regional climate change detection
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Regional Climate Change Detection. What is a climate? How does one define a climate in terms of measured variables? - PowerPoint PPT PresentationTRANSCRIPT
Regional Climate Change Detection
What is a climate? How does one define a climate in terms of
measured variables? After defining it, how does one measure
actual change in a statically defensible manner. Most of local climate change is simply assumed to be occurring because global change is occurring
Anecdotal Evidence Often Used
More frequent extreme-heat days A longer growing season An increase in heavy rainfall events Earlier breakup of winter ice on lakes and
rivers Earlier spring snowmelt resulting in earlier
high spring river flows Less precipitation falling as snow and more
as rain Reduced snowpack and increased snow
density
Use an Indexing Method
Climate is largely a monthly/seasonal phenomena – not annual
Take a weather site and say it has 100 years of data for all 12 months and pick a variable like max temperature. Use all 100 months of January to compose the average max.
For each month then in each year, compute the Z-score for that month/year
Z-Score = (x - µ) /
Now Generate a Composite Index
NEIyr = (Zmxyr + Zmnyr + Zrnyr + Zswyr) / 4 Can then weight each of the 4Z’s The result is a wave form some given site for
one of the Z parameters
1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106-0.8-0.6-0.4-0.2
00.20.40.60.8
Vermont SiteMinTemp
'432769'
IND
EX
This form of Indexing
Is identical to the approach used for the Stock Market; what matters is the behavior over time of the relative amplitude of the Index.
Weighting the Indicators:
WMAX 0.25 0.25 0.25 0.25 (equal) WGD1 0.4 0.4 0.1 0.1 (emphasize temp) WGD2 0.2 0.1 0.6 0.7 (emphasize rain) Just try all kinds of combinations: Dick with
the data! There is no “right” way to do this just a
consistent way.
Sum up all the good stations1 4 7
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Annual Northeast Climate Index Comparisons for All Variables Combined
NEI
Linear (NEI)
IND
EX
Warm and Wet
Cool and Dry