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RECENT FROST DATE TRENDS IN THE NORTH-EASTERN USA
Citation:
Cooter, E. AND S. LeDuc. RECENT FROST DATE TRENDS IN THE NORTH-EASTERN USA. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-95/244.
Description:
Global climate change resulting from increases in CO2 and trace gas emissions is an active area of impact assessment research. ncertainty in projections of future climate along with a need for policy makers and management to respond appropriately leads to research addressing the detection of trends in climatological time series. rea-weighted time series of climatological variables for the Northeastern United States are scrutinized for the presence of simple time dependent trends. nalysis indicates that simple area weighting impacts the location and scale of the climate variables examined. rea weighting may also provide inaccurate portraits of changing regional conditions, the results of the influence of a few, heavily weighted station records. lthough this is the case for most climate variables examined in this study, an exception is the time series of reported date of last spring hard freeze (TMIN < =-2.2 degrees C). These data contain a significant linear trend towards an earlier initiation of frost-free conditions. he presence of a time trend does not appear to be related to the geographic location of the observing station or by the weighting method employed. either does it appear to be affected by the use of aggregated (means) or individual station data or the choice of univariate, multivariate or autoregressive model forms. ime dependent trends were detected in individual station records representing a large portion of the New England region. omparison of these results, with results of a similar study performed for the Southeastern region of the United States indicates significant geographic differences in the direction of trends in frost date and growing season length. lthough there is no evidence linking these study results to increased concentrations of greenhouse gases, they serve to highlight the large degree of interregional variability in extremes and threshold behavior and reinforce the importance of developing a better understanding of the mesoscale processes that drive regional climate.