Abstract
In this paper, we introduce a cloud top-height (CTH) retrieval algorithm using simultaneous observations from the Himawari-8 and FengYun (FY)-2E geostationary (GEO) satellites (hereafter, dual-GEO CTH algorithm). The dual-GEO CTH algorithm estimates CTH based on the parallax, which is the difference in the apparent position of clouds observed from two GEO satellites simultaneously. The dual-GEO CTH algorithm consists of four major procedures: (1) image remapping, (2) image matching, (3) CTH calculation, and (4) quality control. The retrieved CTHs were compared with other satellite CTHs from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and the Cloud-Profiling Radar (CPR), on three occasions. Considering the geometric configuration and footprint sizes of the two GEO satellites, the theoretical accuracy of the dual-GEO CTH algorithm is estimated as ±0.93 km. The comparisons show that the retrieval accuracy generally tends to fall within the theoretical accuracy range. As the dual-GEO CTH algorithm is based on parallax, it could be easily applied for the estimation of the height of any elevated feature in various fields.
Highlights
Clouds play an important role in impacting the energy balance of the Earth
We propose a cloud-top height (CTH) retrieval algorithm using simultaneous observations from the Himawari-8 and FengYun 2E (FY-2E)
The Himawari-8 channel 3 and FY-2E VIS images were transformed so that both the images could be defined inTthhee psaarmalelacxoeoffredcitnisateevisdyesnttemwh. eTnhciosmpproarciendgutwreoisGcEaOllseadteilmlitaegime aregmes.aHppowinegv.erC, odnuseidtoetrhine g that the Hilmargaewlaornig-8itucdhiannalndeilff3eraenndceFbYet-w2EeeVn ItSheimHaimgeaswaarrie-8parnodjecFtYe-d2Eopnotositaiognrs,idthseyssatmeme cdloeufidnleodokussing a different in both images, which could cause an error in the parallax calculation
Summary
Clouds play an important role in impacting the energy balance of the Earth. Clouds cool the surface of the Earth by reflecting solar shortwave radiation. When a cloud is optically thin or partially fills the satellite FOV, the additional terrestrial radiation increases the observed IR brightness temperature, which eventually causes CTH to be underestimated [5,6]. To overcome this problem, the CO2-slicing method [7] has been developed. V20e2r0c,o1m2, 1e95t3his problem, the CO2-slicing method [7] has been developed This me2tohfo2d0 retrieves the optimal cloud-top pressure (CTP) by selecting two channels where the two observed radiances are different but cloud emissivity is the same. Based on the dual-satellite approach, simultaneous observations from these GEOs allow CTH retrieval within the overlapping area over East Asia.
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