Measurements of Aerosol Optical Properties Over the Ocean Using Sunphotometry and Lidar PDF Download

Author: Ellsworth Judd Welton
Publisher:
ISBN:
Category : Aerosols
Languages : en
Pages : 300

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Author: Rudra P Aryal
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Optical and chemical properties of size-resolved aerosols in near-surface air at Tudor Hill, Bermuda were measured between July 2006 and June 2009. Vertical distributions of aerosol backscattering and column-averaged aerosol optical properties were characterized with a Micro-pulse lidar (MPL) and a CIMEL automated sun-sky radiometer. The chemical species in size-segregated aerosols in marine air were compared with the surface level aerosol optical properties. The aerosol concentration, along with chemical components, was compared with the surface level wind speed and showed a significant correlation with the sea salt components. The non-sea salt components such as non-sea salt sulfate and ammonium did not show a correlation with the surface level wind speed. A comparison between scattering data at surface level with the extinction coefficient at the lowest altitude bin (75m) from the lidar inversion shows a consistent correlation but is quantitatively different. This quantitative discrepancy was explained based on the hygroscopic growth due to differences in relative humidity in measurement conditions. Aerosol optical properties measured near the surface were often significantly correlated with those averaged over the column. These include scattering by near-surface bulk aerosol at 530 nm versus column aerosol optical depth (AOD), near-surface sub-[mu]m scattering fraction versus column averaged sub-[mu]m scattering fraction, and the average angstrom exponent over column and lidar ratio derived using column integrated size distribution and complex refractive index. We also found that the single scattering albedo ([omega]o) measured at the surface by combining daily averages of the aerosol absorption and aerosol light scattering were in the same range as the instantaneous [omega]o retrieved for the column. The relative contribution of submicron aerosol light scattering to total aerosol light scattering is slightly higher in the column relative to the surface. Surface level wind speed was found to have a more important affect on bulk aerosol light scattering at the surface than in column.

Author: Alexander A. Kokhanovsky
Publisher: Springer Science & Business Media
ISBN: 3540499091
Category : Science
Languages : en
Pages : 154

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This new text offers experienced students a comprehensive review of available techniques for the remote sensing of aerosols. These small particles influence both atmospheric visibility and the thermodynamics of the atmosphere. They are also of great importance in any consideration of climate change problems. Aerosols may also be responsible for the loss of harvests, human health problems and ecological disasters. Thus, this detailed study of aerosol properties on a global scale could not be more timely.

Author: Raghavendra Kumar Kanike
Publisher: LAP Lambert Academic Publishing
ISBN: 9783659706226
Category :
Languages : en
Pages : 228

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In this book, we have described the optical and physical properties of aerosol which are considered to be an important in the Earth's radiation budget. The method of detection of various aerosol properties using ground-based automated Sun-sky radiometer is mentioned, by illustrating the measurements taken over one of a station, as part of Sun photometer worldwide network, named AERONET (AErosol RObotic NETwork). Besides, the basic details of Sun photometer, we have also illustrated the importance of synoptic weather parameters and use of trajectory analysis. Aerosol measurements from Sun photometer and satellite are compared and assessed the instruments capabilities. Using a large amount of data measured over a sub-tropical site in South Africa, we have studied the various optical properties of aerosol and their mutual relationship for addressing aerosol types. Classification and identification of different types of aerosol are elucidated by various methods. Apart from the results obtained, the study location has been considered to be significant due to only very few studies reported on aerosol properties, especially in the Southern Hemisphere and in Southern Africa region.

Author: Jedol Dayou
Publisher: Springer
ISBN: 9812871012
Category : Science
Languages : en
Pages : 67

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This book gives a detailed review on ground-based aerosol optical depth measurement with emphasis on the calibration issue. The review is written in chronological sequence to render better comprehension on the evolution of the classical Langley calibration from the past to present. It not only compiles the existing calibration methods but also presents a novel calibration algorithm in Langley sun-photometry over low altitude sites which conventionally is a common practice performed at high observatory stations. The proposed algorithm avoids travelling to high altitudes for frequent calibration that is difficult both in logistics and financial prospects. We addressed the problem by combining clear-sky detection model and statistical filter to strictly imitate the ideal clear-sky condition at high altitude for measurements taken over low altitudes. In this way, the possible temporal atmospheric drifts, abundant aerosol loadings and short time interval cloud transits are properly constrained. We believe that this finding has an integral part of practicality and versatility in ground-based aerosol optical depth measurement, which is nowadays an important climate agent in many atmospheric studies. Finally, the outcome of this book introduces a new calibration technique for the study and measurement of aerosol monitoring with emphasis on aerosol optical depth that we believe could be very beneficial to researchers and scientists in the similar area.

Author: John A. Reagan
Publisher:
ISBN:
Category :
Languages : en
Pages : 25

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Aerosol extinction profiles and aerosol extinction-to-back-scatter ratio, S(a), values have been determined for numerous days over the period May, 1979 to May, 1982 in Tucson, AZ via slant-path lidar measurements. These results have been analyzed to obtain a model aerosol extinction profile and a model S(a) value. The model extinction profile is characterized by rapidly, nearly linearly decreasing extinction through a 3km mixing layer (decreasing from 0.018/km at 200 m to 0.003/km at 3km), and a much more slowly decreasing extinction above the mixing layer. The mixing layer optical depth is about 0.04, and the optical depth to the maximum observation height (19km) is about 0.07. The inverse variance weighted S(a) value is about 25, and the majority of the S(a) determinations fell between 20 and 35. A limited number of cooperative lidar and balloon-borne cascade impactor measurements were also made to investigate aerosol size distribution and refractive index properties and their effects on the lidar observations. Impactor measurements yielded size distributions that were generally similar in shape, the distributions being perturbed Junge types with a dominance of coarse mode particles causing a bulge in the distributions in the large particle range.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 50

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Multi-year sets of ground-based sun-photometer measurements conducted at 12 Arctic sites and 9 Antarctic sites were examined to determine daily mean values of aerosol optical thickness [tau]([lambda]) at visible and near-infrared wavelengths, from which best-fit values of Ångström's exponent [alpha] were calculated. Analysing these data, the monthly mean values of [tau](0.50 [mu]m) and [alpha] and the relative frequency histograms of the daily mean values of both parameters were determined for winter-spring and summer-autumn in the Arctic and for austral summer in Antarctica. The Arctic and Antarctic covariance plots of the seasonal median values of [alpha] versus [tau](0.50 [mu]m) showed: (i) a considerable increase in [tau](0.50 [mu]m) for the Arctic aerosol from summer to winter-spring, without marked changes in [alpha]; and (ii) a marked increase in [tau](0.50 [mu]m) passing from the Antarctic Plateau to coastal sites, whereas [alpha] decreased considerably due to the larger fraction of sea-salt aerosol. Good agreement was found when comparing ground-based sun-photometer measurements of [tau]([lambda]) and [alpha] at Arctic and Antarctic coastal sites with Microtops measurements conducted during numerous AERONET/MAN cruises from 2006 to 2013 in three Arctic Ocean sectors and in coastal and off-shore regions of the Southern Atlantic, Pacific, and Indian Oceans, and the Antarctic Peninsula. Lidar measurements were also examined to characterise vertical profiles of the aerosol backscattering coefficient measured throughout the year at Ny-Ålesund. Satellite-based MODIS, MISR, and AATSR retrievals of [tau]([lambda]) over large parts of the oceanic polar regions during spring and summer were in close agreement with ship-borne and coastal ground-based sun-photometer measurements. An overview of the chemical composition of mode particles is also presented, based on in-situ measurements at Arctic and Antarctic sites. Fourteen log-normal aerosol number size-distributions were defined to represent the average features of nuclei, accumulation and coarse mode particles for Arctic haze, summer background aerosol, Asian dust and boreal forest fire smoke, and for various background austral summer aerosol types at coastal and high-altitude Antarctic sites. The main columnar aerosol optical characteristics were determined for all 14 particle modes, based on in-situ measurements of the scattering and absorption coefficients. Diurnally averaged direct aerosol-induced radiative forcing and efficiency were calculated for a set of multimodal aerosol extinction models, using various Bidirectional Reflectance Distribution Function models over vegetation-covered, oceanic and snow-covered surfaces. These gave a reliable measure of the pronounced effects of aerosols on the radiation balance of the surface-atmosphere system over polar regions.

Author: Gerald William Grams
Publisher:
ISBN:
Category : Atmosphere
Languages : en
Pages :

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Author: Ruth Signorell
Publisher: CRC Press
ISBN: 142008562X
Category : Nature
Languages : en
Pages : 513

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Helping you better understand the processes, instruments, and methods of aerosol spectroscopy, Fundamentals and Applications in Aerosol Spectroscopy provides an overview of the state of the art in this rapidly developing field. It covers fundamental aspects of aerosol spectroscopy, applications to atmospherically and astronomically relevant problem

Author:
Publisher:
ISBN:
Category : Oceanography
Languages : en
Pages : 104

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