(a) Aug. 26^ 2005 at 12:54
(b) Aug. 26? 2005 at 12:56
Figure 4. Overlaying clouds area discriminated from whole sky
image to MODIS image.
Comparing with two figures of two minutes difference, there is
no big movement on the image. Measured approximate distance
of movement for two minutes on two figures is about 500m
(velocity: 4-5m/s). As one of others applications of the
overlaying clouds area to satellite image, there is clouds motion
analysis by calculating the moving distance for two minutes in
this case. For more high accuracy of horizontal clouds
distribution, cloud height data with high accuracy is needed. As
for the measurement of cloud height with high accuracy, Seiz et
al. (2002) have developed the method to estimate cloud bottom
height by digital photogrammetric technique using two more
cameras.
Furthermore, there is another application for cloud fraction
analysis of different cloud fraction definitions. Satellite-based
observation derives cloud fraction which means the horizontal
area fraction covered by clouds as viewed from nadir, it
corresponds clouds horizontal distribution on satellite image.
On the other hand, ground-based cloud observation using whole
sky camera derives the cloud fraction as hemispherical sky
covered by clouds. It is the definition of ground meteorological
studies, so-called cloud amount. As for the calculation of both
defined cloud fractions, Kassianov et al. (2005) have
demonstrated using hemispherical ground-based observation.
Also, there is the possibility of this study on the assumption that
this ground-based clouds observation method is applied across a
wide area. For the validation of satellite-based clouds and earth
surface observation, it seems that this observation system is
suitable to set up at many sites, and also useful to collaborate
with the existing ground-based observation networks such Asia
Flux, AERONET and SKYNET etc. The proposed observation
method and its applications should be connected to satellite
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B8, 2012
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia
products with high quality by implementation of sky and clouds
observation covering a wide area.
5. CONCLUSION
We proposed the simple ground-based observation method to
discriminate clouds on whole sky image and one of extensions
to the satellite-based observation by overlaying both ground and
satellite-based images.
Through this study, we confirmed that our developed ground-
based cloud observation method is useful to discriminate cloud
existence and area of cloud coverage, and to overlay with
satellite-based cloud image. Also, this ground-based cloud
observation can be expanded into wide area and set many
observation points for application to various satellite images
including geostationary satellites with very high temporal
resolution.
References
Calbo J. and Sabburg J., 2008. Feature Extraction from Whole-
Sky Ground-Based Images for Cloud-Type Recognition.
Journal of Atomospheric and Oceanic Technology, 25, pp.3-14.
Clement C. A., Burgman R. and Norris R. J. 2009.
Observational and Model Evidence for Positive Low-Level
Cloud Feedback, SCIENCE, 325, pp.460-464.
Freedman J. M., Fitzjarrld D. R, Moore K. E., and Sakai R. K.,
2001. Boundary Layer Clouds and vegetation - Atmosphere
Feedbaks. Journal of Climate, 14, pp.180-197.
Heinle A., Macke A. and Srivastav A., 2010. Automatic cloud
classification of whole sky images. Atmospheric Measurement
Techniques Discussions, 3, pp.269-299.
Kassianov E., Long N. C. and Ovtchinnikov M. (2005): Cloud
Sky Cover versus Cloud Fraction: Whole-Sky Simulation and
Observations. Journal of Applied Meteorology, 44, pp.86-98.
Seiz G., Baltsavias E.P., and Gruen A. (2002): Cloud Mapping
from the Ground: Use of Photgrammetric Methods.
Photogrammetric Engineering & Remote Sensing, 68(9),
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Tsuchida S., Nishida K., Iwao K., Kawato A., Oguma H. and
Iwasaki A., 2005. Phenological Eyes Network for Validation of
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Yamashita M. and Yoshimura M., 2008. Development of Sky
Conditions Observation Method using Whole Sky Camera
(abstract only). Journal of the Japan Society of Photogrammetry
and Remote Sensing, 47(2), pp.50-59.
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