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Sensor Networks and the Arrival of Spring

Thursday, April 30, 2015
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Harvard Forest stream weir

The field wireless network at Harvard Forest was recently expanded to enable (near-) real-time data from four stream gages, two wetland gages, and a snow pillow. Data from these stations and the Fisher Meteorological Station are collected, processed, and uploaded to our website every 15 minutes along with 30-day graphs of selected variables. The graphs, which contain about 3,000 data points for each variable, reveal a physical environment that is in constant flux, with variations on daily, synoptic, and seasonal time scales.

These variations are particularly striking in spring. In addition to longer days and (generally) warmer air temperatures, the melting of the snowpack can lead to abrupt changes, including an increase in soil temperature (as sunlight reaches the soil), net radiation (as the ground absorbs more of the sun's energy), and water temperature (as snowmelt declines and the soil warms), as well as pulses in stream discharge and wetland water levels (as water stored in the snowpack is released). As minimum air temperatures rise above freezing, daily fluctuations in stream flow and wetland water levels may be seen as first conifers and then hardwoods begin to transpire. Changes in plant phenology, soon to follow, will be captured by the Harvard Forest webcams.

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