Climate Indices

Climate indices are simple diagnostic quantities that are used to characterize an aspect of a geophysical system such as a circulation pattern. They track droughts, ENSO events, wind patterns, internal modes of climate variability, and extreme events like wildfires and heatwaves. Climate indices play a key role in climate monitoring and prediction. The climate index overview page summarizes the philosophy of climate indices.

To find a specific climate index, jump to the search box below or click your desired index from among the blue sub-category buttons.

To see only the indices with in-depth commentary, select the "Datasets with guidance" button when using the search box.

Dataset Overviews

Climate datasets

Has expert guidance
Hurrell wintertime SLP-based Northern Annular Mode (NAM) Index Hurrell wintertime SLP-based Northern Annular Mode (NAM) Index

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The NAM (or Arctic Oscillation) is defined as the first EOF of NH (20°-90°N) winter SLP data. It explains 23% of the extended winter mean (December-March)…

Main variables and Earth System components

Atmosphere Sea Level Pressure
Overview: Climate Indices Overview: Climate Indices

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A climate index is a simple diagnostic quantity that is used to characterize an aspect of a geophysical system such as a circulation pattern. A variety of…

Main variables and Earth System components

Atmosphere Ocean

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Station based DJFM NAO Index Hurrell North Atlantic Oscillation (NAO) Index (station-based)

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The winter (December thru March) station-based index of the NAO is based on the difference of normalized sea level pressure (SLP) between Lisbon, Portugal and…

Main variables and Earth System components

Atmosphere Sea Level Pressure
Hurrell North Atlantic Oscillation (NAO) Index (PC-based) Hurrell North Atlantic Oscillation (NAO) Index (PC-based)

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The principal component (PC)-based indices of the North Atlantic Oscillation (NAO) are the time series of the leading Empirical Orthogonal Function (EOF) of SLP…

Main variables and Earth System components

Atmosphere Sea Level Pressure
Pacific Decadal Oscillation (PDO): Definition and Indices Pacific Decadal Oscillation (PDO): Definition and Indices

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The Pacific Decadal Oscillation (PDO) is defined by the leading pattern (EOF) of sea surface temperature (SST) anomalies in the North Pacific basin (typically,…

Main variables and Earth System components

Ocean SST - sea surface temperature
Amundsen Sea Low indices Amundsen Sea Low indices

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The Amundsen Sea Low (ASL) is a climatological low pressure center located over the extreme southern Pacific Ocean, off the coast of West Antarctica. …

Main variables and Earth System components

Atmosphere Sea Level Pressure
Marshall Southern Annular Mode (SAM) Index (Station-based) Marshall Southern Annular Mode (SAM) Index (Station-based)

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The station-based index of the Southern Annular Mode (SAM) is based on the zonal pressure difference between the latitudes of 40S and 65S.  As such, the SAM…

Main variables and Earth System components

Atmosphere Sea Level Pressure
Meridional Modes and their indices Meridional Modes and their indices

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In each of the world’s tropical ocean basins, year-to-year climate variability is primarily governed by fluctuations in the zonal sea surface temperature (SST)…

Main variables and Earth System components

Atmosphere Wind Ocean SST - sea surface temperature
MJO: Madden-Julian Oscillation Diagnostics MJO: Madden-Julian Oscillation Diagnostics

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"The Madden–Julian oscillation (MJO) is the largest element of the intraseasonal (30–90 days) variability in the tropical atmosphere. It is a large-scale…

Main variables and Earth System components

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NSIDC Sea Ice Index NSIDC Sea Ice Index

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The NSIDC Sea Ice Index is a suite of easy-to-use sea ice analyses to track changes in Arctic and Antarctic sea ice. The product is produced and supported by the…

Main variables and Earth System components

Cryosphere Sea Ice Concentration
Multivariate ENSO Index Multivariate ENSO Index

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The Multivariate ENSO Index (MEI) is said to capture a more holistic representation of the atmospheric and oceanic anomalies that occur during ENSO events than…

Main variables and Earth System components

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Drought atlases from tree rings Drought atlases from tree rings

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Tree-ring drought atlases provide a paleoclimate analog to modern drought indices, most commonly the Palmer Drought Severity Index (PDSI).  Produced on a regular…

Main variables and Earth System components

Land Drought
North Pacific (NP) Index by Trenberth and Hurrell; monthly and winter North Pacific (NP) Index by Trenberth and Hurrell; monthly and winter

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The North Pacific Index (NP index or NPI) is the area-weighted sea level pressure over the region 30°N-65°N, 160°E-140°W. The NP index is defined to measure…

Main variables and Earth System components

Atmosphere Sea Level Pressure
HadEX2: Gridded Temperature and Precipitation Climate Extremes Indices (CLIMDEX data) HadEX2: Gridded Temperature and Precipitation Climate Extremes Indices (CLIMDEX data)

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HadEX2 provides gridded, station-based indices of temperature- and precipitation- related climate extremes. It is intended for climate change detection and…

Main variables and Earth System components

Atmosphere Maximum Air Temperature Minimum Air Temperature Land Freeze/Thaw

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Standardized Precipitation Index (SPI) Standardized Precipitation Index (SPI)

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The Standardized Precipitation Index (SPI) is a widely used index to characterize meteorological drought on a range of timescales. On short timescales, the SPI…

Main variables and Earth System components

Atmosphere Precipitation Land Drought

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    • Monthly

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Standardized Precipitation Evapotranspiration Index (SPEI) Standardized Precipitation Evapotranspiration Index (SPEI)

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The Standardized Precipitation Evapotranspiration Index (SPEI) is an extension of the widely used Standardized Precipitation Index (SPI). The SPEI is designed to…

Main variables and Earth System components

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    • Monthly, Seasonal, Annual

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Asymmetry and Diversity in the pattern, amplitude and duration of El Niño and La Niña Asymmetry and Diversity in the pattern, amplitude and duration of El Niño and La Niña

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El Niño and La Niña, the two phases of ENSO, are sometimes described as opposites. However, there are asymmetries in their spatial structure, amplitude, duration…

Main variables and Earth System components

Ocean SST - sea surface temperature

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QBO: Quasi-Biennial Oscillation QBO: Quasi-Biennial Oscillation

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The quasi-biennial oscillation (QBO) is a quasi-periodic oscillation of the equatorial zonal wind between easterlies and westerlies in the tropical stratosphere…

Main variables and Earth System components

Atmosphere Wind

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    • Monthly

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Southern Hemisphere westerly jet strength and position Southern Hemisphere westerly jet strength and position

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The dynamics of the Southern Hemisphere westerly jet are described in terms of two indices, jet strength and jet latitude.  Here, these indices are defined using…

Main variables and Earth System components

Atmosphere Wind
NOAA ThreadEx Long-term Station Extremes for America NOAA ThreadEx Long-term Station Extremes for America

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ThreadEx is a data set of extreme daily temperature and precipitation values for 270 locations in the United States. For each day of the year at each station,…

Main variables and Earth System components

Atmosphere Air Temperature Maximum Air Temperature Minimum Air Temperature Precipitation

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U.S. Climate Extremes Index (CEI) U.S. Climate Extremes Index (CEI)

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The U.S. Climate Extremes Index (CEI) was first presented in 1995 as a framework for quantifying observed changes in climate within the contiguous United States…

Main variables and Earth System components

Atmosphere Air Temperature Maximum Air Temperature Minimum Air Temperature Precipitation Wind Land Drought
GHCNDEX: Gridded Temperature and Precipitation Climate Extremes Indices (CLIMDEX data) GHCNDEX: Gridded Temperature and Precipitation Climate Extremes Indices (CLIMDEX data)

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GHCNDEX provides gridded, station-based indices of temperature- and precipitation- related climate extremes. It is intended for climate change detection and…

Main variables and Earth System components

Atmosphere Maximum Air Temperature Minimum Air Temperature Land Freeze/Thaw

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Palmer Drought Severity Index (PDSI) Palmer Drought Severity Index (PDSI)

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The Palmer Drought Severity Index (PDSI) uses readily available temperature and precipitation data to estimate relative dryness. It is a standardized index that…

Main variables and Earth System components

Land Drought
Atlantic Multi-decadal Oscillation (AMO) Atlantic Multi-decadal Oscillation (AMO)

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The Atlantic Multi-decadal Oscillation (AMO) has been identified as a coherent mode of natural variability occurring in the North Atlantic Ocean with an…

Main variables and Earth System components

Ocean SST - sea surface temperature
Southern Oscillation Indices: Signal, Noise and Tahiti/Darwin SLP (SOI) Southern Oscillation Indices: Signal, Noise and Tahiti/Darwin SLP (SOI)

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The Southern Oscillation Index (SOI) is a time series used to characterize the large scale sea level pressure (SLP) patterns in the tropical Pacific. Monthly…

Main variables and Earth System components

Atmosphere Sea Level Pressure
Nino SST Indices (Nino 1+2, 3, 3.4, 4; ONI and TNI) Nino SST Indices (Nino 1+2, 3, 3.4, 4; ONI and TNI)

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There are several indices used to monitor the tropical Pacific, all of which are based on SST anomalies averaged across a given region.  Usually the anomalies…

Main variables and Earth System components

Ocean SST - sea surface temperature
CRU sc-PDSI (self-calibrating PDSI) over Europe & North America CRU sc-PDSI (self-calibrating PDSI) over Europe & North America

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Maps of the monthly self-calibrating Palmer drought severity index (SCPDSI) have been calculated for the period 1901–2002 for the contiguous United States (20°–…

Main variables and Earth System components

Land Drought

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