Fig. 16

Sharp boundaries are also seen in images of Earth taken from weather satellites in the water vapor channel (6.9 µm channel top) and a color composite of three visible channels from Himawari on August 1, 2017, at 23:50 UT. Several sharp boundaries in the water vapor channel can be seen in both hemispheres in the vicinity of Typhoon Noru and the cyclonic circulation further east, and in the southern hemisphere due to different air masses with different lower tropospheric water vapor amounts. The bottom image is a red, green and blue composite view of three images taken simultaneously through different visible filters where the boundaries between the dry and moist air masses are not so easily discerned but can be inferred from the destruction of the clouds due to entrainment of the dry air in the western half of the cyclonic region (central part of the color image). Note also a boundary just west of the brighter Sun glint in the color composite to the right of the frame center which is not seen in the water vapor channel due to variable sea roughness across the boundary. By analogy, the sharp boundaries seen on Venus in the IR2 nighttime images may suggest different “air masses” due to differing trace gas abundance(s) within the Venus cloud layers