Seeing the Heat Dome on a Hot Summer Day

A massive heat wave hit a large part of the United States over the weekend of July 20 and 21, 2019. Temperature in Boston, Massachusetts rose to nearly 100 Fahrenheit. While the heat was baking the country, it was a good opportunity to observe the unusual thermal phenomena with an infrared camera.

Fig. 1: An illustration of a heat dome (source: The Weather Network).

Many heat waves were largely caused by a heat dome that forms when the atmosphere traps hot ocean air like a lid, as illustrated in Figure 1. So I thought I could perhaps see the heat dome with my FLIR ONE thermal camera if I went to the beach where there is a clear view of the sky, the ocean, and the horizon. Of course, I knew that the FLIR ONE camera cannot see hot air directly. But if a large portion of the atmosphere is emitting or reflecting a ton of infrared light, chances are that the camera could show something interesting, especially in the direction that aims at the lower part of the sky. This is probably the direction in which the atmosphere appears to the thickest to the viewer and I would speculate that the thermal radiation would be the strongest in that direction.

True to form, my infrared camera indeed revealed a layer of atmosphere between the upper sky and the ocean that was at a higher temperature than the upper sky and the ocean at noon on July 21. The thermal pattern persisted at night. On the next day when the heat wave was gone, my infrared camera showed that this layer no longer existed. Figure 2 provides a comparison of the time graphs using my own thermal analysis software. For contextualization, I also juxtaposed the visible light photos of the ocean fronts where I took the thermal images in Figure 2.

Fig. 2: Time graphs of temperature at different locations during my brief observations.

Figure 3 provides a space graph of temperature distribution in the vertical direction, which clearly shows that the peak of thermal radiation occurred at the lower part of the sky in the presence of the heat wave on July 21.

Fig. 3: The graphs of temperature vs. altitude at noon on July 21.

Figure 4 shows that the peak vanished in the absence of the heat wave on July 22.

Fig. 4: The graphs of temperature vs. altitude in the afternoon on July 21.

I did a few more observations on July 24 (a cool day) at different locations and times under different cloud conditions. The results are shown in Figure 5. The thermal images of Boston Harbor under a cloudless condition also show a peak in the lower part of the sky, but it is much less significant than the peak shown in the thermal images taken during the heat wave.

Fig. 5: Observation results on July 24 in Quincy and Boston.

Do these pictures provide convincing visual evidence of a heat dome?