Fran Bryan set some blind hides for me today and I ran them as the sun was setting.  This search ended up being much harder than expected and the way that Iona ended up sourcing the hide completely blew my mind.  I believe that this is an interesting example of the lofting effect.  You can find an excellent description HERE.  The wind was moving from R to L in this video.  The reason that the scent is rising is that the ground is cooling quickly but the air still stays warm.  As a result, the relatively warm air is rising.  On that day, this search area was the only one with this strange scent conditions and I originally thought that this was an example of the chimney effect.  However after seeing this effect happen several times with night time searches, I am fairly certain that what we are seeing here is lofting. 
You can see that Iona searches right underneath the hide without picking up odor and eventual sources it by climbing up on the table to catch the rising odor. She then follows it down from there.  You can see her trying to get high up earlier in the search but she can’t quite catch odor. Note that I have sped up the first 2/3 of the search to save you some time.