Human eyes can only see a narrow frequency spectrum, known as visible light, of the electromagnetic wave. The thermal infrared (IR) is another electromagnetic wave outside the visible light spectrum that is of natural origin that we frequently come across. How would the environment look like if we see them in the thermal IR spectrum?

Thermal IR camera pictures the temperature of the object. The thermal IR camera sees the thermal IR emitted by the object itself without any external light source. The hotter the object is, the brighter it appears in the thermal IR camera. While such function may not be useful for observation during day time, it would be useful at night when the target object is not well illuminated. Some examples of thermal IR images are shown in figures 1-3. For comparison, the visible images taken at the same time by another camera nearby is also shown. While during day time, the thermal IR image lacks certain details shown in the visible image (figure 1), it is able to see more at night (figures 2 and 3). For example, in figure 2, the Sunset Peak can be seen in the thermal image but not in the visible image. It is also difficult to tell if it is cloudy from the visible images shown in figure 3 alone while the thermal images can easily distinguish between fine and cloudy sky.

The Observatory is further exploring the use of the thermal IR cameras in weather observations.