Institution
Langley Research Center
Facility•Hampton, Virginia, United States•
About: Langley Research Center is a facility organization based out in Hampton, Virginia, United States. It is known for research contribution in the topics: Mach number & Wind tunnel. The organization has 15945 authors who have published 37602 publications receiving 821623 citations. The organization is also known as: NASA Langley & NASA Langley Research Center.
Topics: Mach number, Wind tunnel, Aerodynamics, Boundary layer, Supersonic speed
Papers published on a yearly basis
Papers
More filters
••
Indian Institute of Tropical Meteorology1, University of Western Ontario2, National Center for Atmospheric Research3, Langley Research Center4, York University5, University of Wuppertal6, Australian Antarctic Division7, Russian Academy of Sciences8, Colorado State University9, Leibniz Association10, National Institute for Space Research11, Stockholm University12
TL;DR: In this article, a review of long-term trends in the temperature of the region from 50 to 100 km is made on the basis of the available datasets and model calculations, and important uncertainly factors are discussed.
Abstract: In recent times it has become increasingly clear that
releases of trace gases from human activity have a potential
for causing change in the upper atmosphere. However,
our knowledge of systematic changes and trends in
the temperature of the mesosphere and lower thermosphere
is relatively limited compared to the Earths lower
atmosphere, and not much effort has been made to synthesize
these results so far. In this article, a comprehensive
review of long-term trends in the temperature of the region
from 50 to 100 km is made on the basis of the available
up-to-date understanding of measurements and model calculations.
An objective evaluation of the available data
sets is attempted, and important uncertainly factors are
discussed. Some natural variability factors, which are
likely to play a role in modulating temperature trends,
are also briefly touched upon. There are a growing number
of experimental results centered on, or consistent with,
zero temperature trend in the mesopause region (80–100
km). The most reliable data sets show no significant trend
but an uncertainty of at least 2 K/decade. On the other
hand, a majority of studies indicate negative trends in
the lower and middle mesosphere with an amplitude of
a few degrees (2–3 K) per decade. In tropical latitudes
the cooling trend increases in the upper mesosphere.
The most recent general circulation models indicate
increased cooling closer to both poles in the middle
mesosphere and a decrease in cooling toward the summer
pole in the upper mesosphere. Quantitatively, the
simulated cooling trend in the middle mesosphere produced
only by CO 2 increase is usually below the observed
level. However, including other greenhouse gases
and taking into account a “thermal shrinking” of the
upper atmosphere result in a cooling of a few degrees
per decade. This is close to the lower limit of the observed
nonzero trends. In the mesopause region, recent
model simulations produce trends, usually below 1 K/decade,
that appear to be consistent with most observations
in this region
264 citations
•
University of Colorado Boulder1, University of Washington2, Goddard Space Flight Center3, Colorado State University4, Langley Research Center5, Environment Canada6, Princeton University7, University of California, San Diego8, Desert Research Institute9, European Centre for Medium-Range Weather Forecasts10, Meteorological Service of Canada11, Ames Research Center12, University of Wisconsin-Madison13
TL;DR: The First ISCCP Regional Experiment (FIRE) Arctic Clouds Experiment was conducted in the Arctic during April through July, 1998 as mentioned in this paper, and the primary goal of the field experiment was to gather the data needed to examine the impact of arctic clouds on the radiation exchange between the surface, atmosphere, and space, and to study how the surface influences the evolution of boundary layer clouds.
Abstract: An overview is given of the First ISCCP Regional Experiment (FIRE) Arctic Clouds Experiment that was conducted in the Arctic during April through July, 1998. The principal goal of the field experiment was to gather the data needed to examine the impact of arctic clouds on the radiation exchange between the surface, atmosphere, and space, and to study how the surface influences the evolution of boundary layer clouds. The observations will be used to evaluate and improve climate model parameterizations of cloud and radiation processes, satellite remote sensing of cloud and surface characteristics, and understanding of cloud-radiation feedbacks in the Arctic. The experiment utilized four research aircraft that flew over surface-based observational sites in the Arctic Ocean and Barrow, Alaska. In this paper we describe the programmatic and science objectives of the project, the experimental design (including research platforms and instrumentation), conditions that were encountered during the field experiment, and some highlights of preliminary observations, modelling, and satellite remote sensing studies.
263 citations
••
TL;DR: The current cloud thermodynamic phase discrimination by Cloud-Aerosol Lidar Pathfinder Satellite Observations (CALIPSO) is based on the depolarization of backscattered light measured by its lidar as discussed by the authors.
Abstract: The current cloud thermodynamic phase discrimination by Cloud-Aerosol Lidar Pathfinder Satellite Observations (CALIPSO) is based on the depolarization of backscattered light measured by its lidar [Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP)]. It assumes that backscattered light from ice crystals is depolarizing, whereas water clouds, being spherical, result in minimal depolarization. However, because of the relationship between the CALIOP field of view (FOV) and the large distance between the satellite and clouds and because of the frequent presence of oriented ice crystals, there is often a weak correlation between measured depolarization and phase, which thereby creates significant uncertainties in the current CALIOP phase retrieval. For water clouds, the CALIOP-measured depolarization can be large because of multiple scattering, whereas horizontally oriented ice particles depolarize only weakly and behave similarly to water clouds. Because of the nonunique depolarization–cloud ph...
263 citations
••
TL;DR: A series of large mesoscale convective systems that occurred during the Brazilian phase of GTE/TRACE A (Transport and Atmospheric Chemistry near the Equator-Atlantic) provided an opportunity to observe deep convective transport of trace gases from biomass burning as discussed by the authors.
Abstract: A series of large mesoscale convective systems that occurred during the Brazilian phase of GTE/TRACE A (Transport and Atmospheric Chemistry near the Equator-Atlantic) provided an opportunity to observe deep convective transport of trace gases from biomass burning. This paper reports a detailed analysis of flight 6, on September 27, 1992, which sampled cloud- and biomass-burning-perturbed regions north of Brasilia. High-frequency sampling of cloud outflow at 9-12 km from the NASA DC-8 showed enhancement of CO mixing ratios typically a factor of 3 above background (200- 300 parts per billion by volume (ppbv) versus 90 ppbv) and significant increases in NOx and hydrocarbons. Clear signals of lightning-generated NO were detected; we estimate that at least 40% of NO x at the 9.5-km level and 32% at 11.3 km originated from lightning. Four types of model studies have been performed to analyze the dynamical and photochemical characteristics of the series of convective events. (1) Regional simulations for the period have been performed with the NCAR/Penn State mesoscale model (MM5), including tracer transport of carbon monoxide, initialized with observations. Middle-upper tropospheric enhancements of a factor of 3 above background are reproduced. (2) A cloud-resolving model (the Goddard cumulus ensemble (GCE) model) has been run for one representative convective cell during the September 26-27 episode. (3) Photochemical calculations (the Goddard tropospheric chemical model), initialized with trace gas observations (e.g., CO, NO x, hydrocarbons, 03) observed in cloud outflow, show appreciable 0 3 formation postconvection, initially up to 7-8 ppbv O3/d. (4) Forward trajectories from cloud outflow levels (postconvective conditions) put the ozone-producing air masses in eastern Brazil and the tropical Atlantic within 2-4 days and over the Atlantic, Africa, and the Indian Ocean in 6-8 days. Indeed, 3-4 days after the convective episode (September 30, 1992), upper tropospheric levels in the Natal ozone sounding show an average increase of -30 ppbv (3 Dobson units (DU) integrated) compared to the September 28 sounding. Our simulated net 0 3 production rates in cloud outflow are a factor of 3 or more greater than those in air undisturbed by the storms. Integrated over the 8- to 16-km cloud outflow layer, the postconvection net 0 3 production (-5-6 DU over 8 days) accounts for -25% of the excess 03 (15-25 DU) over the South Atlantic. Comparison of TRACE A Brazilian ozonesondes and the frequency of deep convection with climatology (Kirchhoff et al., this issue) suggests that the late September 1992 conditions represented an unusually active period for both convection and upper tropospheric ozone formation.
263 citations
••
TL;DR: Modularity of the method is intended to fit the human organization and map well on the computing technology of concurrent processing.
Abstract: BLISS is a method for optimization of engineering systems by decomposition. It separates the system level optimization, having a relatively small number of design variables, from the potentially numerous subsystem optimizations that may each have a large number of local design variables. The subsystem optimizations are autonomous and may be conducted concurrently. Subsystem and system optimizations alternate, linked by sensitivity data, producing a design improvement in each iteration. Starting from a best guess initial design, the method improves that design in iterative cycles, each cycle comprised of two steps. In step one, the system level variables are frozen and the improvement is achieved by separate, concurrent, and autonomous optimizations in the local variable subdomains. In step two, further improvement is sought in the space of the system level variables. Optimum sensitivity data link the second step to the first. The method prototype was implemented using MATLAB and iSIGHT programming software and tested on a simplified, conceptural level supersonic business jet design, and a detailed design of an electronic device. Satisfactory convergence and favorable agreement with the benchmark results were observed. Modularity of the method is intended to fit the human organization and map well on the computing technology of concurrent processing.
263 citations
Authors
Showing all 16015 results
Name | H-index | Papers | Citations |
---|---|---|---|
Daniel J. Jacob | 162 | 656 | 76530 |
Donald R. Blake | 118 | 727 | 49697 |
Veerabhadran Ramanathan | 100 | 301 | 47561 |
Raja Parasuraman | 91 | 402 | 41455 |
Robert W. Platt | 88 | 638 | 31918 |
James M. Russell | 87 | 691 | 29383 |
Daniel J. Inman | 83 | 918 | 37920 |
Antony Jameson | 79 | 474 | 31518 |
Ya-Ping Sun | 79 | 277 | 28722 |
Patrick M. Crill | 79 | 228 | 20850 |
Richard B. Miles | 78 | 759 | 25239 |
Patrick Minnis | 77 | 490 | 23403 |
Robert W. Talbot | 77 | 297 | 19783 |
Raphael T. Haftka | 76 | 773 | 28111 |
Jack E. Dibb | 75 | 344 | 18399 |