sudden speed loss during climb...
The airport was in an area of a very strong high, with the QNH of 1040 hPa, and the temperature @ minus 12 degrees centigrade. There was a light headwind, and no turbulence. We were flying an ATR-72 about 1 tonne short of the MTOW. During the initial climb-out, I noticed that the ROC was 2000-ish and the pitch attitude in excess 15 degrees - rather unusual for the ATR-72, which, especially when heavy, isn't a good climber. Then, at ~1000 ft the speed abruptly dropped from ~130kts to ~105kts - about 10kt below V2. My first thought was power loss, but the engine gauges showed only slight (but clearly visible) variations of power. Then, with speed regained, the a/c settled at V2+10 and the ROC was about 1500ft/min (more ATR-like) and the engines showed no abnormalities.
I wonder what actually happend... My guess is a strong temperature inversion, checked the SAT some 1000ft higher, and it was some 5-10 (don't remember exactly) degrees higher than on the ground... But then again, the speed change was very abrupt (almost windshear-like, though there was no turbulence). Never experienced it before. Besides, the ATR's engines are flat-rated up to much higher temperatures, so it should make no difference if it's -5 or -15 degrees - the power output should be the same. My other suspects are a brief power loss, or some kind of windshear.
Thoughts, anyone??