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David Garcianieto - One of the best experts on this subject based on the ideXlab platform.
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is a Scaling Factor required to obtain closure between measured and modelled atmospheric o4 absorptions an assessment of uncertainties of measurements and radiative transfer simulations for 2 selected days during the mad cat campaign
Atmospheric Measurement Techniques, 2019Co-Authors: Thomas Wagner, Steffen Beirle, Nuria Benavent, Tim Bosch, Sebastian Donner, Steffen Dorner, C Fayt, Udo Fries, Lok K Chan, David GarcianietoAbstract:In this study the consistency between MAX-DOAS measurements and radiative transfer simulations of the atmospheric O 4 absorption is investigated on 2 mainly cloud-free days during the MAD-CAT campaign in Mainz, Germany, in summer 2013. In recent years several studies indicated that measurements and radiative transfer simulations of the atmospheric O 4 absorption can only be brought into agreement if a so-called Scaling Factor (<1) is applied to the measured O 4 absorption. However, many studies, including those based on direct sunlight measurements, came to the opposite conclusion, that there is no need for a Scaling Factor. Up to now, there is no broad consensus for an explanation of the observed discrepancies between measurements and simulations. Previous studies inferred the need for a Scaling Factor from the comparison of the aerosol optical depths derived from MAX-DOAS O 4 measurements with that derived from coincident sun photometer measurements. In this study a different approach is chosen: the measured O 4 absorption at 360nm is directly compared to the O 4 absorption obtained from radiative transfer simulations. The atmospheric conditions used as input for the radiative transfer simulations were taken from independent data sets, in particular from sun photometer and ceilometer measurements at the measurement site. This study has three main goals: first all relevant error sources of the spectral analysis, the radiative transfer simulations and the extraction of the input parameters used for the radiative transfer simulations are quantified. One important result obtained from the analysis of synthetic spectra is that the O 4 absorptions derived from the spectral analysis agree within 1% with the corresponding radiative transfer simulations at 360nm. Based on the results from sensitivity studies, recommendations for optimised settings for the spectral analysis and radiative transfer simulations are given. Second, the measured and simulated results are compared for 2 selected cloud-free days with similar aerosol optical depths but very different aerosol properties. On 18 June, measurements and simulations agree within their (rather large) uncertainties (the ratio of simulated and measured O 4 absorptions is found to be 1.01±0.16). In contrast, on 8 July measurements and simulations significantly disagree: for the middle period of that day the ratio of simulated and measured O 4 absorptions is found to be 0.82±0.10, which differs significantly from unity. Thus, for that day a Scaling Factor is needed to bring measurements and simulations into agreement. Third, recommendations for further intercomparison exercises are derived. One important recommendation for future studies is that aerosol profile data should be measured at the same wavelengths as the MAX-DOAS measurements. Also, the altitude range without profile information close to the ground should be minimised and detailed information on the aerosol optical and/or microphysical properties should be collected and used. The results for both days are inconsistent, and no explanation for a O 4 Scaling Factor could be derived in this study. Thus, similar but more extended future studies should be performed, including more measurement days and more instruments. Also, additional wavelengths should be included. © 2019 Author(s).
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is a Scaling Factor required to obtain closure between measured and modelled atmospheric o 4 absorptions a case study for two days during the madcat campaign
Atmospheric Measurement Techniques Discussions, 2018Co-Authors: Thomas Wagner, Steffen Beirle, Nuria Benavent, Tim Bosch, Kai Lok Chan, Sebastian Donner, Steffen Dorner, C Fayt, Udo Fries, David GarcianietoAbstract:Abstract. In this study the consistency between MAX-DOAS measurements and radiative transfer simulations of the atmospheric O 4 absorption is investigated on two mainly clear days during the MAD-CAT campaign in Mainz, Germany, in Summer 2013. In recent years several studies indicated that measurements and radiative transfer simulations of the atmospheric O 4 absorption can only be brought into agreement if a so-called Scaling Factor ( 4 absorption. However, many studies, in particular based on direct sun light measurements, came to the opposite conclusion, that there is no need for a Scaling Factor. Up to now, there is no explanation for the observed discrepancies between measurements and simulations. Previous studies infered the need for a Scaling Factor from the comparison of the aerosol optical depth derived from MAX-DOAS O 4 measurements with that derived from coincident sun photometer measurements. In this study a different approach is chosen: the measured O 4 absorption at 360 nm is directly compared to the O 4 absorption obtained from radiative transfer simulations. The atmospheric conditions used as input for the radiative transfer simulations were taken from independent data sets, in particular from sun photometer and ceilometer measurements at the measurement site. The comparisons are performed for two selected clear days with similar aerosol optical depth but very different aerosol properties. For both days not only the O 4 absorptions are compared, but also all relevant error sources of the spectral analysis, the radiative transfer simulations as well as the extraction of the input parameters used for the radiative transfer simulations are quantified. One important result obtained from the analysis of synthetic spectra is that the O 4 absorptions derived from the spectral analysis agree within 1 % with the corresponding radiative transfer simulations. The performed tests and sensitivity studies might be useful for the analysis and interpretation of O 4 MAX-DOAS measurements in future studies. Different comparison results are found for both days: On 18 June, measurements and simulations agree within their (rather large) errors (the ratio of simulated and measured O 4 absorptions is found to be 1.01 ± 0.16). In contrast, on 8 July measurements and simulations significantly disagree: For the middle period of that day the ratio of simulated and measured O 4 absorptions is found to be 0.71 ± 0.12, which differs significantly from unity. Thus for that day a Scaling Factor is needed to bring measurements and simulations into agreement. One possible reason for the comparison results on 18 June is the rather large aerosol extinction (and its large uncertainty) close to the surface, which has a large effect on the radiative transfer simulations. Besides the inconsistent comparison results for both days, also no explanation for a O 4 Scaling Factor could be derived in this study. Thus similar, but more extended future studies should be performed, which preferably include more measurement days, more instruments and should be supported by more detailed independent aerosol measurements. Also additional wavelengths should be included. The MAX-DOAS measurements collected during the recent CINDI-2 campaign are probably well suited for that purpose.
William R Cluett - One of the best experts on this subject based on the ideXlab platform.
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optimal choice of time Scaling Factor for linear system approximations using laguerre models
IEEE Transactions on Automatic Control, 1994Co-Authors: Liuping Wang, William R CluettAbstract:Clowes (1965) illustrated how to select the optimal time-Scaling Factor for approximations of rational transfer functions using a series expansion of Laguerre functions. The present paper extends this result to approximations for general, L/sub 2/ stable, linear systems. As a direct application of this extended result, we are able to obtain approximations for irrational transfer functions which minimize the frequency domain error in the L/sub 2/ sense. Also, we give empirical solutions for the optimal time-Scaling Factor for approximations of first order plus delay systems which can then be applied to a larger class of overdamped systems. >
Thomas Wagner - One of the best experts on this subject based on the ideXlab platform.
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is a Scaling Factor required to obtain closure between measured and modelled atmospheric o4 absorptions an assessment of uncertainties of measurements and radiative transfer simulations for 2 selected days during the mad cat campaign
Atmospheric Measurement Techniques, 2019Co-Authors: Thomas Wagner, Steffen Beirle, Nuria Benavent, Tim Bosch, Sebastian Donner, Steffen Dorner, C Fayt, Udo Fries, Lok K Chan, David GarcianietoAbstract:In this study the consistency between MAX-DOAS measurements and radiative transfer simulations of the atmospheric O 4 absorption is investigated on 2 mainly cloud-free days during the MAD-CAT campaign in Mainz, Germany, in summer 2013. In recent years several studies indicated that measurements and radiative transfer simulations of the atmospheric O 4 absorption can only be brought into agreement if a so-called Scaling Factor (<1) is applied to the measured O 4 absorption. However, many studies, including those based on direct sunlight measurements, came to the opposite conclusion, that there is no need for a Scaling Factor. Up to now, there is no broad consensus for an explanation of the observed discrepancies between measurements and simulations. Previous studies inferred the need for a Scaling Factor from the comparison of the aerosol optical depths derived from MAX-DOAS O 4 measurements with that derived from coincident sun photometer measurements. In this study a different approach is chosen: the measured O 4 absorption at 360nm is directly compared to the O 4 absorption obtained from radiative transfer simulations. The atmospheric conditions used as input for the radiative transfer simulations were taken from independent data sets, in particular from sun photometer and ceilometer measurements at the measurement site. This study has three main goals: first all relevant error sources of the spectral analysis, the radiative transfer simulations and the extraction of the input parameters used for the radiative transfer simulations are quantified. One important result obtained from the analysis of synthetic spectra is that the O 4 absorptions derived from the spectral analysis agree within 1% with the corresponding radiative transfer simulations at 360nm. Based on the results from sensitivity studies, recommendations for optimised settings for the spectral analysis and radiative transfer simulations are given. Second, the measured and simulated results are compared for 2 selected cloud-free days with similar aerosol optical depths but very different aerosol properties. On 18 June, measurements and simulations agree within their (rather large) uncertainties (the ratio of simulated and measured O 4 absorptions is found to be 1.01±0.16). In contrast, on 8 July measurements and simulations significantly disagree: for the middle period of that day the ratio of simulated and measured O 4 absorptions is found to be 0.82±0.10, which differs significantly from unity. Thus, for that day a Scaling Factor is needed to bring measurements and simulations into agreement. Third, recommendations for further intercomparison exercises are derived. One important recommendation for future studies is that aerosol profile data should be measured at the same wavelengths as the MAX-DOAS measurements. Also, the altitude range without profile information close to the ground should be minimised and detailed information on the aerosol optical and/or microphysical properties should be collected and used. The results for both days are inconsistent, and no explanation for a O 4 Scaling Factor could be derived in this study. Thus, similar but more extended future studies should be performed, including more measurement days and more instruments. Also, additional wavelengths should be included. © 2019 Author(s).
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is a Scaling Factor required to obtain closure between measured and modelled atmospheric o 4 absorptions a case study for two days during the madcat campaign
Atmospheric Measurement Techniques Discussions, 2018Co-Authors: Thomas Wagner, Steffen Beirle, Nuria Benavent, Tim Bosch, Kai Lok Chan, Sebastian Donner, Steffen Dorner, C Fayt, Udo Fries, David GarcianietoAbstract:Abstract. In this study the consistency between MAX-DOAS measurements and radiative transfer simulations of the atmospheric O 4 absorption is investigated on two mainly clear days during the MAD-CAT campaign in Mainz, Germany, in Summer 2013. In recent years several studies indicated that measurements and radiative transfer simulations of the atmospheric O 4 absorption can only be brought into agreement if a so-called Scaling Factor ( 4 absorption. However, many studies, in particular based on direct sun light measurements, came to the opposite conclusion, that there is no need for a Scaling Factor. Up to now, there is no explanation for the observed discrepancies between measurements and simulations. Previous studies infered the need for a Scaling Factor from the comparison of the aerosol optical depth derived from MAX-DOAS O 4 measurements with that derived from coincident sun photometer measurements. In this study a different approach is chosen: the measured O 4 absorption at 360 nm is directly compared to the O 4 absorption obtained from radiative transfer simulations. The atmospheric conditions used as input for the radiative transfer simulations were taken from independent data sets, in particular from sun photometer and ceilometer measurements at the measurement site. The comparisons are performed for two selected clear days with similar aerosol optical depth but very different aerosol properties. For both days not only the O 4 absorptions are compared, but also all relevant error sources of the spectral analysis, the radiative transfer simulations as well as the extraction of the input parameters used for the radiative transfer simulations are quantified. One important result obtained from the analysis of synthetic spectra is that the O 4 absorptions derived from the spectral analysis agree within 1 % with the corresponding radiative transfer simulations. The performed tests and sensitivity studies might be useful for the analysis and interpretation of O 4 MAX-DOAS measurements in future studies. Different comparison results are found for both days: On 18 June, measurements and simulations agree within their (rather large) errors (the ratio of simulated and measured O 4 absorptions is found to be 1.01 ± 0.16). In contrast, on 8 July measurements and simulations significantly disagree: For the middle period of that day the ratio of simulated and measured O 4 absorptions is found to be 0.71 ± 0.12, which differs significantly from unity. Thus for that day a Scaling Factor is needed to bring measurements and simulations into agreement. One possible reason for the comparison results on 18 June is the rather large aerosol extinction (and its large uncertainty) close to the surface, which has a large effect on the radiative transfer simulations. Besides the inconsistent comparison results for both days, also no explanation for a O 4 Scaling Factor could be derived in this study. Thus similar, but more extended future studies should be performed, which preferably include more measurement days, more instruments and should be supported by more detailed independent aerosol measurements. Also additional wavelengths should be included. The MAX-DOAS measurements collected during the recent CINDI-2 campaign are probably well suited for that purpose.
Raghu N. Kacker - One of the best experts on this subject based on the ideXlab platform.
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Uncertainties in Scaling Factors for ab initio vibrational zero-point energies
The Journal of chemical physics, 2009Co-Authors: Karl K. Irikura, Russell D. Johnson, Raghu N. Kacker, Ruediger KesselAbstract:Vibrational zero-point energies (ZPEs) determined from ab initio calculations are often scaled by empirical Factors. An empirical Scaling Factor partially compensates for the effects arising from vibrational anharmonicity and incomplete treatment of electron correlation. These effects are not random but are systematic. We report Scaling Factors for 32 combinations of theory and basis set, intended for predicting ZPEs from computed harmonic frequencies. An empirical Scaling Factor carries uncertainty. We quantify and report, for the first time, the uncertainties associated with Scaling Factors for ZPE. The uncertainties are larger than generally acknowledged; the Scaling Factors have only two significant digits. For example, the Scaling Factor for B3LYP/6-31G(d) is 0.9757±0.0224 (standard uncertainty). The uncertainties in the Scaling Factors lead to corresponding uncertainties in predicted ZPEs. The proposed method for quantifying the uncertainties associated with Scaling Factors is based upon the Guide t...
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Uncertainties in Scaling Factors for ab Initio Vibrational Frequencies
The journal of physical chemistry. A, 2005Co-Authors: Karl K. Irikura, Russell D. Johnson, Raghu N. KackerAbstract:Vibrational frequencies determined from ab initio calculations are often scaled by empirical Factors. An empirical Scaling Factor partially compensates for the errors arising from vibrational anharmonicity and incomplete treatment of electron correlation. These errors are not random but are systematic biases. We report Scaling Factors for 40 combinations of theory and basis set, intended for predicting the fundamental frequencies from computed harmonic frequencies. An empirical Scaling Factor carries uncertainty. We quantify and report, for the first time, the uncertainties associated with the Scaling Factors. The uncertainties are larger than generally acknowledged; the Scaling Factors have only two significant digits. For example, the Scaling Factor for HF/6-31G(d) is 0.8982 ± 0.0230 (standard uncertainty). The uncertainties in the Scaling Factors lead to corresponding uncertainties in predicted vibrational frequencies. The proposed method for quantifying the uncertainties associated with Scaling Factor...
Karl K. Irikura - One of the best experts on this subject based on the ideXlab platform.
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Uncertainties in Scaling Factors for ab initio vibrational zero-point energies
The Journal of chemical physics, 2009Co-Authors: Karl K. Irikura, Russell D. Johnson, Raghu N. Kacker, Ruediger KesselAbstract:Vibrational zero-point energies (ZPEs) determined from ab initio calculations are often scaled by empirical Factors. An empirical Scaling Factor partially compensates for the effects arising from vibrational anharmonicity and incomplete treatment of electron correlation. These effects are not random but are systematic. We report Scaling Factors for 32 combinations of theory and basis set, intended for predicting ZPEs from computed harmonic frequencies. An empirical Scaling Factor carries uncertainty. We quantify and report, for the first time, the uncertainties associated with Scaling Factors for ZPE. The uncertainties are larger than generally acknowledged; the Scaling Factors have only two significant digits. For example, the Scaling Factor for B3LYP/6-31G(d) is 0.9757±0.0224 (standard uncertainty). The uncertainties in the Scaling Factors lead to corresponding uncertainties in predicted ZPEs. The proposed method for quantifying the uncertainties associated with Scaling Factors is based upon the Guide t...
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Uncertainties in Scaling Factors for ab Initio Vibrational Frequencies
The journal of physical chemistry. A, 2005Co-Authors: Karl K. Irikura, Russell D. Johnson, Raghu N. KackerAbstract:Vibrational frequencies determined from ab initio calculations are often scaled by empirical Factors. An empirical Scaling Factor partially compensates for the errors arising from vibrational anharmonicity and incomplete treatment of electron correlation. These errors are not random but are systematic biases. We report Scaling Factors for 40 combinations of theory and basis set, intended for predicting the fundamental frequencies from computed harmonic frequencies. An empirical Scaling Factor carries uncertainty. We quantify and report, for the first time, the uncertainties associated with the Scaling Factors. The uncertainties are larger than generally acknowledged; the Scaling Factors have only two significant digits. For example, the Scaling Factor for HF/6-31G(d) is 0.8982 ± 0.0230 (standard uncertainty). The uncertainties in the Scaling Factors lead to corresponding uncertainties in predicted vibrational frequencies. The proposed method for quantifying the uncertainties associated with Scaling Factor...
