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Murry L. Salby, Harry H. Hendon, Karen Woodberry, and Ken Tanaka

Synoptic images of the global cloud field have been created from infrared measurements taken aboard four geostationary and two polar-orbiting platforms simultaneously observing the earth. A series of spatial and temporal interpolations together with data reliability criteria are used to composite data from the individual satellites into synoptic images of the global cloud pattern. The composite Global Cloud Imagery (GCI) have a horizontal resolution of about half a degree and a temporal resolution of 3 h, providing an unprecedented view of the earth's cloud field. Each composite image represents a nearly instantaneous snapshot of the global cloud pattern. Collectively, the composite imagery resolve, on a global basis, most of the variability associated with organized convection, including several harmonics of the diurnal cycle.

The dense and 3-dimensional nature of the GCI make them a formidable volume of information to treat in a practical and efficient manner. To facilitate analysis of global cloud behavior, the GCI has been constructed with certain homogeneous properties. In addition to synoptic coverage of the globe, data are spaced uniformly in longitude, latitude, and time, and contain no data voids. An interactive Image Analysis System (IAS) has been developed to investigate the space-time behavior of global cloud activity. In the IAS, data, hardware, and software are integrated into a single system capable of providing a variety of space-time covariance analyses. Because of its customized architecture and the homogeneous properties of the GCI, the IAS can perform such analyses on the 3-dimensional data with interactive speed. Statistical properties of cloud variability are presented along with other preliminary results derived from the GCI.

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Ken Tanaka, Karen Woodberry, Harry Hendon, and Murry Salby

Abstract

Synoptic images of the global cloud field have been created from measurements of infrared radiation taken aboard four geostationary and two polar-orbiting platforms simultaneously observing the earth's cloud field. A series of spatial and temporal interpolations, together with data reliability criteria, are used to map synoptic measurements from the geostationary satellites and asynoptic measurements from the polar-orbiting satellites. The synoptic global cloud imagery (GCI) that results has a horizontal resolution of 0.7° in longitude by 0.35° in latitude and a temporal resolution of 3 h, providing an unprecedented view of the global cloud pattern. Each composite image represents a nearly instantaneous snapshot of the entire earth's cloud field. Collectively, the composite imagery resolve, on a global basis, most of the variability inherent to organized convection, including several harmonics of the diurnal cycle. Because of its homogeneous properties, the GCI lends itself easily to a variety of space-time analyses useful for studying global cloud behavior.

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Karen Woodberry, Ken Tanaka, Harry Hendon, and Murry Salby

Abstract

Synoptic images of the global cloud pattern composited from six contemporaneous satellites provide an unprecedented view of the global cloud field. Having horizontal resolution of about 0.5° and temporal resolution of 3 h, the global cloud imagery (GCI) resolves most of the variability of organized convection, including several harmonies of the diurnal cycle. Although the GCI has these attractive features, the dense and three-dimensional nature of that data make it a formidable volume of information to treat in a practical and efficient manner.

An interactive image analysis system (IAS) has been developed to investigate the space-time variability of global cloud behavior. In the IAS, data, hardware, and software are integrated into a single system providing a variety of space-time covariance analyses in menu-driven format. Owing to its customized architecture and certain homogeneous properties of the GCI, the IAS calculates such quantities with exceptional performance. Many covariance statistics are derived from three-dimensional data with interactive speed, allowing the user to interrogate the archive iteratively in a single session. The three-dimensional nature of those analyses and the speed with which they are performed distinguish the IAS from conventional image processing of two-dimensional data and suggest the IAS as a prototype for dealing with large volumes of multidimensional data as will be produced by NASA's Earth Observing System.

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Ichiro Yasuda, Shin-Ichi Ito, Yugo Shimizu, Kaoru Ichikawa, Ken-Ichi Ueda, Takayuki Honma, Masashi Uchiyama, Kentaro Watanabe, Noriyuki Sunou, Kazushi Tanaka, and Koji Koizumi

Abstract

Summer hydrographic surveys from 1993 to 1997 in the area south of the Kuril Islands in the northwestern subarctic Pacific showed the existence of anticyclonic eddies south of the Bussol’ Strait at almost the same location but with variable sizes and intensities depending on the year. Every eddy had a cold, low salinity and low potential vorticity core, suggesting a strong influence from the Okhotsk Sea water. Two formation processes and annual variations were found with satellite data analyses. One is the case where eddies are locally formed south of the Bussol’ Strait and intensified from summer to fall with the supply of Okhotsk Sea water as observed in 1993. In the other case, Kuroshio warm-core rings that had translated northeastward are arrested near the Bussol’ Strait and amplified with the supply of Okhotsk Sea water as seen from summer to autumn in 1995. In winter, eddies tend to move northeastward with decay. The 1992 eddy moved northeastward then northward in winter and was eventually absorbed into the East Kamchatka Current. Mechanisms of the northeastward movements and the formations of the Bussol’ eddies were discussed. A pseudo-β effect due to deep northeastward currents along the Kuril–Kamchatka Trench could be responsible for the northeastward movement. Since the volume transport of the coastal Oyashio water along the southern Kuril Islands is constrained by the potential vorticity difference between the Okhotsk Sea and the western subarctic gyre (WSAG), eddies could be generated and intensified when a outflow rate from the Okhotsk Sea exceeds the critical transport. The observed annual variations of the eddy evolution might be explained by the critical transport variation associated with an annual change of the WSAG.

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