The Experts below are selected from a list of 25554 Experts worldwide ranked by ideXlab platform
Jae Hee Jung - One of the best experts on this subject based on the ideXlab platform.
-
effect of relative humidity and variation of particle number size distribution on the inactivation effectiveness of airborne silver nanoparticles against bacteria bioAerosols deposited on a filter
Journal of Aerosol Science, 2010Co-Authors: Jae Hee JungAbstract:Airborne silver nanoparticles were found to be effective in controlling bacteria bioAerosols deposited on filters. However, the applicability of those findings is still unclear because the findings were obtained under limited environmental and experimental conditions. To increase the applicability of the findings, this study examines how airborne silver nanoparticles affect airborne bacteria on filters under various experimental conditions, especially with regard to relative humidity and the particle number size distribution of airborne silver nanoparticles. In this study, bacteria bioAerosols and airborne silver nanoparticles are quantitatively generated, and bioAerosols deposited on filters are exposed to airborne silver particles under various experimental conditions. The properties of the airborne bacteria and airborne silver nanoparticles are measured with Aerosol Measurement devices. The study tests three bacteria species: gram-positive Staphylococcus epidermidis, Bacillus subtilis, and gram-negative Escherichia coli bacteria bioAerosols. The experimental results demonstrate that a particle number concentration threshold is required for the airborne silver nanoparticles effect, and that the effect of airborne silver nanoparticles is stronger when the relative humidity is low.
Michael C Pitts - One of the best experts on this subject based on the ideXlab platform.
-
an evaluation of the sage iii version 4 Aerosol extinction coefficient and water vapor data products
Atmospheric Chemistry and Physics, 2010Co-Authors: L W Thomason, Michael C Pitts, J R Moore, J M Zawodny, E W ChiouAbstract:Abstract. Herein, we provide an assessment of the data quality of Stratospheric Aerosol and Gas Experiment (SAGE III) Version 4 Aerosol extinction coefficient and water vapor data products. The evaluation is based on comparisons with data from four instruments: SAGE II, the Polar Ozone and Aerosol Measurement (POAM III), the Halogen Occultation Experiment (HALOE), and the Microwave Limb Sounder (MLS). Since only about half of the SAGE III channels have a direct comparison with Measurements by other instruments, we have employed some empirical techniques to evaluate Measurements at some wavelengths. We find that the Aerosol extinction coefficient Measurements at 449, 520, 755, 869, and 1021 nm are reliable with accuracies and precisions on the order of 10% in the mission's primary Aerosol target range of 15 to 25 km. We also believe this to be true of the Aerosol Measurements at 1545 nm though we cannot exclude some positive bias below 15 km. We recommend use of the 385 nm Measurements above 16 km where the accuracy is on par with other Aerosol channels. The 601 nm Measurement is much noisier (~20%) than other channels and we suggest caution in the use of these data. We believe that the 676 nm data are clearly defective particularly above 20 km (accuracy as poor as 50%) and the precision is also low (~30%). We suggest excluding this channel under most circumstances. The SAGE III Version 4 water vapor data product appears to be high quality and is recommended for science applications in the stratosphere below 45 km. In this altitude range, the mean differences with all four corroborative data sets are no bigger than 15% and often less than 10% with exceptional agreement with POAM III and MLS. Above 45 km, it seems likely that SAGE III water vapor values are increasingly too large and should be used cautiously or avoided. We believe that SAGE III meets its preflight goal of 15% accuracy and 10% precision between 15 and 45 km. SAGE III water vapor data does not appear to be affected by Aerosol loading in the stratosphere.
-
A unified, long-term, high-latitude stratospheric Aerosol and cloud database using SAM II, SAGE II, and POAM II/III data: Algorithm description, database definition, and climatology
Journal of Geophysical Research, 2003Co-Authors: Michael Fromm, Jerome Alfred, Michael C PittsAbstract:A 22 year, high-latitude, stratospheric Aerosol and cloud database has been formed in a "unified" manner by combining the Stratospheric Aerosol Measurement (SAM) II, Stratospheric Aerosol and Gas Measurement (SAGE) II, Polar Ozone and Aerosol Measurement (POAM) II, and POAM III 1 μm Aerosol extinction profiles. The database is "unified" in that it embodies similar Aerosol extinction Measurements, uses a single meteorological data set, and employs a single algorithm for calculating background extinction and cloud detection thresholds. Latitude is constrained to poleward of 45° in each hemisphere. The Unified cloud detection algorithm and database are designed for the straightforward addition of new data when other compatible data sets (e.g., SAGE III) become available. "Unified" cloud detection is similar to, but a refinement of, earlier attempts to identify polar stratospheric clouds (PSCs) with SAM II and POAM II data. The Unified algorithm is instrument-independent and circumvents fundamental cloud detection pitfalls. The database contains over 73,000 (36,000) polar vortex-region profiles in the Antarctic (Arctic) and over 21,000 (2000) PSC observations. An introductory climatology of Unified "background" extinction is presented. It is seen that volcanic effects dominate the evolution of outside-vortex background extinctions, but perturbations apparently not related to volcanoes are seen as well. Interannual variations of background extinction fsinside the austral vortex are seen to be nearly decoupled from volcanic effects, while in the Arctic, inside-vortex extinctions show a considerable volcanic influence. An analysis of long-term PSC sighting is presented. Midwinter (July and January) PSC and clear-sky Measurements at 20 km, in a fixed temperature range, are used for computing PSC probability. The grand average PSC probability calculated this way is nearly identical between hemispheres. In the Antarctic the interannual PSC probability pattern is distinctly cyclic but is convoluted by volcanic perturbations in background Aerosol. In the Arctic the PSC probability has much less temporal coherence than in the Antarctic but is similarly impacted by volcanic background increases. An explanation for the variation in PSC probabilities, in terms of interannual differences in denitrification, is discussed. Finally, a statistical analysis of tropopause height in relation to PSC formation is also presented. PSC observations are seen to be strongly associated with elevated tropopause heights, indicating that tropospheric, synoptic-scale flow perturbations are the primary forcing mechanism for Arctic PSC formation, as evidenced in this long-term satellite record.
L W Thomason - One of the best experts on this subject based on the ideXlab platform.
-
an evaluation of the sage iii version 4 Aerosol extinction coefficient and water vapor data products
Atmospheric Chemistry and Physics, 2010Co-Authors: L W Thomason, Michael C Pitts, J R Moore, J M Zawodny, E W ChiouAbstract:Abstract. Herein, we provide an assessment of the data quality of Stratospheric Aerosol and Gas Experiment (SAGE III) Version 4 Aerosol extinction coefficient and water vapor data products. The evaluation is based on comparisons with data from four instruments: SAGE II, the Polar Ozone and Aerosol Measurement (POAM III), the Halogen Occultation Experiment (HALOE), and the Microwave Limb Sounder (MLS). Since only about half of the SAGE III channels have a direct comparison with Measurements by other instruments, we have employed some empirical techniques to evaluate Measurements at some wavelengths. We find that the Aerosol extinction coefficient Measurements at 449, 520, 755, 869, and 1021 nm are reliable with accuracies and precisions on the order of 10% in the mission's primary Aerosol target range of 15 to 25 km. We also believe this to be true of the Aerosol Measurements at 1545 nm though we cannot exclude some positive bias below 15 km. We recommend use of the 385 nm Measurements above 16 km where the accuracy is on par with other Aerosol channels. The 601 nm Measurement is much noisier (~20%) than other channels and we suggest caution in the use of these data. We believe that the 676 nm data are clearly defective particularly above 20 km (accuracy as poor as 50%) and the precision is also low (~30%). We suggest excluding this channel under most circumstances. The SAGE III Version 4 water vapor data product appears to be high quality and is recommended for science applications in the stratosphere below 45 km. In this altitude range, the mean differences with all four corroborative data sets are no bigger than 15% and often less than 10% with exceptional agreement with POAM III and MLS. Above 45 km, it seems likely that SAGE III water vapor values are increasingly too large and should be used cautiously or avoided. We believe that SAGE III meets its preflight goal of 15% accuracy and 10% precision between 15 and 45 km. SAGE III water vapor data does not appear to be affected by Aerosol loading in the stratosphere.
-
a global climatology of stratospheric Aerosol surface area density deduced from stratospheric Aerosol and gas experiment ii Measurements 1984 1994
Journal of Geophysical Research, 1997Co-Authors: L W Thomason, Lamont R Poole, Terry DeshlerAbstract:A global climatology of stratospheric Aerosol surface area density has been developed using the multiwavelength Aerosol extinction Measurements of the Stratospheric Aerosol and Gas Experiment (SAGE) II for 1984–1994. The spatial and temporal variability of Aerosol surface area density at 15.5, 20.5, and 25.5 km are presented as well as cumulative statistical distributions as a function of altitude and latitude. During this period, which encompassed the injection and dissipation of the Aerosol associated with the June 1991 Mount Pinatubo eruption as well as the low loading period of 1989–1991, Aerosol surface area density varied by more than a factor 30 at some altitudes. Aerosol surface area density derived from SAGE II and from the University of Wyoming optical particle counters are compared for 1991–1994 and are shown to be in generally good agreement though some differences are noted. An extension of the climatology using single-wavelength Measurements by the Stratospheric Aerosol Measurement II (1978–1994) and SAGE (1979–1981) instruments is also presented.
D J Debrestian - One of the best experts on this subject based on the ideXlab platform.
-
the polar ozone and Aerosol Measurement poam iii instrument and early validation results
Journal of Geophysical Research, 1999Co-Authors: Robert L Lucke, E P Shettle, R M Bevilacqua, J S Hornstein, J D Lumpe, M Fromm, D R Korwan, Davidson T Chen, M Daehler, D J DebrestianAbstract:Polar Ozone and Aerosol Measurement (POAM) III, a follow-on to the successful POAM II, is a spaceborne experiment designed to measure the vertical profiles of ozone, water vapor, nitrogen dioxide, and Aerosol extinction in the polar stratosphere and upper troposphere with a vertical resolution of 1–2 km. Measurements are made by the solar occultation technique. POAM III, now in polar orbit aboard the SPOT 4 satellite, is providing data on north- and south-polar ozone phenomena, including the south-polar ozone hole, and on the spatial and temporal variability of stratospheric Aerosols, polar stratospheric clouds, and polar mesospheric clouds. Differences between the POAM III and POAM II instruments are described. First validations of POAM III data products by comparison with Halogen Occultation Experiment and ozonesonde data are presented.
-
poam ii early results and comparisons with the cospar international reference atmosphere ozone models
Advances in Space Research, 1996Co-Authors: E P Shettle, R M Bevilacqua, J S Hornstein, K Hoppel, J D Lumpe, S S Krigman, D J Debrestian, M Fromm, W J GlaccumAbstract:Abstract NRL's Polar Ozone and Aerosol Measurement Experiment (POAM II) makes solar occultation Measurements through the earth's atmospheric limb to provide the distribution of atmospheric Aerosols, PSC's, and several molecular species critical for understanding ozone chemistry in the polar stratosphere. The early results from POAM II are presently being validated against in situ balloon borne instruments and remote sensing Measurements from both the surface and other satellite platforms. The monthly zonal mean profiles of the POAM II results will be compared with the CIRA (COSPAR International Reference Atmosphere) ozone models.
E W Chiou - One of the best experts on this subject based on the ideXlab platform.
-
an evaluation of the sage iii version 4 Aerosol extinction coefficient and water vapor data products
Atmospheric Chemistry and Physics, 2010Co-Authors: L W Thomason, Michael C Pitts, J R Moore, J M Zawodny, E W ChiouAbstract:Abstract. Herein, we provide an assessment of the data quality of Stratospheric Aerosol and Gas Experiment (SAGE III) Version 4 Aerosol extinction coefficient and water vapor data products. The evaluation is based on comparisons with data from four instruments: SAGE II, the Polar Ozone and Aerosol Measurement (POAM III), the Halogen Occultation Experiment (HALOE), and the Microwave Limb Sounder (MLS). Since only about half of the SAGE III channels have a direct comparison with Measurements by other instruments, we have employed some empirical techniques to evaluate Measurements at some wavelengths. We find that the Aerosol extinction coefficient Measurements at 449, 520, 755, 869, and 1021 nm are reliable with accuracies and precisions on the order of 10% in the mission's primary Aerosol target range of 15 to 25 km. We also believe this to be true of the Aerosol Measurements at 1545 nm though we cannot exclude some positive bias below 15 km. We recommend use of the 385 nm Measurements above 16 km where the accuracy is on par with other Aerosol channels. The 601 nm Measurement is much noisier (~20%) than other channels and we suggest caution in the use of these data. We believe that the 676 nm data are clearly defective particularly above 20 km (accuracy as poor as 50%) and the precision is also low (~30%). We suggest excluding this channel under most circumstances. The SAGE III Version 4 water vapor data product appears to be high quality and is recommended for science applications in the stratosphere below 45 km. In this altitude range, the mean differences with all four corroborative data sets are no bigger than 15% and often less than 10% with exceptional agreement with POAM III and MLS. Above 45 km, it seems likely that SAGE III water vapor values are increasingly too large and should be used cautiously or avoided. We believe that SAGE III meets its preflight goal of 15% accuracy and 10% precision between 15 and 45 km. SAGE III water vapor data does not appear to be affected by Aerosol loading in the stratosphere.