by ARM scientists based on ARM observations was implemented recently in the Global Spectral Model (GSM) at the Japan Meteorological Agency (JMA) to improve surface precipitation forecasts. The new triggering mechanism introduces a simple dynamic constraint on the initiation of convection that emulates the collective effects of lower-level [...]
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Numerous studies based on satellite observations have reported a positive correlation between cloud amount and aerosol optical thickness (AOT). This positive correlation can be explained as a result of physical phenomena such as the humidification of aerosols in the relatively moist cloud environment or a transition between aerosol and clouds where the cloud signature [...]
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Atmospheric column absorption of solar radiation (Acol) is a fundamental part of the Earth’s energy cycle but is extremely difficult to measure directly. It has been the subject of several ARM field campaigns. To investigate Acol, surface observations were taken under optically thick Deep Convective Systems (DCS) over the Department of Energy Atmospheric Radiation Measurement [...]
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Recent research shows that surface temperatures predicted by Global Climate Models (GCMs) depend mostly on two physical parameters; the efficiency by which clear air is mixed into thunderstorms (i.e., entrainment) and the fall speed of ice particles in cirrus clouds. Our research demonstrates the dependence of the representative ice fall speed on the concentration [...]
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