The Experts below are selected from a list of 76419 Experts worldwide ranked by ideXlab platform
Michel Grutter - One of the best experts on this subject based on the ideXlab platform.
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Volcanic SO2 and SiF4 visualization using 2-D thermal emission spectroscopy - Part 1: Slant-columns and their ratios
Atmospheric Measurement Techniques, 2012Co-Authors: Wolfgang Stremme, Arne Krueger, Roland Harig, Michel GrutterAbstract:Abstract. The composition and emission rates of volcanic gas plumes provide insight of the geologic internal activity, atmospheric chemistry, aerosol formation and radiative processes around it. Observations are necessary for public security and the aviation industry. Ground-based thermal emission infrared spectroscopy, which uses the radiation of the volcanic gas itself, allows for continuously monitoring during day and night from a safe distance. We present measurements on Popocatepetl volcano based on thermal emission spectroscopy during different campaigns between 2006–2009 using a Scanning Infrared Gas Imaging System (SIGIS). The experimental set-up, measurement geometries and analytical algorithms are described. The equipment was operated from a safe distance of 12 km from the volcano at two different spectral resolutions: 0.5 and 4 cm−1. The 2-dimensional scanning capability of the instrument allows for an on-line visualization of the volcanic SO2 plume and its animation. SiF4 was also identified in the infrared spectra recorded at both resolutions. The SiF4/SO2 molecular ratio can be calculated from each image and used as a highly useful parameter to follow changes in volcanic activity. A small Vulcanian eruption was monitored during the night of 16 to 17 November 2008 and strong ash emission together with a pronounced SO2 cloud was registered around 01:00 a.m. LST (Local Standard Time). Enhanced SiF4/SO2 ratios were observed before and after the eruption. A validation of the results from thermal emission measurements with those from absorption spectra of the moon taken at the same Time, as well as an error analysis, are presented. The inferred propagation speed from sequential images is used in a subsequent paper (Part 2) to calculate the emission rates at different distances from the crater.
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Volcanic SO 2 and SiF 4 visualization and their ratio monitored using 2-D thermal emission spectroscopy
Atmospheric Measurement Techniques Discussions, 2011Co-Authors: Wolfgang Stremme, Arne Krueger, Roland Harig, Michel GrutterAbstract:Abstract. The composition and emission rates of volcanic gas plumes provide insight of the geologic internal activity, atmospheric chemistry, aerosol formation and radiative processes around it. Observations are necessary for public security and the aviation industry. Ground-based thermal emission infrared spectroscopy, which uses the radiation of the volcanic gas itself, allows for continuously monitoring during day and night from a save distance. We present measurements on Popocatépetl volcano based on thermal emission spectroscopy during different campaigns between 2006–2009 using a Scanning Infrared Gas Imaging System (SIGIS). The experimental set-up, measurement geometries and analytical algorithms are described. The equipment was operated from a safe distance of 12 km from the volcano at two different spectral resolutions: 0.5 and 4 cm−1. The 2-dimensional scanning capability of the instrument allows for an on-line visualization of the volcanic SO2 plume, animation and determination of its propagation speed. SiF4 was also identified in the infrared spectra recorded at both resolutions. The SiF4/SO2 molecular ratio can be calculated from each image and used as a highly useful parameter to follow changes in volcanic activity. A small Vulcanian eruption was monitored during the night of 16 to 17 November 2008 which was confirmed from the strong ash emission registered around 01:00 a.m. LST (Local Standard Time) and a pronounced SO2 cloud was registered. Enhanced SiF4/SO2 ratios were observed before and after the eruption. A validation of the results from thermal emission measurements with those from absorption spectra of the moon taken at the same Time, as well as an error analysis, are presented. The inferred propagation speed from sequential imagees is used to calculate the emission rates at different distances from the crater.
Daniel J. Cecil - One of the best experts on this subject based on the ideXlab platform.
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Tropical Cyclone Diurnal Cycle as Observed by TRMM
Monthly weather review, 2016Co-Authors: Kenneth D. Leppert, Daniel J. CecilAbstract:AbstractPrevious work has indicated a clear, consistent diurnal cycle in rainfall and cold cloudiness coverage around tropical cyclones. This cycle may have important implications for structure and intensity changes of these storms and the forecasting of such changes. The goal of this paper is to use passive and active microwave measurements from the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) and Precipitation Radar (PR), respectively, to better understand the tropical cyclone diurnal cycle throughout a deep layer of a tropical cyclone’s clouds.The composite coverage by PR reflectivity ≥20 dBZ at various heights as a function of Local Standard Time (LST) and radius suggests the presence of a diurnal signal for radii
Wolfgang Stremme - One of the best experts on this subject based on the ideXlab platform.
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Volcanic SO2 and SiF4 visualization using 2-D thermal emission spectroscopy - Part 1: Slant-columns and their ratios
Atmospheric Measurement Techniques, 2012Co-Authors: Wolfgang Stremme, Arne Krueger, Roland Harig, Michel GrutterAbstract:Abstract. The composition and emission rates of volcanic gas plumes provide insight of the geologic internal activity, atmospheric chemistry, aerosol formation and radiative processes around it. Observations are necessary for public security and the aviation industry. Ground-based thermal emission infrared spectroscopy, which uses the radiation of the volcanic gas itself, allows for continuously monitoring during day and night from a safe distance. We present measurements on Popocatepetl volcano based on thermal emission spectroscopy during different campaigns between 2006–2009 using a Scanning Infrared Gas Imaging System (SIGIS). The experimental set-up, measurement geometries and analytical algorithms are described. The equipment was operated from a safe distance of 12 km from the volcano at two different spectral resolutions: 0.5 and 4 cm−1. The 2-dimensional scanning capability of the instrument allows for an on-line visualization of the volcanic SO2 plume and its animation. SiF4 was also identified in the infrared spectra recorded at both resolutions. The SiF4/SO2 molecular ratio can be calculated from each image and used as a highly useful parameter to follow changes in volcanic activity. A small Vulcanian eruption was monitored during the night of 16 to 17 November 2008 and strong ash emission together with a pronounced SO2 cloud was registered around 01:00 a.m. LST (Local Standard Time). Enhanced SiF4/SO2 ratios were observed before and after the eruption. A validation of the results from thermal emission measurements with those from absorption spectra of the moon taken at the same Time, as well as an error analysis, are presented. The inferred propagation speed from sequential images is used in a subsequent paper (Part 2) to calculate the emission rates at different distances from the crater.
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Volcanic SO 2 and SiF 4 visualization and their ratio monitored using 2-D thermal emission spectroscopy
Atmospheric Measurement Techniques Discussions, 2011Co-Authors: Wolfgang Stremme, Arne Krueger, Roland Harig, Michel GrutterAbstract:Abstract. The composition and emission rates of volcanic gas plumes provide insight of the geologic internal activity, atmospheric chemistry, aerosol formation and radiative processes around it. Observations are necessary for public security and the aviation industry. Ground-based thermal emission infrared spectroscopy, which uses the radiation of the volcanic gas itself, allows for continuously monitoring during day and night from a save distance. We present measurements on Popocatépetl volcano based on thermal emission spectroscopy during different campaigns between 2006–2009 using a Scanning Infrared Gas Imaging System (SIGIS). The experimental set-up, measurement geometries and analytical algorithms are described. The equipment was operated from a safe distance of 12 km from the volcano at two different spectral resolutions: 0.5 and 4 cm−1. The 2-dimensional scanning capability of the instrument allows for an on-line visualization of the volcanic SO2 plume, animation and determination of its propagation speed. SiF4 was also identified in the infrared spectra recorded at both resolutions. The SiF4/SO2 molecular ratio can be calculated from each image and used as a highly useful parameter to follow changes in volcanic activity. A small Vulcanian eruption was monitored during the night of 16 to 17 November 2008 which was confirmed from the strong ash emission registered around 01:00 a.m. LST (Local Standard Time) and a pronounced SO2 cloud was registered. Enhanced SiF4/SO2 ratios were observed before and after the eruption. A validation of the results from thermal emission measurements with those from absorption spectra of the moon taken at the same Time, as well as an error analysis, are presented. The inferred propagation speed from sequential imagees is used to calculate the emission rates at different distances from the crater.
Kenneth D. Leppert - One of the best experts on this subject based on the ideXlab platform.
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Tropical Cyclone Diurnal Cycle as Observed by TRMM
Monthly weather review, 2016Co-Authors: Kenneth D. Leppert, Daniel J. CecilAbstract:AbstractPrevious work has indicated a clear, consistent diurnal cycle in rainfall and cold cloudiness coverage around tropical cyclones. This cycle may have important implications for structure and intensity changes of these storms and the forecasting of such changes. The goal of this paper is to use passive and active microwave measurements from the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) and Precipitation Radar (PR), respectively, to better understand the tropical cyclone diurnal cycle throughout a deep layer of a tropical cyclone’s clouds.The composite coverage by PR reflectivity ≥20 dBZ at various heights as a function of Local Standard Time (LST) and radius suggests the presence of a diurnal signal for radii
Xinghua Yang - One of the best experts on this subject based on the ideXlab platform.
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Characteristics of dust devil and its dust emission in northern margin of the Taklimakan Desert
Aeolian Research, 2020Co-Authors: Xinghua Yang, Wen Huo, Ali Mamtimin, Chenglong Zhou, Fan YangAbstract:Abstract Dust aerosol has significant impacts on weather, climate, ecology, and global matter cycling, and dust devils are an important source of dust aerosol. The Taklimakan Desert is a major dust source area in East Asia, yet the characteristics of dust devils and their dust emissions are unclear in this region. In this study, the characteristics of dust devils at the northern margin of the Taklimakan Desert were analyzed. Existing equations for estimating dust emission by dust devils were revised based on our observed data, and dust emissions were estimated for the study area. The results showed that dust devils in the study area mainly occurred between March and September, which accounted for 90.9% of the total number of occurrence days in the year. Dust devil occurrence days displayed clear seasonal variation, ranked in the following descending order: summer > spring > autumn > winter. Dust devils tended to occur more frequently during the day, with relatively high occurrences from around 12:00 to 16:00 Local Standard Time (LST) with peak occurrence 14:00–15:00 LST. Of the observed dust devils, 72.5% had a duration of 4 min or less while only 5.9% lasting for more than 6 min. The average annual dust emission from dust devils in the study area was approximately 1.96 t/km2. The occurrence of dust devils and the calculated amounts of dust emitted were closely related to surface temperature and thermodynamic efficiency.
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Saltation activity and its threshold velocity in the Gurbantunggut Desert, China
Natural Hazards, 2017Co-Authors: Xinghua Yang, Xinchun Liu, Fan Yang, Wen Huo, Shuanghe Shen, Ali MamtiminAbstract:A field experiment was conducted from 2 May 2010 to 1 May 2012 in the Gurbantunggut Desert, the second largest desert in China, to investigate saltation activity and its threshold velocity, and their relations with atmospheric and soil conditions. The results showed that saltation activity occurred more frequently during 08:00–20:00 Local Standard Time in spring and summer, with air temperatures between 20.0 and 29.0 °C, water vapor pressures between 0.6 and 0.9 kPa, soil temperatures between 25.0 and 30.0 °C, and a soil moisture lower than 0.04 m3/m3. At 2 m height, the saltation threshold velocity varied between 11.1 and 13.9 m/s, with a mean of 12.5 m/s. Threshold velocity showed clear seasonal variations in the following sequence: spring (11.7 m/s)
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Diurnal variations of saltation activity at Tazhong: the hinterland of Taklimakan Desert
Meteorology and Atmospheric Physics, 2012Co-Authors: Xinghua Yang, Wen Huo, Ali Mamtimin, Xinchun LiuAbstract:The Taklimakan Desert of China is a region of frequent sandstorms and, thus, is a major sand and dust source area. Tazhong, a small mining village, is located near the center of the Taklimakan Desert at a distance of 220 km from the desert margins. Near Tazhong, we conducted a 2-year field investigation designed to monitor the diurnal variation of saltation activity using fast-responding piezoelectric saltation sensors (Sensits). Results suggest that saltation activity tends to occur more frequently during dayTime in all seasons, relatively high levels of saltation activity are maintained from around 11:30 to around 16:30 Local Standard Time (LST), because of stronger wind speed, higher soil temperature and lower relative humidity. During the spring and summer seasons, the saltation activity can occur at any Time of the day, while there are some periods with zero saltation seconds at night and in the early morning during autumn and winter seasons. The results confirm that sandstorms tend to occur more frequently during daylight hours, so it may be helpful to forecast and guard against the occurrence of blowing sand or sandstorms in the Taklimakan Desert.
