Plume estimation using correlation measurements at isolated spatial points
Repeated simultaneous concentration measurements at spatially separated points are used to provide information on the lateral spatial extent of a gas plume. More specifically the spatial correlations in this data provide this information. Fitting a gas plume model directly to this multi-point data can provide good estimates of total plume emission. The distance between the plume source and the measurement points does not need to be known to provide these estimates. It is also not necessary to perform any detailed atmospheric modeling.
1. A method for estimating a spatial width w of a gas plume, the method comprising:
performing multiple gas concentration measurements at two or more separated measurement points, wherein each data point is a simultaneous concentration measurement at the measurement points;
providing a time-independent gas plume model having at least the spatial width w as a fitting parameter, wherein the gas plume model also includes parameters for plume position; and
fitting the gas plume model to the data points, wherein the plume position is allowed to be a random variable to enable fitting to observed scatter in the data points, and wherein an estimate w* of the plume spatial width w is provided as an output;
wherein the method does not depend on a distance between the measurement points and the gas source.
2. A method for estimating widths w y and w z of a gas plume, the method comprising:
performing the method of claim 1 in two orthogonal directions y and z;
wherein all measurement points are in a common measurement plane.
3. The method of claim 2 , wherein the measurement points include three points having y-z coordinates (0,0), (d y ,0), (0,d z ).
4. A method for estimating total emission from a gas source, the method comprising:
performing the method of claim 2 to determine widths w y and w z ;
measuring an average wind speed v x in a direction perpendicular to the measurement plane; and
estimating total plume emission using the data points and a plume emission model that includes at least v x , w y and w z as parameters.
5. The method of claim 4 , wherein the total plume emission estimate is completely determined by fitting parameters of the gas plume model and v x .
6. The method of claim 2 , wherein measurements relating to the two orthogonal directions are performed simultaneously.
7. The method of claim 2 , wherein measurements relating to the two orthogonal directions are performed sequentially and then registered to a common time axis to provide the simultaneous concentration measurement at the measurement points.