A Comparison of GPS-Measured Precipitable Water at Bartlett, NH with Radiosonde Measurements in the Northeast

Remote GPS techniques are rapidly becoming a widely used method for determining the integrated precipitable water (IPW) in the atmosphere. NOAA's Forecast Systems Laboratory expects its GPS Demonstration Network to grow to over 90 sites by the end of 2000 with rapid deployment continuing into an operational network during the next decade.

A recent addition to NOAA's Demonstration Network has been the site at Bartlett, NH, close to Mount Washington Observatory. Integrated precipitable water vapor measurements at Bartlett will be compared to radiosonde measurements taken at several surrounding stations in the Northeast. Comparisons will be done by first using precipitable water measurements directly from soundings at the radiosonde stations and, secondly, by using a Barnes objective analysis scheme to create an initialized sounding from ETA and NGM model data for a grid point positioned over the Mount Washington area. Times of 00Z and 12Z over the first five months (May-September, 2000) of GPS operation at the Bartlett site will be considered only. Based on these comparisons, precipitable water amounts will be reconstructed for the Bartlett location using archived Northeast radiosonde data back to 1998.

In addition, some initial comparisons of the Bartlett GPS data will be made with IPW values from the anticipated, SuomiNet, GPS installation at Plymouth State College in Plymouth, NH, located 33 miles southwest of the Bartlett site. Such comparisons should indicate the variability of moisture over a small spacial domain under common synoptic conditions and be particularly instructive during New England, backdoor, cold-front events.