Drought Monitoring Using Near Real Time PBO H2O Water Cycle Products
Tuesday, April 21, 2015
Eric E Small, Univ of Colorado Boulder, Boulder, CO, United States, Kristine M Larson, University of Colorado at Boulder, Boulder, CO, United States and Clara C Chew, University of Colorado at Boulder, Geological Sciences, Boulder, CO, United States
Abstract:
Data from NSF’s EarthScope Plate Boundary Observatory (PBO), and similar GPS networks worldwide, can be used to monitor the response of the terrestrial water cycle to drought. GPS satellites transmit L-band microwave signals, which are affected by water at Earth’s surface. GPS signals take two paths: (1) the “direct” signal travels from the satellite to the antenna; (2) the “reflected” signal interacts with the Earth’s surface before travelling to the antenna. The direct signal is used by geophysicists to measure position of the antenna, while the effects of reflected signals are generally ignored. We have developed a technique to retrieve terrestrial water cycle variables from GPS reflections. The sensing footprint is intermediate in scale between in situ and remote sensing observations. The PBO H2O data products include estimates of soil moisture, snow depth, and an index of vegetation water content ~400 sites in the western U.S. This PBO H2O dataset is available to the public with latency of one day, and thus can be used to monitor the effects of drought in near real time. Validation studies show that the PBO H2O products are of sufficient quality to be used for this application. We document the response of water cycle variables to the recent California drought, and compare the GPS-based response to that measured with other techniques. This comparison highlights the added value provided by the GPS-based products.
