Simulating Change—Testing COOP Network Precip Homogeneity Methods

As part of the “Health of the Network” (HON) Project at the National Climatic Data Center, we have designed a prototype system to evaluate the homogeneity of daily precipitation observations in the Cooperative Observer Network. The fundamental mechanism of this system is a comparison between target sites and a set of nearest neighbors based on several established verification algorithms (frequency bias, magnitude bias, and equitable threat score). Previously, individual seasons of data from Iowa, Oregon and Washington were used to test these methods. In this paper, simulated precipitation data are used to test the efficacy of the system for detecting changes under a wider variety of contitions. Performance of the system in response to a variety of different possible observation changes is described, and an overall approach for application of the system in an operational setting is described.