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Volume 11, Issue 2 (9-2023) |
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Using Stereographic Observations of two High Resolution Geostationary Satellite Images for Cloud Detection
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Sahar Dehnavi   , Yasser Maghsoudi , MohammadJavad Valadanzoej * |
| K. N. Toosi University of Technology |
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Abstract: (1176 Views) |
Due to their significant impact on the balance of energy on the surface and in the atmosphere, the clouds have always been considered by various researchers in the meteorological and climatological fields. The ability to remotely measure the characteristics and parameters of the cloud has been proven to examine their changes in different locations and times. One of the most important aspects of cloud research is cloud detection in remotely sensed images. The purpose of the present study is to provide a stereographic based technique for detecting clouds according to the height of the clouds with the highest possible spatial resolution and using Geostationary meteorological images. First, a stereo pair is selected on board two platforms of the Meteosat-8 (IODC) and the Meteosat-10, using the SEVIRI Sensor with high resolution spatial resolution (HRV). Then, with respect to the different viewing geometry of the two sensors, both images are reprojected into a similar reference grid and finally, by forming line of sight (LOS) of the two sensors in an epipolar sheet, the parallax value in two images on the clouds is estimated. The advantage of this method in estimating cloud height is that the stereo measurements only depend on the fundamental geometric relationships between observations of the visible components of the clouds. Other estimation methods, require the assumption that the cloud has a local thermodynamic equilibrium and some knowledge about the apparent temperature, etc. But in most cases, the amount of cloud emission is unknown, the temperature profile of the atmosphere is unavailable, and the cloud does not have thermodynamic equilibrium with its surroundings. In this study, a new method for revealing cloud pixels based on cloud height is presented. After estimating the height of the clouds, it is possible to separate the pixels of clouds from the intersection pixels based on the existing altitude difference, and in fact, it is possible to detect the cloud based on the estimated height in pixels. The results of this study indicate the high accuracy and the feasibility of using stereography to detect cloud pixels in satellite imagery. The advantage of our proposed method is the use of cloud-height information that not only increases the spatial resolution, but also helps to extract 3D cloud information, which is of particular importance in the studies of solar irradiance, and other cloud research applications. And finally, having a knowledge in this regard in Iran is also very important, because a new branch of meteorological studies, entitled "Meteorological stereography" will be established in the country and will help to lead to more extensive research in this area.
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| Keywords: Cloud detection, Stereography, Meteorology, Geostationary observations (Meteosat), SEVIRI, High Resolution |
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Full-Text [PDF 1302 kb]
(184 Downloads)
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Type of Study: Research |
Subject:
RS
Received: 2019/05/8 | Accepted: 2019/06/12 | ePublished ahead of print: 2023/07/22 | Published: 2023/10/10
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