Two-parameter model of aerosol extinction in the wavelength range 0.4 to 12 μm

1999 ◽  
Author(s):  
Nikolay N. Shchelkanov ◽  
Yurii A. Pkhalagov
Keyword(s):  
Wavelength Range ◽  
Aerosol Extinction ◽  
Two Parameter

scholarly journals Spectral Aerosol Extinction (SpEx): a new instrument for in situ ambient aerosol extinction measurements across the UV/visible wavelength range

2015 ◽  
Vol 8 (6) ◽  
pp. 6469-6509 ◽  
Author(s):  
C. E. Jordan ◽  
B. E. Anderson ◽  
A. J. Beyersdorf ◽  
C. A. Corr ◽  
J. E. Dibb ◽  
...  
Keyword(s):  
Wavelength Range ◽  
Theoretical Calculations ◽  
Polystyrene Latex ◽  
Aerosol Extinction ◽  
Brown Carbon ◽  
Ambient Aerosol ◽  
Measurement Capability ◽  
New Instrument ◽  
Visible Wavelengths

Abstract. We introduce a new instrument for the measurement of in situ ambient aerosol extinction over the 300–700 nm wavelength range, the Spectral Aerosol Extinction (SpEx) instrument. This measurement capability is envisioned to complement existing in situ instrumentation, allowing for simultaneous measurement of the evolution of aerosol optical, chemical, and physical characteristics in the ambient environment. In this work, a detailed description of the instrument is provided along with characterization tests performed in the laboratory. Measured spectra of NO2 and polystyrene latex spheres (PSLs) agreed well with theoretical calculations. Good agreement was also found with simultaneous aerosol extinction measurements at 450, 530, and 630 nm using CAPS PMex instruments in a series of 22 tests including non-absorbing compounds, dusts, soot, and black and brown carbon analogs. SpEx can more accurately distinguish the presence of brown carbon from other absorbing aerosol due to its 300 nm lower wavelength limit compared to measurements limited to visible wavelengths. Extinction spectra obtained with SpEx contain more information than can be conveyed by a simple power law fit (typically represented by Ångström Exponents). Planned future improvements aim to lower detection limits and ruggedize the instrument for mobile operation.

scholarly journals MAX-DOAS measurements in southern China: 1. automated aerosol profile retrieval using oxygen dimers absorptions

2008 ◽  
Vol 8 (5) ◽  
pp. 17661-17690 ◽  
Author(s):  
X. Li ◽  
T. Brauers ◽  
M. Shao ◽  
R. M. Garland ◽  
T. Wagner ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wavelength Range ◽  
Excellent Agreement ◽  
Pearl River Delta ◽  
Southern China ◽  
Pearl River ◽  
Aerosol Extinction ◽  
Pearl River Delta Region ◽  
The Pearl River Delta ◽  
The Pearl River

Abstract. We performed MAX-DOAS measurements during the PRiDe-PRD2006 campaign in the Pearl River Delta region 50 km north of Guangzhou, China, for 4 weeks in June 2006. We used an instrument which simultaneously sampled the wavelength range from 292 nm to 443 nm at 7 different elevation angles between 3° and 90°. Here we show that the O4 (O2 dimer) absorption at 360 nm can be used to retrieve the aerosol extinction and the height of the boundary layer. A comparison with simultaneously recorded, ground based nephelometer data shows an excellent agreement.

scholarly journals Spectral aerosol extinction (SpEx): a new instrument for in situ ambient aerosol extinction measurements across the UV/visible wavelength range

2015 ◽  
Vol 8 (11) ◽  
pp. 4755-4771 ◽  
Author(s):  
C. E. Jordan ◽  
B. E. Anderson ◽  
A. J. Beyersdorf ◽  
C. A. Corr ◽  
J. E. Dibb ◽  
...  
Keyword(s):  
Wavelength Range ◽  
Theoretical Calculations ◽  
Polystyrene Latex ◽  
Aerosol Extinction ◽  
Brown Carbon ◽  
Ambient Aerosol ◽  
Measurement Capability ◽  
New Instrument ◽  
Visible Wavelengths

Abstract. We introduce a new instrument for the measurement of in situ ambient aerosol extinction over the 300–700 nm wavelength range, the spectral aerosol extinction (SpEx) instrument. This measurement capability is envisioned to complement existing in situ instrumentation, allowing for simultaneous measurement of the evolution of aerosol optical, chemical, and physical characteristics in the ambient environment. In this work, a detailed description of the instrument is provided along with characterization tests performed in the laboratory. Measured spectra of NO2 and polystyrene latex spheres (PSLs) agreed well with theoretical calculations. Good agreement was also found with simultaneous aerosol extinction measurements at 450, 530, and 630 nm using CAPS PMex instruments in a series of 22 tests including nonabsorbing compounds, dusts, soot, and black and brown carbon analogs. SpEx measurements are expected to help identify the presence of ambient brown carbon due to its 300 nm lower wavelength limit compared to measurements limited to longer UV and visible wavelengths. Extinction spectra obtained with SpEx contain more information than can be conveyed by a simple power law fit (typically represented by Ångström exponents). Planned future improvements aim to lower detection limits and ruggedize the instrument for mobile operation.

scholarly journals New in situ aerosol hyperspectral optical measurements over 300–700 nm – Part 1: Spectral Aerosol Extinction (SpEx) instrument field validation during the KORUS-OC cruise

2021 ◽  
Vol 14 (1) ◽  
pp. 695-713 ◽  
Author(s):  
Carolyn E. Jordan ◽  
Ryan M. Stauffer ◽  
Brian T. Lamb ◽  
Charles H. Hudgins ◽  
Kenneth L. Thornhill ◽  
...  
Keyword(s):  
Wavelength Range ◽  
Second Order ◽  
Operating Conditions ◽  
Aerosol Extinction ◽  
Size Distributions ◽  
Data Set ◽  
Extinction Coefficients ◽  
Order Polynomial ◽  
Visible Wavelengths

Abstract. In situ observations of spectrally resolved aerosol extinction coefficients (300–700 nm at ∼ 0.8 nm resolution) from the May–June 2016 Korea–United States Ocean Color (KORUS-OC) oceanographic field campaign are reported. Measurements were made with the custom-built Spectral Aerosol Extinction (SpEx) instrument that previously has been characterized only using laboratory-generated aerosols of known size and composition. Here, the performance of SpEx under realistic operating conditions in the field was assessed by comparison to extinction coefficients derived from commercial instruments that measured scattering and filter-based absorption coefficients at three discrete visible wavelengths. Good agreement was found between these two sets of extinction coefficients with slopes near unity for all three wavelengths within the SpEx measurement error (± 5 Mm−1). The meteorological conditions encountered during the cruise fostered diverse ambient aerosol populations with varying sizes and composition at concentrations spanning 2 orders of magnitude. The sampling inlet had a 50 % size cut of 1.3 µm diameter particles such that the in situ aerosol sampling suite deployed aboard ship measured fine-mode aerosols only. The extensive hyperspectral extinction data set acquired revealed that nearly all measured spectra exhibited curvature in logarithmic space, such that Ångström exponent (α) power law fits could lead to large errors compared to measured values. This problem was particularly acute for α values calculated over only visible wavelengths and then extrapolated to the UV, highlighting the need for measurements in this wavelength range. Second-order polynomial fits to the logarithmically transformed data provided a much better fit to the measured spectra than the linear fits of power laws. Building on previous studies that used total column aerosol optical depth observations to examine the information content of spectral curvature, the relationship between α and the second-order polynomial fit coefficients (a1 and a2) was found to depend on the wavelength range of the spectral measurement such that any given α maps into a line in (a1, a2) coefficient space with a slope of −2LN(λch), where λch is defined as the single wavelength that characterizes the wavelength range of the measured spectrum (i.e., the “characteristic wavelength”). Since the curvature coefficient values depend on λch, it must be taken into account when comparing values from spectra obtained from measurement techniques with different λch. Previously published work has shown that different bimodal size distributions of aerosols can exhibit the same α yet have differing spectral curvature with different (a1, a2). This implies that (a1, a2) contain more information about size distributions than α alone. Aerosol size distributions were not measured during KORUS-OC, and the data reported here were limited to the fine fraction, but the (a1, a2) maps obtained from the SpEx data set are consistent with the expectation that (a1, a2) may contain more information than α – a result that will be explored further with future SpEx and size distribution data sets.

scholarly journals New In Situ Aerosol Hyperspectral Optical Measurements over 300–700 nm, Part 1: Spectral Aerosol Extinction (SpEx) Instrument Field Validation during the KORUS-OC cruise

2020 ◽  
Author(s):  
Carolyn E. Jordan ◽  
Ryan M. Stauffer ◽  
Brian T. Lamb ◽  
Charles H. Hudgins ◽  
Kenneth L. Thornhill ◽  
...  
Keyword(s):  
Wavelength Range ◽  
Second Order ◽  
Operating Conditions ◽  
Aerosol Size Distribution ◽  
Aerosol Extinction ◽  
Extinction Coefficients ◽  
Characteristic Wavelength ◽  
Order Polynomial ◽  
Visible Wavelengths

Abstract. In situ observations of spectrally-resolved aerosol extinction coefficients (300–700 nm at ~ 0.8 nm resolution) from the May–June 2016 Korea U.S. – Ocean Color (KORUS-OC) oceanographic field campaign are reported. Measurements were made with the custom-built Spectral Aerosol Extinction (SpEx) instrument that previously has been characterized only using laboratory-generated aerosols of known size and composition. Here, the performance of SpEx under realistic operating conditions in the field was assessed by comparison to extinction coefficients derived from commercial instruments that measured scattering and filter-based absorption coefficients at three discrete visible wavelengths. Good agreement was found between these two sets of extinction coefficients with slopes near unity for all 3 wavelengths within the SpEx measurement error (±5 Mm−1). The meteorological conditions encountered during the cruise fostered diverse ambient aerosol populations with varying sizes and composition at concentrations spanning two orders of magnitude. The sampling inlet had a 50 % size cut of 1.3 µm diameter particles such that the in situ aerosol sampling suite deployed aboard ship measured fine mode aerosols only. The extensive hyperspectral extinction data set acquired revealed that nearly all measured spectra exhibited curvature in logarithmic space, such that Ångström exponent (α) power law fits led to large errors compared to measured values, especially in the ultraviolet (UV) wavelength range. This problem was particularly acute for α values calculated over only visible wavelengths, then extrapolated to the UV, highlighting the need for measurements in this wavelength range. Second-order polynomial fits to the logarithmically-transformed data provided a much better fit to the measured spectra than the linear fits of power laws. Building on previous studies that used total column AOD observations to examine the information content of spectral curvature, the relationship between α and the second order polynomial fit coefficients (a1 and a2) was shown to depend on the characteristic wavelength (λch) of any given spectral measurement, such that differing curvature among aerosol size distributions with the same α will map to a line in (a1,a2) space with a slope related to λch. Thus, spectral curvature represented by (a1,a2) may provide more detailed aerosol size distribution information than α alone.

Some results of the Barbier-Chalonge-Divan system of stellar classification

1966 ◽  
Vol 24 ◽  
pp. 77-90 ◽  
Author(s):  
D. Chalonge
Keyword(s):  
Early Type ◽  
Parameter System ◽  
Early Type Stars ◽  
Two Parameter

Several years ago a three-parameter system of stellar classification has been proposed (1, 2), for the early-type stars (O-G): it was an improvement on the two-parameter system described by Barbier and Chalonge (3).

Subjective Time Preference and Willingness to Pay for an Energy-Saving Durable Good

2001 ◽  
Vol 32 (3) ◽  
pp. 133-141 ◽  
Author(s):  
Gerrit Antonides ◽  
Sophia R. Wunderink
Keyword(s):  
Willingness To Pay ◽  
Energy Saving ◽  
Subjective Time ◽  
Durable Good ◽  
Discount Function ◽  
Hyperbolic Discount ◽  
The One ◽  
Two Parameter ◽  
Difference Effect ◽  
Better Than

Summary: Different shapes of individual subjective discount functions were compared using real measures of willingness to accept future monetary outcomes in an experiment. The two-parameter hyperbolic discount function described the data better than three alternative one-parameter discount functions. However, the hyperbolic discount functions did not explain the common difference effect better than the classical discount function. Discount functions were also estimated from survey data of Dutch households who reported their willingness to postpone positive and negative amounts. Future positive amounts were discounted more than future negative amounts and smaller amounts were discounted more than larger amounts. Furthermore, younger people discounted more than older people. Finally, discount functions were used in explaining consumers' willingness to pay for an energy-saving durable good. In this case, the two-parameter discount model could not be estimated and the one-parameter models did not differ significantly in explaining the data.

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