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Institution

Langley Research Center

FacilityHampton, 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.


Papers
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Journal ArticleDOI
TL;DR: In this paper, a combination of satellite observational data and detailed radiative transfer calculations is used to quantify the impact of cloud phase and cloud vertical structure on the reflected solar radiation in the Southern Hemisphere summer.
Abstract: The Southern Ocean is a critical region for global climate, yet large cloud and solar radiation biases over the Southern Ocean are a long-standing problem in climate models and are poorly understood, leading to biases in simulated sea surface temperatures. This study shows that supercooled liquid clouds are central to understanding and simulating the Southern Ocean environment. A combination of satellite observational data and detailed radiative transfer calculations is used to quantify the impact of cloud phase and cloud vertical structure on the reflected solar radiation in the Southern Hemisphere summer. It is found that clouds with supercooled liquid tops dominate the population of liquid clouds. The observations show that clouds with supercooled liquid tops contribute between 27% and 38% to the total reflected solar radiation between 40° and 70°S, and climate models are found to poorly simulate these clouds. The results quantify the importance of supercooled liquid clouds in the Southern Ocean environment and highlight the need to improve understanding of the physical processes that control these clouds in order to improve their simulation in numerical models. This is not only important for improving the simulation of present-day climate and climate variability, but also relevant for increasing confidence in climate feedback processes and future climate projections.

142 citations

Journal ArticleDOI
TL;DR: In this paper, the distribution of middle tropospheric carbon monoxide measure by the Measurement of Air Pollution from Satellites (MAPS) instrument carried aboard the space shuttle is reported.
Abstract: The distribution of middle tropospheric carbon monoxide measure by the Measurement of Air Pollution from Satellites (MAPS) instrument carried aboard the space shuttle is reported. The data represent average mixing ratios in the middle troposphere and are presented in the form of maps that show the carbon monoxide mixing ratios averaged for 6 days of the mission. Comparisons with concurrent, direct measurements taken aboard aircraft show that the inferred concentrations are systematically low by from 20 to 40 percent depending upon which direct measurement calibration standard is used. The data show that there are very large CO sources resulting from biomass burning over South America and southern Africa. Measured mixing ratios were high over northeast Asia and were highly variable over Europe.

141 citations

Journal ArticleDOI
TL;DR: A series of water vapor intensive observation periods (WVIOPs) were conducted at the Atmospheric Radiation Measurement (ARM) site in Oklahoma between 1996 and 2000 as discussed by the authors to characterize the accuracy of the operational water vapor observations and to develop techniques to improve the accuracy.
Abstract: A series of water vapor intensive observation periods (WVIOPs) were conducted at the Atmospheric Radiation Measurement (ARM) site in Oklahoma between 1996 and 2000. The goals of these WVIOPs are to characterize the accuracy of the operational water vapor observations and to develop techniques to improve the accuracy of these measurements. The initial focus of these experiments was on the lower atmosphere, for which the goal is an absolute accuracy of better than 2% in total column water vapor, corresponding to ~1 W m−2 of infrared radiation at the surface. To complement the operational water vapor instruments during the WVIOPs, additional instrumentation including a scanning Raman lidar, microwave radiometers, chilled-mirror hygrometers, a differential absorption lidar, and ground-based solar radiometers were deployed at the ARM site. The unique datasets from the 1996, 1997, and 1999 experiments have led to many results, including the discovery and characterization of a large (> 25%) sonde-to-sonde variab...

141 citations

Journal ArticleDOI
TL;DR: In this article, the seasonal variation and the long-term trend of tropospheric aerosol optical depth are discussed, taking into account the stratospheric AOD measured by the Stratospheric Aerosol and Gas Experiment (SAGE II).
Abstract: [1] Ground-based measurements of total aerosol optical depth (AOD), e.g., tropospheric and stratospheric aerosol, have been established at the Koldewey station in Ny-Alesund, Spitzbergen (Norway, 78.95°N, 11.93°E), since 1991. The basic instrumentation is a multichannel photometer using sunlight. New instruments have been developed to extend the measurement period to polar night. The new instruments are a Sun and Moon photometer (1995) and a star photometer (1996). The instruments and applied methods for aerosol optical depth retrieval for Sun, Moon, and star measurements are briefly discussed. The year-round measurements made it possible to study in detail the interannual and seasonal variations of total AOD in the Arctic. The seasonal variation and the long-term trend of tropospheric aerosol optical depth are discussed, taking into account the stratospheric AOD measured by the Stratospheric Aerosol and Gas Experiment (SAGE II). The lowest tropospheric aerosol optical depth values occur in late summer and fall. Each year, strong Arctic haze events were recorded not only during spring but also in late winter as the first star photometer measurements clearly show. Five-day backward trajectories were used to analyze possible sources for high tropospheric AOD. Elevated tropospheric aerosol optical depth appears for northeasterly, easterly, or westerly winds. Finally, the long-term changes of tropospheric AOD have been assessed. A small positive trend of the tropospheric aerosol optical depth is found for the vicinity of Spitzbergen during the measurement period.

141 citations

Journal ArticleDOI
TL;DR: In this article, the observed and modeled HO2 and HO2/OH ratios are largely reconciled within the measurement uncertainty by introducing an undefined HO loss that removed H Ox (HOx=OH+HO2).
Abstract: OH and HO2 were measured with the Airborne Tropospheric Hydrogen Oxides Sensor (ATHOS) as part of a large measurement suite from the NASA DC-8 aircraft during the Intercontinental Chemical Transport Experiment - A (INTEX-A). This mission, which was conducted mainly over North America and the western Atlantic Ocean in summer 2004, was an excellent test of atmospheric oxidation chemistry. Throughout the troposphere, observed OH was generally 0.60 of the modeled OH; below 8 km, observed HO2 was generally 0.78 of modeled HO2. If the over-prediction of tropospheric OH is not due to an instrument calibration error, then it implied less global tropospheric oxidation capacity and longer lifetimes for gases like methane and methyl chloroform than currently thought. This discrepancy falls well outside uncertainties in both the OH measurement and rate coefficients for known reactions and points to a large unknown OH loss. If the modeled OH is forced to agree with observed values by introducing of an undefined OH loss that removed HOx (HOx=OH+HO2), the observed and modeled HO2 and HO2/OH ratios are largely reconciled within the measurement uncertainty. HO2 behavior above 8 km was markedly different. The observed-to-modeled ratio correlating with NO. The observed-to-modeled HO2 ratio increased from approximately 1 at 8 km to more than approximately 2.5 at 11 km with the observed-to-modeled ratio correlating with NO. The observed-to-modeled HO2 and NO were both considerably greater than observations from previous campaigns. In addition, the observed-to-modeled HO2/OH, which is sensitive to cycling reactions between OH and HO2, increased from approximately 1.2 at 8 km to almost 4 above 11 km. In contrast to the lower atmosphere, these discrepancies above 8 km suggest a large unknown HOx source and additional reactants that cycle HOx from OH to HO2. In the continental planetary boundary layer, the OH observed-to-modeled ratio increased from 0.6 when isoprene was less than 0.1 ppbv to over 3 when isoprene was greater than 2 ppbv, suggesting that forests throughout the United States are emitting unknown HOx sources. Progress in resolving these discrepancies requires further examinations of possible unknown OH sinks and HOx sources and a focused research activity devoted to ascertaining the accuracy of the OH and HO2 measurements.

141 citations


Authors

Showing all 16015 results

NameH-indexPapersCitations
Daniel J. Jacob16265676530
Donald R. Blake11872749697
Veerabhadran Ramanathan10030147561
Raja Parasuraman9140241455
Robert W. Platt8863831918
James M. Russell8769129383
Daniel J. Inman8391837920
Antony Jameson7947431518
Ya-Ping Sun7927728722
Patrick M. Crill7922820850
Richard B. Miles7875925239
Patrick Minnis7749023403
Robert W. Talbot7729719783
Raphael T. Haftka7677328111
Jack E. Dibb7534418399
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
202335
202286
2021571
2020540
2019669
2018797