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UNCERTAINTY IN NORTH AMERICAN WET DEPOSITION ISOPLETH MAPS: EFFECT OF SITE SELECTION AND VALID SAMPLE CRITERIA
Citation:
Simpson, J. AND A. Olsen. UNCERTAINTY IN NORTH AMERICAN WET DEPOSITION ISOPLETH MAPS: EFFECT OF SITE SELECTION AND VALID SAMPLE CRITERIA. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/4-90/005.
Description:
This report considers several issues related to the preparation of isopleth maps for the display of spatial patterns of wet deposition. The valid sample criteria and data completeness rating used in the data summarization process are described. The data interpolation technique, kriging, is presented and its derivation in terms of generalized least squares regression is given. Four different annual summaries for pH, sulfate concentration, and sulfate deposition in 1986 are prepared using either the Unified Deposition Database Committee (UDDC) definition of valid sample criteria or a relaxed valid sample criteria and the UDDC data completeness rating or a relaxed data completeness rating. The kriged estimates for the different annual summaries and the differences between these estimates are contoured. The effects of relaxing the valid sample criteria and data completeness rating are discussed. Conclusions are drawn about network operation, network design and the uncertainty of contour maps. It is recommended that in the case where the objective is contour maps to show regional patterns, the emphasis in most regions needs to be on the number of valid samples per site and the regional representativeness of the sites.