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Hyperspectral Sounder Products: SiFSAP and ClimFiSP

Infrared hyperspectral sounders have demonstrated to provide very high value information for a range of weather and climate applications. Traditional retrieval algorithms of hyperspectral sounders use the ‘cloud clearing’ methodology in the retrieval process due to the lack of means to account for cloud scattering effect. The corresponding Level-2 data products are therefore limited by two major factors: the degradation of spatial resolution as compared with the native resolution of the instruments and the lack of ‘radiance closure’ that is critically needed for climate trend studies. The single field-of-view (FOV) sounder atmospheric products (SiFSAP) algorithm has been developed to supplement existing operational products. The SiFSAP algorithm uses the principal component based radiative transfer model (PCRTM) that is ultra-fast and has been extensively validated for the cloud scattering simulation capability. The cloud properties are physically retrieved along with profiles of temperature, moisture, and trace gases of interest, surface properties simultaneously by fitting single FOV spectral measurements. Therefore, SiFSAP ensure the radiometric consistency between the retrieved geophysical properties and the top-of-atmosphere (TOA) spectral measurements. This presentation provides a general introduction of SiFSAP and details about the physical retrieval algorithm. Also introduced here is a derivative data product of SiFSAP, the climate fingerprinting Sounder Products (ClimFiSP). ClimFiSP include the space-time averaged properties of key climate variables that are derived from the space-time averaged radiances via the spectral fingerprinting scheme. The spectral fingerprinting method allows a low latency data update on ClimFiSP following any potential calibration update on satellite measurements. ClimFiSP also include the rigorously defined uncertainty characterization for trends or anomalies of climate variables, being critical for the construction of long-term climate data record. Both SiFSAP and ClimFiSP will be available to users through NASA's Goddard Earth Sciences Data and Information Services Center (GES DISC).

Wan Wu↗

NASA NTRS1986

Relativistic effects in local inertial frames

The concept of a generalized Fermi frame is introduced with the aim of describing the relativistic effects due to a third, distant body (such as the sun) upon the motion of an earth satellite. This extends Fermi's construction of a local inertial frame to the case in which there are local gravitating masses. This is done in the slow-motion, weak-field approximation by splitting the metric into an external part and a local part; Fermi's construction of local inertial coordinates defined with respect to the external metric is then used to transform the complete metric. The results show that the main relativistic effects on an earth satellite are due to the nonlinear correction in the earth's own Schwarzschild field. There are much smaller relativistic corrections in the tidal field of the sun, and an earth-sun interaction term. The spatial axes of the local frame also undergo geodetic precession. Particular care must be taken with respect to the definition of the time coordinate in the generalized Fermi frame in order that the unit of time be consistent with readings of reasonable physical clocks on earth's surface. Also discussed more rigorously is the generalized Fermi frame for a system of two bodies revolving in circular orbits around a common barycenter.

Ashby, Neil↗

NASA NTRS1974

Optimum three-dimensional atmospheric entry from the analytical solution of Chapman's exact equations

The general solution for the optimum three-dimensional aerodynamic control of a lifting vehicle entering a planetary atmosphere is developed. A set of dimensionless variables, modified Chapman variables, is introduced. The resulting exact equations of motion, referred to as Chapman's exact equations, have the advantage that they are completely free of the physical characteristics of the vehicle. Furthermore, a completely general lift-drag relationship is used in the derivation. The results obtained apply to any type of vehicle of arbitrary weight, dimensions and shape, having an arbitrary drag polar, and entering any planetary atmosphere. The aerodynamic controls chosen are the lift coefficient and the bank angle. General optimum control laws for these controls are developed. Several earlier particular solutions are shown to be special cases of this general result. Results are valid for both free and constrained terminal position.

Busemann, A.↗

NASA NTRS1972

Propagation and application of waves in the ionosphere.

This review deals with the propagation of waves, especially radio waves in the ionosphere. In the macroscopic electromagnetic theory, the mathematical structure of wave propagation problems depends entirely on the properties of the dielectric operator in a magnetically nonpermeable medium. These properties can be deduced from general discussions of symmetry and considerations of physical principles. When the medium is specifically the ionosphere, various physical phenomena may occur. Because of a large number of parameters, it is desirable to define a parameter space. A point in the parameter space corresponds to a specific plasma. The parameter space is subdivided into regions whose boundaries correspond to conditions of resonance and cutoff. As the point crosses these boundaries, the refractive index surface transforms continuously.

Yeh, K. C.↗

NASA NTRS1978

Subsonic longitudinal and lateral-directional static aerodynamic characteristics of a general research fighter configuration employing a jet sheet vortex generator

A configuration concept for developing vortex lift, which replaces the physical wing strake with a jet sheet generated fluid strake, was investigated on a general research fighter model. The vertical and horizontal location of the jet sheet with respect to the wing leading edge was studied over a momentum coefficient range from 0 to 0.24 in the Langley 7- by 10-foot high speed tunnel over a Mach number range from 0.3 to 0.8. The angle of attack range studied was from -2 to 30 deg at sideslip angles of 0, -5, and 5 deg. Test data are presented without analysis.

Huffman, J. K.↗

NASA NTRS1977

Integrated circuit process and design rule evaluation techniques

A technique is described for determining the applicability of a particular process for the fabrication of large-scale integrated (LSI) circuits. Test arrays were developed to isolate various critical processing steps in a fabrication sequence and a statistical evaluation of these steps was carried out that related yield or success in achieving a desired result to the number of times the results were attempted. It was found that, in general, yield is a sensitive function of physical dimensions as is the packing density of a particular array. It is, therefore, possible to generate an optimum set of physical dimensions or design rules that maximize the expected number of working circuits on a wafer.

Ipri, A. C.↗

NASA NTRS1978

The current status of super computers

In this paper, commercially available super computers are surveyed. Computer performance in general is limited by circuit speeds and physical size. Assuming the use of the fastest technology, super computers typically use parallelism in the form of either vector processing or array processing to obtain performance. The Burroughs Scientific Processor is an array computer with 16 separate processors, the Cray-1 and CDC STAR-100 are vector processors, the Goodyear Aerospace STARAN is an array processor with up to 8192 single bit processors, and the Systems Development Corporation PEPE is a collection of up to 288 separate processors.

Knight, J. C.↗

NASA NTRS1979

Numerical methods for large-scale, time-dependent partial differential equations

A survey of numerical methods for time dependent partial differential equations is presented. The emphasis is on practical applications to large scale problems. A discussion of new developments in high order methods and moving grids is given. The importance of boundary conditions is stressed for both internal and external flows. A description of implicit methods is presented including generalizations to multidimensions. Shocks, aerodynamics, meteorology, plasma physics and combustion applications are also briefly described.

Turkel, E.↗

NASA NTRS1981

Theories of dynamical phenomena in sunspots

Attempts that have been made to understand and explain observed dynamical phenomena in sunspots within the framework of magnetohydrodynamic theory are surveyed. The qualitative aspects of the theory and physical arguments are emphasized, with mathematical details generally avoided. The dynamical phenomena in sunspots are divided into two categories: aperiodic (quasi-steady) and oscillatory. For each phenomenon discussed, the salient observational features that any theory should explain are summarized. The two contending theoretical models that can account for the fine structure of the Evershed motion, namely the convective roll model and the siphon flow model, are described. With regard to oscillatory phenomena, attention is given to overstability and oscillatory convection, umbral oscillations and flashes. penumbral waves, five-minute oscillations in sunspots, and the wave cooling of sunspots.

Thomas, J. H.↗

NASA NTRS1985

Accuracy of schemes with nonuniform meshes for compressible fluid flows

The accuracy of the space discretization for time-dependent problems when a nonuniform mesh is used is considered. Many schemes reduce to first-order accuracy while a popular finite volume scheme is even inconsistent for general grids. This accuracy is based on physical variables. However, when accuracy is measured in computational variables then second-order accuracy can be obtained. This is meaningful only if the mesh accurately reflects the properties of the solution. In addition, the stability properties of some improved accurate schemes are analyzed and it can be shown that they also allow for larger time steps when Runge-Kutta type methods are used to advance in time.

Turkel, E.↗

NASA NTRS1986

Comments on 'Frontogenesis in a moist semigeostrophic model'

The development of narrow updrafts or jetlike features in the vertical motion field (VMF) over the leading edge of a surface frontal zone is examined on the basis of model simulations, summarizing and clarifying the results presented by Keyser and Anthes (1982) and responding to critical remarks by Mak and Bannon (1984). Typical velocity and potential-temperature cross sections are shown, and it is concluded that the inclusion of generally parameterized planetary-boundary-layer (PBL) physics in the model has a significant effect on the VMF, suggesting that frictional processes alone (without latent heating) can explain the formation of jetlike frontal updrafts. In a reply by Mak and Bannon it is argued that the increased strength of the VMF in models including PBL physics is not significant, whereas other models show that the VMF can be significantly strengthened and narrowed by condensational heating alone.

Keyser, D.↗

NASA NTRS1986

Wavelength dependence of aerosol backscatter coefficients obtained by multiple wavelength Lidar measurements

Aerosols are often classified into several general types according to their origins and composition, such as maritime, continental, and stratospheric aerosols, and these aerosol types generally have different characteristics in chemical and physical properties. The present study aims at demonstrating the potential for distinguishing these aerosol types by the wavelength dependence of their backscatter coefficients obtained from quantitative analyses of multiple wavelength lidar signals. Data from the NASA Airborne Differential Abosrption lidar (DIAL) S ystems, which can measure aerosol backscatter profiles at wavelenghts of 300, 600, and 1064 nm and ozone profiles of backscatter coefficients for these three wavelength were derived from the observations of aerosols of different types. Observations were performed over the Atlantic Ocean, the Southwestern United States, and French Guyana.

Sasano, Y.↗

NASA NTRS1986

Accuracy of schemes with nonuniform meshes for compressible fluid flows

Turkel, Eli↗

NASA NTRS1988

A continued program of planetary study

This program conducts solar system research in support of NASA missions and of general astronomical interest. Investigations of the composition, physical characteristics, and changes in solar system bodies are conducted primarily utilizing facilities of McDonald Observatory, but also utilizing various space vehicles where appropriate. The first detection of 2 micrometer II2 emission from Jupiter's southern auroral zone was made. Previous detection of northern auroral emission from Jupiter's H2 S(1) quadrupole line at 2.12 micrometer was confirmed. Unlike the previously known 8 micrometer aurorae, this phenomenon can not be thermal in origin. Analysis of Raman scattering in the blue and ultraviolet spectrum of Uranus (200 to 500 Angstroms) show that there must be absorbing aerosol particles in the upper 10 mbar region of the atmosphere. Spectra of Pluto-Charon in and out of eclipse in the red and near IR were obtained. These data confirm that CH4 is confined to Pluto and absent on Charon.

Smith, Harlan↗

NASA NTRS1995

Harmonic oscillators and resonance series generated by a periodic unstable classical orbit

The presence of an unstable periodic classical orbit allows one to introduce the decay time as a purely classical magnitude: inverse of the Lyapunov index which characterizes the orbit instability. The Uncertainty Relation gives the corresponding resonance width which is proportional to the Planck constant. The more elaborate analysis is based on the parabolic equation method where the problem is effectively reduced to the multidimensional harmonic oscillator with the time-dependent frequency. The resonances form series in the complex energy plane which is equidistant in the direction perpendicular to the real axis. The applications of the general approach to various problems in atomic physics are briefly exposed.

Kazansky, A. K.↗

NASA NTRS1994

Relativistic induced Compton scattering in synchrotron self-absorbed sources

We present a model of the radio emission from synchrotron self-absorbed sources, including the effects of induced Compton scattering by the relativistic electrons in the source. Order of magnitude estimates show that stimulated scattering becomes the dominant absorption process when (kT(sub B)/m(sub e) c(exp 2))Tau(sub T) greater than or approximately 1.0. Numerical simulations demonstrate that relativistic induced Compton scattering limits the brightness temperature of a self-absorbed synchroton sources to T(sub B) less than or approximately 2 x 10(exp 11) nu(exp -1/p + 3) (sub zero, 9) gamma(exp p + 2/p + 5) (sub min) K, where gamma(sub min) is the low-energy cutoff to the relativistic electron distribution with a power-law index of p. It can also significantly flatten the radio spectrum. The radio spectrum of the core of 3C 279 is well matched by a model in which stimulated scattering is important, and the additional constraint T(sub B) less than 2 x 10(exp 11)K may be important to the interpretation of the broadband spectra in variable extragalactic compact radio sources. Stimulated scattering reduces the amplitude of the radio frequency variability relative to the X-ray variability, an effect which can be detected by multiwavelength variability studies. Data for a sample of resolved compact radio cores indicate that it is inconsistent to neglect induced Compton scattering when inferring the physical parameters of the sources. The necessary generalizations to the standard synchrotron self-Compton theory are p resented.

Sincell, Mark W.↗

NASA NTRS1993

The influence of land surface properties on Sahel climate. Part 1: Desertification

This is a general circulation model sensitivity study of the physical mechanisms of the effects of desertification on the Sahel drought. The model vegetation types were changed in the prescribed desertification area, which led to changes in the surface characteristics. The model was integrated for three months (June, July, August) with climatological surface conditions (control) and desertification conditions (anomaly) to examine the summer season response to the changed surface conditions. The control and anomaly experiments consisted of five pairs of integrations with different initial conditions and/or sea surface temperature boundary conditions. In the desertification experiment, the moisture flux convergence and rainfall were reduced in the test area and increased to the immediate south of this area. The simulated anomaly dipole pattern was similar to the observed African drought patterns in which the axis of the maximum rainfall shifts to the south. The circulation changes in the desertification experiment were consistent with those observed during sub-Saharan dry years. The tropical easterly jet was weaker and the African easterly jet was stronger than normal. Further, in agreement with the observations, the easterly wave disturbances were reduced in intensity but not in number. Descending motion dominated the desertification area. The surface energy budget and hydrological cycle were also changed substantially in the anomaly experiment.

Xue, Yongkang↗

NASA NTRS1998

I/O Parallelization for the Goddard Earth Observing System Data Assimilation System (GEOS DAS)

The National Aeronautics and Space Administration (NASA) Data Assimilation Office (DAO) at the Goddard Space Flight Center (GSFC) has developed the GEOS DAS, a data assimilation system that provides production support for NASA missions and will support NASA's Earth Observing System (EOS) in the coming years. The GEOS DAS will be used to provide background fields of meteorological quantities to EOS satellite instrument teams for use in their data algorithms as well as providing assimilated data sets for climate studies on decadal time scales. The DAO has been involved in prototyping parallel implementations of the GEOS DAS for a number of years and is now embarking on an effort to convert the production version from shared-memory parallelism to distributed-memory parallelism using the portable Message-Passing Interface (MPI). The GEOS DAS consists of two main components, an atmospheric General Circulation Model (GCM) and a Physical-space Statistical Analysis System (PSAS). The GCM operates on data that are stored on a regular grid while PSAS works with observational data that are scattered irregularly throughout the atmosphere. As a result, the two components have different data decompositions. The GCM is decomposed horizontally as a checkerboard with all vertical levels of each box existing on the same processing element(PE). The dynamical core of the GCM can also operate on a rotated grid, which requires communication-intensive grid transformations during GCM integration. PSAS groups observations on PEs in a more irregular and dynamic fashion.

Lucchesi, Rob↗