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Updates on data details & running a hydrologic model on tree rings
Steph McAfee University of Nevada, Reno Nevada State Climate Office
Updates on data details & running a hydrologic model on tree - - PowerPoint PPT Presentation
Updates on data details & running a hydrologic model on tree - - PowerPoint PPT Presentation
Steph McAfee University of Nevada, Reno Nevada State Climate Office Updates on data details & running a hydrologic model on tree rings Data details The number and location of stations changed over time. 1900 1920 1940
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The number and location of stations changed over time.
1900 1920 1940
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Especially since the late 1970s
1970 1980 1960
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Average station elevation* has increased.
* And a host of other things.
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Lapse rates decrease over time.
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Minimum temperatures cool as station elevation increases.
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So what does this mean?
- We might be underestimating high-elevation warming.
- This might mean we’re overestimating the influence of
temperature on flow.
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Running a hydrological model on tree rings
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Theory: plug reconstructions into model
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Reality: resolution mismatch
Monthly grids of data Seasonal basin-wide data
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Resolution: K- nearest neighbor resampling
50 100 150 200 250 300 350 1560 1660 1760 1860 1960 October - April UCRB precipitation (mm)
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K- nearest neighbor resampling
Reconstructed October – April precipitation
PRISM October : September precipitation
Reconstructed May – July temperature
PRISM October : September temperature
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Theory: one-to-one relationship
50 100 150 200 250 300 350 50 100 150 200 250 300 350 Reconstructed Observed
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Reality: reconstructions miss extremes
50 100 150 200 250 300 350 1950 1960 1970 1980 1990 2000 October - April UCRB precipitation (mm) Observed Reconstructed
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Resolution: KNN on percentiles
1.
Translate reconstructed amount to percentile.
2.
Weighted KNN to select a close percentile.
3.
Calculate an adjustment factor.
4.
Find the precipitation amount closes to that percentile.
5.
Pull all months from that water year.
6.
Apply the adjustment to all of them
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How’s it look? Precipitation
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How’s it look? Temperature
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How’s it look? Temperature
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In summary
- Translating the reconstructed temperature and precipitation into
data that the Water Balance Model could use required a number
- f steps, but
- the process seems to be working!