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Long-term trends in uncertainty of element fluxes at the Hubbard Brook Experimental Forest. Mark Green, Donald Buso , John Campbell, Carrie Rose Levine, Gene Likens, Ruth Yanai. Element Fluxes. : Flux [mass per time]. : Concentration [mass per volume]. : Concentration [volume per time]. - PowerPoint PPT Presentation
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Long-term trends in uncertainty of element fluxes at the Hubbard Brook Experimental Forest
Mark Green, Donald Buso, John Campbell, Carrie Rose Levine, Gene Likens, Ruth Yanai
Element Fluxes
: Flux [mass per time]
: Concentration [mass per volume]
: Concentration [volume per time]
Hubbard Brook
New Hampshire
White Mtn. Natl. Forest
Hubbard Brook Experimental ForestWhite Mountain National Forest, NH
Map courtesy of Dr. John Campbell, USFS
Our Guiding Questions
How certain are our flux signals?
Is there new information that may arise from quantifying uncertainty?
ObjectivePropagate some sources of uncertainty through flux estimates.
Approach
• Quantify uncertainty in annual fluxes into and out from Watershed 6 at HBEF– Nitrate– Silicon
• Only a few sources of uncertainty are addressed so far
Modified from Harmon et al. (2007)
UNCERTAINTY
Natural Variability
Spatial Variability
Temporal Variability
Knowledge Uncertainty
Measurement Error
Model Error
Model Selection Uncertainty
Weekly Average
Time
StreamwaterConcentration
Linear Interpolation
Time
StreamwaterConcentration
-1.9%
-3.7%
Model Parameter Uncertainty
Steps in Flux Calculation
For every gap between samples:1. Calculate mean concentration2. Determine the inter-sample residuals
based on season and date3. Add a bootstrapped residual to the mean4. Calculate annual flux
Nitrate
Silica
Summary
Nitrate• Uncertainty in model selection: 3%• Uncertainty in inter-sample mean: 17%
Silicon• Uncertainty in inter-sample mean: 9%
Maybe novel information in IQR:Median
Next: More sources in streamwater, finalize precipitation, and propagate to net hydrologic flux.
http://quantifyinguncertainty.org/
Modified from Harmon et al. (2007)
UNCERTAINTY
Natural Variability
Spatial Variability
Temporal Variability
Knowledge Uncertainty
Measurement Error
Model Error
Atmospheric Inputs
Alternative spatial models for precipitation in the Hubbard Brook Valley
Alternative spatial models for precipitation in the Hubbard Brook Valley
0.36%
0.58%
0.24%
0.77%
0.83%
Coefficient of variation between models