Browsing by Subject "Aerosol"
Now showing 1 - 8 of 8
Results Per Page
Sort Options
Item A critical examination of the residual cloud contamination and diurnal sampling effects on MODIS estimates of aerosol over ocean(IEEE, 2005-11-21) Kaufman, Y. J.; Remer, L. A.; Tanre, D.; Li, Rong-Rong; Kleidman, R.; Mattoo, S.; Levy, R. C.; Eck, Thomas; Holben, B. N.; Ichoku, C.; Martins, J. V.; Koren, IllanObservations of the aerosol optical thickness (AOT) by the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments aboard Terra and Aqua satellites are being used extensively for applications to climate and air quality studies. Data quality is essential for these studies. Here we investigate the effects of unresolved clouds on the MODIS measurements of the AOT. The main cloud effect is from residual cirrus that increases the AOT by 0.015/spl plusmn/0.003 at 0.55 /spl mu/m. In addition, lower level clouds can add contamination. We examine the effect of lower clouds using the difference between simultaneously measured MODIS and AERONET AOT. The difference is positively correlated with the cloud fraction. However, interpretation of this difference is sensitive to the definition of cloud contamination versus aerosol growth. If we consider this consistent difference between MODIS and AERONET to be entirely due to cloud contamination we get a total cloud contamination of 0.025/spl plusmn/0.005, though a more likely estimate is closer to 0.020 after accounting for aerosol growth. This reduces the difference between MODIS-observed global aerosol optical thickness over the oceans and model simulations by half, from 0.04 to 0.02. However it is insignificant for studies of aerosol cloud interaction. We also examined how representative are the MODIS data of the diurnal average aerosol. Comparison to monthly averaged sunphotometer data confirms that either the Terra or Aqua estimate of global AOT is a valid representation of the daily average. Though in the vicinity of aerosol sources such as fires, we do not expect this to be true.Item An overview of regional experiments on biomass burning aerosols and related pollutants in Southeast Asia: From BASE-ASIA and the Dongsha Experiment to 7-SEAS(Elsevier, 2013-10-01) Lin, Neng-Huei; Tsay, Si-Chee; Maring, Hal B.; Yen, Ming-Cheng; Sheu, Guey-Rong; Wang, Sheng-Hsiang; Chi, Kai Hsien; Chuang, Ming-Tung; Ou-Yang, Chang-Feng; Fu, Joshua S.; Reid, Jeffrey S.; Lee, Chung-Te; Wang, Lin-Chi; Wang, Jia-Lin; Hsu, Christina N.; Sayer, Andrew; Holben, Brent N.; Chu, Yu-Chi; Nguyen, Xuan Anh; Sopajaree, Khajornsak; Chen, Shui-Jen; Cheng, Man-Ting; Tsuang, Ben-Jei; Tsai, Chuen-Jinn; Peng, Chi-Ming; Schnell, Russell C.; Conway, Tom; Chang, Chang-Tang; Lin, Kuen-Song; Tsai, Ying I.; Lee, Wen-Jhy; Chang, Shuenn-Chin; Liu, Jyh-Jian; Chiang, Wei-Li; Huang, Shih-Jen; Lin, Tang-Huang; Liu, Gin-RongBy modulating the Earth-atmosphere energy, hydrological and biogeochemical cycles, and affecting regional-to-global weather and climate, biomass burning is recognized as one of the major factors affecting the global carbon cycle. However, few comprehensive and wide-ranging experiments have been conducted to characterize biomass-burning pollutants in Southeast Asia (SEA) or assess their regional impact on meteorology, the hydrological cycle, the radiative budget, or climate change. Recently, BASE-ASIA (Biomass-burning Aerosols in South-East Asia: Smoke Impact Assessment) and the 7-SEAS (7-South-East Asian Studies)/Dongsha Experiment were conducted during the spring seasons of 2006 and 2010 in northern SEA, respectively, to characterize the chemical, physical, and radiative properties of biomass-burning emissions near the source regions, and assess their effects. This paper provides an overview of results from these two campaigns and related studies collected in this special issue, entitled “Observation, modeling and impact studies of biomass burning and pollution in the SE Asian Environment”. This volume includes 28 papers, which provide a synopsis of the experiments, regional weather/climate, chemical characterization of biomass-burning aerosols and related pollutants in source and sink regions, the spatial distribution of air toxics (atmospheric mercury and dioxins) in source and remote areas, a characterization of aerosol physical, optical, and radiative properties, as well as modeling and impact studies. These studies, taken together, provide the first relatively complete dataset of aerosol chemistry and physical observations conducted in the source/sink region in the northern SEA, with particular emphasis on the marine boundary layer and lower free troposphere (LFT). The data, analysis and modeling included in these papers advance our present knowledge of source characterization of biomass-burning pollutants near the source regions as well as the physical and chemical processes along transport pathways. In addition, we raise key questions to be addressed by a coming deployment during springtime 2013 in northern SEA, named 7-SEAS/BASELInE (Biomass-burning Aerosols & Stratocumulus Environment: Lifecycles and Interactions Experiment). This campaign will include a synergistic approach for further exploring many key atmospheric processes (e.g., complex aerosol–cloud interactions) and impacts of biomass burning on the surface–atmosphere energy budgets during the lifecycles of biomass-burning emissions.Item Characterization of aerosols over the Indochina peninsula from satellite-surface observations during biomass burning pre-monsoon season(Elsevier, 2012-05-05) Gautam, Ritesh; Hsu, N. Christina; Eck, Thomas; Holben, Brent N.; Janjai, Serm; Jantarach, Treenuch; Tsay, Si-Chee; Lau, William K.This paper presents characterization of aerosols over the Indochina peninsular regions of Southeast Asia during pre-monsoon season from satellite and ground-based radiometric observations. Our analysis focuses on the seasonal peak period in aerosol loading and biomass burning, prior to the onset of the Asian summer monsoon, as observed in the inter-annual variations of Aerosol Optical Depth (AOD) and fire count data from MODIS. Multi-year (2007–2011) analysis of spaceborne lidar measurements, from CALIOP, indicates presence of aerosols mostly within boundary layer, however extending to elevated altitudes to ~4 km over northern regions of Indochina, encompassing Myanmar, northern Thailand and southern China. In addition, a strong gradient in aerosol loading and vertical distribution is observed from the relatively clean equatorial conditions to heavy smoke-laden northern regions (greater aerosol extinction and smaller depolarization ratio). Based on column-integrated ground-based measurements from four AERONET locations distributed over Thailand, the regional aerosol loading is found to be significantly absorbing with spectral single scattering albedo (SSA) below 0.91 ± 0.02 in the 440–1020 nm range, with lowest seasonal mean SSA (most absorbing aerosol) over the northern location of Chiang Mai (SSA ~ 0.85) during pre-monsoon season. The smoke-laden aerosol loading is found to exhibit a significant diurnal pattern with higher AOD departures during early morning observations relative to late afternoon conditions (peak difference of more than 15% amplitude). Finally, satellite-based aerosol radiative impact is assessed using CERES shortwave Top-of-Atmosphere flux, in conjunction with MODIS AOD. Overall, a consistency in the aerosol-induced solar absorption characteristic is found among selected regions from ground-based sunphotometer-derived spectral SSA retrievals and satellite-based radiative forcing analysis.Item ENVIRONMENTAL FACTORS AFFECTING THE MEASUREMENT OF THE PHYSICAL AND CHEMICAL PROPERTIES OF AEROSOLIZED BIOLOGICAL PARTICLES(2014-01-01) Ratnesar-Shumate, Shanna Ashni; Santarpia, Joshua L; Chemical, Biochemical & Environmental Engineering; Engineering, Chemical and BiochemicalBiological aerosols, also known as bioaerosols, are a subset of organic carbon aerosols that consist of airborne particles that may be alive, may contain other live organisms, or released from living organisms. Many methods can be used to study bioaerosols. These methods range from collection and characterization of samples via culture, polymerase chain reaction, and immunoassay, to spectroscopic methods such as Raman spectroscopy and fluorometry. When biological particles are released into the atmosphere, they have the potential to interact with atmospheric constituents such as water vapor, solar radiation, free radicals, volatile organic, semi-volatile organic and inorganic gas-phase compounds. The objective of this work was to access the environmental factors that affect the physical and chemical properties and measurement of aerosolized biological aerosols. A novel test system was demonstrated to re-create natural fluctuations in biological and non-biological aerosol concentrations in a controllable laboratory setting for evaluating sensor performance. The Dynamic Concentration Aerosol Generator (DyCAG) can be used for bioaerosol sensor evaluation by generation of challenges of biological aerosols of interest at specific concentrations in the presence of varying levels of environmentally relevant aerosols. To understand the limitations of fluorescence-based measurements for detection and characterization of biological aerosols and to develop improved instrumentation and methods for making measurements, changes that occurred to biological particles due atmospheric exposure to ozone and water vapor were measured using a rotating drum chamber. The spectral properties of ultra-violet laser-induced fluorescence (UV-LIF) of two types of biological aerosols, Bacillus thuringiensis Al Hakam (Bt Al Hakam) spores and MS2 bacteriophage when excited at 263, 351, and 355 nm were shown to change when exposed to ozone and water vapor. In addition, changes in the biological activity of these bioaerosols as a function of the exposure conditions were observed. The hygroscopic properties of several types of biological aerosols and the media used for culturing and aerosolized bioaerosols were measured. Media containing high concentrations of salt showed the highest affinity for the uptake of water and dominated the hygroscopic properties of the aerosols measured. The studies presented in this dissertations describe some of the factors that contribute to how the physical and chemical properties of biological aerosols and their measurement are impacted by external factors when in their native state.Item Extending “Deep Blue” aerosol retrieval coverage to cases of absorbing aerosols above clouds: Sensitivity analysis and first case studies(AGU, 2016-04-18) Sayer, Andrew; Hsu, N. C.; Bettenhausen, C.; Lee, J.; Redemann, J.; Schmid, B.; Shinozuka, Y.Cases of absorbing aerosols above clouds (AACs), such as smoke or mineral dust, are omitted from most routinely processed space-based aerosol optical depth (AOD) data products, including those from the Moderate Resolution Imaging Spectroradiometer (MODIS). This study presents a sensitivity analysis and preliminary algorithm to retrieve above-cloud AOD and liquid cloud optical depth (COD) for AAC cases from MODIS or similar sensors, for incorporation into a future version of the “Deep Blue” AOD data product. Detailed retrieval simulations suggest that these sensors should be able to determine AAC AOD with a typical level of uncertainty ~25–50% (with lower uncertainties for more strongly absorbing aerosol types) and COD with an uncertainty ~10–20%, if an appropriate aerosol optical model is known beforehand. Errors are larger, particularly if the aerosols are only weakly absorbing, if the aerosol optical properties are not known, and the appropriate model to use must also be retrieved. Actual retrieval errors are also compared to uncertainty envelopes obtained through the optimal estimation (OE) technique; OE-based uncertainties are found to be generally reasonable for COD but larger than actual retrieval errors for AOD, due in part to difficulties in quantifying the degree of spectral correlation of forward model error. The algorithm is also applied to two MODIS scenes (one smoke and one dust) for which near-coincident NASA Ames Airborne Tracking Sun photometer (AATS) data were available to use as a ground truth AOD data source, and found to be in good agreement, demonstrating the validity of the technique with real observations.Item From BASE-ASIA toward 7-SEAS: A satellite-surface perspective of boreal spring biomass-burning aerosols and clouds in Southeast Asia(Elsevier, 2013-10-01) Tsay, Si-Chee; Hsu, N. Christina; Lau, William K. -M.; Li, Can; Gabriel, Philip M.; Ji, Qiang; Holben, Brent N.; Judd Welton, E.; Nguyen, Anh X.; Janjai, Serm; Lin, Neng-Huei; Reid, Jeffrey S.; Boonjawat, Jariya; Howell, Steven G.; Huebert, Barry J.; Fu, Joshua S.; Hansell, Richard A.; Sayer, Andrew; Gautam, Ritesh; Wang, Sheng-Hsiang; Goodloe, Colby S.; Miko, Laddawan R.; Shu, Peter K.; Loftus, Adrian M.; Huang, Jingfeng; Kim, Jin Young; Jeong, Myeong-Jae; Pantina, PeterIn this paper, we present recent field studies conducted by NASA's SMART-COMMIT (and ACHIEVE, to be operated in 2013) mobile laboratories, jointly with distributed ground-based networks (e.g., AERONET, http://aeronet.gsfc.nasa.gov/ and MPLNET, http://mplnet.gsfc.nasa.gov/) and other contributing instruments over northern Southeast Asia. These three mobile laboratories, collectively called SMARTLabs (cf. http://smartlabs.gsfc.nasa.gov/, Surface-based Mobile Atmospheric Research & Testbed Laboratories) comprise a suite of surface remote sensing and in-situ instruments that are pivotal in providing high spectral and temporal measurements, complementing the collocated spatial observations from various Earth Observing System (EOS) satellites. A satellite-surface perspective and scientific findings, drawn from the BASE-ASIA (2006) field deployment as well as a series of ongoing 7-SEAS (2010–13) field activities over northern Southeast Asia are summarized, concerning (i) regional properties of aerosols from satellite and in-situ measurements, (ii) cloud properties from remote sensing and surface observations, (iii) vertical distribution of aerosols and clouds, and (iv) regional aerosol radiative effects and impact assessment. The aerosol burden over Southeast Asia in boreal spring, attributed to biomass burning, exhibits highly consistent spatial and temporal distribution patterns, with major variability arising from changes in the magnitude of the aerosol loading mediated by processes ranging from large-scale climate factors to diurnal meteorological events. Downwind from the source regions, the tightly coupled-aerosol–cloud system provides a unique, natural laboratory for further exploring the micro- and macro-scale relationships of the complex interactions. The climatic significance is presented through large-scale anti-correlations between aerosol and precipitation anomalies, showing spatial and seasonal variability, but their precise cause-and-effect relationships remain an open-ended question. To facilitate an improved understanding of the regional aerosol radiative effects, which continue to be one of the largest uncertainties in climate forcing, a joint international effort is required and anticipated to commence in springtime 2013 in northern Southeast Asia.Item INFLUENCE OF AERODYNAMIC PARTICLE SIZE ON BOTULINUM NEUROTOXIN POTENCY IN MICE(Tayor and Francis - Inhalation Toxicology, 2020-11-12) Boydston, Jeremy; Yeager, John; Taylor, Jill; Dabisch, Paul; Dabisch, Paul; Hood College Biology; Biomedical and Environmental ScienceFor many agents the aerodynamic particle size can affect both the virulence and disease course in animal models. Botulinum neurotoxins (BoNTs), which are widely known as potential bioterrorism agents, are toxic via multiple routes of exposure, including small particle inhalation (1-3 μm MMAD). However, the impact of larger particle sizes on the potency of BoNT has not been previously reported. Outbred mice were exposed to BoNT-containing aerosols with differing mass median aerodynamic diameters (MMADs) of 1.1, 4.9, and 7.6 microns. Collecting aerosolized BoNT onto gelatin filters or into liquid impingers resulted in equivalent estimates of aerosol concentration. Nose-only and whole-body inhalation exposure resulted in nearly identical estimates of the median lethal dose (LD50). The LD50 for inhaled BoNT increased approximately 50-fold when the median aerodynamic particle size was increased from 1.1 to 4.9 μm, from 139 (95% CI: 111-185) to 7,324 (95% CI: 4,287-10,891) mouse intraperitoneal median lethal doses (MIPLD50).Item Retrieval of aerosol properties using Polarized Imaging Nephelometer (PI-Neph) laboratory measurements and Hyper-Angular Rainbow Polarimeter (HARP) remote sensing observations(2021-01-01) Puthukkudy, Anin; Martins, J. Vanderlei; Physics; Physics, AtmosphericAerosols play an essential role in Earth's climate: they directly perturb Earth's radiation budget and indirectly modify cloud properties, influencing its energy and hydrological budgets. The direct radiative effects of aerosols, the absorption, and scattering of light, depends on the intrinsic optical properties of the particles, the total aerosol loading, and the radiative properties of the surface beneath the aerosol layer. Aerosols are highly variable in their spatial and temporal distributions and their optical and micro-physical properties; it is especially challenging to represent their radiative effect realistically in climate models. Therefore, aerosol radiative forcing remains one of the main uncertainties in global climate change estimation. To better characterize the aerosol role in the global radiation budget and narrow uncertainties in predicting climate change, we need to understand better and constrain these properties' temporal and spatial distributions. Even though we have multidecadal data of aerosol measurement using satellite instruments, to better constrain the aerosol forcing, we need to know more about the properties of aerosols and their effects on cloud formation. It is why less explored multi-angular polarimetric scattering measurements become important in aerosol measurements. Unlike single viewing imaging radiometer measurements, the multi-angular polarimetric measurements have better information on aerosol properties; the methodology in this thesis tries to use this information content to understand the aerosol properties better. Also, demonstrate the aerosol properties retrieval from the measurements made by a novel family of MAP instruments developed at the University of Maryland Baltimore County using an inversion algorithm called GRASP. The thesis includes results from the volcanic ash resuspension measurement using the PI-Neph (Chapter 3). Puthukkudy et al. (2020) made the first demonstration of aerosol retrievals from the AirHARP measurements during the NASA campaign ACEPOL 2017 (Chapter 4). In Chapter 5, the radiometric measurements made by the HARP CubeSat instrument using the prelaunch calibration are validated and tested using existing reference instruments. The results presented in this thesis using the multi-angular polarimetric scattering measurement helps in constraining the aerosol properties and thus reducing the aerosol forcing uncertainties and thus accurately predicting the climate response.