Climate Indices: Monthly Atmospheric and Ocean Time Series

This index replaces the old EP index which is no longer maintained by CPC.

Hurrell, J.W., 1995: Decadal trends in the North Atlantic Oscillation and relationships to regional temperature and precipitation. Science 269, 676-679.
Jones, P.D., Jónsson, T. and Wheeler, D., 1997: Extension to the North Atlantic Oscillation using early instrumental pressure observations from Gibraltar and South-West Iceland. Int. J. Climatol. 17, 1433-1450.

CPC uses the NOAA ERSST V5 anomalies. Now uses https://www.cpc.ncep.noaa.gov/data/indices/ersst5.nino.mth.91-20.ascii. Mean values also available.

Calculated from combining a standardized SOI and a standardized Niño3.4 SST timeseries. Uses the dataset (HadISST1.1) is now used to calculate Niño 3.4 timeseries. Most recent data is based on the NOAA OI V2 SST dataset. PSL

Anomaly of the average of the monthly SST from 5.5N to 23.5N and 15W to 57.5W. HadISST and NOAA OI 1x1 datasets are used to create index. Climatology is 1971-2000.

Enfield, D.B., A.M. Mestas, D.A. Mayer, and L. Cid-Serrano, 1999: How ubiquitous is the dipole relationship in tropical Atlantic sea surface temperatures? JGR-O, 104, 7841-7848.AOML and PSL

Anomaly of the average of the monthly SST from Eq-20S and 10E-30W. HadISST and NOAA OI 1x1 datasets are used to create index. Climatology is 1971-2000.

Enfield, D.B., A.M. Mestas, D.A. Mayer, and L. Cid-Serrano, 1999: How ubiquitous is the dipole relationship in tropical Atlantic sea surface temperatures? JGR-O, 104, 7841-7848.AOMLand PSL

Monthly anomaly of the ocean surface area warmer than 28.5° C in the Atlantic and eastern North Pacific. Based on HadISST and NOAA OI SST (for latest value). Climatology is 1971-2000.

Wang, C., and D.B. Enfield, 2001: The tropical Western Hemisphere warm pool, Geophys. Res. Lett., 28, 1635-1638. AOML and PSL

Three month running mean of NOAA ERSST.V5 SST anomalies in the Niño 3.4 region (5N-5S, 120-170W), based on changing base period which onsist of multiple centered 30-year base periods. These 30-year base periods will be used to calculate the anomalies for successive 5-year periods in the historical record.

Time series is bimonthly so the Jan value represents the Dec-Jan value and is centered between the months. Details and current values are PSL's MEI webpage.

CPC uses the NOAA ERSST V5 anomalies. Now uses https://www.cpc.ncep.noaa.gov/data/indices/ersst5.nino.mth.91-20.ascii. Mean values also available.

CPC uses the NOAA ERSST V5 anomalies. Now uses https://www.cpc.ncep.noaa.gov/data/indices/ersst5.nino.mth.91-20.ascii. Mean values also available.

CPC uses the NOAA ERSST V5 anomalies. Now uses https://www.cpc.ncep.noaa.gov/data/indices/ersst5.nino.mth.91-20.ascii. Mean values also available.

PDO is the leading PC of monthly SST anomalies in the North Pacific Ocean.
UPDATED: Using data from 1948 to 2002. Details and more information are available.

Details and more information are available.

NOI is an index of climate variability based on the difference in SLP anomalies at the North Pacific High and near Darwin Australia. Schwing, F.B., T. Murphree, and P.M. Green. 2002. The Northern Oscillation Index (NOI): a new climate index for the northeast Pacific. Progress in Oceanography 53: 115-139. The time series and more information are available.

NP is the area-weighted sea level pressure over the region 30N-65N, 160E-140W. Time series source
Trenberth and Hurrell (1994): Climate Dynamics 9:303-319.

Calculated at PSL. For longer timeseries, go to http://psl.noaa.gov/Pressure/Timeseries/TNI/

Kevin E. Trenberth and David P. Stepaniak: J. Climate, 14, 1697-1701.

NOT the linear trend of the variable

(Updated to 2016) Each month has the total number of hurricanes or named tropical storms in that month in the Atlantic region. These are provided by Phil Klotabach at CSU.

Note: values are now from CPC as they update their data through the present
The loading pattern of AO (AAO) is defined as the first leading mode from the EOF analysis of monthly mean height anomalies at 1000-hPa (NH) or 700-hPa (SH). Note that year-round monthly mean anomaly data has been used to obtain the loading patterns. Since the AO and AAO have the largest variability during the cold sesaon (variance of AO/AAO), the loading patterns primarily capture characteristics of the cold season patterns.

Daily and monthly AO (AAO) indices are constructed by projecting the daily and monthly mean 1000-hPa (700-hPa) height anomalies onto the leading EOF mode. Both time series are normalized by the standard deviation of the monthly index (1979-2000 base period). Since the loading pattern of AO (AAO) is obtained using the monthly mean height anomaly dataset, the index corresponding to each loading pattern becomes one when it is normalized by the standard deviation of the monthly index.Values and description

Values and references Data from NOAA CPC

Definition: area averaged SST: 60E-170E, 15S-15N Dataset: NOAA ERSSTV5 1948-present
Climatology: 1981-2020
Also available: Long version (1854-present).

Reference: Martin P. Hoerling, Jon Eischeid, and Judith Perlwitz, 2010: Regional Precipitation Trends: Distinguishing Natural Variability from Anthropogenic Forcing. J. Climate, Vol. 23, 2131-2145.

GISST 1948-1949
Reconstructed Reynolds 1950-1981
OI 1982-present

Reference: Martin P. Hoerling, Arun Kumar, and Taiyi Xu, 2001: Robustness of the nonlinear climate response to ENSO's extreme phases. Journal of Climate, Vol.14, No.6, 1277-1293

GISST 1948-1949
Reconstructed Reynolds 1950-1981r OI 1982-present

Note: this index is newly computed from a new dataset. Please use it and note that it supersedes the old indices. The data is calculated from the Kalplan SST. See the AMO webpage for more details.

Enfield, D.B., A. M. Mestas-Nunez and P.J. Trimble, 2001: The Atlantic multidecadal oscillation and it's relation to rainfall and river flows in the continental U.S.. Geophysical Research Letters, Vol. 28, 2077-2080.

Note: this index is computed from a new dataset. See the AMM webpage for more details.

2004 Chiang, J. C. H., and D. J. Vimont: Analogous meridional modes of atmosphere-ocean variability in the tropical Pacific and tropical Atlantic. J. Climate,17(21), 4143-4158.

(Source dataset changed: old version available).The timeseries of SST anomalies averaged over 60W to 20W, 6N to 18N and 20W to 10W, 6N to 10N map. Data is obtained from the ERSST V3b dataset. Anomalies were calculated relative to the 1981-2010 climatology, smoothed by three months running mean procedure and projected onto 20 leading EOFs. Month of data is the center of the 3 months that are smoothed. More information and the indexes forecasted values are available.

Penland, C., and L. Matrosova, 1998: "Prediction of tropical Atlantic sea surface temperatures using Linear Inverse Modeling," J. Climate, March, 483-496 pp.

The timeseries of SST anomalies averaged over the the Caribbean. Data is obtained from the NOAA ERSST V3b dataset. Anomalies were calculated relative to the 1981-2010 climatology, smoothed by three months running mean procedure and projected onto 20 leading EOFs. More information and the indexes forecasted values are available.

Penland, C., and L. Matrosova, 1998: "Prediction of tropical Atlantic sea surface temperatures using Linear Inverse Modeling," J. Climate, March, 483-496 pp.

Note: this index is newly computed from a new dataset. Please use it and note that it supersedes the old indices. The data is calculated from the Kalplan SST. See the AMO webpage for more details.

Enfield, D.B., A. M. Mestas-Nunez and P.J. Trimble, 2001: The Atlantic multidecadal oscillation and it's relation to rainfall and river flows in the continental U.S.. Geophysical Research Letters, Vol. 28, 2077-2080.

Calculated at PSL (from the zonal average of the 30mb zonal wind at the equator as computed from the NCEP/NCAR Reanalysis).

Data is not being updated after Feb 2014. It is not known when or if it will be updated (due to resource issues)..Note that time series is scaled by 1e25. Values are 3-month running means except for the last month which is a 2-month average.

Weickmann, K.M., W.A. Robinson and M.C. Penland, 2000: Stochastic and oscillatory forcing of global atmospheric angular momentum. J. Geophys. Res., 105, D12, 15543-15557.

http://precip.gsfc.nasa.gov/ESPItable.html Please cite "ENSO Indices Based on Patterns of Satellite-Derived Precipitation" Curtis and Adler in J. of Climate, 13,2786 (2000). Time series that uses rainfall data in the Tropical Pacific to describe ENSO events.

http://www.tropmet.res.in/ Please cite the Indian Institute of Tropical Meteorology. CORE-MONSOON INDIA RAINFALL (1871-1999) 7 SUB 776,942 SQ.KM.

http://jisao.washington.edu/data_sets/sahel/ From Mitchell: The averaging region is based on the rotated principal component analysis of average June through September African rainfall presented in Janowiak (1988, J. Climate, 1, 240-255). Stations within 20-8N, 20W-10E are obtained from the National Center for Atmospheric Research World Monthly Surface Station Climatology (WMSSC), and 14 retained which had complete or almost complete records for 1950-93. See link for stations.

Calculated using NCDC's climate division dataset. Monthly precipitation values for each of the climate divisions in Arizona and New Mexico are are averaged to produce a single monthly value. Reference: personal communication, Catherine Smith. Also,
NCDC, 1994, Time Bias Corrected Divisional Temperature-Precipitation-Drought Index. Documentation for dataset TD-9640. Available from DBMB, NCDC, NOAA, Federal Building, 37 Battery Park Ave. Asheville, NC 28801-2733. 12pp.

http://jisao.washington.edu/data_sets/brazil/ From Mitchell: The northeast Brazil rainfall index is calculated from data for Fortaleza (3.7S, 38.5W) and Quixeramobim (5.3S, 39.3W) Brazil obtained from the NCAR World Monthly Surface Station Climatology. Climatological mean is for 1950-79.

ftp://ftp.ngdc.noaa.gov/STP/space-weather/solar-data/solar-features/solar-radio/noontime-flux/penticton/penticton_observed/listings/listing_drao_noontime-flux-observed_monthly.txt
To cite, "The 10.7cm Solar Flux Data are provided as a service by the National Research Council of Canada". They would appreciate a preprint or at least a reference if you use the data URL is http://www.spaceweather.ca/solarflux/sx-4-eng.php.

Values change over time!
Data values are from NASA/GISS. Please read and refer to this web page plus the main web page describing various temperature indices at the main NASA/GISTEMP webpage. Note, the index is an anomaly index. They have comments in the datafile and the writeup on obtaining an absolute global mean temperatures.
Please reference the papers:

• Christy, J.R., R.W. Spencer, and W.D. Braswell 2000. J. Atmos. Oceanic Tech. 17, 1153.
• Hansen, J., R. Ruedy, M. Sato and R. Reynolds 1996. Global surface air temperature in 1995: Return to pre-Pinatubo level. Geophys. Res. Lett. 23, 1665-1668.
• Hansen, J., M. Sato, J. Glascoe and R. Ruedy 1998. A common-sense climate index: Is climate changing noticeably? Proc. Natl. Acad. Sci. 95, 4113-4120.
• Hansen, J., R. Ruedy, J. Glascoe, and M. Sato 1999. GISS analysis of surface temperature change. J. Geophys. Res. 104, 30997-31022.
• Hansen, J., R. Ruedy, M. Sato, M. Imhoff, W. Lawrence, D. Easterling, T. Peterson, and T. Karl 2001. A closer look at United States and global surface temperature change. J. Geophys. Res. 106, 23947-23963
• Intergovernmental Panel on Climate Change 2001. Climate Change 2001 (J.T. Houghton et al., Eds.), Cambridge Univ. Press, New York.
• National Research Council 2000. Reconciling Observations of Global Temperature Change. National Academy Press, Washington, DC, 85 pp.
Peterson, T.C., and R.S. Vose 1997. An overview of the Global Historical Climatology Network temperature database. Bull. Amer. Meteorol. Soc. 78, 2837-2849.
• Rayner, N. 2000. HadISST1 Seaice and sea surface temperature files. Hadley Center, Bracknell, U.K.
• Reynolds, R.W., N.A. Rayner, T.M. Smith, D.C. Stokes, and W. Wang 2002. An improved in situ and satellite SST analysis for climate. J. Climate 15, 1609-1625, doi:10.1175/1520-0442(2002)015<1609:AIISAS> 2.0.CO;2.
• Reynolds, R.W., and T.M. Smith 1994. Improved global sea surface temperature analyses. J. Climate 7, 929-948, doi:10.1175/1520-0442(1994)007<0929:IGSSTA>2.0.CO;2
• Smith, T.M., R.W. Reynolds, R.E. Livesay, and D.C. Stokes 1996. Reconstruction of historical sea surface temperature using empirical orthogonal functions. J. Climate 9, 1403-1420.