Estimating cloud optical thickness and associated surface UV irradiance from SEVIRI by implementing a semi-analytical cloud retrieval algorithm

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Discipline
Earth and related Environmental sciences
Subject
algorithm
cloud cover
cloud radiative forcing
CloudSat
comparative study
estimation method
irradiance
optical depth
parameterization
radiative transfer
satellite imagery
SEVIRI
spectral reflectance
ultraviolet A radiation
ultraviolet B radiation
Europe
Audience
Scientific
Date
2012Metadata
Show full item recordDescription
In this paper, we describe the implementation of the Semi-Analytical Cloud Retrieval Algorithm (SACURA), to obtain scaled cloud optical thickness (SCOT) from satellite imagery acquired with the SEVIRI instrument and surface UV irradiance levels. In estimation of SCOT particular care is given to the proper specification of the background (i.e. cloud-free) spectral albedo and the retrieval of the cloud water phase from reflectance ratios in SEVIRI's 0.6 μm and 1.6 μm spectral bands. The SACURA scheme is then applied to daytime SEVIRI imagery over Europe, for the month of June 2006, at 15-min time increments. The resulting SCOT fields are compared with values obtained by the CloudSat experimental satellite mission, yielding a negligible bias, correlation coefficients ranging from 0.51 to 0.78, and a root mean square difference of 1 to 2 SCOT increments. These findings compare favourably to results from similar intercomparison exercises reported in the literature. Based on the retrieved SCOT from SEVIRI and radiative transfer modelling approach, simple parameterisations are proposed to estimate the surface UV-A and UV-B irradiance. The validation of the modelled UV-A and UV-B irradiance against the measurements over two Belgian stations, Redu and Ostend, indicate good agreement with the high correlation, index of agreement and low bias. The SCOT fields estimated by implementing SACURA on imagery from geostationary satellite are reliable and its impact on surface UV irradiance levels is well produced.
Citation
Pandey, P.; De Ridder, K.; Gillotay, D.; Van Lipzig, N.P.M. (2012). Estimating cloud optical thickness and associated surface UV irradiance from SEVIRI by implementing a semi-analytical cloud retrieval algorithm. , Atmospheric Chemistry and Physics, Vol. 12, Issue 17, 7961-7975, DOI: 10.5194/acp-12-7961-2012.Identifiers
scopus: 2-s2.0-84869068658
Type
Article
Peer-Review
Yes
Language
eng