dendroclimatology. dendroclimatologists are interested in past climate so that the variation and...
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DendroclimatologyDendroclimatology
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Dendroclimatologists are interested in past climate so that the variation and trend of modern climate can be put into perspective
Synoptic climatology – the study of climate from the perspective of atmospheric circulation – circulation patterns can be inferred from reconstructed patterns of precipitation, temp, and pressure
Climate conditions can be estimated from a variety of natural environmental records going back to well before humans existed. Information of this kind is called “proxy data” because it substitutes for, or acts as a proxy for, the actual data we are seeking.
Dendroclimatology
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-Climate reconstruction starts with a site-level analysis of a tree species’ climate response
-Site selection – trees chosen from sensitive sites
-Many ages of trees chosen because trees may change in their climatic response with age
-Older trees yield longer chronologies, but older trees may have a weakened climate signal due to senescence
-Injured trees or those in the understory are avoided
-Sample depth
- Standardization removes non-climatic trends
Dendroclimatology
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PRISM data- takes data from individual climate stations and modles the signal ofer the landscape based on a physiological model. This data set provides accurate climatological info for location not previously monitored
Climate division data from National Climate Data Center
Dendroclimatology
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Response function analysis:
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Correlation analysis
• Correlation analysis complements results from response function analysis.
• RFA primarily concerned with temp and precip. Correlation analysis can be done on ALL climate variables (PDSI, ENSO, PDO, etc.)
• Correlation analysis best done with stats packages (SAS, Systat) or PRECON.
• Range of values = -1.0 < r < +1.0
• Associated with each r-value is its p-value which tests for statistical significance.
• In general, we want p-values less than 0.05, or p < 0.05.
• As in response function analysis, we also analyze months from the previous growing season (why?).
• As in response function analysis, we look for groupings of monthly variables to indicate seasonal response by trees.
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Correlation analysis
Graphical output from PRECON. Any value above +0.2 or below -0.2 is significant.
Positive!
Negative!
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Note how response function analysis (top) and correlation analysis (bottom) are complementary (but different).
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Pearson Correlation Coefficients Prob > |r| under H0: Rho=0 Number of Observations
lmayt ljunt ljult laugt lsept loctt lnovt
-0.08019 -0.03131 -0.34233 -0.16914 -0.29516 -0.09849 -0.02712 0.4941 0.7897 0.0023 0.1414 0.0096 0.4071 0.8173 75 75 77 77 76 73 75
Correlation analysis
• R-values also known as Pearson correlation coefficients
• SAS output below: r-value (top), p-value (middle), n size (bottom)
• How do you interpret negative correlations?
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Trends in reconstructed Northern Hemisphere temperatures.
Reconstructed Climate Variables1) Temperature
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Trends in reconstructed precipitation for the American Southwest.
2) Precipitation
Reconstructed Climate Variables
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Dendroclimatology
Primary Variables:- Temperature (ave, min, max)- Precipitation (total)- Palmer Drought Severity Index (PDSI)- Palmer Hydrologic Drought Index (PHDI)
Derived Variables:- El Nino Southern Oscillation (ENSO)- North Atlantic Oscillation (NAO)- Atlantic Multidecadal Oscillation (AMO)- Pacific Decadal Oscillation (PDO)
Teleconnection – the interconnection of physical parameters over long distances
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ENSO
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Pacific Decadal Oscillation
• Discovered late 1990s by salmon fisheries experts
• Long-lived El Niño-like pattern of Pacific climate variability
• Operates on longer 20 to 30 year periods
• Note when shifts occurred…
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Pacific Decadal Oscillation
Warm phase PDO Cool phase PDO
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North Atlantic Oscillation
• Large scale seesaw in atmospheric mass between the subtropical high and the polar low
• Dominant mode of winter climate variability in the North Atlantic region ranging from central North America to Europe
• Operates on 20 to 30 year periods
• …
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Atlantic Multidecadal Oscillation
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