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At least 217 records · Page 12

A comparison of observed and simulated properties of sudden stratospheric warmings

Review of observational data and dynamical numerical simulations of stratospheric warmings. Classes of warmings, major and minor (major if poleward movement of planetary-scale thermal systems entails reversal of polar circulation at 10 mb or below), trajectories of warm cells, vertical and horizontal scale of warm-air systems, the time-scale of warming, initial zonal flow conditions prior to a warming, circulation reversals, and details of the energy budget before and after a warming are discussed. The 1963 and 1973 types of warmings are contrasted: the strong baroclinic conversion of eddy potential to eddy kinetic energy was not repeated in the latter, but both events were preceded by very large fluxes from the troposphere. Numerical model simulations by various authors are compared and evaluated.

Quiroz, R. S.↗

SIDS-toADF File Mapping Manual

The "CFD General Notation System" (CGNS) consists of a collection of conventions, and conforming software, for the storage and retrieval of Computational Fluid Dynamics (CFD) data. It facilitates the exchange of data between sites and applications, and helps stabilize the archiving of aerodynamic data. This effort was initiated in order to streamline the procedures in exchanging data and software between NASA and its customers, but the goal is to develop CGNS into a National Standard for the exchange of aerodynamic data. The CGNS development team is comprised of members from Boeing Commercial Airplane Group, NASA-Ames, NASA-Langley, NASA-Lewis, McDonnell-Douglas Corporation (now Boeing-St. Louis), Air Force-Wright Lab., and ICEM-CFD Engineering. The elements of CGNS address all activities associated with the storage of data on external media and its movement to and from application programs. These elements include: 1) The Advanced Data Format (ADF) Database manager, consisting of both a file format specification and its I/O software, which handles the actual reading and writing of data from and to external storage media; 2) The Standard Interface Data Structures (SIDS), which specify the intellectual content of CFD data and the conventions governing naming and terminology; 3) The SIDS-to-ADF File Mapping conventions, which specify the exact location where the CFD data defined by the SIDS is to be stored within the ADF file(s); and 4) The CGNS Mid-level Library, which provides CFD-knowledgeable routines suitable for direct installation into application codes. The SIDS-toADF File Mapping Manual specifies the exact manner in which, under CGNS conventions, CFD data structures (the SIDS) are to be stored in (i.e., mapped onto) the file structure provided by the database manager (ADF). The result is a conforming CGNS database. Adherence to the mapping conventions guarantees uniform meaning and location of CFD data within ADF files, and thereby allows the construction of universal software to read and write the data.

McCarthy, Douglas↗

Advanced Data Format (ADF) Software Library and Users Guide

The "CFD General Notation System" (CGNS) consists of a collection of conventions, and conforming software, for the storage and retrieval of Computational Fluid Dynamics (CFD) data. It facilitates the exchange of data between sites and applications, and helps stabilize the archiving of aerodynamic data. This effort was initiated in order to streamline the procedures in exchanging data and software between NASA and its customers, but the goal is to develop CGNS into a National Standard for the exchange of aerodynamic data. The CGNS development team is comprised of members from Boeing Commercial. Airplane Group, NASA-Ames, NASA-Langley, NASA-Lewis, McDonnell-Douglas Corporation (now Boeing-St. Louis), Air Force-Wright Lab., and ICEM-CFD Engineering. The elements of CGNS address all activities associated with the storage of data on external media and its movement to and from application programs. These elements include: 1) The Advanced Data Format (ADF) Database manager, consisting of both a file format specification and its 1/0 software, which handles the actual reading and writing of data from and to external storage media; 2) The Standard Interface Data Structures (SIDS), which specify the intellectual content of CFD data and the conventions governing naming and terminology; 3) The SIDS-to-ADF File Mapping conventions, which specify the exact location where the CFD data defined by the SIDS is to be stored within the ADF file(s); and 4) The CGNS Mid-level Library, which provides CFD-knowledgeable routines suitable for direct installation into application codes. The ADF is a generic database manager with minimal intrinsic capability. It was written for the purpose of storing large numerical datasets in an efficient, platform independent manner. To be effective, it must be used in conjunction with external agreements on how the data will be organized within the ADF database such defined by the SIDS. There are currently 34 user callable functions that comprise the ADF Core library and are described in the Users Guide. The library is written in C, but each function has a FORTRAN counterpart.

Smith, Matthew↗

CGNS Mid-Level Software Library and Users Guide

The "CFD General Notation System" (CGNS) consists of a collection of conventions, and conforming software, for the storage and retrieval of Computational Fluid Dynamics (CFD) data. It facilitates the exchange of data between sites and applications, and helps stabilize the archiving of aerodynamic data. This effort was initiated in order to streamline the procedures in exchanging data and software between NASA and its customers, but the goal is to develop CGNS into a National Standard for the exchange of aerodynamic data. The CGNS development team is comprised of members from Boeing Commercial Airplane Group, NASA-Ames, NASA-Langley, NASA-Lewis, McDonnell-Douglas Corporation (now Boeing-St. Louis), Air Force-Wright Lab., and ICEM-CFD Engineering. The elements of CGNS address all activities associated with the storage of data on external media and its movement to and from application programs. These elements include: - The Advanced Data Format (ADF) Database manager, consisting of both a file format specification and its I/O software, which handles the actual reading and writing of data from and to external storage media; - The Standard Interface Data Structures (SIDS), which specify the intellectual content of CFD data and the conventions governing naming and terminology; - The SIDS-to-ADF File Mapping conventions, which specify the exact location where the CFD data defined by the SIDS is to be stored within the ADF file(s); and - The CGNS Mid-level Library, which provides CFD-knowledgeable routines suitable for direct installation into application codes. The CGNS Mid-level Library was designed to ease the implementation of CGNS by providing developers with a collection of handy I/O functions. Since knowledge of the ADF core is not required to use this library, it will greatly facilitate the task of interfacing with CGNS. There are currently 48 user callable functions that comprise the Mid-level library and are described in the Users Guide. The library is written in C, but each function has a FORTRAN counterpart.

Poirier, Diane↗

Small Aircraft Transportation System Simulation Analysis of the HVO and ERO Concepts

It is acknowledged that the aviation and aerospace industries are primary forces influencing the industrial development and economic well being of the United States and many countries around the world. For decades the US national air transportation system has been the model of success - safely and efficiently moving people, cargo, goods and services and generating countless benefits throughout the global community; however, the finite nature of the system and many of its components is becoming apparent. Without measurable increases in the capacity of the national air transportation system, delays and service delivery failures will eventually become intolerable. Although the recent economic slowdown has lowered immediate travel demands, that trend is reversing and cargo movement remains high. Research data indicates a conservative 2.5-3.0% annual increase in aircraft operations nationwide through 2017. Such growth will place additional strains upon a system already experiencing capacity constraints. The stakeholders of the system will continue to endure ever-increasing delays and abide lesser levels of service to many lower population density areas of the country unless more efficient uses of existing and new transportation resources are implemented. NASA s Small Aircraft Transportation System program (SATS) is one of several technologies under development that are aimed at using such resources more effectively. As part of this development effort, this report is the first in a series outlining the findings and recommendations resulting from a comprehensive program of multi-level analyses and system engineering efforts undertaken by NASA Langley Research Center s Systems Analysis Branch (SAB). These efforts are guided by a commitment to provide systems-level analysis support for the SATS program. Subsequent efforts will build upon this early work to produce additional analyses and benefits studies needed to provide the technical and economic basis for national investment and policy decisions related to further development and potential deployment of a small aircraft transportation system. This report primarily serves two purposes. First, it presents results attained from an initial evaluation and analysis of the Higher Volume Operations (HVO) and EnRoute Operations (ERO) concepts - both designated operational capabilities within the SATS Program s Concept of Operations (CONOPS) document. It further outlines areas of the concepts that would benefit from follow-on analyses and system engineering efforts. It is intended that these processes will aid continued maturation of the concepts and promote additional studies of their effects and influences in combination with other designated CONOPS currently under development. In essence, it establishes a baseline of data upon which subsequent analyses and studies can be built and identifies performance characteristics the concept must exhibit in order to provide, at minimum, levels of safety and usage equal to or better than the current system.

Millsaps, Gary D.↗

Reduction of Weather-Related Terminal Area Delays in the Free-Flight Era

While much of the emphasis of the free-flight movement has been concentrated on reducing en-route delays, airport capacity is a major bottleneck in the current airspace system, particularly during bad weather. According to the Air Transport Association (ATA) Air Carrier Delay Reports, ground delays (gate-hold, taxi-in, and taxi-out) comprise 75 percent of total delays. It is likely that the projected steady growth in traffic will only exacerbate these losses. Preliminary analyses show that implementation of the terminal area technologies and procedures under development in NASA s Terminal Area Productivity program can potentially save the airlines at least $350M annually in weather-related delays by the year 2005 at Boston Logan and Detroit airports alone. This paper briefly describes the Terminal Area Productivity program, outlines the costhenefit analyses that are being conducted in support of the program, and presents some preliminary analysis results.

Johnson, Sally C.↗

Creating Interactive Graphical Overlays in the Advanced Weather Interactive Processing System Using Shapefiles and DGM Files

Graphical overlays can be created in real-time in the Advanced Weather Interactive Processing System (AWIPS) using shapefiles or Denver AWIPS Risk Reduction and Requirements Evaluation (DARE) Graphics Metafile (DGM) files. This presentation describes how to create graphical overlays on-the-fly for AWIPS, by using two examples of AWIPS applications that were created by the Applied Meteorology Unit (AMU) located at Cape Canaveral Air Force Station (CCAFS), Florida. The first example is the Anvil Threat Corridor Forecast Tool, which produces a shapefile that depicts a graphical threat corridor of the forecast movement of thunderstorm anvil clouds, based on the observed or forecast upper-level winds. This tool is used by the Spaceflight Meteorology Group (SMG) at Johnson Space Center, Texas and 45th Weather Squadron (45 WS) at CCAFS to analyze the threat of natural or space vehicle-triggered lightning over a location. The second example is a launch and landing trajectory tool that produces a DGM file that plots the ground track of space vehicles during launch or landing. The trajectory tool can be used by SMG and the 45 WS forecasters to analyze weather radar imagery along a launch or landing trajectory. The presentation will list the advantages and disadvantages of both file types for creating interactive graphical overlays in future AWIPS applications. Shapefiles are a popular format used extensively in Geographical Information Systems. They are usually used in AWIPS to depict static map backgrounds. A shapefile stores the geometry and attribute information of spatial features in a dataset (ESRI 1998). Shapefiles can contain point, line, and polygon features. Each shapefile contains a main file, index file, and a dBASE table. The main file contains a record for each spatial feature, which describes the feature with a list of its vertices. The index file contains the offset of each record from the beginning of the main file. The dBASE table contains records for each attribute. Attributes are commonly used to label spatial features. Shapefiles can be viewed, but not created in AWIPS. As a result, either third-party software can be installed on an AWIPS workstation, or new software must be written to create shapefiles in the correct format.

Barrett, Joe H., III↗

Survey of Quantitative Research Metrics to Assess Pilot Performance in Upset Recovery

Accidents attributable to in-flight loss of control are the primary cause for fatal commercial jet accidents worldwide. The National Aeronautics and Space Administration (NASA) conducted a literature review to determine and identify the quantitative standards for assessing upset recovery performance. This review contains current recovery procedures for both military and commercial aviation and includes the metrics researchers use to assess aircraft recovery performance. Metrics include time to first input, recognition time and recovery time and whether that input was correct or incorrect. Other metrics included are: the state of the autopilot and autothrottle, control wheel/sidestick movement resulting in pitch and roll, and inputs to the throttle and rudder. In addition, airplane state measures, such as roll reversals, altitude loss/gain, maximum vertical speed, maximum/minimum air speed, maximum bank angle and maximum g loading are reviewed as well.

Le Vie, Lisa R.↗

Progress on the Development of Future Airport Surface Wireless Communications Network

Continuing advances in airport surface management and improvements in airport surface safety are required to enable future growth in air traffic throughout the airspace, as airport arrival and departure delays create a major system bottleneck. These airport management and safety advances will be built upon improved communications, navigation, surveillance, and weather sensing, creating an information environment supporting system automation. The efficient movement of the digital data generated from these systems requires an underlying communications network infrastructure to connect data sources with the intended users with the required quality of service. Current airport surface communications consists primarily of buried copper or fiber cable. Safety related communications with mobile airport surface assets occurs over 25 kHz VHF voice and data channels. The available VHF spectrum, already congested in many areas, will be insufficient to support future data traffic requirements. Therefore, a broadband wireless airport surface communications network is considered a requirement for the future airport component of the air transportation system. Progress has been made on defining the technology and frequency spectrum for the airport surface wireless communications network. The development of a test and demonstration facility and the definition of required testing and standards development are now underway. This paper will review the progress and planned future work.

Kerczewski, Robert J.↗

Comparison of Different Control Schemes for Strategic Departure Metering

Airports and their terminal airspaces are key choke points in the air transportation system causing major delays and adding to pollution. A solution aimed at mitigating these chokepoints integrates the scheduling of runway operations, flight release from the gates and ramp into the airport movement area, and merging with other traffic competing for downstream airspace points. Within this integrated concept, we present a simulation-based analysis of the departure metering process, which delays the release of flights into the airport movement area while balancing two competing objectives: (1) maintaining large enough queues at the airport resources to maximize throughput and (2) absorbing excess delays at the gates or in ramp areas to save on fuel consumption, emissions, noise, and passenger discomfort. Three metering strategies are compared which respectively attempt to control the number of flights that (1) left the gate but did not take off, (2) left the ramp but did not take off, and (3) spent their unimpeded transit time to the runway but did not take off. It was observed that under deterministic and demand uncertainty conditions, the first strategy performed better than the other two strategies in terms of maintaining the runway throughput while transferring a significant average delay of two minutes to the gate. On the other hand, under uncertainties of flight transit time and runway service rate, all the strategies struggled to delay flights at the gate without a significant impact on the runway throughput.

air traffic management↗

Change of 180 degrees in the direction of a uniform current of air

In the construction of aerodynamic tunnels, it is a very important matter to obtain a uniform current of air in the sections where measurements are to be made. The straight type ordinarily used for attaining a uniform current and generally recommended for use, has great defects. If we desire to avoid these defects, it is well to give the canals of the tunnel such a form that the current, after the change of direction of its asymptotes, approximates a uniform and rectilinear movement. But for this, the condition must be met that at no place does the flow exceed the maximum velocity assumed, equal to the velocity in the straight parts of the canal.

WIND TUNNELS - AIR FLOW↗

Reformulation of dicamba herbicide: Impacts on offsite transport and soybean damage

Abstract The herbicide dicamba (3,6‐dichloro‐2‐methoxybenzoic acid) is commonly used to control broadleaf weeds in soybeans. Dicamba, however, is susceptible to volatilization and drift, thereby causing significant plant damage to nontarget crops downwind. Dicamba was reformulated to reduce volatility and off‐target movement. The effectiveness of the dicamba reformulation was assessed by quantifying dicamba emissions following spray application and investigated how meteorological factors influenced the off‐target movement. The experiments were conducted at the University of Minnesota Agricultural Experiment Station (UMORE Park) during the growing season of 2018, 2019, 2021, and 2022. Multiple high‐flow polyurethane foam air samplers were used to measure dicamba concentrations downwind from a 4‐ha soybean field sprayed with dicamba. Dicamba emissions were estimated using backward Lagrangian modeling constrained by the air sample observations. The results indicate that dicamba emissions and downwind transport were significant for several days following application. Further, non‐traited soybeans located within 15–45 m showed substantial dicamba‐related damage. In warmer, drier seasons, increased dicamba emissions caused more severe damage to downwind soybeans, likely worsened by drought stress preventing recovery. Favorable atmospheric conditions that reduced potential drift can be difficult to achieve in terms of the typical weather experienced over agricultural sites in the Upper Midwest. These results indicate that the dicamba reformulation has not adequately prevented significant post‐spray volatilization losses and downwind transport.

Agriculture↗

Southern ocean sea-ice morphology and kinematics

A pilot satellite experiment is described which would employ shuttle imaging radar (SIR) to determine the applicability of imaging radar for the description of sea ice type and movement. The experimental objectives, design, and anticipated results are discussed. The results are expected to constitute an important contribution to the understanding of the role of sea ice in air-sea interactions in polar regions. It is proposed that shuttle photography, thematic mapper imagery, and SIR data be utilized in this remote sensing project.

Carsey, F.↗

GRACE Follow-On Early In-Flight Challenges

The Gravity Recovery and Climate Experiment (GRACE) Follow-On Mission is a successor to the highly successful GRACE Mission, which operated from 2002-2017. It is a partnership between the National Aeronautics and Space Administration (NASA) and the German Research Center for Geosciences, GeoForschungsZentrum Potsdam (GFZ). Under this partnership, the United States provides the project management, satellites and instruments, Germany provides the launch and mission operations. The partners share responsibilities for producing science data products. GRACE Follow-On, like its predecessor GRACE, consists of twin satellites which fly in a tandem formation at a near polar orbit separated by about 200 km along track. The mission continues the work of GRACE by tracking the movement of water, observing changes in ice sheets and sea level to provide a unique view of Earth’s changing climate. The satellites were launched May 22, 2018 from Vandenberg Air Force Base, in California, on a SpaceX Falcon 9 Rocket. Launch and Early Operations (LEOP) were completed within the first week and on-orbit commissioning proceeded for the next 8 months. The GRACE Follow-On mission is designed to last five years. The mission operations team has had to address several technical challenges early into the planned five-year mission life. The commissioning period was extended by 5 months to successfully address these issues, making it possible for the mission to meet key requirements for delivery and quality of the science data products. This paper will address the challenges faced by GRACE Follow-On and the actions taken by the mission operations team to continue to safely operate the mission.

Witkowski, M.M.↗

Airport Surface Delays and Causes: A Preliminary Analysis

This report summarizes FAA Program Analysis and Operations Research Service (ASD-400)/Lockheed Martin activities and findings related to airport surface delays and causes, in support of NASA Langley Research Center's Terminal Area Productivity (TAP) Program. The activities described in this report were initiated in June 1995. A preliminary report was published on September 30, 1995. The final report incorporates data collection forms filled out by traffic managers, other FAA staff, and an airline for the New York City area, some updates, data previously requested from various sources to support this analysis, and further quantification and documentation than in the preliminary report. This final report is based on data available as of April 12, 1996. This report incorporates data obtained from review and analysis of data bases and literature, discussions/interviews with engineers, air-traffic staff, other FAA technical personnel, and airline staff, site visits, and a survey on surface delays and causes. It includes analysis of delay statistics; preliminary findings and conclusions on surface movement, surface delay sources and causes, runway occupancy time (ROT), and airport characteristics impacting surface operations and delays; and site-specific data on the New York City area airports, which are the focus airports for this report.

Chin, David K.↗

Multiple Hub Network Choice in the Liberalized European Market

A key question that so far has received relatively little attention in the germane literature is that of the changes at various airports as a result of the EU liberalization policies. That is, presently, most major European airports still benefit from the so-called home-carrier phenomenon where the country's publicly or semi-publicly owned carrier uses the country's main airport as its gateway hub and, consequently, the home-carrier is also the principal user of this airport (in terms of proportion of total aircraft movements, number of passengers transported, connections, slots ownership, etc.). The country's main airport has substantially benefited from these monopoly conditions of airline captivity, strongly determined by the bilateral system of international air transport regulation. Therefore, European major airports were used to operate in essentially different markets, compared to the increasingly competitive markets of their home based carriers. This partly explains relative stability of transport volumes and financial results of European major airports compared to the relatively volatile financial results of most European national airlines. However, the liberalization of European aviation is likely to change this situation. Market access is open now to all community carriers, i.e. carriers with majority ownership and effective control in the hands of EU citizens. Ticket prices are free, governments can only intervene in case of dumping or excessive pricing. A community airline can choose its seat in any of the 15 member states. Licensing procedures are harmonized between member states. In the last few months community carriers have had unrestricted route access within the EU. Most probably this development will be extended to countries inside and outside Europe. Last year the European Commission got the mandate to start negotiations with 10 other European countries. In the meantime the EC has also started negotiations with the USA on so-called soft rights. In the meantime, open skies agreements have been concluded between the USA and most of the EU member states to facilitate strategic alliances between airlines of the states involved. As a result of this on-going liberalization the model of the single 'national' carrier using the national home base as its single hub for the designated third, fourth and sixth freedom operations will stepwise disappear. Within the EU the concept of the national carrier has already been replaced by that of the community carrier. State ownership in more and more European carriers is reduced. On the longer run mergers or even bankruptcy will further undermine the "single national carrier - single national hub" model in Europe. In the meantime, strategic alliances between national carriers in Europe will already reduce the airlines' loyalty to a single airport. Profit maximization and accountability to share holders will supersede the loyalty of these newly emerging alliances, probably looking for the opportunities of a multiple hub network to adequately cover the whole European market. As a consequence, some European airports might see a substantial decline in arriving, departing and transfer traffic, thus in revenues and financial solvency, as well as in their connection to other inter-continental and intra-European destinations. At the same time, other airports might realize a significant increase in traffic as they will be sought after by the profit maximizing airlines as their major gateway hubs. Which will be the losing airports and which will be the winning ones? Can airports anticipate the actions of airlines in deregulated markets and utilize policies which will improve their relative position? If so, what should be these anticipatory policies? These questions become the more urgent, since an increasing number of major European airports will be privatized in the near future. Although increasing airport congestion in Europe will also be reflected in a growing demand pressure for airport slots, this is not a guarantee for a stable transport volume growth of individual airports. The more volatile the market is, the more vulnerable privatized airports become. Therefore, the main issue of this study is the analysis of the opportunities of major European airports to become a central hub as a result of the network choices made by the new European airlines in a completely liberalized market. In a previous study (Berechman and de Wit, 1996), we already explored the potential of Amsterdam Airport Schiphol of becoming the major West-European hub, once European aviation markets are deregulated. A major hindrance of that study was the use of a single hub-and-spoke network. For example that model could not analyze the viability of different combinations of European hubs within a multiple hub network of alternative airline alliances. In this study, we have formulated the model of a multi-hub network where two West-European airports are used for inter-continental and intra-European travel to enable a more realistic analysis of hub choice. Like the previous one also this multi-hub model is primarily used to assess the potential ability of Amsterdam Airport Schiphol for becoming a major West-European hub. Thus, in particular, the policy tests focus on this airport in a double hub network.

Berechman, Joseph↗

Aft-End Flow of a Large-Scale Lifting Body During Free-Flight Tests

Free-flight tests of a large-scale lifting-body configuration, the X-38 aircraft, were conducted using tufts to characterize the flow on the aft end, specifically in the inboard region of the vertical fins. Pressure data was collected on the fins and base. Flow direction and movement were correlated with surface pressure and flight condition. The X-38 was conceived to be a rescue vehicle for the International Space Station. The vehicle shape was derived from the U.S. Air Force X-24 lifting body. Free-flight tests of the X-38 configuration were conducted at the NASA Dryden Flight Research Center at Edwards Air Force Base, California from 1997 to 2001.

Banks, Daniel W.↗

Satellite measurements of large-scale air pollution - Measurements of forest fire smoke

The transport, optical properties, total mass, and removal of smoke produced by forest fires in western Canada during late July and early August 1982 are studied using NOAA 7 AVHRR data. Color composite imagery is produced to track the movement of the smoke over Canada and the U.S. as the smoke traveled thousands of km from the source region. Smoke optical thickness, particle size, and single scattering albedo are computed using radiances measured by AVHRR bands 1 and 2. Results show that smoke optical thickness ranged from less that 0.1 to greater than 3.7 and the geometric mean mass radii ranged from 300 to 900 nm. The smoke single scattering albedo ranged from 0.9 to nearly 1.0. The total smoke mass over the eastern U.S. ranged from 0.1 to 0.5 Tg, which is close to the 0.5 Tg estimated from the forest fuel content. The smoke lifetime is estimated to be between 15 and 20 days.

Ferrare, Richard A.↗