The precipitable water vapour (PWV) is the crucial parameter that determines the atmospheric transparency for sub-millimetre observations. At the APEX site on Llano de Chajnantor the amount of PWV is typically 1.0 mm and falls below 0.5 mm up to 25% of the time.

Weather data

Check here the current weather conditions at the APEX site in Chajnantor: PWV, temperature, humidity, pressure, wind speed. Access also historical data…

Atmospheric transmission

To prepare the observations and make time estimates for different atmospheric conditions check our instrument setup tool, based on the ATM model .
You can find here an interface to check only the atmospheric transmission without the instrumental layouts.

Related links

Forecast and satellite imagery

Here there are some links to relevant weather forecasts

And here you find links to some interesting sites with relevant satellite images