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NASA NTRS2022

File Specification for MERRA-2 Climate Statistics Products

The Modern Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) contains a wealth of information that can be used for weather and climate studies. By combining the assimilation of observations with a frozen version of the Goddard Earth Observing System (GEOS), a global analysis is produced at an hourly temporal resolution spanning from January 1980 through present (Gelaro et al., 2017). It can be difficult to parse through a multidecadal dataset such as MERRA-2 to evaluate the interannual variability of weather that occurs on a daily timescale, let alone determine the occurrence of an extreme weather event. Furthermore, it was recognized that standard metrics were needed to evaluate climate change among climate models and international research efforts. As a result of these concerns, the Expert Team on Climate Change Detection and Indices (ETCCDI) developed a set of indices that represent the frequency and intensity of extreme weather events using a daily time series of 2-m air temperature (T2m) and precipitation (Alexander et al., 2016). These indices were used as a basis to comprise a list of fields that represent daily extreme temperature and precipitation events, heatwaves, multi-day precipitation, as well monthly percentile statistics from the MERRA-2 dataset. Also included in this data product is a climatological long term mean and standard deviation representing the interannual variability on a monthly timescale.

MERRA-2↗
NASA NTRS1997

Applications of Data Assimilation to Analysis of the Ocean on Large Scales

It is commonplace to begin talks on this topic by noting that oceanographic data are too scarce and sparse to provide complete initial and boundary conditions for large-scale ocean models. Even considering the availability of remotely-sensed data such as radar altimetry from the TOPEX and ERS-1 satellites, a glance at a map of available subsurface data should convince most observers that this is still the case. Data are still too sparse for comprehensive treatment of interannual to interdecadal climate change through the use of models, since the new data sets have not been around for very long. In view of the dearth of data, we must note that the overall picture is changing rapidly. Recently, there have been a number of large scale ocean analysis and prediction efforts, some of which now run on an operational or at least quasi-operational basis, most notably the model based analyses of the tropical oceans. These programs are modeled on numerical weather prediction. Aside from the success of the global tide models, assimilation of data in the tropics, in support of prediction and analysis of seasonal to interannual climate change, is probably the area of large scale ocean modeling and data assimilation in which the most progress has been made. Climate change is a problem which is particularly suited to advanced data assimilation methods. Linear models are useful, and the linear theory can be exploited. For the most part, the data are sufficiently sparse that implementation of advanced methods is worthwhile. As an example of a large scale data assimilation experiment with a recent extensive data set, we present results of a tropical ocean experiment in which the Kalman filter was used to assimilate three years of altimetric data from Geosat into a coarsely resolved linearized long wave shallow water model. Since nonlinear processes dominate the local dynamic signal outside the tropics, subsurface dynamical quantities cannot be reliably inferred from surface height anomalies. Because of its potential for large scale synoptic coverage of the deep ocean, acoustic travel time data should be a natural complement to satellite altimetry. Satellite data give us vertical integrals associated with thermodynamic and dynamic processes.

Miller, Robert N.↗
NASA NTRS1982

Some statistical performance characteristics of the 'ITD' modal identification algorithm

Performance characteristics of the Ibrahim time-domain algorithms are examined on a statistical basis. The method uses multiple free-response measurements from a test structure directly in the time domain, and displays varying accuracy, with the strongly excited modes identified most accurately and the weakly excited modes least accurately. Sets of computer-generated free-response functions for a simple 1-mode model are used to study the identification performance for several basic changes in the modal characteristics of the data, the user-selectable analysis constants, and the level of superimposed noise. Results indicate the existence of a direct and often linear effect of noise on the scatter of identified parameters, and good identification is maintained at the 1% noise level down to the point in frequency when only 1/4-cycle of data is analyzed.

Pappa, R. S.↗
NASA NTRS1993

Marslink

The Marslink Project focuses on the development, dissemination, and evaluation of instructional materials about the composition, structure, and dynamics of the Martian atmosphere, surface, and interior. A multi-year effort is underway so that middle and high school students can follow a full Martian year of seasonal changes using data from NASA's Mars Observer spacecraft, and the Mars Observer Project has time to process and release the appropriate data sets. Monthly activity packets for students, teacher enhancement sessions, a teacher resource center, an on-call Mars data specialist, daily SPACELINK electronic bulletin board updates, and semi-annual NASA Select TV broadcasts will constitute the basis of the Marslink Project. Various aspects of the Marslink Project are briefly discussed.

Arvidson, R. E.↗
NASA NTRS1998

First results from the aerosol lidar and backscatter sonde intercomparison campaign STRAIT'1997 at table mountain facility during February-March 1997

First results of an intercomparison measurement campaign between three aerosol lidar instruments and in-situ backscatter sondes performed at Table Mountain Facility (34.4 deg N, 117.7 deg E, 2280 m asl) in February-March 1997 are presented. During the campaign a total of 414 hours of lidar data were acquired by the Aerosol-Temperature-Lidar (ATL, Goddard Space Flight Center) the Mobile-aerosol-Raman-Lidar (MARL, Alfred Wegener Institute), and the TMF-Aerosol-Lidar (TAL, Jet Propulsion Laboratory), and four backscatter sondes were launched. From the data set altitude profiles of backscatter ratio and volume depolarization of stratospheric background aerosols at altitudes between 15 and 25 km and optically thin high-altitude cirrus clouds at altitudes below 13 km are derived. On the basis of a sulfuric acid aerosol model color ratio profiles obtained from two wavelength lidar data are compared to the corresponding profiles derived from the sonde observations. We find an excellent agreement between the in-situ and ATL lidar data with respect to backscatter and color ratio. Cirrus clouds were present on 16 of 26 nights during the campaign. Lidar observations with 17 minute temporal and 120-300 m spatial resolution indicate high spatial and temporal variability of the cirrus layers. Qualitative agreement is found between concurrent lidar measurements of backscatter ratio and volume depolarization.

Beyerle, G.↗
NASA NTRS2004

Real-Time 12-Lead High-Frequency QRS Electrocardiography for Enhanced Detection of Myocardial Ischemia and Coronary Artery Disease

Several studies have shown that diminution of the high-frequency (HF; 150-250 Hz) components present within the central portion of the QRS complex of an electrocardiogram (ECG) is a more sensitive indicator for the presence of myocardial ischemia than are changes in the ST segments of the conventional low-frequency ECG. However, until now, no device has been capable of displaying, in real time on a beat-to-beat basis, changes in these HF QRS ECG components in a continuously monitored patient. Although several software programs have been designed to acquire the HF components over the entire QRS interval, such programs have involved laborious off-line calculations and postprocessing, limiting their clinical utility. We describe a personal computer-based ECG software program developed recently at the National Aeronautics and Space Administration (NASA) that acquires, analyzes, and displays HF QRS components in each of the 12 conventional ECG leads in real time. The system also updates these signals and their related derived parameters in real time on a beat-to-beat basis for any chosen monitoring period and simultaneously displays the diagnostic information from the conventional (low-frequency) 12-lead ECG. The real-time NASA HF QRS ECG software is being evaluated currently in multiple clinical settings in North America. We describe its potential usefulness in the diagnosis of myocardial ischemia and coronary artery disease.

Software↗
NASA NTRS2009

On-Orbit Operation and Performance of MODIS Blackbody

MODIS collects data in 36 spectral bands, including 20 reflective solar bands (RSB) and 16 thermal emissive bands (TES). The TEB on-orbit calibration is performed on a scan-by-scan basis using a quadratic algorithm that relates the detector response with the calibration radiance from the sensor on-board blackbody (BB). The calibration radiance is accurately determined each scan from the BB temperature measured using a set of 12 thermistors. The BB thermistors were calibrated pre-launch with traceability to the NIST temperature standard. Unlike many heritage sensors, the MODIS BB can be operated at a constant temperature or with the temperature continuously varying between instrument ambient (about 270K) and 315K. In this paper, we provide an overview of both Terra and Aqua MODIS on-board BB operations, functions, and on-orbit performance. We also examine the impact of key calibration parameters, such as BB emissivity and temperature (stability and gradient) determined from its thermistors, on the TEB calibration and Level I (LIB) data product uncertainty.

Xiong, X.↗
NASA NTRS2003

Software Helps Retrieve Information Relevant to the User

The Adaptive Indexing and Retrieval Agent (ARNIE) is a code library, designed to be used by an application program, that assists human users in retrieving desired information in a hypertext setting. Using ARNIE, the program implements a computational model for interactively learning what information each human user considers relevant in context. The model, called a "relevance network," incrementally adapts retrieved information to users individual profiles on the basis of feedback from the users regarding specific queries. The model also generalizes such knowledge for subsequent derivation of relevant references for similar queries and profiles, thereby, assisting users in filtering information by relevance. ARNIE thus enables users to categorize and share information of interest in various contexts. ARNIE encodes the relevance and structure of information in a neural network dynamically configured with a genetic algorithm. ARNIE maintains an internal database, wherein it saves associations, and from which it returns associated items in response to a query. A C++ compiler for a platform on which ARNIE will be utilized is necessary for creating the ARNIE library but is not necessary for the execution of the software.

Mathe, Natalie↗
NASA NTRS2017

Status and Plans for Finalization of SRT's Contribution to AIRS Version-7 and Version-7 AO

Version-6.46 temperature profiles, water vapor profiles, and especially total O3, are very much compared to Version-6. With minor tweaking, Version-6.46 is a good candidate for use in Version-7. JPL Version-6.4.6 and Version-6.4.6 AO monthly mean products agree extremely well with each other. Version-6.4.6 AO is accurate enough that there is not necessarily a need to process both Version-7 and Version-7 AO data sets. Single day comparisons show Version-6.46 CrIS/ATMS and Version-6.46 AIRS/AMSU products agree extremely well with each other. We need to demonstrate agreement of Version-6.46 CrIS/ATMS and Version-6.46 AO products on a monthly mean basis for different months and years. CrIS/ATMS and AIRS/AMSU monthly mean comparisons showed excellent agreement using a previous version.

CrIS/ATMS↗
NASA NTRS2020

Neural Network Repair of Lossy Compression Artifacts in the Sept 2015 – March 2016 Duration of the MMS/FPI Dataset

During the Sept 2015 –March 2016 duration (sometimes referred to as Phase 1A) of the Magnetospheric Multiscale Mission (MMS), the Dual Electron Spectrometers (DES) were configured to generously utilize lossy compression. While this maximized the number of velocity distribution functions downlinked, it cameat the expense of lost information content for a fractionof the frames. Following this period of lossy compression, the DES was re-configured in a way that allowed for 95% of the framesto arrive to the ground without loss. Using this high-quality set offrameson-orbit observations, we compressed and decompressed the frameson the ground to create a side-by-side record of the compression effect. This record was used to drive an optimization method that (a) derived basis functions capable of approximating the lossless sample space and with non-negative coefficients and (b) fitted a function which maps the lossy framesto basis weights that recreate the framewithout compression artifacts. This methodis introduced and evaluated in this paper.Data users should expect a higher level of confidence in the absolute scale of density/temperature measurements andnotice less sinusoidal bias in the velocity X and Y components(GSE).

Magnetosphere, Neural Networks, Image Processing, ↗
NASA NTRS1972

UK-5 Van Allen belt radiation exposure: A special study to determine the trapped particle intensities on the UK-5 satellite with spatial mapping of the ambient flux environment

Vehicle encountered electron and proton fluxes were calculated for a set of nominal UK-5 trajectories with new computational methods and new electron environment models. Temporal variations in the electron data were considered and partially accounted for. Field strength calculations were performed with an extrapolated model on the basis of linear secular variation predictions. Tabular maps for selected electron and proton energies were constructed as functions of latitude and longitude for specified altitudes. Orbital flux integration results are presented in graphical and tabular form; they are analyzed, explained, and discussed.

Stassinopoulos, E. G.↗
NASA NTRS1974

Transmitter efficiency considerations in MAPSK signal selection

A simple model of the efficiency-power relationship for a microwave transmitter permits comparison of M-ary amplitude and phase shift keyed (MAPSK) signal array performance on the basis of average DC power in, rather than average RF signal power out. This is of interest in comparing MAPSK arrays with comparable polyphase, since the polyphase transmitter is operated at a single power level, while MAPSK varies over a range of power levels, each of differing efficiency. A constant efficiency-power curve permits comparison of signal arrays in terms of array average power, while a linear curve requires comparison on the basis of array peak power. Since typical efficiency curves will lie between these extremes, the array peak and average power levels provide bounds on array requirements for average DC input power. Examination of the performance of several MAPSK sets reveals a distinct power advantage of quadrature amplitude shift keying (QASK) over most viable signal sets.

Smith, J. G.↗
NASA NTRS1980

First Scientific Working Group Meeting of Airborne Doppler Lidar Wind Velocity Measurement Program

The purpose of the first scientific working group meeting was fourfold: (1) to identify flight test options for engineering verification of the MSFC Doppler Lidar; (2) to identify flight test options for gathering data for scientific/technology applications; (3) to identify additional support equipment needed on the CV 990 aircraft for the flight tests; and (4) to identify postflight data processing and data sets requirements. The working group identified approximately ten flight options for gathering data on atmospheric dynamics processes, including turbulence, valley breezes, and thunderstorm cloud anvil and cold air outflow dynamics. These test options will be used as a basis for planning the fiscal year 1981 tests of the Doppler Lidar system.

Kaufman, J. W.↗
NASA NTRS1987

Near Identifiability of Dynamical Systems

Concepts regarding approximate mathematical models treated rigorously. Paper presents new results in analysis of structural identifiability, equivalence, and near equivalence between mathematical models and physical processes they represent. Helps establish rigorous mathematical basis for concepts related to structural identifiability and equivalence revealing fundamental requirements, tacit assumptions, and sources of error. "Structural identifiability," as used by workers in this field, loosely translates as meaning ability to specify unique mathematical model and set of model parameters that accurately predict behavior of corresponding physical system.

Hadaegh, F. Y.↗
NASA NTRS1989

Impact cratering in low-gravity environments - Results of reconnaissance experimentation on the NASA KC-135A reduced-gravity aircraft

A program of flight experimentation was performed on the NASA KC-135A reduced-gravity aircraft to evaluate the potential for conducting impact experiments in reduced-gravity environments and to collect impact-cratering data at gravity levels below 1 g. Lead pellets were launched into coarse-grained sand at velocities of about 65-130 m/sec while the gravitational acceleration was maintained at 0.59-0.05 g. A total of 64 craters were studied and, after allowance is made for the atmospheric pressure over the target (0.83 atm), their diameters are found to have been consistent with scaling predictions made on the basis of ground-based experimentation. Formation times were also obtained for 33 of these craters and constitute a distribution that is somewhat different from that described by the ground-based data. Nevertheless, the KC-135 data set as a whole falls on the trend formed by the ground-based results. The overall agreement between the two data sets attests to the stability of the aircraft as a platform for impact experimentation.

Cintala, M. J.↗
NASA NTRS1989

Asteroid lightcurve observations from 1979-1981

An account is given of the results of photometric light curve observations in the V band for asteroids, yielding estimates of the mean and maximum reduced magnitudes for each object. On the basis of fits of the H-G magnitude relation for 33 objects, the mean values of the slope parameter are examined for different taxonomic classes; these values are then applied to the analysis of less complete data sets. While in the case of the moderate albedo S and M class asteroids the H-G relation appears to fit the available data, the relation for dark asteroids appears to predict more of an opposition than is characteristically present.

Harris, A. W.↗
NASA NTRS2002

General Aviation Pilots' Perceived Usage and Valuation of Aviation Weather Information Sources

Aviation suffers many accidents due to the lack of good weather information in flight. Existing aviation weather information is difficult to obtain when it is most needed and is not well formatted for in-flight use. Because it is generally presented aurally, aviation weather information is difficult to integrate with spatial flight information and retain for reference. Efforts, by NASA's Aviation Weather Information (AWIN) team and others, to improve weather information accessibility, usability and decision aiding will enhance General Aviation (GA) pilots' weather situation awareness and decision-making and therefore should improve the safety of GA flight. Consideration of pilots' economic concerns will ensure that in-flight weather information systems are financially accessible to GA pilots as well. The purpose of this survey was to describe how aviation operator communities gather and use weather information as well as how weather related decisions are made between flight crews and supporting personnel. Pilots of small GA aircraft experience the most weather-related accidents as well as the most fatal weather related accident. For this reason, the survey design and advertisement focused on encouraging participation from GA pilots. Perhaps as a result of this emphasis, most responses, 97 responses or 85% of the entire response set, were from GA pilots, This paper presents only analysis of these GA pilots' responses. The insights provided by this survey regarding GA pilots' perceived value and usage of current aviation weather information. services, and products provide a basis for technological approaches to improve GA safety. Results of this survey are discussed in the context of survey limitations and prior work, and serve as the foundation for a model of weather information value, guidance for the design of in-flight weather information systems, and definition of further research toward their development.

Latorella, Kara↗
NASA NTRS2005

Solution Concepts for Distributed Decision-Making without Coordination

Consider a single-stage problem in which we have a group N agents who are attempting to minimize the expected cost of their joint actions, without the benefit of communication or a pre-established protocol but with complete knowledge of the expected cost of any joint set of actions for the group. We call this situation a static coordination problem. The central issue in defining an appropriate solution concept for static coordination problems is considering how to deal with the fact that if the agents axe faced with a set of multiple (mixed) strategies that are equally attractive in terms of cost, a failure of coordination may lead to an expected cost value that is worse than that of any of the strategies in the set. In this proposal, we describe the notion of a general coordination problem, describe initial efforts at developing a solution concept for static coordination problems, and then outline a research agenda that centers on activities that will be basis for obtaining a complete understanding of solutions to static coordination problems.

Beling, Peter A.↗