On the Eulerian source-receptor relationship

Abstract

A new approach is proposed to delineate the source-receptor relationship in an Eulerian model. A small, unique oscillatory signal is superimposed on each emission source in the airshed. At receptor sites the concentration time series axe analyzed by a Fourier transform to give the amplitudefrequency spectrum. Distinct peaks found in the spectrum are identified at the emission frequencies.The amplitude of the spectrum at the source frequency represents the individual contribution from that emitter. Various atmospheric transport and diffusion models are solved to show the effects of different physical and chemical processes on the oscillatory signals. Both analytical and numerical solutions are used to demonstrate the performance of the method.

Application of a Signal Technique to the Source–Receptor Relationship in Three-Dimensional Tracer Simulations

“…Hsu and Chang (1987) pointed out that the damping of the signal amplitude by the diffusion effect is proportional to the frequency. Therefore, frequencies that are too high should be avoided for this approach.…”

“…The analytic solution of Hsu and Chang (1987) at the receptor x in such a system indicates that 1) the leading frequency is the emitting frequency v i , 2) both processes can contribute to a phase shift [v i (x 2 x i )/U due to advection and p/4 due to diffusion], and 3) the amplitude modulation factors from advection and diffusion are 2 cos[v i (x 2 x i )/U] and (gv i ) 21/2 respectively. Please refer to Hsu and Chang (1987) for details about deriving the analytic solutions.…”

“…Hsu and Chang (1987) proposed a signal technique to alleviate the computational burden of the online tracer method. In their experiments, a unique oscillatory signal S was superimposed onto emission data (i.e., tracers) with the form (1) at each source point:…”

“…Thus, this approach needs tremendous computational memory and time for a big-airshed case. The implementation of a signal technique (Hsu and Chang 1987) into this online approach can solve this problem to some degree. The main concept of this signal technique, as described in Hsu and Chang (1987), is that a unique oscillatory signal is superimposed onto emission data at each source point and propagates with the tracers; the frequency spectrum is obtained by analyzing the time series of pollutant concentration at the receptors.…”

“…The implementation of a signal technique (Hsu and Chang 1987) into this online approach can solve this problem to some degree. The main concept of this signal technique, as described in Hsu and Chang (1987), is that a unique oscillatory signal is superimposed onto emission data at each source point and propagates with the tracers; the frequency spectrum is obtained by analyzing the time series of pollutant concentration at the receptors. Because each source point was tagged with a unique frequency of the oscillatory signal, it is expected that the source-receptor relationship could potentially be identified from the spectrum at the receptor.…”