Water, as an important part of ecosystems, is also an important topic in the field of remote sensing. Shadows and dense vegetation negatively affect most traditional methods used to extract water body information from remotely sensed images. As a result, extracting water body information with high precision from a wide range of remote sensing images which contain complex ground-based objects has proved difficult. In the present study, a method used for extracting water body information from remote sensing imagery considers the greenness and wetness of ground-based objects. Ground objects with varied water content and vegetation coverage have different characteristics in their greenness and wetness components obtained by the Tasseled Cap transformation (TCT). Multispectral information can be output as brightness, greenness, and wetness by Tasseled Cap transformation, which is widely used in satellite remote sensing images. Hence, a model used to extract water body information was constructed to weaken the influence of shadows and dense vegetation. Jiangsu and Anhui provinces are located along the Yangtze River, China, and were selected as the research area. The experiment used the wide-field-of-view (WFV) sensor onboard the Gaofen-1 satellite to acquire remotely sensed photos. The results showed that the contours and spatial extent of the water bodies extracted by the proposed method are highly consistent, and the influence of shadow and buildings is minimized; the method has a high Kappa coefficient (0.89), overall accuracy (92.72%), and user accuracy (88.04%). Thus, the method is useful in updating a geographical database of water bodies and in water resource management.

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In this paper, the long-term hemispheric variation of the polar faculae is investigated. It is found that, (1) both the N-S asymmetry and N-S asynchrony of the polar faculae exhibit a long-term persistence, which suggests that they should not be regarded as a stochastic phenomenon; (2) both the N-S asynchrony and N-S asymmetry of the polar faculae are functions of the latitude, implying that the N-S asynchrony of the polar faculae is related to the N-S asymmetry of the polar faculae; (3) from a long-term view, the dominant hemisphere of the polar faculae seems to have close connection with the phase-leading hemisphere of the polar faculae.

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