A Fast Running Test Bed Model to Evaluate Atmospheric Plume Source Properties II: Source Location Inversion Sensitivity Tests

Abstract

A technique has been developed to obtain selected source parameters for a release of toxic material into the atmosphere by inversion of a set of sensor observations. The technique utilizes the Marquardt inversion method coupled to a Gaussian puff atmospheric dispersion model. The major objective of this report is to perform a set of sensitivity calculations to explore the robustness of the source location inversion procedure to variations in source location relative to sensor location, spacing of sensors, sensor integration period, and sensor observation times. The results of the tests for variation of source location show that the inversion accuracy is sensitive to source placement relative to a rectangular sensor array with most accurate inversions occurring when the source is aligned with a downwind row of sensors and least accurate when the source is placed between downwind sensor rows. When the density of the sensor array was increased by a factor of 4, i.e. spacing cut in half, the case with the poorest source location inversion accuracy in the first test significantly improved. The results of tests for variation of sensor integration time show that the most accurate source location inversion occurs for the smallest integration time and the least accurate for the largest integration time. The results of tests for variation of the number of observations show that the most accurate source location inversion occurs for the case with the most observation times and the accuracy degrades as the number of observation times decreases. As a general rule throughout all of the sensitivity tests performed here, the most accurate source inversions occur when the number of data points (in both time and space) is maximized.