1. Cari G. Kaufman is Assistant Professor, Department of Statistics, University of California, Berkeley, CA 94720 . Mark J. Schervish is Professor and Head, Department of Statistics, Carnegie Mellon University, Pittsburgh, PA 15214 . Douglas W. Nychka is Director, Institute for Mathematics Applied to Geosciences and Senior Scientist, Geophysical Statistics Project, National Center for Atmospheric Research, Boulder, CO 80305 . This work was supported in part by National Science Foundation grant DMS-0355474....