Basics of Remote Sensing From Satellites Tutorial Chapter 4.6

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4.6 The BD enhancement curve

Figure 4.6-1 is a plot of an images's input vs output counts. The indicated curve is the BD enhancement curve.

4.6-1. BD enhancement curve.

Figure 4.6-2 shows the BD enhancement curve applied to infrared imagery

Figure 4.6-2. IR image with BD enhancement.

Compare the structure of the tropical cyclone eye with the BD enhancement to that with no enhancement (Figure 4.1-2). Notice that the eye does not show up as well with the BD as with the MB enhancement. This does not matter since how well the hurricane's eye is defined (and thus intensity estimates) can only be measured by viewing changes using the same enhancement.

The BD enhancement curve for thermal IR imagery is the most complicated of all the main black and white enhancement curves. This is the result of the recurring series of gray level steps as the brightness temperature decreases. This curve is usually displayed to measure the intensity of tropical cyclones that contain eyes. Dvorak (1984) developed a technique for measuring the intensity of these tropical cyclones by comparing the warmest spot within the eye and the warmest cloud top temperature within the cold cloud ring surrounding the eye. The greater that difference, the more intense the tropical cyclone. This curve assists those estimating tropical cyclone intensity by highlighting the differences between the eye temperature and that of the cold cloud ring by performing severe contrast stretches in both warm and cold portions of the enhancement curve.