Estimation of the radiation extinction coefficient of natural fuel beds

2004 ◽  
Vol 13 (1) ◽  
pp. 65 ◽  
Author(s):  
Gilberto C. Vaz ◽  
Jorge C. S. André ◽  
Domingos X. Viegas
Keyword(s):  
White Light ◽  
Extinction Coefficient ◽  
Laboratory Experiments ◽  
Pine Needles ◽  
Light Radiation ◽  
Parallel Beam ◽  
Standard Formula ◽  
Maximum Angle ◽  
Radiation Extinction ◽  
Radiation Extinction Coefficient

. The standard formula used to estimate the radiation extinction coefficient, kb (m–1), of solid porous natural fuel beds is examined and tested against laboratory experiments with isotropic beds of pine needles in the range of packing ratio, β, of 0.01–0.02. To measure kb in the tests, a setup using a parallel beam of white light radiation was constructed. The error of the standard formula is observed to be smaller than 10%. Similar tests were performed for a non-isotropic bed of pine needles with β ≈ 0.02, in which the maximum angle of inclination of the needles was limited to 30°, for two directions of incidence of radiation: horizontal and vertical. For each one of these two cases, original estimation formulae for kb are proposed alternative to the standard one. In these cases it is concluded that, while the standard formula may be in error by up to 20%, the new formulae have errors around 5% or smaller.

Numerical Evaluation of Radiation Extinction Coefficient Using Fractal Geometry for Vegetation Modeling

2009 ◽  
Vol 56 (4) ◽  
pp. 360-377 ◽  
Author(s):  
A. Lamorlette ◽  
A. Collin ◽  
P. Boulet ◽  
O. Séro-Guillaume
Keyword(s):  
Extinction Coefficient ◽  
Fractal Geometry ◽  
Numerical Evaluation ◽  
Vegetation Modeling ◽  
Radiation Extinction ◽  
Radiation Extinction Coefficient

Normal light dispersion in laboratory experiments

2021 ◽  
Vol 57 (1) ◽  
pp. 015013
Author(s):  
V V Mayer ◽  
E I Varaksina
Keyword(s):  
Quantitative Study ◽  
White Light ◽  
Laboratory Experiments ◽  
Mercury Vapour ◽  
Mercury Lamp ◽  
Quantitative Investigation ◽  
Normal Dispersion ◽  
Light Dispersion ◽  
Normal Light ◽  
Object Of Study

Abstract We propose a laboratory experiment on the quantitative study of the normal dispersion of light. A triangular isosceles prism made of flint glass TF3 is used as the object of study, and we describe a simple and affordable device for observing and photographing the dispersion spectrum on a smartphone. A possibility of the quantitative investigation of light dispersion is provided by using a modern miniature mercury lamp emitting a line spectrum of mercury vapour against the background of a solid spectrum of white light. The method of processing experimental results is stated.

scholarly journals The white-light humidified optical particle spectrometer (WHOPS) – a novel airborne system to characterize aerosol hygroscopicity

2014 ◽  
Vol 7 (7) ◽  
pp. 7321-7366 ◽  
Author(s):  
B. Rosati ◽  
G. Wehrle ◽  
P. Zieger ◽  
M. Gysel ◽  
U. Baltensperger ◽  
...  
Keyword(s):  
Optical Properties ◽  
Ammonium Sulfate ◽  
White Light ◽  
Laboratory Experiments ◽  
Effective Index ◽  
Index Of Refraction ◽  
Hygroscopic Growth ◽  
Airborne Measurements ◽  
New Instrument ◽  
Effective Index Of Refraction

Abstract. Aerosol particles experience hygroscopic growth at enhanced relative humidity (RH) which leads to changes in their optical properties. We developed the white-light humidified optical particle spectrometer (WHOPS), a new instrument to investigate the particles' hygroscopic growth. Here we present a detailed technical description and characterization of the WHOPS in laboratory and field experiments. The WHOPS consists of a differential mobility analyzer, a humidifier/bypass and a WELAS (white-light aerosol spectrometer) connected in series to provide fast measurements of particle hygroscopicity at sub-saturated RH and optical properties on airborne platforms. The WELAS employs a white-light source to minimize ambiguities in the optical particle sizing. In contrast to other hygroscopicity instruments, the WHOPS retrieves information of relatively large particles (i.e. diameter D > 280 nm), therefore investigating the more optically relevant size ranges. The effective index of refraction of the dry particles is retrieved from the optical diameter measured for size-selected aerosol samples with a well-defined dry mobility diameter. The data analysis approach for the optical sizing and retrieval of the index of refraction was extensively tested in laboratory experiments with polystyrene latex size standards and ammonium sulfate particles of different diameters. The hygroscopic growth factor (GF) distribution and aerosol mixing state is inferred from the optical size distribution measured for the size-selected and humidified aerosol sample. Laboratory experiments with pure ammonium sulfate particles revealed good agreement with Köhler theory (mean bias of ~ 3% and maximal deviation of 9% for GFs at RH = 95%). First airborne measurements in the Netherlands observed GFs (mean value of the GF distribution) at RH = 95% between 1.74 and 2.67 with a median of 1.94 for particles with a dry diameter of 500 nm. This corresponds to hygroscopicity parameters (κ) between 0.21 and 0.93 with a median of 0.33. The GF distributions indicate externally mixed particles covering the whole range of GFs between ~ 1.0–3.0. On average ~ 74% of the particles were "more hygroscopic" with GFs > 1.5, ~ 15% were non- or slightly hygroscopic with GF < 1.1 and the remaining ~ 11% were "less hygroscopic" with 1.1 < GF < 1.5. The more hygroscopic mode sometimes peaked at GF > 2, indicating influence of sea salt particles, consistent with previous ground-based particle hygroscopicity measurements in this area. The mean dry effective index of refraction for 500 nm particles was found to be rather constant with a value of 1.42 ± 0.04.

Formation of Highly Directional White Light Radiation in Air Filament

2020 ◽  
Vol 84 (7) ◽  
pp. 766-769
Author(s):  
D. M. Lubenko ◽  
N. G. Ivanov ◽  
S. V. Alekseev ◽  
V. E. Prokopev ◽  
V. F. Losev
Keyword(s):  
White Light ◽  
Light Radiation

Etude de l'Effet des Paramètres d'Appareil sur la Décroissance de la Visibilité du Spectre Cannelé

1971 ◽  
Vol 49 (17) ◽  
pp. 2237-2249 ◽  
Author(s):  
C. Delisle ◽  
M. Brochu ◽  
J. M. St-Arnaud
Keyword(s):  
Spectral Density ◽  
White Light ◽  
Michelson Interferometer ◽  
Finite Size ◽  
Path Difference ◽  
Parallel Beam ◽  
Density Modulation ◽  
Theory And Experiment

The visibility of the channelled spectrum, or in other words the visibility of the spectral density modulation at the exit of a Michelson interferometer illuminated with a parallel beam of white light, is theoretically independent of the frequency and path difference of the two beams formed in the interferometer. Up to now there has been no agreement between theory and experiment. It is shown here, theoretically and experimentally, that the decrease in visibility with increasing path difference is related to both the finite size of the slits and the limit of resolution of the apparatus.

Sign in / Sign up

Export Citation Format

Share Document