Search results for "oceanic"
showing 10 items of 642 documents
A Flux Method for the Numerical Solution of the Stochastic Collection Equation: Extension to Two-Dimensional Particle Distributions
2000
Abstract In the present paper a new method is introduced for the numerical solution of the stochastic collection equation in cloud models dealing with two-dimensional cloud microphysics. The method is based on the assumption that the probability for the collision of two cloud drops only depends on the water mass of each and not on the mass of the aerosol nuclei. With this assumption it is possible to reduce the two-dimensional solution of the stochastic collection equation to a one-dimensional approach. First, the two-dimensional particle spectrum is integrated over the aerosol mass yielding a one-dimensional drop spectrum in the water mass grid. For this intermediate drop distribution the …
The Dynamics of Eye Formation and Maintenance in Axisymmetric Diabatic Vortices
2009
Abstract This paper investigates the occurrence, formation, and maintenance of eyes in idealized axisymmetric balanced vortices with diabatic forcing. Two key elements of the model setup are temperature relaxation toward a specified equilibrium temperature Te and Ekman pumping from a turbulent boundary layer. Furthermore, the flow is assumed to be almost inviscid in the interior. The model does not attempt any closure for moist convection. Previous work by the authors has shown that there is a continuous transition from monsoonlike vortices to hurricane-like vortices. This transition is governed by the ratio ℱ = αT /cD, where αT is the thermal relaxation rate and cD the surface drag coeffic…
A Theoretical Model to Describe the Motion of Aerosol Particles Due to the Combined Action of Inertia, Brownian Diffusion and Phoretic and Electric F…
1978
Abstract General principles of non-equilibrium thermodynamics are used to formulate a model which describes the motion of aerosol particles affected simultaneously by Brownian diffusion, inertial impaction, electric forces and phoretic forces. The theory presented applies to an ideal mixture consisting of dry air, water vapor and aerosol particles where temperature, pressure as well as vapor and particle concentration inhomogeneities are to be considered. In addition, the system is subjected to the earth's gravity, to an external electric field as well as to a Coulomb force due to a charged collecting water drop. The basic model assumptions are as follows: 1) the diffusive kinetic energy of…
Performance of a Focused Cavity Aerosol Spectrometer for Measurements in the Stratosphere of Particle Size in the 0.06–2.0-µm-Diameter Range
1995
A focused cavity aerosol spectrometer aboard a NASA ER-2 high-altitude aircraft provided high-resolution measurements of the size of the stratospheric particles in the 0.06-2.0-micrometer-diameter range in flights following the eruption of Mount Pinatubo in 1991. Effects of anisokinetic sampling and evaporation in the sampling system were accounted for by means adapted and specifically developed for this instrument. Calibrations with monodisperse aerosol particles provided the instrument's response matrix, which upon inversion during data reduction yielded the particle size distributions. The resultant dataset is internally consistent and generally shows agreement to within a factor of 2 wi…
Nonlinear Critical Layers in Barotropic Stability
1991
Abstract Applying the method of matched asymptotic expansions (MAE) to the shallow water equations on a rotating sphere, the structure of critical layers that occur in the linear and inviscid analysis of neutral disturbances of barotropic zonal flows is investigated, assuming that the critical layers are controlled by nonlinearity rather than viscosity or nonparallel flow effects. It turns out that nonlinearity is insufficient to resolve the critical layer singularity completely. It suffices however to connect linear and nondissipative solutions across critical latitudes.
A Fast Solar Radiation Transfer Code for Application in Climate Models
1983
A method is presented for the calculation of solar heating rates in turbid and cloudy atmospheres. In contrast to other typical two-stream procedures, the system of differential equations describing the radiative transfer is decoupled through the application of a series expansion of the flux densities resulting in a single analytical expression for each flux. The present method (PM) yields a solution for the entire atmosphere instead of individual atmospheric layers. This procedure avoids as part of the solution scheme the inversion of a rather complex matrix thus resulting in high numerical efficiency. The model includes the absorption by atmospheric gases such as water vapor, CO2, O3 and …
Determination of sea surface temperature at large observation angles using an angular and emissivity-dependent split-window equation
2007
Abstract This paper proposes an angular and emissivity-dependent split-window equation that permits the determination of the sea surface temperature (SST) to a reasonable level of accuracy for any observation angle, including large viewing angles at the image edges of satellite sensors with wide swaths. This is the case of the MODIS radiometer both on EOS Terra/Aqua platforms, with observation angles of up to 65° at the surface, for which the split-window equation has been developed in this study. The algorithm takes into account the angular dependence of both the atmospheric correction (due to the increase of the atmospheric optical path with angle) and the emissivity correction (since sea…
Subvisible cirrus clouds – a dynamical system approach
2016
Abstract. Ice clouds, so-called cirrus clouds, occur very frequently in the tropopause region. A special class are subvisible cirrus clouds with an optical depth lower than 0.03. Obviously, the ice crystal number concentration of these clouds is very low. The dominant pathway for these clouds is not known well. It is often assumed that heterogeneous nucleation at solid aerosol particles is the preferred mechanism although homogeneous freezing of aqueous solution droplets might be possible. For investigating subvisible cirrus clouds as formed by homogeneous freezing we develop a simple analytical cloud model from first principles; the model consists of a three dimensional set of ordinary dif…
Target states and control of molecular alignment in a dissipative medium
2006
Received 17 August 2006; published 14 November 2006We investigate how and to what extent molecular alignment can be controlled in a dissipative medium by asuitable train of laser pulses. We focus primarily on the extension of a scheme of control originally constructedfor unitary evolution. The procedure is applied to control the alignment of CO molecules in an Ar gas. Theparameters of the train of kicks—i.e., the intensity of each kick and the delay between them—are eitherobtained by a systematic procedure maximum strategy or by optimization by evolutionary algorithms.DOI: 10.1103/PhysRevA.74.053411 PACS number s : 32.80.Lg, 33.80. b, 42.50.Hz
Quantum state engineering in a cavity by Stark chirped rapid adiabatic passage
2006
We propose a robust scheme to generate single-photon Fock states and atom-photon and atom-atom entanglement in atom-cavity systems. We also present a scheme for quantum networking between two cavity nodes using an atomic channel. The mechanism is based on Stark-chirped rapid adiabatic passage (SCRAP) and half-SCRAP processes in a microwave cavity. The engineering of these states depends on the design of the adiabatic dynamics through the static and dynamic Stark shifts.