PROCEEDINGS: Index of Abstracts
DELINEATION OF CLIMATE REGIONS IN THE NORTHEASTERN
Northeast Regional Climate Center, Cornell
University, Ithaca NY 14850.
Climate is a primary criterion for the development, description
and validation of subregional levels of the National Hierarchical
Framework of Ecological Units. However, climate information is not
currently available in the form or level of detail required for
integration with other biophysical factors at the section or subsection
levels. In this study, historical climate data from 640 observing
sites in the northeastern United States and Canada are used to delineate
climatic zones with sufficient detail to be incorporated into subsection
levels of the National Hierarchical Framework of Ecological Units.
For each site a total of 110 climatological variables representing
such parameters as monthly average temperature, temperature extremes,
frost occurrence, precipitation, and potential evapotranspiration
were quality controlled and adjusted to a standard observation hour.
In addition, missing temperature observations were estimated to
yield a serially complete temperature data set. All variables are
representative of the 1961-1990 climatological normals period. Using
principal component analysis, the intercorrelation of these variables
is eliminated and thus the size of the original data set can be
reduced. Eight components, explaining 94 percent of the variability
in the original 110 variables, are retained for subsequent analysis.
Based on the retained components, Ward's method of cluster analysis
is used to define 54 climate zones within the region. These zones
are used as initial seeds for nonhierachical K-means clustering.
This second clustering eliminates several of the shortfalls associated
with hierarchical clustering and allows the grouping of stations
based on a variable number of initial components.
Once this grouping of stations was established, discriminant functions
were calculated to express the station grouping in terms of variables
derived from latitude, longitude and elevation. Cross validation
showed that more than 60 percent of the stations were correctly
classified based on the discriminant functions. Since the spatial
resolution of the 640 climatological stations is relatively low,
a 5 minute grided elevation data set was used in conjunction with
the discriminant functions to produce the final climate delineations.