circIndexGrid: Calculation of circulation indices of grids

In SantanderMetGroup/climate4R.indices: Climate Index calculation for climate4R data

Calculation of circulation indices of grids

Description

Calculate circulation indices of grids or multimember grids.

Usage

circIndexGrid(
  zg = NULL,
  z = NULL,
  sst = NULL,
  psl = NULL,
  index.code,
  season = NULL,
  base = NULL,
  ref = NULL,
  match = "spatial",
  n.pcs = 10,
  rot = TRUE,
  centers = NULL,
  center.point = c(-5, 55),
  members = NULL
)

Arguments

zg	A grid or multimember grid object of geopotential height.
z	A grid or multimember grid object of geopotential.
sst	A grid or multimember grid object of sea surface temperature.
psl	A grid or multimember grid object of sea level pressure.
index.code	Circulation index (or vector of indices with same input variables) to be computed. See circIndexShow() for details.
season	Selected month(s) for the calculation. Default: NULL (i.e. as input grid).
base	Baseline grid to be substracted for the calculation of anomalies. Default: NULL. See ?scaleGrid.
ref	Reference grid to be added for the calculation of anomalies. Default: NULL. See ?scaleGrid.
match	Character string with the criterion to be used for the detection of CPC indices. Options "spatial" or "temporal". Default: "spatial". See details.
n.pcs	Integer vector with the number of EOFs to be retained for the CPC indices. Default: 10. See details.
rot	Logical. Should VARIMAX-Rotation be performed? Default: TRUE. This argument is only relevant for CPC indices. See details.
centers	Integer value indicating the number of clusters, k, or center points. See details.
center.point	A two value vector that must include lon and lat from a location that will work as center point for the Lamb WT. See details.
members	Select number of members. Default: NULL (all members of the grid).

Details

circIndexShow displays on screen the full list of available circulation indices and their codes. Several indices can be calculated at the same time, as long as they depend on the same input variable(s) and spatial domain. CPC and ENSO indices are calculated on a monthly basis. Therefore a temporal aggregation is performed if input data is daily. Results for the desired months in season are provided, but it is recommended to have full series as input, since CPC and ENSO indices use a moving window for the calculation.

CPC indices

Either z or zg are valid input variables. CPC indices are obtained, by default, as the first 10 Varimax-rotated EOFs, as explained in https://www.cpc.ncep.noaa.gov/data/teledoc/telecontents.shtml. The core of this function is stats::prcomp including Varimax rotation. The rotated EOFs are obtained from the monthly standardized anomalies of geopotential or geopotential height at 500hPa, with a 3-month moving window. The argument match is used to assign each rEOF to a circulation index and pattern. Matching is based on 'temporal' or 'spatial' correction of the CPC original (NCEP Reanalysis-based) indices.

ENSO indices

The calculation of ENSO indices is based on https://climatedataguide.ucar.edu/climate-data/nino-sst-indices-nino-12-3-34-4-oni-and-tni, consisting of SST anomalies, using a moving window of different size for each index.

WT indices

(to be added)

Value

A list of circulation indices (and members, if applicable) with:

• index: vector with the time series of the teleconnection/circulation index.

• pattern: matrix with the spatial pattern of the teleconnection.

• dates and coordinates as list attributes.

• further arguments related to the CPC indices, such as the corresponding (r)EOF and (temporal or spatial, depending on 'match') correlation with the original index.

Author(s)

A. Casanueva

Examples

## Not run: 
data(NCEP_hgt500_2001_2010)
cpc <- circIndexGrid(zg=NCEP_hgt500_2001_2010, index.code = c("NAO", "EA","PNA"), season=1)
data(ERAInterim_sst_1981_2010)
nino <- circIndexGrid(sst=ERAInterim_sst_1981_2010, index.code = "NINO3.4")
data(NCEP_slp_2001_2010)
wt <- circIndexGrid(psl = NCEP_slp_2001_2010, index.code = "WT.LAMB")

## End(Not run)

SantanderMetGroup/climate4R.indices documentation built on July 3, 2023, 11:02 p.m.