Identification

Title

Standardized Precipitation Index (SPI) for Global Land Surface (1949-2012)

Alternative title(s)

d298000

Abstract

<p> This dataset includes the Standardized Precipitation Index (SPI) at three-, six-, and 12-month scales for global land surfaces. It was produced for a study to determine the relationship between climate variability and armed conflict in Sub-Saharan Africa (O'Loughlin et al. 2012). The precipitation data (1949-2012) are resampled from the original University of East Anglia Climate Research Unit (CRU) global time series, TS3.21, monthly 0.5 degree by 0.5 degree grids to the study unit of analysis, 1.0 degree by 1.0 degree grids, thereby facilitating regression with environmental and socioeconomic variables. </p> <p> The Standardized Precipitation Index (SPI) is commonly used to monitor drought and anomalous wet periods. It was formulated by Tom McKee, Nolan Doesken, and John Kleist of the Colorado Climate Center, Colorado State University (McKee et al. 1993). The SPI at a given location is based only on the long-term precipitation record for a desired period. The long-term precipitation time series is fitted to a gamma probability distribution, which is then transformed into a normal distribution so that the mean SPI is zero. Theoretically, the SPI is the number of standard deviations by which the observed value would lie above or below the long-term mean, for a normally distributed random variable. Thus, the index can be used to compare precipitation across a region with different climates. The SPI can be calculated for multiple time scales, which allows assessment of impacts on different water resources. For example, soil moisture responds to precipitation departures on a short time scale, while stream flow responds to anomalies on a longer time scale. Precipitation amounts that indicate wet conditions at one time scale could indicate dry conditions at another time scale. </p>

Resource type

dataset

Resource locator

https://gdex.ucar.edu/datasets/d298000/

protocol: https

name: Dataset Description

description: Related Link

function: information

https://gdex.ucar.edu/datasets/d298000/dataaccess/

protocol: https

name: Data Access

description: Related Link

function: download

Unique resource identifier

code

codeSpace

Dataset language

Spatial reference system

code identifying the spatial reference system

Classification of spatial data and services

Topic category

climatologyMeteorologyAtmosphere

Keywords

Keyword set

keyword value

dataset

originating controlled vocabulary

title

reference date

date type

revision

effective date

2021-03-30

Keyword set

keyword value

GROUND-BASED OBSERVATIONS > GROUND-BASED OBSERVATIONS

originating controlled vocabulary

title

reference date

date type

revision

effective date

2025-10-03

Keyword set

keyword value

EARTH SCIENCE > CLIMATE INDICATORS > ATMOSPHERIC/OCEAN INDICATORS > PRECIPITATION INDICES > STANDARDIZED PRECIPITATION INDEX

originating controlled vocabulary

title

reference date

date type

revision

effective date

2025-10-03

Geographic location

West bounding longitude

-180.0

East bounding longitude

180.0

North bounding latitude

90.0

South bounding latitude

-90.0

Temporal reference

Temporal extent

Begin position

1949-01-16T0000+00

End position

2012-12-16T0000+00

Dataset reference date

date type

publication

effective date

2013-12-19

Frequency of update

notPlanned

Quality and validity

Lineage

Conformity

Data format

name of format

version of format

Constraints related to access and use

Constraint set

Use constraints

Creative Commons Attribution 4.0 International License

Limitations on public access

None

Responsible organisations

Responsible party

organisation name

email address

datahelp@ucar.edu

responsible party role

pointOfContact

Metadata on metadata

Metadata point of contact

organisation name

NSF NCAR Geoscience Data Exchange

email address

datahelp@ucar.edu

web address

https://gdex.ucar.edu

name: NSF NCAR Geoscience Data Exchange

description: The Geoscience Data Exchange (GDEX), managed by the Computational and Information Systems Laboratory (CISL) at NSF NCAR, contains a large collection of meteorological, atmospheric composition, and oceanographic observations, and operational and reanalysis model outputs, integrated with NSF NCAR High Performance Compute services to support atmospheric and geosciences research.

function: download

responsible party role

pointOfContact

Metadata date

2025-10-09T01:23:01Z

Metadata language