extractareacru: Function for extracting the climate data of an area from CRU...

In ahmad-alkadri/simpleRCRU: Simple R package for extracting climate information from CRU datasets

Description

A wrapper for raster() function, useful for extracting climate date of a rectangular area from CRU datasets.

Usage

extractareacru(file, lonmin, lonmax,
latmin, latmax, var, year, month, precision)

Arguments

file	The CRU dataset file, usually with ".dat.nc" extension
lonmin	The minimum longitude value of the rectangular area
lonmax	The maximum longitude value of the rectangular area
latmin	The minimum latitude value of the rectangular area
latmax	The maximum latitude value of the rectangular area
var	The variable from the CRU dataset that we would like to obtain, could be "tmp" for temperature, "pre" for precipitation, and so on.
year	A single given year, must be within the span measured in the CRU dataset.
month	A given month, must be from the Gregorian calendar and can be written either in English ("January", "February", etc.) or number (1, 2, 3, etc.).

Value

A matrix with the desired climate values (precipitation, temperature, etc.) of the rectangular region on the requested year and month. Rows refer to latitude and columns refer to longitude.

Examples

# Selected time
year <- 2000
month <- "December"

# Selected area: a rectangular region
# from the Central Java island, Indonesia
lonmin <- 104.0
lonmax <- 118.0
latmin <- -9.0
latmax <- -5.0

# Climate parameter (precipitation)
var <- "pre"

# CRU dataset
library(simpleRCRU)
library(R.utils)

# Download the climate dataset
download.file("https://crudata.uea.ac.uk/cru/data/hrg/cru_ts_4.02/cruts.1811131722.v4.02/pre/cru_ts4.02.1991.2000.pre.dat.nc.gz",
              destfile = "cru_ts4.02.1991.2000.pre.dat.nc.gz")
# Unzipping the dataset
gunzip("cru_ts4.02.1991.2000.pre.dat.nc.gz",
remove = TRUE, overwrite = TRUE)

file <- ("cru_ts4.02.1991.2000.pre.dat.nc")

# Coordinate precision of 1 digit behind decimal
precision <- 1

# Matrix with results
matReg <- extractareacru(file, lonmin, lonmax, latmin, latmax,
          var, year, month, precision)

file.remove("cru_ts4.02.1991.2000.pre.dat.nc")

ahmad-alkadri/simpleRCRU documentation built on Aug. 15, 2019, 7:24 p.m.