Introduction

Climate modes are recurrent patterns, usually of pressure or sea-surface temperature (SST), typically characterized by negative and positive phases, which each have distinctive effects on the distribution of rainfall, temperature and other meteorological elements on time scales varying from days to seasons and beyond.

Key messages

Dataset and processing details

Nino 3.4

The data in the above plot are available in a zip file containing a csv file for each data set.

Data file: Nino_3.4_data_files.zip
Checksum: fff7d9b8f3af492d096a9ecf12167e49 Copy
Format: BADC CSV format

ERSSTv5

Original data file (external link)

To produce the plot, the following processing steps were performed:

• Data set created from file ['nina34.data'] downloaded from ['https://psl.noaa.gov/data/correlation/nina34.data'] at ['2026-01-22 15:53:31']
• Rebaselined to 1991-2020 for each month separately by calculating the arithmetic mean of the data over the baseline period and subtracting the mean from all data values. This is done for each month separately (Januarys, Februarys etc).
• Selected years within the range 1950 to 2025.

Southern Oscillation Index

The data in the above plot are available in a zip file containing a csv file for each data set.

Data file: Southern_Oscillation_Index_data_files.zip
Checksum: b21016cb37e6dd79ff30b2c6e682252e Copy
Format: BADC CSV format

CPC SOI

Original data file (external link)

To produce the plot, the following processing steps were performed:

• Data set created from file ['soi.data'] downloaded from ['https://psl.noaa.gov/data/correlation/soi.data'] at ['2026-01-22 15:53:32']
• Selected years within the range 1950 to 2025.

Pacific Decadal Oscillation

The data in the above plot are available in a zip file containing a csv file for each data set.

Data file: Pacific_Decadal_Oscillation_data_files.zip
Checksum: 38a226b56e15acc55bac53635497b3de Copy
Format: BADC CSV format

NOAA CPC

Original data file (external link)

Citation:

• https://www.ncei.noaa.gov/access/monitoring/pdo/.

To produce the plot, the following processing steps were performed:

• Data set created from file ['ersst.v5.pdo.dat'] downloaded from ['https://www.ncei.noaa.gov/pub/data/cmb/ersst/v5/index/ersst.v5.pdo.dat'] at ['2026-01-22 15:51:19']
• Calculated lowess smoothed series with 0.029069767441860465 of data used for each fit
• Selected years within the range 1850 to 2025.

Indian Ocean Dipole

The data in the above plot are available in a zip file containing a csv file for each data set.

Data file: Indian_Ocean_Dipole_data_files.zip
Checksum: 09f2fd21035a0a164975cb43572d1a73 Copy
Format: BADC CSV format

NOAA OSMC

Original data file (external link)

Citation:

• Huang, B., C. Liu, V. Banzon, E. Freeman, G. Graham, B. Hankins, T. Smith, and H.-M. Zhang, 2021: Improvements of the Daily Optimum Interpolation Sea Surface Temperature (DOISST) Version 2.1, Journal of Climate, 34, 2923-2939. doi: 10.1175/JCLI-D-20-0166.1.

To produce the plot, the following processing steps were performed:

• Data set created from file ['dmi.nc'] downloaded from ['https://stateoftheocean.osmc.noaa.gov/sur/data/dmi.nc'] at ['2026-01-22 15:53:30']
• Calculated monthly average from values using arithmetic mean of all dates that fall within each month
• Selected years within the range 1980 to 2025.

North Atlantic Oscillation

The data in the above plot are available in a zip file containing a csv file for each data set.

Data file: North_Atlantic_Oscillation_data_files.zip
Checksum: f721f830d8170939066711258f010068 Copy
Format: BADC CSV format

NOAA CPC

Original data file (external link)

Citation:

• https://www.ncei.noaa.gov/access/monitoring/nao/.

To produce the plot, the following processing steps were performed:

• Data set created from file ['norm.nao.monthly.b5001.current.ascii.table'] downloaded from ['https://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/norm.nao.monthly.b5001.current.ascii.table'] at ['2026-01-14 14:46:32']
• Selected years within the range 2010 to 2025.

Arctic Oscillation

The data in the above plot are available in a zip file containing a csv file for each data set.

Data file: Arctic_Oscillation_data_files.zip
Checksum: 76ab1d0fa59f494192aa4f9c79d89dea Copy
Format: BADC CSV format

NOAA CPC

Original data file (external link)

Citation:

• https://www.ncei.noaa.gov/access/monitoring/ao/.

To produce the plot, the following processing steps were performed:

• Data set created from file ['monthly.ao.index.b50.current.ascii.table'] downloaded from ['https://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/monthly.ao.index.b50.current.ascii.table'] at ['2026-01-14 14:46:31']
• Selected years within the range 2010 to 2025.

Antarctic Oscillation

The data in the above plot are available in a zip file containing a csv file for each data set.

Data file: Antarctic_Oscillation_data_files.zip
Checksum: 6ba09ce2a482f6136cf011c0eea9678d Copy
Format: BADC CSV format

NOAA CPC

Original data file (external link)

Citation:

• https://www.ncei.noaa.gov/access/monitoring/ao/.

To produce the plot, the following processing steps were performed:

• Data set created from file ['monthly.aao.index.b79.current.ascii.table'] downloaded from ['https://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/aao/monthly.aao.index.b79.current.ascii.table'] at ['2026-01-22 15:44:03']
• Selected years within the range 2010 to 2025.