Fig. 20

a Cloud cover at the ultraviolet shows the same vortex morphology over both hemispheres. These polar stereographic views of northern (top) and southern hemisphere (bottom) on dayside are from a 365-nm images taken on May 17, 2016, on orbit 15 of Akatsuki. Brightness normalization has been applied using Minnaert law. b North (bottom) and south (top) hemispheres in polar stereographic projection of a 2.02-µm contrast filtered image with overlaid latitude and longitude grid. The calibrated image was first subjected to a contrast filter to bring out the local structures and then projected. The pattern at higher latitudes resembles the spiral arms of the vortex seen at ultraviolet, but the inclination to latitude circles appears slightly different. Also, a lot more structure is seen in the contrast filtered versions closer to the poles. c Polar stereographic view of the southern hemisphere (top) from the LIR camera on September 16, 2016 (06:47:47 UT), and of the northern hemisphere (bottom) imaged on November 11, 2016 (16:08:12 UT). The respective pole is in the center and the periphery marks the equator in both of the images. Higher brightness temperatures near both poles are consistent with lower cloud tops as also seen in the 2.02-µm data. Faint arcs in both images are believed to be signatures of the spiral bands seen in the ultraviolet images as a result of the vortex organization of the circulation. The cold collar is clearly visible as a region of lower brightness temperatures in the northern hemisphere, but its appearance is not so distinct in the southern hemisphere indicating that the circulation plays a significant part in the cloud cover structure