Environmental Conditions on ESO Observatories

The first Trimestrial Meteorological Report was issued in Austral Spring 1984. At that time one year of data on cloud and water vapor were already pointing towards Paranal as an outstanding place. This tendency was confirmed over the years and the basis of the 1990 Council decision to build the VLT on Paranal still held at the end of 1996 as the project was reaching completion (read more about it in the 100th Issue Special Report(1996)). The picture got slightly blurred during the commissioning of the VLT-UT1 with a noticeable increase of bad seeing periods believed to be linked to a strong El Niño aftershock (see The Messenger 97 - September 1999)

The Trimestrial Report Series has been discontinued

The 110th report (Autumn 99) is the last one of the serie: at the time when UT1 is opened to the community, both La Silla and Paranal Astronomical Site Monitors (ASM) are in operation, delivering in real time the full environmental picture into the ESO Archive Database from which data can be viewed using the Ambient Condition Server. An engineering tool is also being developped for data statistics and query. The cloudiness statistics, as in the past, remain under the responsibility of each observatory.

The page Astroclimatology and Related Topics provides additional information on this and related subjects.

We thank Julio Navarrete, now member of the team of VLT Telescope Operators at Paranal, for those many years of dedication to the compilation of the reports.

Reports 1999

Reports 1998

Reports 1997

Reports 1996

In March and April 1996 anomalies in Paranal weather conditions were experienced - please read the special report.

Reports 1995

Reports 1994