Small errors in the time or calibration of the weather stations could result in significant errors, espcially in quantities derived from differences or ratios in the measured values, such as the water vapor scale height. It has been suggested that there is often an inversion layer about 500 m above the Chajnantor site. The weather stations currently deployed in Chile measure all of the meteorological parameters required to identify an inversion layer except for the atmospheric pressure. If new weather stations are obtained for work in Chile, they should be able to measure wind speed and direction, solar flux, water vapor presure, temperature. and atmospheric pressure. WS1 is weather station 1, WS2 is weather station 2, and RM is the radio seeing monitor and radiometer.
Winds are generally from the northwest.
Night time comparison of PWV calculated by integrating the water vapor distribution vs. PWV calculated from the opacity.