Marine Stratocumulus Clouds Research Articles

Observations of Marine Stratocumulus Clouds During FIRE

The First International Satellite Cloud Climatology Project Regional Experiment (FIRE) to study extensive fields of stratocumulus clouds off the coast of California is presented. Measurements on the regional and detailed local scales were taken, allowing for a wide interpretation of the mean, turbulent, microphysical, radiative, and chemical characteristics of stratocumulus. Multiple aircraft and ground-based remote-sensing systems were used to study the time evolution of the boundary layer structure over a three-week period, and probes from tethered balloons were used to measure turbulence and to collect cloud-microphysical and cloud-radiative data. The observations provide a base for studying the generation maintenance and dissipation of stratocumulus clouds, and could aid in developing numerical models and improved methods for retrieving cloud properties by satellite.

Marine Stratocumulus Cloud Fields off the Coast of Southern California Observed Using LANDSAT Imagery. Part I: Structural Characteristics

The structural characteristics of stratocumulus cloud fields off the coast of southern California are investigated using Landsat Multispectral Scanner imagery. Twelve scenes in this area are examined along with three other stratocumulus scenes near San Francisco, over central Oregon, and in the Gulf of Mexico. Results from this initial study of stratocumulus clouds indicate that cloud-background threshold selection techniques based upon edge detection gradient assumptions are not appropriate for cloud segmentation and classification algorithms, cloud size distributions obey a power law, and cell horizontal aspect ratio increases with cell diameter. It was also found that stratocumulus clouds are bifractal in nature with fractal dimension of d of about 1.2 for cells with diameter D smaller than 0.5 km and d of about 1.5 for cells with D greater than 0.5 km; stratocumulus cloud fields appear to be homogeneous over regions of about 100 km x 100 km, a much smaller region than the 2.5-deg x 2.5-deg boxes to be used in the ISCCP regional averaging algorithms; and that structural properties of stratocumulus clouds observed off the coast of southern California are similar to those observed for stratocumulus clouds at three other locations.

A numerical study of the marine stratocumulus cloud layer

A one-dimensional grid-level model including longwave radiative transfer and a level-4 second-order turbulent transfer closure which contains prognostic equations for turbulent quantities, is used to study the physics and dynamics of inversion-capped marine stratocumulus clouds.

On the Dynamics of Stratocumulus Formation and Dissipation

Results obtained with a mixed layer model are used to study the dynamics of stratocumulus formation and dissipation in subtropical marine stratocumulus cloud regimes. The model used allows entrainment to be driven by shear as well as buoyancy, and includes a very crude parameterization of the partial blackness of thin cloud layers. Model results show that for some values of the large-scale divergence there are three equilibrium mixed layer structures, two of which are stable. One of the stable equilibria is cloudy, deep, and buoyancy-driven, while the other is clear, shallow, and shear-driven. It is found that as a result of hysteresis effects a transient increase in the large-scale divergence can produce a long-lasting break in the clouds.

Marine Stratocumulus Convection. Part I: Governing Equations and Horizontally Homogeneous Solutions

Abstract A coupled, convective-radiative, boundary-layer model of marine stratocumulus clouds is presented. The model, which is a slight generalization of the cloud-topped, mixed-layer model of Lilly (1968), has as dependent variables the cloud-top height, cloud-base height, mixed-layer moist static energy and total water content, the turbulent fluxes of moist static energy and total water, the cloud-top jumps of moist static energy and total water, the cloud-top temperature, and the net radiative flux divergence at cloud top and in the mixed layer. Under horizontally homogeneous steady-state conditions the governing equations reduce to a system of algebraic equations which is easily solved. This system has been solved for sea surface temperatures between 13 and 18°C and large-scale divergences between 1×10−6 and 6×10−6 s−1. These calculations have been performed for the case when all the radiative cooling is confined to the cloud-top jump condition and for the case when some of the cooling is allowed to ...