Astroclimatology of La Silla

Precipitable Water Vapour at La Silla

A median nighttime value of 3.9 mm H2O was measured at La Silla during the VLT Site Survey, 1983-1989 (VLT Report 62, 1990), using the KPNO Infrared Sky Radiance Monitor (Morse, D and Gillett,F. 1982: AURA Eng. Report 73)

PWV at La Silla: Annual Statistics from Satellite Imagery (tentative, still subject to calibration checks)

Average Precipitable Water Vapour (mm H2O, clear time only)

3-hourly GOES8 Satellite Images	1999	2000	2001	2002
January		10.7	7.0	8.5
February		9.2	8.2	9.7
March		7.4	9.7	10.1
April		7.0	6.8	6.9
May		5.2	5.8	5.8
June		5.7	4.4
July		4.4	2.7
August	4.6	5.0	4.2
September	5.3	4.4	5.2
October	6.0	4.5	6.5
November	6.6	5.8	6.6
December	6.4	7.4	9.1

Clear time PWV at Paranal (red) from 3-hourly satellite images

(data file, format: YYYY MM DD HH PWV)