This is also my understanding: thermal cameras detect infrared radiation emitted by objects which permit conclusions on the surface (and not the air!) temperature.
I can imagine that thermal cameras can help to answer different questions related to frost hollows, but I'm aware that this technology has it's difficulties and drawbacks:
- Which is the coldest point in a frost hollow? This question seems to be trivial in cone-shaped frost hollows: here it is the lowest point. But what if a depression has a more complex topography? This example of a depression near Brünigpass in Central Switzerland is, if you look at the map, not so clear. It is roughly divided into two parts: the southeastern part is a little bit deeper, but is surrounded by steeper slopes. If you zoom in, you recognize the small hill called 'Benedichtenwald' with a forest on it. East of this little hill there is a secondary depression which is not as deep as the main depression but it has a more open character. You can of course distribute several loggers over the area but with a thermal cam I would expect to receive an approximation of the spatial distribution of the temperature. Here is another nice example from the Jura with a complex topography.
- Where on a slope is the cold air produced? Where are the preferential flowpaths of the cold air? For the first question I assume that a thermal camera with sufficient reach can provide insight which is very difficult to gain with point measurements. For the second question a thermal camera can give hints where the most appropriate location for a smoke experiment is.
P.S. Thanks again for the hint to the book from David Whiteman - a must-read!