Structure and reflectance of winter maritime stratocumulus clouds

Abstract

To obtain the relationship between the structure and reflectance of winter maritime stratocumulus cloud tops, observations using an aerial stereophotographic method were carried out from January 1989 to January 1991 in the area off Wakasa Bay in the Japan Sea, and around the Amami Islands in the Pacific Ocean. The relationship between cloud top heights and the reflectance of the cloud was first investigated, and a positive correlation was found to exist. An especially high correlation was obtained for the clouds over the Amami Island data. Next, the relationship between the cloud area ratio and the reflectance of the cloud top surface was examined. Results indicated that in areas of low reflectance, the cloud top heights were relatively low and widely distributed. The cloud tops were sharp and jagged in shape. In contrast, in areas of high reflectance, high cloud top heights were found, being uniform on the average. Their shapes were flat and trapezoidal in comparison with the jagged nature of the other clouds. For the clouds north of the Amami Islands, the cloud top heights were lower than those found in other cases. The difference between the maximum and minimum cloud top heights was more than 400 m and the values of reflectance were greater than those in the other observations. The difference in the reflectance of the clouds over the Amami Islands may result from the difference between the liquid-water paths.