Astroclimatology of ESO Sites
ESO WIDE REVIEW
M. Sarazin, April 2000, 7/10
Historical Southern Oscillation Index, representative of Niño/Niña activity: after
applying a 3 months moving average, the data set was arbitrarily re-scaled and an offset
of 0.7 was added for comparison with seeing. The dashed line indicates the Niño/Niña
transition, the strong El Niños
of 1983, 1987, 1992 and 1998 are well visible.
The monthly mean seeing measured at Paranal since the beginning of the VLT site survey
has been overplotted with the same 3 months moving average.