Abstract:

The mountainous channel of the Yangtze River from Yibin city to Yichang city, has complex and diverse climate.The terrain navigation is seriously influenced by the heavy fog. There are very sparse 36 artificial observation platforms along the river,with the distance from 3 to 10 km or more. How to get the unknown point reliable fog information, change the limitation of the subjective judgment alone and provide the scientific basis for waterway traffic control on the basis of the limited observation pointsis very necessary and urgent. In this study,fisher discriminant analysis method is adopted, the unknown point of meteorological elements and the fog around for the center with its rank as the dependent variable, in order to realize the target fog levels of interpolation. According to the data characteristics and interpolation requires of fog along the Yangtze River Waterway, discriminant analysis method is used for five adjacent stations. The fog situation grade and the quarter points of corresponding meteorological elements are divided into different scenarios to establish interpolation equations.Most of the actual grade of fog can be accurately reported. When two neighboring stations and observed fog over the situation, most of the actual target station fog level can accurately calculate;when three or more stations fog are graded 0,meteorological judgment is depended.Vapor pressure and the diurnal range also have a significant positive correlation to the formation of the fog. Breeze promote the formation of fog, the wind tends to increase naturally dissipate. Spring and winter fog situations are highly correlated with meteorological factors,and the compliance rates is high. The probability of reported empty is higher in summer and autumn. Many factors affect the space of fog, including meteorological stations topography, river width, camber back inlets, a tributary of River Inlet and the others alike. Because there is only one year of the fog situation observations, the season of the sample after three cases are limited segments, we need to extend the time scale, increase the number of samples to obtain a better result of discrimination.However, this method has some limitations，the visibility grade interpolation can only provide a reference to the shipping,and visibility values spatial interpolation remains to be further studied