Future changes in the distribution of daily precipitation totals
across North America
R. L. Wilby
Department of Geography, King's College London, Strand, London, WC2R
2LS, UK
T. M. L. Wigley
National Center for Atmospheric Research, Boulder, Colorado
The shape and scale parameters of the two-parameter gamma distribution were
estimated for daily distributions of precipitation at individual grid-points in
two General Circulation Models (HadCM2 and CSM). Maps of the changing parameter
distributions under anthropogenic forcing show the extent to which future
precipitation scenarios for North America are consistent with observed trends in
the the twentieth century. The scale parameter is found to be more variable,
both spatially and temporally, than the shape parameter. Patterns of changes in
mean wet-day amounts are strongly correlated with changes in the scale
parameter. While the two models show quite different results for the spatial
patterns of change, both indicate that the proportion of total precipitation
derived from extreme and heavy events will continue to increase relative to
moderate and light precipitation events.
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Hongjun Zhang:
zhangho@ucar.edu