I've had this happen to me on a few shots. I would suggest that even though it wasn't smoggy it may have been "foggy". 8KM of open, moist air between you and your subject can have a huge distortion effect. At least that's been my experience here on the East Coast of Canada. Also 1/20 second at 200mm can be a problem if your tripod is not rock steady. I would think that any wind at all might have an effect on a shot like this. (someone please correct me if I am wrong)