R: Teleconnection indices in European Atlantic Ocean region

EuroAtlanticTC {s2dv}

R Documentation

Teleconnection indices in European Atlantic Ocean region

Description

Calculate the four main teleconnection indices in European Atlantic Ocean region: North Atlantic oscillation (NAO), East Atlantic Pattern (EA), East Atlantic/Western Russia (EAWR), and Scandinavian pattern (SCA). The function REOF() is used for the calculation, and the first four modes are returned.

Usage

EuroAtlanticTC(
  ano,
  lat,
  lon,
  ntrunc = 30,
  time_dim = "sdate",
  space_dim = c("lat", "lon"),
  corr = FALSE,
  ncores = NULL
)

Arguments

`ano`	A numerical array of anomalies with named dimensions to calculate REOF then the four teleconnections. The dimensions must have at least 'time_dim' and 'space_dim', and the data should cover the European Atlantic Ocean area (20N-80N, 90W-60E).
`lat`	A vector of the latitudes of 'ano'. It should be 20N-80N.
`lon`	A vector of the longitudes of 'ano'. It should be 90W-60E.
`ntrunc`	A positive integer of the modes to be kept. The default value is 30. If time length or the product of latitude length and longitude length is less than ntrunc, ntrunc is equal to the minimum of the three values.
`time_dim`	A character string indicating the name of the time dimension of 'ano'. The default value is 'sdate'.
`space_dim`	A vector of two character strings. The first is the dimension name of latitude of 'ano' and the second is the dimension name of longitude of 'ano'. The default value is c('lat', 'lon').
`corr`	A logical value indicating whether to base on a correlation (TRUE) or on a covariance matrix (FALSE). The default value is FALSE.
`ncores`	An integer indicating the number of cores to use for parallel computation. The default value is NULL.

Value

A list containing:

`patterns`	An array of the first four REOF patterns normalized to 1 (unitless) with dimensions (modes = 4, the rest of the dimensions of 'ano' except 'time_dim'). The modes represent NAO, EA, EAWR, and SCA, of which the order and sign changes depending on the dataset and period employed, so manual reordering may be needed. Multiplying 'patterns' by 'indices' gives the original reconstructed field.
`indices`	An array of the first four principal components with the units of the original field to the power of 2, with dimensions (time_dim, modes = 4, the rest of the dimensions of 'ano' except 'space_dim').
`var`	An array of the percentage ( explained by each mode. The dimensions are (modes = ntrunc, the rest of the dimensions of 'ano' except 'time_dim' and 'space_dim').
`wght`	An array of the area weighting with dimensions 'space_dim'. It is calculated by the square root of cosine of 'lat' and used to compute the fraction of variance explained by each REOFs.

Examples

# Use synthetic data
set.seed(1)
dat <- array(rnorm(800), dim = c(dat = 2, sdate = 5, lat = 8, lon = 15))
lat <- seq(10, 90, length.out = 8)
lon <- seq(-100, 70, length.out = 15)
res <- EuroAtlanticTC(dat, lat = lat, lon = lon)