Three Qs here: reducing heat haze/shimmer; increasing it; dealing with "scintillations".
Scintillations are bright lights, usually like sparks, so I don;t think they apply at all.
I can start with reducing heat haze shimmer...
First, since it's ever-present as unstable air over hot surfaces, try to avoid the latter. (Open slather, I know.)
Then, if you must photograph through it, remember that telephoto
lenses will magnify (ie, actually enlarge) the
image of the unstable air, and so, any subject through it.
A high
shutter speed will only freeze the distorted image, and a lower one will only blur the same image. So,
shorter focal lengths for, if not full avoidance of, photographing the subject.
Alternatively, just shoot the scene as is.
To filters and the like as a means of reducing heat haze: none that I know of, and unlikely in
light of the foregoing.
And finally, what's all this malarky about summer coming?
- A quick trip to the Northern hemisphere should fix that.
Actual finally: thread moved to
General Shooting Help.