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Effective cloud optical depth and enhancement effects for broken liquid water clouds in Valencia (Spain)

Citation

Marin, MJ and Serrano, D and Utrillas, MP and Nunez, M and Martinez-Lozano, JA, Effective cloud optical depth and enhancement effects for broken liquid water clouds in Valencia (Spain), Atmospheric Research, 195 pp. 1-8. ISSN 0169-8095 (2017) [Refereed Article]

Copyright Statement

Copyright 2017 Elsevier B.V.

DOI: doi:10.1016/j.atmosres.2017.05.008

Abstract

Partly cloudy skies with liquid water clouds have been analysed, founding that it is essential to distinguish data if the Sun is obstructed or not by clouds. Both cases can be separated considering simultaneously the Cloud Modification Factor (CMF) and the clearness index (kt). For partly cloudy skies and the Sun obstructed the effective cloud optical depth (τ) has been obtained by the minimization method for overcast skies. This method was previously developed by the authors but, in this case, taking into account partial cloud cover. This study has been conducted for the years 20112015 with the multiple scattering model SBDART and irradiance measurements for the UV Erythemal Radiation (UVER) and the broadband ranges. Afterwards a statistical analysis of τ has shown that the maximum value is much lower than for overcast skies and there is more discrepancy between the two spectral ranges regarding the results for overcast skies. In order to validate these results the effective cloud optical depth has been correlated with several transmission factors, giving similar fit parameters to those obtained for overcast skies except for the clearness index in the UVER range. As our method is not applicable for partly cloudy skies with the visible Sun, the enhancement of radiation caused by clouds when the Sun is visible has been studied. Results show that the average enhancement CMF values are the same for both ranges although enhancement is more frequent for low cloud cover in the UVER and medium-high cloud cover in the broadband range and it does not depend on the solar zenith angle.

Item Details

Item Type:Refereed Article
Keywords:effective cloud optical depth (τ), enhancement, broken clouds, liquid water clouds, UV erythemal radiation (UVER), broadband irradiance, multiple scattering models
Research Division:Earth Sciences
Research Group:Atmospheric Sciences
Research Field:Cloud Physics
Objective Division:Environment
Objective Group:Atmosphere and Weather
Objective Field:Atmospheric Processes and Dynamics
Author:Nunez, M (Dr Manuel Nunez)
ID Code:117642
Year Published:2017
Deposited By:Geography and Spatial Science
Deposited On:2017-06-22
Last Modified:2018-05-21
Downloads:0

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