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Articles 1 - 12 of 12
Full-Text Articles in Physical Sciences and Mathematics
Reactive Nitrogen Budget During The Nasa Sonex Mission, R. Talbot, Jack E. Dibb, Eric Scheuer, Y Kondo, M Koike, H B. Singh, L Salas, F Fukui, J O. Ballenthin, R F. Meads, T M. Miller, D E. Hunton, A A. Viggiano, D R. Blake, N J. Blake, Elliot Atlas, F Flocke, D J. Jacob, L Jaegle
Reactive Nitrogen Budget During The Nasa Sonex Mission, R. Talbot, Jack E. Dibb, Eric Scheuer, Y Kondo, M Koike, H B. Singh, L Salas, F Fukui, J O. Ballenthin, R F. Meads, T M. Miller, D E. Hunton, A A. Viggiano, D R. Blake, N J. Blake, Elliot Atlas, F Flocke, D J. Jacob, L Jaegle
Earth Sciences
The SASS Ozone and Nitrogen Oxides Experiment (SONEX) over the North Atlantic during October/November 1997 offered an excellent opportunity to examine the budget of reactive nitrogen in the upper troposphere (8–12 km altitude). The median measured total reactive nitrogen (NOy) mixing ratio was 425 parts per trillion by volume (pptv). A data set merged to the HNO3 measurement time resolution was used to calculate NOy (NOy sum) by summing the reactive nitrogen species (a combination of measured plus modeled results) and comparing it to measured NOy (NOy meas.). Comparisons were done for tropospheric …
Mapping A Continental Shelf And Slope In The 1990s: A Tale Of Three Multibeams, James V. Gardner, J.E. Hughes Clarke, Larry A. Mayer, Art Kleiner, Mark Paton
Mapping A Continental Shelf And Slope In The 1990s: A Tale Of Three Multibeams, James V. Gardner, J.E. Hughes Clarke, Larry A. Mayer, Art Kleiner, Mark Paton
Center for Coastal and Ocean Mapping
Increasing societal pressures on the U.S. continental shelves adjacent to dense population centers have brought to light the lack of accurate base maps in these areas. Existing bathymetric maps and random sidescan sonar surveys are either not accurate enough or do not provide the coverage necessary to make policy decisions. Until the mid 1990s, it was not financially prudent nor technically efficient to map the shallow shelves. However, the availability of high-resolution multibeam mapping systems now allow efficient and accurate mapping of the continental margins. In 1996 the U.S. Geological Survey began a large-scale seafloor mapping campaign on the continental …
Data Handling Methods And Target Detection Results For Multibeam And Sidescan Data Collected As Part Of The Search For Swissair Flight 111, John E. Hughes Clarke, Larry A. Mayer, John Shaw, R Parrott, Mike Lamplugh, Jim Bradford
Data Handling Methods And Target Detection Results For Multibeam And Sidescan Data Collected As Part Of The Search For Swissair Flight 111, John E. Hughes Clarke, Larry A. Mayer, John Shaw, R Parrott, Mike Lamplugh, Jim Bradford
Center for Coastal and Ocean Mapping
The crash of SwissAir Flight 111, off Nova Scotia in September 1998, triggered one of the largest seabed search surveys in Canadian history. The primary search tools used were sidescan sonars (both conventional and focussed types) and multibeam sonars. The processed search data needed to be distributed on a daily basis to other elements of the fleet for precise location of divers and other optical seabed search instruments (including laser linescan and ROV video). As a result of the glacial history of the region, many natural targets, similar in gross nature to aircraft debris were present. These included widespread linear …
Maximum Temperature Trends In The Himalaya And Its Vicinity: An Analysis Based On Temperature Records From Nepal For The Period 1971–94, Arun B. Shrestha, Cameron P. Wake, Paul A. Mayewski, Jack E. Dibb
Maximum Temperature Trends In The Himalaya And Its Vicinity: An Analysis Based On Temperature Records From Nepal For The Period 1971–94, Arun B. Shrestha, Cameron P. Wake, Paul A. Mayewski, Jack E. Dibb
Earth Sciences
Analyses of maximum temperature data from 49 stations in Nepal for the period 1971–94 reveal warming trends after 1977 ranging from 0.068 to 0.128C yr21 in most of the Middle Mountain and Himalayan regions, while the Siwalik and Terai (southern plains) regions show warming trends less than 0.038C yr21. The subset of records (14 stations) extending back to the early 1960s suggests that the recent warming trends were preceded by similar widespread cooling trends. Distributions of seasonal and annual temperature trends show high rates of warming in the high-elevation regions of the country (Middle Mountains and Himalaya), while low warming …
Chemical Characteristics Of Air From Differing Source Regions During The Pacific Exploratory Mission-Tropics A (Pem-Tropics A), Ashley S. Board, H Fuelberg, G L. Gregory, B J. Heikes, Martin G. Schultz, D R. Blake, Jack E. Dibb, S T. Sandholm, R. Talbot
Chemical Characteristics Of Air From Differing Source Regions During The Pacific Exploratory Mission-Tropics A (Pem-Tropics A), Ashley S. Board, H Fuelberg, G L. Gregory, B J. Heikes, Martin G. Schultz, D R. Blake, Jack E. Dibb, S T. Sandholm, R. Talbot
Earth Sciences
Ten-day backward trajectories are used to determine the origins of air parcels arriving at airborne DC-8 chemical measurement sites during NASA's Pacific Exploratory Mission-Tropics A (PEM-T) that was conducted during August-October 1996. Those sites at which the air had a common geographical origin and transport history are grouped together, and statistical measures of chemical characteristics are computed. Temporal changes in potential temperature are used to determine whether trajectories experience a significant convective influence during the 10-day period. Those trajectories that do not experience a significant convective influence are divided into four geographical categories depending on their origins and paths. Air …
Constraints On The Age And Dilution Of Pacific Exploratory Mission-Tropics Biomass Burning Plumes From The Natural Radionuclide Tracer 210pb, Jack E. Dibb, R. Talbot, David Meeker, Eric Scheuer, N J. Blake, D R. Blake, G L. Gregory, G W. Sachse
Constraints On The Age And Dilution Of Pacific Exploratory Mission-Tropics Biomass Burning Plumes From The Natural Radionuclide Tracer 210pb, Jack E. Dibb, R. Talbot, David Meeker, Eric Scheuer, N J. Blake, D R. Blake, G L. Gregory, G W. Sachse
Earth Sciences
During the NASA Global Troposphere Experiment Pacific Exploratory Mission-Tropics (PEM-Tropics) airborne sampling campaign we found unexpectedly high concentrations of aerosol-associated 210Pb throughout the free troposphere over the South Pacific. Because of the remoteness of the study region, we expected specific activities to be generally less than 35 μBq m−3 but found an average in the free troposphere of 107 μBq m−3. This average was elevated by a large number of very active (up to 405 μBq m−3) samples that were associated with biomass burning plumes encountered on nearly every PEM-Tropics flight in the southern …
Ozone And Aerosol Distributions And Air Mass Characteristics Over The South Pacific During The Burning Season, Marta Fenn, Edward V. Browell, Carolyn Butler, William B. Grant, Susan A. Kooi, Marian B. Clayton, G L. Gregory, Reginald E. Newell, Yong Zhu, Jack E. Dibb, H Fuelberg, Bruce E. Anderson, A R. Bandy, D R. Blake, J D. Bradshaw, B J. Heikes, G W. Sachse, S T. Sandholm, H B. Singh, R. Talbot, D C. Thornton
Ozone And Aerosol Distributions And Air Mass Characteristics Over The South Pacific During The Burning Season, Marta Fenn, Edward V. Browell, Carolyn Butler, William B. Grant, Susan A. Kooi, Marian B. Clayton, G L. Gregory, Reginald E. Newell, Yong Zhu, Jack E. Dibb, H Fuelberg, Bruce E. Anderson, A R. Bandy, D R. Blake, J D. Bradshaw, B J. Heikes, G W. Sachse, S T. Sandholm, H B. Singh, R. Talbot, D C. Thornton
Earth Sciences
In situ and laser remote measurements of gases and aerosols were made with airborne instrumentation to establish a baseline chemical signature of the atmosphere above the South Pacific Ocean during the NASA Global Tropospheric Experiment (GTE)/Pacific Exploratory Mission-Tropics A (PEM-Tropics A) conducted in August-October 1996. This paper discusses general characteristics of the air masses encountered during this experiment using an airborne lidar system for measurements of the large-scale variations in ozone (O3) and aerosol distributions across the troposphere, calculated potential vorticity (PV) from the European Centre for Medium-Range Weather Forecasting (ECMWF), and in situ measurements for comprehensive air …
Concentrations And Snow-Atmosphere Fluxes Of Reactive Nitrogen At Summit, Greenland, J W. Munger, D J. Jacob, S M. Fan, A S. Colman, Jack E. Dibb
Concentrations And Snow-Atmosphere Fluxes Of Reactive Nitrogen At Summit, Greenland, J W. Munger, D J. Jacob, S M. Fan, A S. Colman, Jack E. Dibb
Earth Sciences
Concentrations and fluxes of NOy (total reactive nitrogen), ozone concentrations and fluxes of sensible heat, water vapor, and momentum were measured from May 1 to July 20, 1995 at Summit, Greenland. Median NOy concentrations declined from 947 ppt in May to 444 ppt by July. NOy fluxes were observed into and out of the snow, but the magnitudes were usually below 1 μmol m−2 h−1 because of the low HNO3 concentration and weak turbulence over the snow surface. Some of the highest observed fluxes may be due to temporary storage by equilibrium sorption of …
A Process Model Of Risk Communication: The Case Of Global Climate Change, Fiona Clark, Keith R. Stamm, Paula Reynolds Eblacas
A Process Model Of Risk Communication: The Case Of Global Climate Change, Fiona Clark, Keith R. Stamm, Paula Reynolds Eblacas
RISK: Health, Safety & Environment (1990-2002)
The authors describe a survey of public media use as it relates to different stages of awareness and concern regarding risk issues.
Aerosol Chemical Composition And Distribution During The Pacific Exploratory Mission (Pem) Tropics, Jack E. Dibb, R. Talbot, Eric Scheuer, D R. Blake, N J. Blake, G L. Gregory, G W. Sachse, D C. Thornton
Aerosol Chemical Composition And Distribution During The Pacific Exploratory Mission (Pem) Tropics, Jack E. Dibb, R. Talbot, Eric Scheuer, D R. Blake, N J. Blake, G L. Gregory, G W. Sachse, D C. Thornton
Earth Sciences
Distributions of aerosol-associated soluble ions over much of the South Pacific were determined by sampling from the NASA DC-8 as part of the Pacific Exploratory Mission (PEM) Tropics campaign. The mixing ratios of all ionic species were surprisingly low throughout the free troposphere (2-12 km), despite the pervasive influence from biomass burning plumes advecting over the South Pacific from the west during PEM-Tropics. At the same time, the specific activity of 7Be frequently exceeded 1000 fCi m-3 through much of the depth of the troposphere. These distributions indicate that the plumes must have been efficiently scavenged by precipitation (removing the …
Influence Of Biomass Combustion Emissions On The Distribution Of Acidic Trace Gases Over The Southern Pacific Basin During Austral Springtime, R. Talbot, Jack E. Dibb, Eric Scheuer, D R. Blake, N J. Blake, G L. Gregory, G W. Sachse, J D. Bradshaw, S T. Sandholm, H B. Singh
Influence Of Biomass Combustion Emissions On The Distribution Of Acidic Trace Gases Over The Southern Pacific Basin During Austral Springtime, R. Talbot, Jack E. Dibb, Eric Scheuer, D R. Blake, N J. Blake, G L. Gregory, G W. Sachse, J D. Bradshaw, S T. Sandholm, H B. Singh
Earth Sciences
This paper describes the large-scale distributions of HNO3, HCOOH, and CH3COOH over the central and South Pacific basins during the Pacific Exploratory Mission-Tropics (PEM-Tropics) in austral springtime. Because of the remoteness of this region from continental areas, low part per trillion by volume (pptv) mixing ratios of acidic gases were anticipated to be pervasive over the South Pacific basin. However, at altitudes of 2–12 km over the South Pacific, air parcels were encountered frequently with significantly enhanced mixing ratios (up to 1200 pptv) of acidic gases. Most of these air parcels were centered in the 3–7 …
Evidence Of Nox Production Within Or Upon Ice Particles In The Greenland Snowpack, R E. Honrath, Matthew C. Peterson, S Guo, Jack E. Dibb, P B. Shepson, Bradley M. Campbell
Evidence Of Nox Production Within Or Upon Ice Particles In The Greenland Snowpack, R E. Honrath, Matthew C. Peterson, S Guo, Jack E. Dibb, P B. Shepson, Bradley M. Campbell
Earth Sciences
NOx and NOy were determined in the interstitial air of surface snow and in ambient air at Summit, Greenland. NOx levels in interstitial air were 3 to >10 times those in ambient air, and were generally greater than ambient NOy levels. [NOy] in interstitial air varied diurnally in a manner consistent with photochemical generation within the snowpack. These observations imply that photochemical reactions occurring within or upon the ice crystals of surface snow produced NOx from a N-reservoir compound within the snow. Average [NOX]:[HNO3] and [NOx]:[NOy] ratios in ambient air above the snow were elevated relative to other remote sites, …