For pilots of gliders or sailplanes, the 'thermal' is the most important phenomena of the air. A thermal is classically described as an upward flow of air caused by ground level heating of air that rises in bubbles or a connected stream of warmed air. Given sufficient velocity of the rising air, a gliding craft, bird or even trash and debris can be lifted thousands of feet. It can be also noted that 'dust devils' can result from especially vigorous flows and that other even stronger phenomena like tornadoes and cyclonic storms are related.
But in the absence of markers like dust, the air flow is generally invisible until possibly the flow reaches an altitude where the water vapor contained, condenses to form a cloud. And again if the flow is strong enough and contains enough water, a thunder storm is possible.
So, the question. Given all of the above is it possible to see the mass of air that makes up the thermal? Is there anything in the difference between the thermal and the surrounding air that could be detected and presented graphically?