Wavelength Dependence of Cirrus Optical Depth

2001 ◽  
Author(s):  
D. K. Lynch ◽  
S. M. Mazuk
Keyword(s):  
Optical Depth ◽  
Wavelength Dependence

scholarly journals Spectral absorption properties of atmospheric aerosols

2007 ◽  
Vol 7 (23) ◽  
pp. 5937-5943 ◽  
Author(s):  
R. W. Bergstrom ◽  
P. Pilewskie ◽  
P. B. Russell ◽  
J. Redemann ◽  
T. C. Bond ◽  
...  
Keyword(s):  
Optical Depth ◽  
Atmospheric Aerosols ◽  
Wavelength Dependence ◽  
Single Scattering ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Spectral Absorption ◽  
Solar Absorption ◽  
Airborne Measurements ◽  
Aerosol Absorption

Abstract. We have determined the solar spectral absorption optical depth of atmospheric aerosols for specific case studies during several field programs (three cases have been reported previously; two are new results). We combined airborne measurements of the solar net radiant flux density and the aerosol optical depth with a detailed radiative transfer model for all but one of the cases. The field programs (SAFARI 2000, ACE Asia, PRIDE, TARFOX, INTEX-A) contained aerosols representing the major absorbing aerosol types: pollution, biomass burning, desert dust and mixtures. In all cases the spectral absorption optical depth decreases with wavelength and can be approximated with a power-law wavelength dependence (Absorption Angstrom Exponent or AAE). We compare our results with other recent spectral absorption measurements and attempt to briefly summarize the state of knowledge of aerosol absorption spectra in the atmosphere. We discuss the limitations in using the AAE for calculating the solar absorption. We also discuss the resulting spectral single scattering albedo for these cases.

scholarly journals Daytime aerosol optical depth above low-level clouds is similar to that in adjacent clear skies at the same heights: airborne observation above the southeast Atlantic

2020 ◽  
Author(s):  
Yohei Shinozuka ◽  
Meloë S. Kacenelenbogen ◽  
Sharon P. Burton ◽  
Steven G. Howell ◽  
Paquita Zuidema ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Wavelength Dependence ◽  
Single Scattering ◽  
Airborne Lidar ◽  
Aerosol Layer ◽  
Low Level ◽  
Satellite Retrieval ◽  
Biomass Burning Aerosol ◽  
The Difference

Abstract. To help satellite retrieval of aerosols and studies of their radiative effects, we demonstrate that daytime 532 nm aerosol optical depth over low-level clouds is similar to that in neighboring clear skies at the same heights in recent airborne lidar and sunphotometer observations above the southeast Atlantic. The mean AOD difference is between 0 and −0.01, when comparing the two sides, each up to 20 km wide, of cloud edges. The difference is not statistically significant according to a paired t-test. Systematic differences in the wavelength dependence of AOD and in situ single scattering albedo are also minute. These results hold regardless of the vertical distance between cloud top and aerosol layer bottom. AOD aggregated over ~ 2° grid boxes for each of September 2016, August 2017 and October 2018 also shows little correlation with the presence of low-level clouds. We posit that a satellite retrieval artifact is entirely responsible for a previous finding of generally smaller AOD over clouds (Chung et al., 2016), at least for the region and season of our study. Our results also suggest that the same values can be assumed for the intensive properties of free-tropospheric biomass-burning aerosol regardless of whether clouds exist below.

Wavelength dependence of the optical depth of biomass burning, urban, and desert dust aerosols

1999 ◽  
Vol 104 (D24) ◽  
pp. 31333-31349 ◽  
Author(s):  
T. F. Eck ◽  
B. N. Holben ◽  
J. S. Reid ◽  
O. Dubovik ◽  
A. Smirnov ◽  
...  
Keyword(s):  
Optical Depth ◽  
Biomass Burning ◽  
Wavelength Dependence ◽  
Desert Dust ◽  
Dust Aerosols

Wavelength dependence of the effective cloud optical depth

2015 ◽  
Vol 130-131 ◽  
pp. 14-22 ◽  
Author(s):  
D. Serrano ◽  
M.J. Marín ◽  
M. Núñez ◽  
M.P. Utrillas ◽  
S. Gandía ◽  
...  
Keyword(s):  
Optical Depth ◽  
Wavelength Dependence ◽  
Cloud Optical Depth

scholarly journals Daytime aerosol optical depth above low-level clouds is similar to that in adjacent clear skies at the same heights: airborne observation above the southeast Atlantic

2020 ◽  
Vol 20 (19) ◽  
pp. 11275-11285 ◽  
Author(s):  
Yohei Shinozuka ◽  
Meloë S. Kacenelenbogen ◽  
Sharon P. Burton ◽  
Steven G. Howell ◽  
Paquita Zuidema ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Wavelength Dependence ◽  
Single Scattering ◽  
Airborne Lidar ◽  
Aerosol Layer ◽  
Low Level ◽  
Satellite Retrieval ◽  
Biomass Burning Aerosol ◽  
The Difference

Abstract. To help satellite retrieval of aerosols and studies of their radiative effects, we demonstrate that daytime aerosol optical depth over low-level clouds is similar to that in neighboring clear skies at the same heights. Based on recent airborne lidar and sun photometer observations above the southeast Atlantic, the mean aerosol optical depth (AOD) difference at 532 nm is between 0 and −0.01, when comparing the cloudy and clear sides, each up to 20 km wide, of cloud edges. The difference is not statistically significant according to a paired t test. Systematic differences in the wavelength dependence of AOD and in situ single scattering albedo are also minuscule. These results hold regardless of the vertical distance between cloud top and aerosol layer bottom. AOD aggregated over ∼2∘ grid boxes for each of September 2016, August 2017 and October 2018 also shows little correlation with the presence of low-level clouds. We posit that a satellite retrieval artifact is entirely responsible for a previous finding of generally smaller AOD over clouds (Chung et al., 2016), at least for the region and time of our study. Our results also suggest that the same values can be assumed for the intensive properties of free-tropospheric biomass-burning aerosol regardless of whether clouds are present below.

scholarly journals Estimation of the Internal Extinction of Spiral Galaxies for Multi-color Tully-Fisher Relations

1999 ◽  
Vol 183 ◽  
pp. 73-73
Author(s):  
Masaru Watanabe ◽  
Naoki Yasuda
Keyword(s):  
Optical Depth ◽  
Zero Point ◽  
Wavelength Dependence ◽  
Color Difference ◽  
Stellar Disk ◽  
Cluster Galaxies ◽  
Extinction Process ◽  
Upper Limits ◽  
Extinction Model ◽  
The One

We calculate B-, R- and I-band internal extinction A(λ)i (absorption + scattering) for spirals consisting of an exponential dust layer, a stellar disk and a bulge. The result is applied to local calibrators and cluster spirals (Virgo and Ursa Major) to examine whether or not the wavelength dependence of the relative zero point difference of Tully-Fisher (TF) relations between for local calibrators and for cluster spirals (Pierce & Tully, 1992) could be accounted for by a variation of A(λ)i on the optical depth of galaxies. The extinction is calculated using Monte-Carlo simulations prescribed by Bianchi et al. (1996). For the extinction curve we adopted the one of Cardelli et al. (1989). It is found that a differential extinction A(R or I)i – A(B)i as a function of the optical depth σ(B) has finite upper limits of ∼ 0.3–0.5 mag, depending on an inclination of the spiral. These limits are generally smaller than the offset of the TF relative zero point difference. This indicates that the offset may be fully due to an intrinsic color difference between local calibrators and cluster galaxies, or else that the current extinction model is yet to realize a practical extinction process or geometrical configuration of spirals.

scholarly journals Horizontal variability of aerosol optical depth observed during the ARCTAS airborne experiment

2011 ◽  
Vol 11 (5) ◽  
pp. 16245-16264 ◽  
Author(s):  
Y. Shinozuka ◽  
J. Redemann
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Satellite Remote Sensing ◽  
Wavelength Dependence ◽  
Long Range Transport ◽  
Straight Line ◽  
Relative Standard ◽  
Range Transport ◽  
Local Emissions ◽  
Airborne Experiment

Abstract. We present statistics on the horizontal variability of aerosol optical depth (AOD) directly measured from the NASA P-3 aircraft. Our measurements during two contrasting phases (in Alaska and Canada) of the ARCTAS mission arguably constrain the variability in most aerosol environments common over the globe. In the Canada phase, which features local emissions, 499 nm AOD has a median relative standard deviation (stdrel,med) of 19 % and 9 % and an autocorrelation (r) of 0.37 and 0.71 over 20 km and 6 km horizontal segments, respectively. In the Alaska phase, which features long-range transport, the variability is considerably lower (stdrel,med = 3 %, r = 0.92 even over 35.2 km). Compared to the magnitude of AOD, its wavelength dependence varies less in the Canada phase, more in the Alaska phase. We translate these findings from straight-line flight tracks into grid boxes and points, to help interpretation and design of satellite remote sensing, suborbital observations and transport modeling.

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