# VIIRS Day/Night Band--Correcting Striping and Nonuniformity over a Very Large Dynamic Range
## 3 Results
### Histogram Matching Method Results
Figure 19 shows the same image of Hurricane Patricia as was shown in Figure 1, but after HMM destriping. In this image the fine ridge structures around the eye of the hurricane can be seen much more clearly. Figure 17: NCC twilight scene (**a**) before and (**b**) after HMM destriping from 22 September 2014 at 00:19 UTC in a region of Antarctica. The image is 650 by 1000 pixels and the right edge is end of scan. The median radiance in this image is about \(5\times 10^{-4}\) W\(\cdot\)cm\({}^{-2}\cdot\)sr\({}^{-1}\). Figure 20 shows the same image over a wider view so that the dynamic range of the image and of the HMM destriping can be better appreciated. On the right Mexico appears in full darkness with no moonlight. In the middle right, the city lights of the coast city of Acapulco appears, and near the upper right edge Mexico City is seen. There is no visible striping in this image anywhere. Figure 18: (a) NCC twilight scene over Antarctica before destriping; and (b) after HMM destriping from 22 September 2014 at 00:19 UTC. The image is 700 by 1100 pixels and is centered near nadir. The median radiance in image is about \(1\times 10^{-5}\) W\(\cdot\)cm\({}^{-2}\cdot\)sr\({}^{-1}\). In Figure 4 we noted a light vertical band that appears near the beginning of scan at the left edge. This is aggregation mode 29, which has a strong bias relative to the other adjacent aggregation modes. This light vertical band also appears symmetrically near the end of scan, also in aggregation mode 29. This artifact also appears in Figures 6, 8 and 14. In Figure 17 we noted that by itself HMM destriping was not able to correct this. Notice, however, that this band does not appear in Figure 19 or Figure 12.0 In this case it has been corrected by a special technique that extends HMM to aggregation mode discontinuities. This technique does not always work, but it did work for this  
Figure 12.1 **(a)** Nighttime scene of Hurricane Patricia before destriping; and **(b)** with HMM destriping from 23 October 2015 at 07:45 UTC over the Pacific Ocean west of Mexico. The radiances are plotted on a linear scale over the range of 0 to \(6\times 10^{-9}\) W\(\cdot\)cm\({}^{-2}\cdot\)sr\({}^{-1}\) from black to white. The image is 500 by 700 pixels and the left edge is the start of scan. particular scene. We are continuing to test this technique to make it applicable to all scenes and all aggregation mode discontinuities. Figure 21 shows the same image of Typhoon Vongfong before and after destriping. There is no striping apparent in the corrected image, so the structure of the typhoon can be better analyzed (including the clarity of the transverse banding of the cirrus shield, which is a physical characteristic of the storm [32]). In Figures 19 and 20 the moon is low to the horizon and this creates shadows that highlight Patricia's structure. However, in the image of Vongfong the moon is nearly full and is almost directly overhead. Therefore, there are fewer dramatic shadows to highlight the structure of Vongfong, and the image is much lower in contrast across the storm top. In such cases of lower contrast, destriping becomes even more important. Figure 22 shows sea ice illuminated by a full moon off the Antarctic coast on 9 September 2014. In the right half of the images there is a low layer of thin fog over the ice. In many places the fog layer is thin enough to see fractures and leads in the sea ice. The ability to probe through cloud layers that typically are opaque at infrared wavelengths is an important capability of nocturnal DNB imagery at high latitudes [2]. Also, thermal infrared also cannot easily detect ice edges at night. This example highlights the significant benefits of destriping as a prerequisite to automatic image processing to identify quasi-linear features such as ice edges. The amount of blurring in the ice cracks reveals the thickness of the fog as does the shadows at its edges.