Monday, 10 February 2003
Variability of Precipitable Water over Arizona and Northwestern Mexico
We are installing GPS receivers in the Southwestern US and Northwestern Mexico area as part of the greater Suominet precipitable water (PW) network to study PW behavior in the region. Initial validation has been accomplished via comparisons with 12 hour PW from the Tucson radiosonde and hourly clear-sky GOES PW. This data measures the near-continuous time evolution of PW over selected locations under clear and cloudy conditions. The data captures the sharp onset of the summer monsoon this year and reveals interesting low frequency temporal variability of the PW results in the region including diurnal variations. In general, the observed variations are significantly larger than the error contributions we have considered suggesting the observed variability is real for the most part. We are characterizing the temporal scales of the variability and cross correlating PW observed at different sites to constrain horizontal scales. We are also relating the GPS PW temporal variations to the horizontal variations visible in the clear sky GOES PW estimates and the larger synoptic scale weather context. We have begun comparing the observed PW with the PW in model forecasts and analyses in the region to assess the quality and ability of the forecasts and analyses to capture the true behavior of PW in the area and how this may be related to precipitation forecast quality. We will summarize our instrumentation and initial findings regarding PW behavior in the region.