scholarly journals The solar zenith angle dependence of desert albedo

2005 ◽  
Vol 32 (5) ◽  
Author(s):  
Zhuo Wang
Keyword(s):  
Zenith Angle ◽  
Solar Zenith Angle ◽  
Angle Dependence

scholarly journals Calibrating Broadband UV Instruments: Ozone and Solar Zenith Angle Dependence

1998 ◽  
Vol 15 (4) ◽  
pp. 916-926 ◽  
Author(s):  
Barry A. Bodhaine ◽  
Ellsworth G. Dutton ◽  
Richard L. McKenzie ◽  
Paul V. Johnston
Keyword(s):  
Zenith Angle ◽  
Solar Zenith Angle ◽  
Angle Dependence

Solar zenith angle dependence of ionospheric ion and electron temperatures and density on Venus

1980 ◽  
Vol 85 (A13) ◽  
pp. 7759 ◽  
Author(s):  
Kent L. Miller ◽  
William C. Knudsen ◽  
Karl Spenner ◽  
Robert C. Whitten ◽  
Vit Novak
Keyword(s):  
Zenith Angle ◽  
Solar Zenith Angle ◽  
Angle Dependence

scholarly journals Inter-calibration of nine UV sensing instruments over Antarctica and Greenland since 1980

2020 ◽  
Vol 13 (10) ◽  
pp. 5715-5723
Author(s):  
Clark J. Weaver ◽  
Pawan K. Bhartia ◽  
Dong L. Wu ◽  
Gordon J. Labow ◽  
David E. Haffner
Keyword(s):  
Zenith Angle ◽  
Solar Zenith Angle ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Term Trend ◽  
Enso Events ◽  
Angle Dependence ◽  
Long Term Trend ◽  
Cloud Response

Abstract. Nadir-viewed intensities (radiances) from nine UV sensing satellite instruments are calibrated over the East Antarctic Plateau and Greenland during summer. The calibrated radiances from these UV instruments ultimately will provide a global long-term record of cloud trends and cloud response from ENSO events since 1980. We first remove the strong solar zenith angle dependence from the intensities using an empirical approach rather than a radiative transfer model. Then small multiplicative adjustments are made to these solar zenith angle normalized intensities in order to minimize differences when two or more instruments temporally overlap. While the calibrated intensities show a negligible long-term trend over Antarctica and a statistically insignificant UV albedo trend of −0.05 % per decade over the interior of Greenland, there are small episodic reductions in intensities which are often seen by multiple instruments. Three of these darkening events are explained by boreal forest. Other events are caused by surface melting or volcanoes. We estimate a 2-sigma uncertainty of 0.35 % for the calibrated radiances.

scholarly journals Inter-Calibration of nine UV sensing instruments over Antarctica and Greenland since 1980

2020 ◽  
Author(s):  
Clark Weaver ◽  
Pawan K. Bhartia ◽  
Dong L. Wu ◽  
Gordon Labow ◽  
David Haffner
Keyword(s):  
Zenith Angle ◽  
Forest Fires ◽  
Solar Zenith Angle ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Enso Events ◽  
Angle Dependence ◽  
Modeling Analysis ◽  
Long Term Trend

Abstract. Nadir viewed intensities (radiances) from nine UV sensing satellite instruments are calibrated over the East Antarctic Plateau and Greenland during summer. The calibrated radiances from these UV instruments ultimately will provide a global long-term record of cloud trends and cloud response from ENSO events since 1980. We first remove the strong solar zenith angle dependence from the intensities using an empirical approach rather than a radiative transfer model. Then small multiplicative adjustments are made to these solar zenith angle normalized intensities in order to minimize differences when two or more instruments temporally overlap. While the calibrated intensities show negligible long-term trend over Antarctica, and a statistically insignificant UV albedo trend of −0.05 % per decade over the interior of Greenland, there are small episodic reductions in intensities which are often seen by multiple instruments. Three of these darkening events are explained by boreal forest fires using trajectory modeling analysis. Other events are caused by surface melting or volcanoes. We estimate a 2-sigma uncertainty of 0.35 % for the calibrated radiances.

scholarly journals Solar Zenith Angle Dependence of Sudden Cosmic Noise Absorptions

1977 ◽  
Vol 30 (4) ◽  
pp. 531
Author(s):  
SBSS Sarma ◽  
MC Sharma
Keyword(s):  
Zenith Angle ◽  
Solar Zenith Angle ◽  
Angle Dependence ◽  
Cosmic Noise

The zenith angle dependence of the flare-time absorption of SCNAs-(sudden cosmic noise absorptions) is investigated experimentally using riometer data at five widely spaced stations. A cos� X dependence is found with n = 1�4�O�04.

scholarly journals Investigation of Solar Zenith Angle Dependence of NOAA GVI Data and its Correction.

1991 ◽  
Vol 30 (3) ◽  
pp. 34-41 ◽  
Author(s):  
Masao MATSUMOTO ◽  
Takayuki ODAJIMA ◽  
Koji KAJIWARA ◽  
Ryutaro TATEISHI
Keyword(s):  
Zenith Angle ◽  
Solar Zenith Angle ◽  
Angle Dependence

scholarly journals Rethinking the correction for absorbing aerosols in the satellite-based surface UV products

2021 ◽  
Author(s):  
Antti Arola ◽  
William Wandji Nyamsi ◽  
Antti Lipponen ◽  
Stelios Kazadzis ◽  
Nickolay A. Krotkov ◽  
...  
Keyword(s):  
Optical Depth ◽  
Uv Radiation ◽  
Correction Factor ◽  
Zenith Angle ◽  
Solar Zenith Angle ◽  
Retrieval Algorithm ◽  
Angle Dependence ◽  
Aerosol Absorption ◽  
Uv Irradiance ◽  
Absorbing Aerosols

Abstract. Satellite estimates of surface UV irradiance have been available since 1978 from TOMS UV spectrometer and continued with significantly improved ground resolution using Ozone Monitoring Instrument (OMI 2004-current) and Sentinel 5 Precursor (S5P 2017-current). The surface UV retrieval algorithm remains essentially the same: it first estimates the clear-sky UV irradiance based on measured ozone and then accounts for the attenuation by clouds and aerosols applying two consecutive correction factors. When estimating the total aerosol effect in surface UV irradiance, there are two major classes of aerosols to be considered: 1) aerosols that only scatter UV radiation and 2) aerosols that both scatter and absorb UV radiation. The former effect is implicitly included in the measured effective Lambertian Equivalent scene reflectivity (LER), so the scattering aerosol influence is estimated through cloud correction factor. Aerosols that absorb UV radiation attenuate the surface UV radiation more strongly than non-absorbing aerosols of the same extinction optical depth (AOD). Moreover, since these aerosols also attenuate the outgoing satellite-measured radiance, the cloud correction factor that treats these aerosols as purely scattering underestimates their AOD causing underestimation of LER and overestimation of surface UV irradiance. Therefore, for correction of aerosol absorption additional information is needed, such as the UV absorbing Aerosol Index (UVAI) or a model-based monthly climatology of aerosol absorption optical depth (AAOD). A correction for absorbing aerosols was proposed almost a decade ago and later implemented in the operational OMI and TROPOMI UV algorithms. In this study, however, we show that there is still room for an improvement to better account for the solar zenith angle dependence and non-linearity in the absorbing aerosol attenuation and as a result we propose an improved correction scheme. There are two main differences between the new proposed correction and the one that is currently operational in OMI and TROPOMI UV-algorithms. First, the currently operational correction for absorbing aerosols is a function of AAOD only, while the new correction takes additionally the solar zenith angle dependence into account. Second, the 2nd order polynomial of the new correction takes better into account the non-linearity in the correction as a function of AAOD, if compared to the currently operational one, and thus better describes the effect by absorbing aerosols over larger range of AAOD. To illustrate the potential impact of the new correction in the global UV estimates, we applied the current and new proposed correction for global fields of AAOD from the aerosol climatology currently used in OMI UV algorithm, showing a typical differences of ±5 %. This new correction is easy to implement operationally using information of solar zenith angle and existing AAOD climatology.

Influence of scattering phenomena on the solar zenith angle dependence of in-water irradiance levels

1982 ◽  
Vol 21 (4) ◽  
pp. 642 ◽  
Author(s):  
J. H. Jerome ◽  
J. E. Bruton ◽  
R. P. Bukata
Keyword(s):  
Zenith Angle ◽  
Solar Zenith Angle ◽  
Angle Dependence

scholarly journals Improving the solar zenith angle dependence of broadband UV radiometers calibration

2007 ◽  
Vol 7 (6) ◽  
pp. 17873-17892 ◽  
Author(s):  
M. L. Cancillo ◽  
A. Serrano ◽  
M. Antón ◽  
J. A. García ◽  
J. M. Vilaplana
Keyword(s):  
Zenith Angle ◽  
Solar Zenith Angle ◽  
New Method ◽  
Independent Data ◽  
Step Method ◽  
Data Set ◽  
Angle Dependence ◽  
Calibration Methods ◽  
One Step ◽  
Actual Response

Abstract. This paper focusses on the proposal of a new method for the calibration of broadband ultraviolet radiometers. The advantage of the method proposed is the accurate modelling of the dependence on the solar zenith angle. The new model is compared with other one-step calibration methods and with the two-step method, which requires the knowledge of the actual response of the broadband radiometer. For this purpose, three broadband radiometers are calibrated against a spectrophotometer of reference. The new method is validated comparing its predictions with the spectrophotometer measurements using an independent data set.

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