Abstract:

Based on meteorological data of 9 observation stations along the Yangtze River in the Three Gorges Reservoir Area,river surface wind,water temperature,and visibility of the Yangtze River waterway have been analyzed.The intensity of visibility and the spatialtemporal distribution characteristics of low visibility were analyzed statistically,and furthermore the correspondent weather conditions of low visibility were also studied.The results showed that (1) the direction and velocity of wind and the water temperature in this region cannot exert obvious influence on sailing safety; (2) visibility is a fundamental factor influencing sailing safety in this region; (3) the weather inducing low visibility exhibits obvious characteristics of spatialtemporal distribution: low visibility is more probable to appear in winter than in summer,and compared with the section from Wanzhou to Wushan,low visibility is more possible to emerge in the section from Chongqing to Zhongxian; (4) except for Chongqing City and Zhongxian County,there is a decreasing trend of annual low visibility phenomenon in the Yangtze River waterway generally,with the lasting time of low visibility phenomenon less than two hours each time,most probable to appear in winter,then in autumn and spring,and least probable in summer；(5) in addition to the city environment,the weather condition contributes to the low visibility phenomenon in the waterway,and the main weather cause is that the basin is controlled by surface cold highpressure,which induces cloudy or rainy weather.The fog or rain fog of cloudy or rainy day resulting in low visibility phenomenon.

Key words: Three Gorges Reservior Area, shipping, visibility, meteorolgical conditions