The Kitt Peak Observatory has installed a GPS receiver for monitoring Precipitable Water Vapor in the atmosphere.
The Precipitable Water Vapor is calculated by Suominet at UCAR (University Corporation for Atmospheric Research), using data from a GPS receiver and meteorology station at Kitt Peak, both are at WIYN. Precipitable Water Vapor (PWV) is derived using the differential (between vacuum and measured) delay in radio signals from GPS satellites at the ground receiver. The delay is caused by refraction in the ionosphere and troposphere. The ionospheric delay is estimated using dual-band information at the receiver. The tropospheric delay (labeled Total Zenith Delay or TZD: bottom plot) is composed of Zenith Hydrostatic Delay (ZHD: attributed to dry air) and Zenith Wet Delay (ZWD: attributed to Precipitable Water Vapor). The large part of ZTD is ZHD, which is calculated from empirical models that use the absolute ground air pressure (refer to the ZTD plot, bottom plot below). The ZWD is then converted to PWV (refer to the PWV plot, top plot below). This requires the mean tropospheric temperature, obtained primarily from the surface air temperature (refer to the temp plot, middle plot below).
References: See further at SuomiNet and Wang et al. 2013. We acknowledge the effort of Michael Wood-Vasey (U. Pittsburgh) for initiating the Precipitable Water Vapor project and obtaining funding for the GPS receiver through National Science Foundation grant AST 1311862. The GPS receiver was purchased by the University of Arizona, through their membership in UNAVCO. We would also like to acknowledge Teresa Van Hove at UCAR for her help in getting this project going.
PWV GPS receiver (top of pole) mounted on the WIYN building.
Looking for Data? Here's Some Useful Startup Help
Here is a snippet of Python code that reads in the files you can download below. ====
Below: create a link and download data files (from SuomiNet) for the KPNO and/or the UofA sites for the year of your choice, then plot the entire year
Please enter the year [format=(YYYY)] for the data you want to download
[For Kitt Peak site]
[For University of Arizona site]
Plots display here: Kitt Peak plot at top, UofA plot beneath.