The estimate of cloud attenuation factor for real-time incoming solar radiation by using
geostationary satellite data
Jong-Min Yeom1, Kyung-Soo Han2, Youn-Soo Kim1 and Sang-Ill Kim2
1Satellite
Data Application Department, Satellite Information Research Institute, Korea
Aerospace Research Institute, 115 Gwahanno [45 Eoeun-Dong], Yuseong Daejeon, Korea
2Department
of geoinformatic engineering, Pukyong National University, Daeyeon-3
Nam-Gu, Busan 608-737, Korea E-mail: Kyung-soo.han@pknu.ac.kr
The incoming solar radiation provides information on how much solar radiation energy
reaches the Earth’s surface at a specified location during the daytime. The amount of solar
radiation reaching surface is important variable for surface energy balance system,
determining the amount of reflected radiative energy to the atmosphere, agriculture
meteorological system. In this study, we calculate incident solar radiation from the
multifunctional transport satellite-1 Replacement (MTSAT-1R) data using physical model for
Chollian communication, ocean and meteorological satellite (COMS) operational system with
simplified cloud factor. The use of retrieved incoming solar radiation data mainly depends on
how to accurately parameterize cloud attenuation effects, which have large spatial and
temporal variability. We present a cloud factor optimized for the modified Kawamura
physical model to calculate attenuated cloud transmittance from MTSAT-1R channel data.
Before the new cloud attenuation coefficients are determined, a reference data set that agrees
well with pyranometer measurements is selected from all the collocated data sets to determine
the cloud factor. Estimating or measuring real cloud attenuation values impinging on solar
radiation from the top of the atmosphere is generally difficult, as these values depend on
various factors, including the cloud type, the structure of the vertical profile, multiple
scattering among cloud droplets, height, and relative temperature and pressure. Applying the
new cloud factor with dimensions of 8 (10° solar zenith angle interval) by 10 (10% cloudy
reflectance interval) results in improved estimated accuracy.