# Sandwich products - satellite imagery visualisation technique

## Print Version

## Chapter IV: Common visualisation of the enhanced images - 2-panel visualisation

- Common visualisation of the enhanced images - 2-panel visualisation

### Common visualisation of the enhanced images - 2-panel visualisation

After enhancing the IR window and the solar channel image (or RGB using solar channels) one can visualise them in two-panel images to simultaneously analyse the cloud top features on them. Fig. 4.1 shows such an image pair. The left panel is a NOAA/AVHRR RGB image created from two solar and one IR channel, while the right panel is a colour-enhanced IR channel visualised with the standard colour scale. Several cloud top features are indicated in the figure.

Figure 4.1: Cloud top features shown in the RGB composite of AVHRR band 1, 2 and 4 (left) and in the AVHRR band 4 IR image (right) of NOAA-15 satellite, taken on 25 June 2006 at 16:08 UTC, Czech Republic. (Courtesy of Martin Setvák, CHMI)

Figs. 4.2-4.4 show further examples of visible and IR window pairs of storm tops.

The next two figures (Figs. 4.2 and 4.3) show visible and IR window image pairs of the same storm, observed by two polar satellites, with a 21 minutes time shift between them. In the MODIS image (Fig 4.2) several OTs are seen, while in the VIIRS image (Fig 4.3) one OT is seen and there is a 'corresponding' local BT minimum in the IR image.

Figure 4.2: Overshooting tops, cold-U and above-anvil ice plumes in form of 'ship waves' in MODIS band 01 (0.65 μm) visible image (left) and colour-enhanced band 31 (11.0 μm) IR window image (right), taken on 16 September 2016 at 12:22 UTC over the Tyrrhenian Sea and Italy. The spatial resolution of band 1 is 250 m, for band 31 it is 1 km. (Courtesy of Martin Setvák, CHMI)

Figure 4.3: Same storm as above, as seen in the S-NPP VIIRS images. Left panel shows Band I1 visible image (0.64 μm), right panel shows colour-enhanced Band I5 IR window image (11.45 μm) taken on 16 September 2016 at 12:43 UTC over the Tyrrhenian Sea and Italy. The spatial resolution of both bands is 375 m. (Courtesy of Martin Setvák, CHMI)

Figure 4.4a: Meteosat SEVIRI HRV (left) and IR10.8 (right) images of storms over Germany, taken on 12 July 2011 at 17:40 UTC. (Courtesy of Martin Setvák, CHMI)

Another possibility is to put the two images on the top of each other and study them with a 'slider'. In that way one can more exactly fit the infrared and visible characteristics. Fig. 4.4b shows the panels of Fig. 4.4a on the top of each other. Hover your mouse over the image to use the slider.

Figure 4.4b: Meteosat SEVIRI HRV and IR10.8 images over Germany, taken on 12 July 2011 at 17:40 UTC. (Courtesy of Martin Setvák, CHMI)

Summary

Cloud top features can be analysed on 2-panel visible and IR images, looking at them simultaneously, side by side. However, in that case the accurate spatial fitting of the VIS and IR characteristics should be made by a human eye and brain, and so the proper allocation of certain features may be somewhat uncertain.

By putting the two panels on the top of each other and studying them with a slider method the spatial fitting of the VIS and IR characteristics is more accurate, but this method can be used for a fixed pair only and, therefore, it is not adequate for animations.