SeparateSpectra: Calculate signal and noise spectra

In EarthSystemDiagnostics/proxysnr: Separate Signal and Noise in Climate Proxy Records

Calculate signal and noise spectra

Description

SeparateSpectra calculates the raw signal and noise spectra, and the corresponding signal-to-noise ratio, as estimated from a core array of N proxy records, and allows one to correct these, where applicable, for the effects of time uncertainty and water vapour diffusion (relevant for firn and ice cores).

Usage

SeparateSpectra(spectra, neff = spectra$N, diffusion, time.uncertainty)

Arguments

spectra	a list of the raw spectral estimates from a proxy core array. Expected is the output from ArraySpectra, but sufficient is a named list of two components giving the mean and stack spectra.
neff	the effective number of records (e.g. to account for an expected spatial correlation of the local noise). Per default set to element N in spectra, otherwise supply it explicitly here.
diffusion	numeric vector of diffusion correction values (inverse transfer function); must be of the same length as the spectral estimates in spectra. By omitting this parameter no correction will be applied.
time.uncertainty	numeric vector of time uncertainty correction values (inverse transfer function); must be of the same length as the spectral estimates in spectra. By omitting this parameter no correction will be applied.

Details

This function is an implementation of Eq. (4) in Münch and Laepple (2018). While the diffusion correction is relevant only for diffusing proxies such as stable isotopes from firn and ice cores, this function can be applied to a large set of proxy data since only one of the two correction functions, or none, need to be supplied; thus, e.g., it can also be used for non-diffusing proxy data where only time uncertainty is relevant, or for estimating raw signal and noise spectra by supplying no correction functions at all.

Value

A list of three components, each of class "spec":

signal:

the raw or corrected signal spectrum.

noise:

the raw or corrected noise spectrum.

snr:

the signal-to-noise ratio as calculated from the previous components.

Author(s)

Thomas Münch

References

Münch, T. and Laepple, T.: What climate signal is contained in decadal- to centennial-scale isotope variations from Antarctic ice cores? Clim. Past, 14, 2053–2070, https://doi.org/10.5194/cp-14-2053-2018, 2018.

See Also

ArraySpectra

EarthSystemDiagnostics/proxysnr documentation built on Sept. 15, 2024, 7:47 a.m.