Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “reanalysis”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Intraseasonal Oscillations over South America: A Study with a Regional Climate Model

The National Center for Atmospheric Research (NCAR) regional climate model version 2 (RegCM2) is used to investigate the observed characteristics of intraseasonal oscillations over South America. Our study is mainly concentrated on an intraseaonal mode, which is observed to account for a large portion of the intraseasonal variation, to have a standing feature and to be independent of the MJO. The NCEPDOE AMIP-II reanalysis is utilized to provide initial and lateral boundary conditions for the RegCM2 based upon the OOZ, 062, 122 and 182 data.Our results indicate that the intraseasonal oscillation still exists with time- averaged lateral boundary condition, which prevents the MJO and other outside disturbances from entering the model's domain, suggesting a locally forced oscillation responsible for ths intraseasonal mode independent of the MJO. Further experiments show that the annual and daily variabilities and a radiative-convective interaction are not essential to the locally forced intraseasonal oscillation. The intraseasonal oscillations over Amazon in our model essentially result from interactions among atmospheric continental- scale circulation, surface radiation, surface sensible and latent heat fluxes, and cumulus convection. The wavelet analyses of various surface energy fluxes and surface energy budget also verify that the primary cause of intraseasonal oscillation is the interaction of land surface processes with the atmosphere.

Chen, Baode↗
NASA NTRS2004

The Development of Two Science Investigator-led Processing Systems (SIPS) for NASA's Earth Observation System (EOS)

In 2001, NASA Goddard Space Flight Center's Laboratory for Terrestrial Physics started the construction of a science Investigator-led Processing System (SIPS) for processing data from the Ozone Monitoring Instrument (OMI) which will launch on the Aura platform in mid 2004. The Ozone Monitoring Instrument (OMI) is a contribution of the Netherlands Agency for Aerospace Programs (NIVR) in collaboration with the Finnish Meteorological Institute (FMI) to the Earth Observing System (EOS) Aura mission. It will continue the Total Ozone Monitoring System (TOMS) record for total ozone and other atmospheric parameters related to ozone chemistry and climate. OMI measurements will be highly synergistic with the other instruments on the EOS Aura platform. The LTP previously developed the Moderate Resolution Imaging Spectrometer (MODIS) Data Processing System (MODAPS), which has been in full operations since the launches of the Terra and Aqua spacecrafts in December, 1999 and May, 2002 respectively. During that time, it has continually evolved to better support the needs of the MODIS team. We now run multiple instances of the system managing faster than real time reprocessings of the data as well as continuing forward processing. The new OMI Data Processing System (OMIDAPS) was adapted from the MODAPS. It will ingest raw data from the satellite ground station and process it to produce calibrated, geolocated higher level data products. These data products will be transmitted to the Goddard Distributed Active Archive Center (GDAAC) instance of the Earth Observing System (EOS) Data and Information System (EOSDIS) for long term archive and distribution to the public. The OMIDAPS will also provide data distribution to the OMI Science Team for quality assessment, algorithm improvement, calibration, etc. We have taken advantage of lessons learned from the MODIS experience and software already developed for MODIS. We made some changes in the hardware system organization, database and software to adapt the system for OMI. We replaced the fundamental database system, Sybase, with an Open Source RDBMS called PostgreSQL, and based the entire OMIDAPS on a cluster of Linux based commodity computers rather than the large SGI servers that MODAPS uses. Rather than relying on a central I/O server host, the new system distributes its data archive among multiple server hosts in the cluster. OMI is also customizing the graphical user interfaces and reporting structure to more closely meet the needs of the OMI Science Team. Prior to 2003, simulated OMI data and the science algorithms were not ready for production testing. We initially constructed a prototype system and tested using a 25 year dataset of Total Ozone Mapping Spectrometer (TOMS) and Solar Backscatter Ultraviolet Instrument (SBUV) data. This prototype system provided a platform to support the adaptation of the algorithms for OMI, and provided reprocessing of the historical data aiding in its analysis. In a recent reanalysis of the TOMS data, the OMIDAPS processed 108,000 full orbits of data through 4 processing steps per orbit, producing about 800,000 files (400 GiB) of level 2 and greater data files. More recently we have installed two instances of the OMIDAPS for integration and testing of OM1 science processes as they get delivered from the Science Team. A Test instance of the OMIDAPS has also supported a series of "Interface Confidence Tests" (ICTs) and End-to-End Ground System tests to ensure the launch readiness of the system. This paper will discuss the high-level hardware, software, and database organization of the OMIDAPS and how it builds on the MODAPS heritage system. It will also provide an overview of the testing and implementation of the production OMIDAPS.

Tilmes, Curt↗
NASA NTRS2004

The North Pacific as a Regulator of Summertime Climate Over North America and the Asian Monsoon

The interannual variability of summertime rainfall over the U.S. may be linked to climate anomalies over Pacific and East Asia through teleconnection patterns that may be components of recurring global climate modes in boreal summer (Lau and Weng 2002). In this study, maintenance of the boreal summer teleconnection patterns is investigated. The particular focus is on the potential effects of North Pacific air-sea interaction on climate anomalies over the U.S. Observational data, reanalysis and outputs of a series of NASA NSIPP AGCM and AGCM coupled to NASA GSFC MLO model experiments are used. Statistical analysis of observations and NSIPP AMIP type simulations indicates that, the interannual variability of observed warm season precipitation over the U.S. is related to SST variation in both tropical and North Pacific, whereas the NSIPP AMIP simulated summertime US. precipitation variation mainly reflects impact of ENS0 in tropical Pacific. This implies the potential importance of air-sea interaction in North Pacific in contributing to the interannual variability of observed summer climate over the U.S. The anomalous atmospheric circulation associated with the dominant summertime teleconnection modes in both observations and NSIPP AMIP simulations are further diagnosed, using stationary wave modeling approach. In observations, for the two dominant modes, both anomalous diabatic heating and anomalous transients significantly contribute to the anomalous circulation. The distributions of the anomalous diabatic heating and transient forcing are quadrature configured over North Pacific and North America, so that both forcings act constructively to maintain the teleconnection patterns. The contrast between observations and NSIPP AMIP simulations from stationary wave modeling diagnosis confirms the previous conclusion based on statistical analysis. To better appreciate the role of extra-tropical air-sea interaction in maintaining the summertime teleconnection pattern, various dynamical and physical fields and their inter- linkage in the series of NSIPP AGCM and AGCM coupled to MLO model experiments are examined in-depth. Based on comparison between different model experiments, we will discuss the physical and dynamical mechanisms through which the air-sea interaction in extratropics, and transient mean flow interactions over the North Pacific, affects interannual variation of U.S. climate during boreal summer.

Lau, William K. M.↗
NASA NTRS1998

Envelope structure on 700 AU scales and the molecular outflows of low-mass young stellar objects

Aperture synthesis observations of HCO+ J = 1-0, 13CO 1-0, and C18O 1-0 obtained with the Owens Valley Millimeter Array are used to probe the small-scale (5" approximately 700 AU) structure of the molecular envelopes of a well-defined sample of nine embedded low-mass young stellar objects in Taurus. The interferometer results can be understood in terms of: (1) a core of radius approximately or less than 1000 AU surrounding the central star, possibly flattened and rotating; (2) condensations scattered throughout the envelope that may be left over from the inhomogeneous structure of the original cloud core or that may have grown during collapse; and (3) material within the outflow or along the walls of the outflow cavity. Masses of the central cores are 0.001-0.1 M (solar), and agree well with dust continuum measurements. Averaged over the central 20" (3000 AU) region, an HCO+ abundance of 4 x 10(-8) is inferred, with a spread of a factor of 3 between the different sources. Reanalysis of previously presented single-dish data yields an HCO+ abundance of (5.0 +/- 1.7) x 10(-9), which may indicate an average increase by a factor of a few on the smaller scales sampled by the interferometer. Part of this apparent abundance variation could be explained by contributions from extended cloud emission to the single-dish C18O lines, and uncertainties in the assumed excitation temperatures and opacities. The properties of the molecular envelopes and outflows are further investigated through single-dish observations of 12CO J = 6-5, 4-3, and 3-2, 13CO 6-5 and 3-2, and C18O 3-2 and 2-1, obtained with the James Clerk Maxwell and IRAM 30 m telescopes, along with the Caltech Submillimeter Observatory. Ratios of the mid-J CO lines are used to estimate the excitation temperature, with values of 25-80 K derived for the gas near line centre. The outflow wings show a similar range, although Tex is enhanced by a factor of 2-3 in at least two sources. In contrast to the well-studied L1551 IRS 5 outflow, which extends over 10' (0.4 pc), seven of the remaining eight sources are found to drive 12CO 3-2 outflows over < or = 1' (0.04 pc); only L1527 IRS has a well-developed outflow of some 3'(0.12 pc). Estimates are obtained for the outflow kinetic luminosity, Lkin, and the flow momentum rate, FCO, applying corrections for line opacity and source inclination. The flow force FCO correlates with the envelope mass and with the 2.7 mm flux of the circumstellar disk. Only a weak correlation is seen with Lbol, while none is found with the relative age of the object as measured by integral Tmb(HCO+ 3-2)dV/Lbol. These trends support the hypothesis that outflows are driven by accretion through a disk, with a global mass infall rate determined by the mass and density of the envelope. The association of compact HCO+ emission with the walls of the outflow cavities indicates that outflows in turn influence the appearance of the envelopes. It is not yet clear, however, whether they are actively involved in sweeping up envelope material, or merely provide a low-opacity pathway for heating radiation to reach into the envelope.

NASA Discipline Exobiology↗
NASA NTRS1989

The biology of mass extinction: a palaeontological view

Extinctions are not biologically random: certain taxa or functional/ecological groups are more extinction-prone than others. Analysis of molluscan survivorship patterns for the end-Cretaceous mass extinctions suggests that some traits that tend to confer extinction resistance during times of normal ('background') levels of extinction are ineffectual during mass extinction. For genera, high species-richness and possession of widespread individual species imparted extinction-resistance during background times but not during the mass extinction, when overall distribution of the genus was an important factor. Reanalysis of Hoffman's (1986) data (Neues Jb. Geol. Palaont. Abh. 172, 219) on European bivalves, and preliminary analysis of a new northern European data set, reveals a similar change in survivorship rules, as do data scattered among other taxa and extinction events. Thus taxa and adaptations can be lost not because they were poorly adapted by the standards of the background processes that constitute the bulk of geological time, but because they lacked--or were not linked to--the organismic, species-level or clade-level traits favoured under mass-extinction conditions. Mass extinctions can break the hegemony of species-rich, well-adapted clades and thereby permit radiation of taxa that had previously been minor faunal elements; no net increase in the adaptation of the biota need ensue. Although some large-scale evolutionary trends transcend mass extinctions, post extinction evolutionary pathways are often channelled in directions not predictable from evolutionary patters during background times.

Non-NASA Center↗
NASA NTRS2004

A Subsonic Aircraft Design Optimization With Neural Network and Regression Approximators

The Flight-Optimization-System (FLOPS) code encountered difficulty in analyzing a subsonic aircraft. The limitation made the design optimization problematic. The deficiencies have been alleviated through use of neural network and regression approximations. The insight gained from using the approximators is discussed in this paper. The FLOPS code is reviewed. Analysis models are developed and validated for each approximator. The regression method appears to hug the data points, while the neural network approximation follows a mean path. For an analysis cycle, the approximate model required milliseconds of central processing unit (CPU) time versus seconds by the FLOPS code. Performance of the approximators was satisfactory for aircraft analysis. A design optimization capability has been created by coupling the derived analyzers to the optimization test bed CometBoards. The approximators were efficient reanalysis tools in the aircraft design optimization. Instability encountered in the FLOPS analyzer was eliminated. The convergence characteristics were improved for the design optimization. The CPU time required to calculate the optimum solution, measured in hours with the FLOPS code was reduced to minutes with the neural network approximation and to seconds with the regression method. Generation of the approximators required the manipulation of a very large quantity of data. Design sensitivity with respect to the bounds of aircraft constraints is easily generated.

Patnaik, Surya N.↗
NASA NTRS2004

Cloud Detection Using Measured and Modeled State Parameters

In this study, hourly RUC analyses were used to examine the differences between RH and temperature values from RUC reanalysis data and from radiosonde atmospheric profiles obtained at the ARM SCF. The results show that the temperature observations from the SONDE and RUC are highly correlated. The RHs are also well-correlated, but the SONDE values generally exceed those from RUC. Inside cloud layers, the RH from RUC is 2-14% lower than the RH from SONDE for all RUC layers. Although the layer mean RH within clouds is much greater than the layer mean RH outside cloud or in the clear-sky, RH thresholds chosen as a function of temperature can more accurately diagnose cloud occurrence for either dataset. For overcast clouds, it was found that the 50% probability RH threshold for diagnosing a cloud, within a given upper tropospheric layer is roughly 90% for the Vaisala RS80-15LH radisonde and 80% for RUC data. While for the partial cloud (cloud amount is less than 90%), the RH thresholds of SONDE are close to RUC for a given probability in upper tropospheric layers. The probabilities of detecting clouds at a given RH and temperature should be useful for a variety of application such as the development of new cloud parameterizations or for estimating the vertical profile of cloudiness underneath a given cloud observed from the satellite to construct a 3-D cloud data set for computing atmospheric radiative heating profiles or determining potential aircraft icing conditions.

Yi, Y.↗
NASA NTRS2004

Stratospheric Impact of Varying Sea Surface Temperatures

The Finite-Volume General Circulation Model (FVGCM) has been run in 50 year simulations with the: 1) 1949-1999 Hadley Centre sea surface temperatures (SST), and 2) a fixed annual cycle of SSTs. In this presentation we first show that the 1949-1999 FVGCM simulation produces a very credible stratosphere in comparison to an NCEP/NCAR reanalysis climatology. In particular, the northern hemisphere has numerous major and minor stratospheric warming, while the southern hemisphere has only a few over the 50-year simulation. During the northern hemisphere winter, temperatures are both warmer in the lower stratosphere and the polar vortex is weaker than is found in the mid-winter southern hemisphere. Mean temperature differences in the lower stratosphere are shown to be small (less than 2 K), and planetary wave forcing is found to be very consistent with the climatology. We then will show the differences between our varying SST simulation and the fixed SST simulation in both the dynamics and in two parameterized trace gases (ozone and methane). In general, differences are found to be small, with subtle changes in planetary wave forcing that lead to reduced temperatures in the SH and increased temperatures in the NH.

Newman, Paul A.↗
NASA NTRS2003

Data Assimilation Office (DAO) Operational Analyses and Reanalyses for Coordinated Enhanced Observing Period (CEOP)

The DAO operational assimilation system has produced and archived gridded data since 1998, and will continue through the CEOP period. However, major system upgrades and new assimilation variables will significantly affect the surface energy balance and data product. These changes will be discussed and the prospects for a CEOP reanalysis will be presented. W e will also review the data currently available and describe how to access the data.

Bosilovich, M.↗
NASA NTRS2004

NASA GEOS-3/TRMM Re-analysis: Capturing Observed Tropical Rainfall Variability in Global Analysis for Climate Research

Understanding climate variability over a wide range of space-time scales requires a comprehensive description of the earth system. Global analyses produced by a fixed assimilation system (i.e., re-analyses) - as their quality continues to improve - have the potential of providing a vital tool for meeting this challenge. But at the present time, the usefulness of re-analyses is limited by uncertainties in such basic fields as clouds, precipitation, and evaporation - especially in the tropics, where observations are relatively sparse. Analyses of the tropics have long been shown to be sensitive to. the treatment of cloud precipitation processes, which remains a major source of uncertainty in current models. Yet, for many climate studies it is crucial that analyses can accurately reproduce the observed rainfall intensity and variability since a small error of 1 mm/d in surface rain translates into an error of approx. 30 W/sq m in energy (latent heat) flux. Currently, discrepancies between the observed and analyzed monthly-mean rain rates averaged to 100 km x 100 km resolution can exceed 4 mm/d (or 120 W/sq m ), compared to uncertainties in surface radiative fluxes of approx. 10-20 W/sq m . Improving precipitation in analyses would reduce a major source of uncertainty in the global energy budget. Uncertainties in tropical precipitation have also been a major impediment in understanding how the tropics interact with other regions, including the remote response to El Nino/Southern Oscillation (ENSO) variability on interannual time scales, the influence of Madden-Julian Oscillation (MJO) and monsoons on intraseasonal time scales. A global analysis that can replicate the observed precipitation variability together with physically consistent estimates of other atmospheric variables provides the key to breaking this roadblock. NASA Goddard Space Flight Center has been exploring the use of satellite-based microwave rainfall measurements in improving global analyses and has recently produced a multi-year, 1 x 1 TRMM re-analysis , which assimilates 6-hourly TMI and SSM/I surface rain rates over tropical oceans using a ID variational continuous assimilation (VCA) procedure in the GEOS-3 global data assimilation system. The analysis period extends from 1 November 1997 through 3 1 December 2002. The goal is to produce a multi-year global analysis that is dynamically consistent with available tropical precipitation observations for the community to assess its utility in climate applications and identify areas for further improvements. A distinct feature of the GEOS-3RRMh4 re-analysis is that its precipitation analysis is not derived from a short-term forecast (as done in most operational systems) but is given by a time- continuous model integration constrained by precipitation observations within a 6-h analysis window, while the wind, temperature, and pressure fields are allowed to directly respond to the improved precipitation and associated latent heating structures within the same analysis window. In this talk, I will assess the impact VCA precipitation assimilation on analyses of climate signals ranging from a few weeks to interannual time scales and compare results against other operational and reanalysis products.

Hou, Arthur Y.↗
NASA NTRS2002

SEARCH Workshop on Large-Scale Atmosphere/Cryosphere Observations

The purpose of the workshop held in Seattle during 27-29 November 2001 was to review existing land, sea ice, and atmospheric observations and the prospect for an Arctic System Reanalysis, through white papers, invited speakers, and panels. A major task for SEARCH was to determine how existing observation systems can be best used and enhanced to understand and anticipate the course of the ongoing changes in the Arctic. The primary workshop conclusion is that there is no cohesion among various Arctic disciplines and data types to form a complete observation set of Arctic change; a second workshop conclusion is that present data sets are vastly underutilized in understanding Arctic change; a third conclusion is that a distributed observing system must accommodate a wide range of spatial patterns of variability.

Source record↗
NASA NTRS2004

How Consistent are Recent Variations in the Tropical Energy and Water Cycle Resolved by Satellite Measurements?

One notable aspect of Earth's climate is that although the planet appears to be very close to radiative balance at top-of-atmosphere (TOA), the atmosphere itself and underlying surface are not. Profound exchanges of energy between the atmosphere and oceans, land and cryosphere occur over a range of time scales. Recent evidence from broadband satellite measurements suggests that even these TOA fluxes contain some detectable variations. Our ability to measure and reconstruct radiative fluxes at the surface and at the top of atmosphere is improving rapidly. One question is 'How consistent, physically, are these diverse remotely-sensed data sets'? The answer is of crucial importance to understanding climate processes, improving physical models, and improving remote sensing algorithms. In this work we will evaluate two recently released estimates of radiative fluxes, focusing primarily on surface estimates. The International Satellite Cloud Climatology Project 'FD' radiative flux profiles are available from mid-1983 to near present and have been constructed by driving the radiative transfer physics from the Goddard Institute for Space Studies (GISS) global model with ISCCP clouds and TOVS (TIROS Operational Vertical Sounder)thermodynamic profiles. Full and clear sky SW and LW fluxes are produced. A similar product from the NASA/GEWEX Surface Radiation Budget Project using different radiative flux codes and thermodynamics from the NASA/Goddard Earth Observing System (GEOS-1) assimilation model makes a similar calculation of surface fluxes. However this data set currently extends only through 1995. We also employ precipitation measurements from the Global Precipitation Climatology Project (GPCP) and the Tropical Rainfall Measuring Mission (TRMM). Finally, ocean evaporation estimates from the Special Sensor Microwave Imager (SSM/I) are considered as well as derived evaporation from the NCAR/NCEP Reanalysis. Additional information is included in the original extended abstract.

Robertson, F. R.↗
NASA NTRS2004

A Mechanism For Solar Forcing of Climate: Did the Maunder Minimum Cause the Little Ice Age?

The mechanism we wish to demonstrate exploits chemical, radiative, and dynamical sensitivities in the stratosphere to affect the climate of the troposphere. The sun, while its variability in total radiative output over the course of the solar cycle is on the order of 0.1%, exhibits variability in the UV output on the order of 5%. We expect to show that a substantially decreased solar UV output lessened the heating of the Earth's stratosphere during the Maunder Minimum, through decreased radiative absorption by ozone and oxygen. These changes in stratospheric heating would lead to major changes in the stratospheric zonal wind pattern which would in turn affect the propagation characteristics of planetary-scale waves launched in the winter hemisphere. Until recently, there was no quantitative data to relate the changes in the stratosphere to those at the surface. There is now empirical evidence from the NCEP Reanalysis data that a definitive effect of the solar cycle on climate in the troposphere exists. Our recent work is summarized as follows (see complete list of publications in later part of this report).

Yung, Yuk L.↗
NASA NTRS2005

K-shell Photoabsorption of Oxygen Ions

The high spectral resolutions of the Chandra and XMM-Newton X-ray observatories have unveiled the useful diagnostic possibilities of oxygen K absorption. To mention a few, strong O VII and O VIII edges are almost ubiquitous in the spectra of Seyfert 1 galaxies which have been used by Lee et al. (2001) to predict of a warm dust absorber along the line of sight; although this conclusion has been criticized in the light of a data reanalysis (SA0 et al. 2003), Steenbrugge et al. (2003) have detected inner-shell transitions of O III-O VI in the spectrum of NGC 5548 that point to a warm absorber that spans three orders of magnitude in ionization parameter. Moreover, Behar et al. (2003) have stressed that, in the case of both Seyfert 1 and Seyfert 2 galaxies, a broad range of oxygen charge states are usually observed along the line of sight that must be fitted simultaneously, and may imply strong density gradients of 2-4 orders of magnitude over short distances.

Garcia, J.↗
NASA NTRS2005

Discovery of a Be/X-Ray Binary Consistent with the Location of GRO J2058+42

GRO J2058+42 is a 195 s transient X-ray pulsar discovered in 1995 with BATSE. In 1996, RXTE located GRO J2058+42 to a 90% confidence error circle with a 4 radius. On 2004 February 20, the region including the error circle was observed with Chandra ACIS-I. No X-ray sources were detected within the error circle; however, two faint sources were detected in the ACIS-I field of view. We obtained optical observations of the brightest object, CXOU J205847.5+414637, which had about 64 X-ray counts and was just 013 outside the error circle. The optical spectrum contains a strong Ha line and corresponds to an inhued object in the Two Micron All Sky Survey catalog, indicating a Be/X-ray binary system. Pulsations were not detected in the Chandra observations, but similar flux variations and distance estimates suggest that CXOU J205847.5+414637 and GRO J2058+42 are the same object. We present results from the Chandra observation, optical observations, new and previously unreported RXTE observations, and a reanalysis of a ROSAT observation.

Wilson, Colleen↗
NASA NTRS2005

Spatial Extent of a Deep Moonquake Nest: A Preliminary Report of Reexamination

Deep moonquakes, occurring at depths about halfway to the center of the Moon, were discovered during the Apollo lunar landing missions, 1969-1972. Their near-monthly occurrence with nearly identical waveforms at any given seismic station suggests that they are strongly influenced by tides, caused by the Earth and the Sun, acting on certain limited regions of the deep lunar interior. However, much about them is unknown, why they are restricted to certain depths and to limited source regions (nests), and what they tell us about the nature of the material and dynamics of the interior of the Moon. A piece of information helpful to decipher their true nature is the spatial extent and distribution of their hypocenters. The occurrence of nearly identical waveforms suggests groups of hypocenters appear in close proximity to one another, but can we tell how closely they are located and how they are distributed? The Apollo PSE (Passive Seismic Experiment) data from all stations of the seismic network were received in real time at a common receiving station on Earth in digital form. This provided extremely high inter-station timing accuracy not achievable for most earthquake data on Earth at that time. We took advantage of this to compute relative locations of waveform-matched events, and concluded that deep moonquake foci in the A1 moonquake nest were concentrated on a nearly horizontal plane of less than 1 km in diameter. This earlier study was based on deep moonquake events visually identified on seismograms. A recent reanalysis of earlier unidentified seismic events fully utilizing the high capability of present-day computers expanded the list of positively identified deep moonquakes by more than a factor of five. The new list contains many events that are not visually matched in waveforms, yet correlated at a significant level when cross-correlated with a computer. Thus it became imperative to reexamine the spatial distribution of deep moonquake hypocenters including the newly identified events. Additional information is included in the original extended abstract.

Nakamura, Yosio↗
NASA NTRS1998

Design Process for High Speed Civil Transport Aircraft Improved by Neural Network and Regression Methods

A key challenge in designing the new High Speed Civil Transport (HSCT) aircraft is determining a good match between the airframe and engine. Multidisciplinary design optimization can be used to solve the problem by adjusting parameters of both the engine and the airframe. Earlier, an example problem was presented of an HSCT aircraft with four mixed-flow turbofan engines and a baseline mission to carry 305 passengers 5000 nautical miles at a cruise speed of Mach 2.4. The problem was solved by coupling NASA Lewis Research Center's design optimization testbed (COMETBOARDS) with NASA Langley Research Center's Flight Optimization System (FLOPS). The computing time expended in solving the problem was substantial, and the instability of the FLOPS analyzer at certain design points caused difficulties. In an attempt to alleviate both of these limitations, we explored the use of two approximation concepts in the design optimization process. The two concepts, which are based on neural network and linear regression approximation, provide the reanalysis capability and design sensitivity analysis information required for the optimization process. The HSCT aircraft optimization problem was solved by using three alternate approaches; that is, the original FLOPS analyzer and two approximate (derived) analyzers. The approximate analyzers were calibrated and used in three different ranges of the design variables; narrow (interpolated), standard, and wide (extrapolated).

Hopkins, Dale A.↗
NASA NTRS2005

Interannual Variability of Tropical Ocean Evaporation: A Comparison of Microwave Satellite and Assimilation Results

Remote sensing methodologies for turbulent heat fluxes over oceans depend on driving bulk formulations of fluxes with measured surface winds and estimated near surface thermodynamics from microwave sensors of the Special Sensor Microwave Imager (SSM/I) heritage. We will review recent work with a number of SSM/I-based algorithms and investigate the ability of current data sets to document global, tropical ocean-averaged evaporation changes in association with El Nino and La Nina SST changes. We show that in addition to interannual signals, latent heat flux increases over the period since late 1987 range from approx. .1 to .6 mm/ day are present; these represent trends 2 to 3 times larger than the NCEP Reanalysis. Since atmospheric storage cannot account for the difference, and since compensating evapotranspiration changes over land are highly unlikely to be this large, these evaporation estimates cannot be reconciled with ocean precipitation records such as those produced by the Global Precipitation Climatology Project, GPCP. The reasons for the disagreement include less than adequate intercalibration between SSM/I sensors providing winds and water vapor for driving the algorithms, biases due to the assumption that column integrated water vapor mirrors near surface water vapor variations, and other factors as well. The reanalyses have their own problems with spin-up during assimilation, lack of constraining input data at the ocean surface, and amplitude of synoptic transients.

Robertson, Franklin R.↗