In the Chinese Arctic scientific expedition during Jul y to September

1999

a set of digital images by helicopter remote sensing are o btained. With high ground resolution of 30 cm

these images can be used to analy ze detailed sea ice parameters. In this paper

a method for determining the thr eshold value is adopted to separate ice and water. A ratio of radiance is de fined as the ratio of the ice element number that with large difference compared with the neighbor element over the total element number with the same radiance value. By the result

not only ice edge and ice concentration are accurately cal culated

but some new parameters are also chosen to present the status of sea i ce. Ice area is a parameter to give the area of each ice to show the size of ice. Sea ice is divided into five types by its area size to show the ice dis tribution ratio in different types. As many big ice packs consist of small ice pieces crowded each other

a new parameter called breaking degree is propos ed to express the complexion degree of ice shape. These parameters can be used t o distinguish ice size in a big ice

which can greatly affect vessel navigation and air-ice-ocean heat exchange. By combining these parameters

people can get more information of sea ice for its concentration

area of big ice and broken degree of ice pack. It seems that these parameters are useful in the studies in ice melting process and interaction between atmosphere and ocean water. These pa rameters are hardly determined by satellite imagery. The method can be used to c alculate water’s area

and complexion degree of water regions to express lead

l ane

polynya

etc. The methods can be used in sea ice analysis for either polar ice or the ice in Bohai Sea.