Get evaporative stress index (ESI) data

Get evaporative stress index (ESI) from SERVIR Global via ClimateSERV API Client. ESI is available every four (or twelve) weeks from 2001 to present. The dataset may contain cloudy data which is returned as NAs. ClimateSERV works with 'geojson' of type 'Polygon'. The input object is then transformed into polygons with a small buffer area around the point.

Usage

get_esi(object, dates, operation = 5, period = 1, ...)

# Default S3 method
get_esi(object, dates, operation = 5, period = 1, ...)

# S3 method for class 'sf'
get_esi(object, dates, operation = 5, period = 1, as.sf = FALSE, ...)

# S3 method for class 'geojson'
get_esi(object, dates, operation = 5, period = 1, as.geojson = FALSE, ...)

Arguments

object: input, an object of class data.frame (or any other object that can be coerced to data.frame) with longitude and latitude in the first two columns, SpatVector, SpatRaster, SpatExtent, sf, sfc or geojson
dates: a character or Date vector "YYYY-MM-DD", with one date for a single day or two dates for the start and end of the period
operation: optional, an integer that represents which type of statistical operation to perform on the dataset
period: an integer value for the period of ESI data, four weeks period = 1, twelve weeks = 2
...: additional arguments passed to get_chirps_raw and extract. See details
as.sf: logical, returns an object of class sf
as.geojson: logical, returns an object of class geojson

Value

A data frame of ESI data:

id: the index for the rows in object
dates: the dates from which ESI was requested
lon: the longitude as provided in object
lat: the latitude as provided in object
esi: the ESI value

Details

operation: supported operations are:

operation		value
max	=	0
min	=	1
median	=	2
sum	=	4
average	=	5 (default value)

dist: numeric, buffer distance for each object coordinate

nQuadSegs: integer, number of segments per buffer quadrant

Note

get_esi() may return some warning messages given by sf, please check the sf documentation for possible issues.

Future deprecation

get_esi() reads from the ClimateSERV API, which chirps no longer recommends. get_esi() will be deprecated in a future release, and a notice says so once per session. CHIRPS rainfall is available from the CHC server with get_chirps().

Examples

if (FALSE) { # interactive()

lonlat = data.frame(lon = c(-55.0281,-54.9857),
                     lat = c(-2.8094, -2.8756))

dates = c("2017-12-15","2018-06-20")

# by default the function sets a very small buffer around the points which
# can return NAs due to cloudiness in ESI data

dt = get_esi(lonlat, dates = dates)

# the argument dist passed through sf increase the buffer area

dt = get_esi(lonlat, dates = dates, dist = 0.1)
}