Search results for "Physics::Atmospheric and Oceanic Physics"
showing 10 items of 284 documents
Simulataneous application of charge coupled device array-detected Raman spectroscopy and differential scanning calorimetry to in situ investigation o…
1992
The combination of differential scanning calorimetry (DSC) with charge coupled device (CCD) array-detected Raman spectroscopy for the in situ investigation of phase transition is illustrated using ammonium nitrate as an example. This method aids unambiguous characterization of different phases by providing a simultaneous probe of thermodynamic and vibrational data. The availability of real-time vibrational data, including both the internal and external mode regions, is unique to array-detected Raman spectroscopy. The intensity changes of the symmetric stretching mode ν1 of the nitrate ions and the lattice vibrations, that accompany the phase transition IV → II of ammonium nitrate, are ratio…
Diagnosing the Horizontal Propagation of Rossby Wave Packets along the Midlatitude Waveguide
2017
AbstractIt has been suggested that upper-tropospheric Rossby wave packets propagating along the midlatitude waveguide may play a role for triggering severe weather. This motivates the search for robust methods to detect and track Rossby wave packets and to diagnose their properties. In the framework of several observed cases, this paper compares different methods that have been proposed for these tasks, with an emphasis on horizontal propagation and on a particular formulation of a wave activity flux previously suggested by Takaya and Nakamura. The utility of this flux is compromised by the semigeostrophic nature of upper-tropospheric Rossby waves, but this problem can partly be overcome by…
Can turbulence within the field of view cause significant biases in radiative transfer modeling at the 183 GHz band?
2018
The hypothesis whether turbulence within the passive microwave sounders field of view can cause significant biases in radiative transfer modeling at the 183 GHz water vapor absorption band is tested. A novel method to calculate the effects of turbulence in radiative transfer modeling is presented. It is shown that the turbulent nature of water vapor in the atmosphere can be a critical component of radiative transfer modeling in this band. Radiative transfer simulations are performed comparing a uniform field with a turbulent one. These comparisons show frequency dependent biases which can be up to several kelvin in brightness temperature. These biases can match experimentally observe…
A Budget Equation for the Amplitude of Rossby Wave Packets Based on Finite-Amplitude Local Wave Activity
2020
AbstractRecently, the authors proposed a novel diagnostic to quantify the amplitude of Rossby wave packets. This diagnostic extends the local finite-amplitude wave activity (LWA) of N. Nakamura and collaborators to the primitive-equations framework and combines it with a zonal filter to remove the phase dependence. In the present work, this diagnostic is used to investigate the dynamics of upper-tropospheric Rossby wave packets, with a particular focus on distinguishing between conservative dynamics and nonconservative processes. For this purpose, a budget equation for filtered LWA is derived and its utility is tested in a hierarchy of models. Idealized simulations with a barotropic and a d…
Calculations and measurements of the spectral radiance of the solar aureole
1968
The application of the theory of primary scattering to describe and interpret the spectral distribution of the sky radiance is discussed. It is shown that within the solar aureole the influence of the scattering of higher order can be neglected. Theoretical calculations of the spectral distribution of the sky radiance, carried out by Bullrich et al . (1965) based on an exponential aerosol size distribution with an upper limiting particle radius r = 10 ?, have been extended to r = 150 ?. The detailed study of the influence of these “giant” particles revealed that aerosol particles of r >30 ? have no effect on the sky radiation any more. Representative measurements taken at Mainz, Germany, at…
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.