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Articles 1 - 9 of 9
Full-Text Articles in Physical Sciences and Mathematics
Wet Deposition In A Global Size-Dependent Aerosol Transport Model: 2. Influence Of The Scavenging Scheme On 210pb Vertical Profiles, Surface Concentrations, And Deposition, W Guelle, Y J. Balkanski, Jack E. Dibb, M Schulz, F Dulac
Wet Deposition In A Global Size-Dependent Aerosol Transport Model: 2. Influence Of The Scavenging Scheme On 210pb Vertical Profiles, Surface Concentrations, And Deposition, W Guelle, Y J. Balkanski, Jack E. Dibb, M Schulz, F Dulac
Earth Sciences
The main atmospheric sink for submicron aerosols is wet removal. Lead 210, the radioactive decay product of 222Rn, attaches immediately after being formed to submicron particles. Here we compare the effects of three different wet-scavenging schemes used in global aerosol simulations on the 210Pb aerosol distribution using an off-line, size-resolved, global atmospheric transport model. We highlight the merits and shortcomings of each scavenging scheme at reproducing available measurements, which include concentrations in surface air and deposition, as well as vertical profiles observed over North America and western and central North Pacific. We show that model-measurement comparison of total …
Soluble Species In Aerosol And Snow And Their Relationship At Glacier 1, Tien Shan, China, Junying Sun, Dahe Qin, Paul A. Mayewski, Jack E. Dibb, Sallie I. Whitlow, Zhongqin Lee, Qinzhao Yang
Soluble Species In Aerosol And Snow And Their Relationship At Glacier 1, Tien Shan, China, Junying Sun, Dahe Qin, Paul A. Mayewski, Jack E. Dibb, Sallie I. Whitlow, Zhongqin Lee, Qinzhao Yang
Earth Sciences
Simultaneous sampling of aerosol (n = 20) and snow (n = 114) was made at Glacier 1, Tien Shan, between May 19 and June 29, 1996. Similar temporal patterns of some major ion (calcium, magnesium, potassium, sodium, chloride, and sulfate) concentrations between snow and aerosol show that snow chemistry basically reflects changes in the chemistry of the atmosphere. This gives us confidence in the reconstruction of past atmospheric change using some snow data. There are no significant correlations between aerosol and snow samples for ammonium and nitrate. This suggests that post-depositional and/or post-collection processes may alter ammonium and nitrate concentrations …
Nitric Acid Scavenging By Mineral And Biomass Burning Aerosols, A Tabazadeh, M Z. Jacobson, H B. Singh, O Brian Toon, J S. Lin, R B. Chatfield, A N. Thakur, R. Talbot, Jack E. Dibb
Nitric Acid Scavenging By Mineral And Biomass Burning Aerosols, A Tabazadeh, M Z. Jacobson, H B. Singh, O Brian Toon, J S. Lin, R B. Chatfield, A N. Thakur, R. Talbot, Jack E. Dibb
Earth Sciences
The abundance of gas phase nitric acid in the upper troposphere is overestimated by global chemistry-transport models, especially during the spring and summer seasons. Recent aircraft data obtained over the central US show that mineral aerosols were abundant in the upper troposphere during spring. Chemical reactions on mineral dust may provide an important sink for nitric acid. In regions where the mineral dust abundance is low in the upper troposphere similar HNO3 removal processes may occur on biomass burning aerosols. We propose that mineral and biomass burning aerosols may provide an important global sink for gas phase nitric acid, …
The Limits Of Spatial Resolution Achievable Using A 30khz Multibeam Sonar: Model Predictions And Field Results, John E. Hughes Clarke, James V. Gardner, Mike Torresan, Larry A. Mayer
The Limits Of Spatial Resolution Achievable Using A 30khz Multibeam Sonar: Model Predictions And Field Results, John E. Hughes Clarke, James V. Gardner, Mike Torresan, Larry A. Mayer
Center for Coastal and Ocean Mapping
A Simrad EM300 multibeam sonar was used to attempt to resolve small (-5m high) targets in 450m of water. The targets had previously been surveyed using a deeply towed 59 kHz sidescan sonar. Using multisector active yaw, pitch and roll compensation, together with dynamically altering angular sectors, the sonar is capable of maintaining sounding densities of as tight as 10m spacing in these water depths. This is significantly smaller than the largest dimension of the projected beam footprints (1 6-64m). The observed data suggest that the targets are intermittently resolved. The field results compare well to the output of a …
Influence Of Vertical Transport On Free Tropospheric Aerosols Over The Central Usa In Springtime, R. Talbot, Jack E. Dibb, M Loomis
Influence Of Vertical Transport On Free Tropospheric Aerosols Over The Central Usa In Springtime, R. Talbot, Jack E. Dibb, M Loomis
Earth Sciences
Measurements of the atmospheric aerosol chemical composition during the Subsonic Aircraft: Contrail and Cloud Effects Special Study (SUCCESS) indicate substantial vertical transport of boundary layer aerosol to the free troposphere over the south-central United States during springtime. Mixing ratios of water-soluble aerosol Ca 2+ at 6 - 12 km altitude exhibited a median mixing ratio of 20 pptv, with 15% of the measurements > 100 pptv and a maximum of ! 235 pptv. In air parcels with enhanced Ca 2+, the ratios K+/Ca 2+, Mg2+/Ca 2+, and Na+/Ca 2+ in the bulk aerosol were distinctly characteristic of those in limestone and/or …
Tropospheric Sulfate Distribution During Success: Contributions From Jet Exhaust And Surface Sources, Jack E. Dibb, R. Talbot, M Loomis
Tropospheric Sulfate Distribution During Success: Contributions From Jet Exhaust And Surface Sources, Jack E. Dibb, R. Talbot, M Loomis
Earth Sciences
The distribution of SO4= aerosol over the central US during SUCCESS indicates that surface sources of SO4= and SO2 in the western US caused SO4= enhancements up to 10 km altitude. The mean (median) SO4= mixing ratio in the mid- and upper-troposphere increased from 24 (16) pptv over the Pacific ocean to 58 (29) pptv over the central plains. Above 10 km the SO4=mixing ratio was essentially the same in both regions, and also when the geographic classifications were further partitioned into upper tropospheric and lower stratospheric categories …
Relationship Between Continuous Aerosol Measurements And Firn Core Chemistry Over A 10-Year Period At The South Pole, M H. Bergin, E A. Meyerson, Jack E. Dibb, Paul A. Mayewski
Relationship Between Continuous Aerosol Measurements And Firn Core Chemistry Over A 10-Year Period At The South Pole, M H. Bergin, E A. Meyerson, Jack E. Dibb, Paul A. Mayewski
Earth Sciences
Before ice core chemistry can be used to estimate past atmospheric chemistry it is necessary to establish an unambiguous link between concentrations of chemical species in the air and snow. For the first time a continuous long-term record of aerosol properties (aerosol light scattering coefficient, σsp, and Ångström exponent, å) at the South Pole are compared with the chemical record from a high resolution firn core (∼10 samples per year) covering the period from 1981 to 1991. Seasonal signals in å, associated with winter minima due to coarse mode seasalt and summer maxima due to accumulation mode sulfate …
Air-Snow Exchange Of Hno3 And Noy At Summit, Greenland, Jack E. Dibb, R. Talbot, J W. Munger, Daniel J. Jacob, S M. Fan
Air-Snow Exchange Of Hno3 And Noy At Summit, Greenland, Jack E. Dibb, R. Talbot, J W. Munger, Daniel J. Jacob, S M. Fan
Earth Sciences
Ice core records of NO3− deposition to polar glaciers could provide unrivaled information on past photochemical status and N cycling dynamics of the troposphere, if the ice core records could be inverted to yield concentrations of reactive N oxides in the atmosphere at past times. Limited previous investigations at Summit, Greenland, have suggested that this inversion may be difficult, since the levels of HNO3 and aerosol-associated NO3− over the snow are very low in comparison with those of NO3− in the snow. In addition, it appears that some fraction of the NO3 …
The Pursuit Of Isotopic And Molecular Fire Tracers In The Polar Atmosphere And Cryosphere, L A. Currie, Jack E. Dibb, G A. Klouda, B A. Benner Jr., J M. Conny, S R. Biegalski, D B. Klinedinst, D R. Cahoon, N C. Hsu
The Pursuit Of Isotopic And Molecular Fire Tracers In The Polar Atmosphere And Cryosphere, L A. Currie, Jack E. Dibb, G A. Klouda, B A. Benner Jr., J M. Conny, S R. Biegalski, D B. Klinedinst, D R. Cahoon, N C. Hsu
Earth Sciences
We present an overview of recent multidisciplinary, multi-institutional efforts to identify and date major sources of combustion aerosol in the current and paleoatmospheres. The work was stimulated, in part, by an atmospheric particle 'sample of opportunity' collected at Summit, Greenland in August 1994, that bore the 14C imprint of biomass burning. During the summer field seasons of 1995 and 1996, we collected air filter, surface snow and snowpit samples to investigate chemical and isotopic evidence of combustion particles that had been transported from distant fires. Among the chemical tracers employed for source identification are organic acids, potassium and ammonium ions, …