Station P208

Science Spotlight


Researcher: Sarah Evans
University of Colorado


The view from GPS Station P208 in April 2012.


Name: SALTCANYON
State: CA
Country: United States
Elevation: 74.3 m
Lat/Long:  39.1093 / -122.3039

Vegetation Studies in Northern California

The PBO-H2O group has developed methods that use reflected GPS signals to determine vegetation growth. Figure 1 shows the vegetation growth cycle from 2007-2012 for GPS site P208. With some variations we see that vegetation measured by GPS generally peaks in May. The amplitude of this peak varies from year to year and is especially dampened in 2007 when precipitation was well below average. Field exercises in 2012 verified these results: at top (April) we see the site lush with green oatgrass while in Figure 2 (August) we see the same site with vegetation dry and brown.

Figure 1. Record of vegetation growth from GPS and precipitation, 2007-2012. NDVI data measure greenness. GPS data (NMRI) are linked to the water content of the vegetation.


Figure 3. Close-up view of the NMRI and NDVI data in the 2010 vegetation season. You can see that the NMRI data have a very pronounced peak around May 1, but that the much sparser NDVI data shown greenness over a longer time interval.

 

Figure 2. Photo of P208 in August 2012. The dry season for California's Central Valley runs from May until September.


Figure 4. Field studies are essential to refine the model for measuring vegetation using GPS signals.

Spotlight Questions

The "P208 Vegetation Data" button above gives more information about GPS vegetation data, NDVI, precipitation, and temperature data for station P208
  • What years have had above average precipitation? How did the vegetation respond?
  • Can you find other sites on the PBO-H2O database that had a low vegetation response in 2007?

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