OperatSDI {PowerSDI}

Calculate Routine NASA-SPI and NASA-SPEI Estimates

Description

Calculates the SPI (Standardized Precipitation Index) and SPEI (Standardized Precipitation-Evapotranspiration Index) using NASA POWER data.

Usage

OperatSDI(
  lon,
  lat,
  start.date,
  end.date,
  PEMethod = "HS",
  distr = "GEV",
  parms,
  TS = 4L
)

Arguments

lon

longitude in decimal degrees.

lat

latitude in decimal degrees.

start.date

Date at each time when the calculation must start (“YYYY-MM-DD”).

end.date

Date at each time when the calculation must end (“YYYY-MM-DD”).

PEMethod

A character variable (“HS” (Hargreaves & Samani) or “PM” (Penman-Monteith) defining the potential evapotranspiration method. Default is “HS”.

distr

A character variable (“GEV” or “GLO”) defining which distribution is used to calculate the SPEI. Default is “GEV” (generalized extreme value) with “GLO” (generalized logistic distributions) as an option.

parms

Parameters required for calculating the SPI and SPEI. It is provided by the ScientSDI function's DistPar.

TS

Time scale on the “quart.month” basis (integer values between 1 and 96).

Value

A data frame with six columns

• rainfall,

• potential evapotranspiration (PE),

• difference between rainfall and PE (in millimiters),

• the NASA-SPI,

• the NASA-SPEI and

• the SDI categories corresponding to each indices estimates.

Examples

# This example is not run as it requires data to be downloaded from an API,
#  which may fail.  It also uses data included in this package, "DistPar" for
#  `parms` here

OperatSDI(
  lon = -47.3,
  lat = -22.67,
  start.date = "2023-06-01",
  end.date = "2023-06-30",
  PEMethod = "HS",
  distr = "GEV",
  parms = DistPar,
  TS = 4)