GPS Water Vapor Images

I am working on using zenith delay measurements from fixed GPS receivers to generate precipitable water images for California and Nevada.  This technique is in use by other groups but the great thing about California and Nevada is that there are so many GPS sites that high-resolution images are possible.  The trick is that you need the station pressure at the GPS site when the delay is measured and most of these sites don't have barometers.  For historical images I'm interpolating North American Regional Reanalysis (NARR) data to get the pressure.  In the future I may be able to make near realtime images by using the Rapid Update Cycle (RUC) analysis to generate the station pressures.

You can see my first attempts at this sort of image below.  The two images show precipitable water for California on days one week apart in June of 2006.  You can clearly see the difference in how moist the airmass is.  Below the images there is a link to an animation of this week, with frames every 3 hours. You can clearly see the increase in moisture during the week, more or less spreading from south/southeast.  It is not monotonic, though, for perhaps many reasons.






Download 2006 summer monsoon onset animation (3MB)

Here is another animation, this time of an "atmospheric river" event from January 6-12, 2005

Download January 6-12 2005 atmospheric river animation  (7 MB)