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Precipitable Water Vapor Monitoring on Kitt Peak

The Kitt Peak Observatory has installed a GPS receiver for monitoring Precipitable Water Vapor in the atmosphere.

The plots are computed by Suominet ( link to Suominet website ) – live page displayed below, 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.

PWV GPS receiver (top of pole) mounted on the WIYN building.

Looking for Data? Here's Some Useful Startup Help

The current year's collection of data as calculated by Suominet is available here:
Here is a snippet of Python code that reads in this file

from astropy.table import Table
from astropy.time import Time
from import ascii
def readSuominetPwv(datafile):
data =
datafile, format='ascii',
names=('Station','DateTime','PWV','PWV_err','WetZenithDelay','TotalZenithDelay','pifactor','SurfacePressure','SurfaceTempreature','SurfaceRelativeHumidity','SomethingDelay','A','B','C'), converters={'col2': [ascii.convert_numpy(Time)]} )
return data

Units are in mm for PWV, mbar for pressure, C for temperature
The columns are partially documented at

Kitt Peak PWV Page at Souminet

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