where c(t) is the simulated methane concentration time series (or vector); ∥ • ∥ 1 is the L 1 norm of a vector and | • | is the length of a vector. The value of A will typically be set as a function of the sensor quality, with lower quality sensors requiring a higher threshold to distinguish true spikes from the noisy background which consists of ambient atmospheric concentrations and sensor noise. Since we use simulated concentrations in this step, representing concentration enhancements in the observed data, the detection threshold A should be based on the background variations in the observed data to ensure that the signal corresponding to true emissions stands out. Specifically, A is set to be the difference between the upper bound and the lower bound of the background concentration, ensuring that any concentration enhancement above A is guaranteed not to be drowned out by the background.