The tenth IMSC, Beijing, China, 2007 - International Meetings on ...

address new policies for changing climate normals using the results here as a starting point,
and (b) NOAA initiate a program for improved estimates and forecasts of official U. S. normals,
including operational implementation of a simple hybrid system that combines the advantages
of both the OCN and the hinge fit.
Changepoint Detection in Multinomial Logistic Regression with Application to Sky-Cloudiness
Conditions in Canada
Speaker: QiQi Lu
QiQi Lu
Mississippi State University
qlu@math.msstate.edu
Xiaolan Wang
Climate Research Division, ASTD, STB, Environment Canada
Detecting changepoints in a sequence of continuous random variables has been
extensively explored in both statistics and climatology literature. <strong>The</strong>re is little, however, for
studying the case with multicategory response variables. For instance, the sky-cloudiness
condition in Canada is reported in <strong>tenth</strong>s of the sky dome and has 11 categories (0 for clear
sky, 1/10 for one <strong>tenth</strong> of sky covered, and 10/10 for overcast). To model and homogenize
such a multinomial variable, this paper develops an overall likelihood-ratio test statistic in an
ordinal logistic regression model setting. A method of partitioning of the overall test statistics is
also proposed to enable one to test the changes in the individual categories. This technique is
applied in the analysis of the real cloudiness data.
A cloud-based reconstruction of surface solar radiation trends for Australia
Speaker: Manuel Nunez
Manuel Nunez
School of Geography and Environmental Studies, University of Tasmania, Hobart 7005, Australia
Yun Li
CSIRO Mathematical and Information Sciences, Wembley, WA 6913, Australia
Despite its importance to climate change, reliable and calibrated measurements of solar
radiation are available only after 1992 for Australia. In this study we extend the data base by
developing a cloud-based solar radiation model and extending the data set back from 1967 to
2004. Results show no significant change in the majority of stations, although slightly more
than one quarter of the stations report a significant decrease of solar radiation with a maximum
of just less than one percent per decade. Trend analyses also detect an upturn in many of the
17