|Paleo Slide Set: Tree Rings: Ancient Chronicles of Environmental Change|
|Observed & reconstructed number of precipitation days in winter, northern Arizona & New Mexico.|
| A tree-ring chronology
built from old, sensitive trees will reveal the common climate
signal found in the trees throughout an area. The chronology, usually in
the form of a time series of ring width or density
indices, is calibrated with a climate record for the period of time common
to both climate records and the chronology. The character of the relationship
between climate and tree growth is assessed and a statistical model is derived
to describe that relationship. In this figure, the total number of precipitation
days in winter for a region in northern Arizona and New Mexico was reconstructed
from a set of tree-ring chronologies in the southwestern United States.
The purple line shows the observed record of numbers of precipitation days
while the green line shows the values reconstructed from the chronologies.
The match, although not perfect, is very close, and reflects both high and
low frequency variations in precipitation days in this region for centuries
prior to the availability of instrumental observation.
NOAA Paleoclimatology Program
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