@Article{LuizMartCostPere:2018:CaSt,
author = "Luiz, Eduardo Weide and Martins, Fernando Ramos and Costa, Rodrigo
Santos and Pereira, Enio Bueno",
affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and
{Universidade Federal de S{\~a}o Paulo (UNIFESP)} and {Instituto
Nacional de Pesquisas Espaciais (INPE)} and {Instituto Nacional de
Pesquisas Espaciais (INPE)}",
title = "Comparison of methodologies for cloud cover estimation in Brazil:
a case study",
journal = "Energy for Sustainable Development",
year = "2018",
volume = "43",
pages = "15--22",
month = "mar.",
keywords = "Cloud cover estimation, All-sky camera, Satellite, Long-wave
radiation.",
abstract = "Clouds are the major modulator of the shortwave and longwave
radiation components of the Earth's energy balance and, as such,
help to regulate the planet's temperature. In the energy sector,
clouds are a source of instability in the generation of energy
using solar technologies. This study aims at comparing three
approaches to get cloud cover information in the Southeastern
region of Brazil during the period of approximately three months.
The first method, assumed as reference, uses all-sky camera
pictures for the cloud cover estimation. The other two
methodologies use downward longwave radiation with surface
meteorological data and geostationary satellite data. Both methods
presented good agreement with the camera for clear sky and
overcast conditions, with probabilities of detection of 92.8% and
80.7% for the longwave method and 93.3% and 87.6% for the
satellite method, respectively. The major problem occurs with the
broken-clouds sky scenario, with probabilities of detection above
38%, where each method has its own specificity, such as, longwave
emissivity of the atmosphere, spatial resolution and view
geometry. The long-wave method has the minor R correlation with
the camera (87%) when compared with the satellite method (93%) and
requires a daily normalization, which make it not usable for
instantaneous measurements. Regarding the satellite method, the
most important issue is the spatial resolution, which has the
major impact on the broken-clouds sky scenarios. The cloud masking
works properly for large clouds with, at least, the size
comparable to the satellite image pixel. Furthermore, the method
using the all-sky camera also needs to be improved, because it
presented some deficiencies, like very bright areas around the
sun, sometimes identified as clouds, leading to cloud cover
overestimation.",
doi = "10.1016/j.esd.2017.12.001",
url = "http://dx.doi.org/10.1016/j.esd.2017.12.001",
issn = "0973-0826",
language = "en",
urlaccessdate = "03 maio 2024"
}