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The most up-to-date version is known as Kaplan Extended SST v2, which combines statistically infilled grids of UK Met Office SSTs for 1856-1981 with a statistically reduced and coarser resolution version of Smith and Reynolds Optimally Interpolated …

NCAR Sea Level Pressure is a gridded analysis of SLP based on land station reports, covering 1899 to present for latitudes 30°N-90°N. Quality controlled raw data plus empirical corrections for changes in instrumentation and station location.

ICOADS (International Comprehensive Ocean-Atmosphere Data Set) is the most comprehensive archive of global marine surface climate observations available. Variables include SST, SLP, air temperature, wind speed, cloud amount, and others. There is no …

Reanalysis a systematic approach to produce data sets for climate monitoring and research. Reanalyses are created via an unchanging ("frozen") data assimilation scheme and model(s) which ingest all available observations every 6-12 hours over the pe…

NCEP-NCAR (R1) is the original reanalysis effort. It uses a frozen global state-of-the-art global data assimilation system (as of 11 January 1995). The original database was enhanced (additional, quality checked datasets) by NCAR's Data Support Sect…

Data assimilation is the process of combining observations from a wide variety of sources and forecast output from a weather prediction model. The resulting analysis is considered to be the 'best' estimate of the state of the atmosphere at a particu…

The Modern Era Retrospective-Analysis for Research and Applications (MERRA) was undertaken by NASA’s Global Modeling and Assimilation Office with two primary objectives: to place observations from NASA’s Earth Observing System satellites into a clim…

Spanning 1958-present, JRA-55 is the longest third-generation reanalysis that uses the full observing system (in contrast, products like ERA-20C and NOAA 20CR assimilate a very limited set of observations while NCEP R1 uses an antiquated model and a…

Using a much improved atmospheric model and assimilation system from those used in ERA-40, ERA-Interim represents a third generation reanalysis. Several of the inaccuracies exhibited by ERA-40 such as too-strong precipitation over oceans from the ea…

The Twentieth Century Reanalysis (20CR) provides a comprehensive global atmospheric circulation data set spanning 1850-2014. Its chief motivation is to provide an observational validation data set, with quantified uncertainties, for assessing climat…

A high resolution (32km x 29 pressure levels) data set focused upon the North American Region. Relative to the NCEP-DOE (R2) it has a much improved land-hydrology, diurnal cycle and land-atmosphere interaction. As such, it can be considered a second…

The Arctic System Reanalysis is a multi-agency, university-led retrospective analysis (reanalysis) of the Greater Arctic. ASR is produced using high-resolution versions of the Polar Weather Forecast Model (PWRF) and the WRF-VAR and High Resolution L…

The CFSR is a third generation reanalysis product. It is a global, high resolution, coupled atmosphere-ocean-land surface-sea ice system designed to provide the best estimate of the state of these coupled domains over this period. The CFSR includes …

The International Satellite Cloud Climatology Project (ISCCP) makes use of routine observations by operational weather satellites to provide a long-term (1983-2009), gridded, global record of cloud properties. ISCCP uses observations in the visible …

The CERES-EBAF product provides 1-degree regional, zonal and global monthly mean Top-of-Atmosphere (TOA) and surface (SFC) longwave (LW), shortwave (SW), and net (NET) fluxes under clear and all-sky conditions. EBAF is used for climate model evaluat…

Precipitation (rain, snow, hail, ...) is one of the key components of the hydrological cycle. Its societal importance cannot be over stated. For climate research, precipitation is one of the key terms for balancing the energy budget, and one of the …

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 methods have been used to derive assorted indices. Classically, selected station, grid point o…

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 mean SLP at Tahiti [T] and Darwin [D] are used. An optimal SOI can be constructed. It consi…

There are several indices used to monitor the tropical Pacific, all of which are based on sea surface temperature (SST) anomalies averaged across a given region.  Usually the anomalies are computed relative to a base period of 30 years.  The Niño 3.4 index and the Oceanic Ni…

The Atlantic Multi-decadal Oscillation (AMO) has been identified as a coherent mode of natural variability occurring in the North Atlantic Ocean with an estimated period of 60-80 years. It is based upon the average anomalies of sea surface temperatu…

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 Stykkisholmur/Reykjavik, Iceland since 1864. Positive values of the NAO index are typicall…

The Palmer Drought Severity Index (PDSI) uses readily available temperature and precipitation data to estimate relative dryness. It is a standardized index that generally spans -10 (dry) to +10 (wet). Maps of operational agencies like NOAA typically…

The Standardized Precipitation Index (SPI) is a widely used index to characterize meteorological drought on a range of timescales. On short timescales, the SPI is closely related to soil moisture, while at longer timescales, the SPI can be related t…

Data from rain gauge stations, satellites, and sounding observations have been merged to estimate monthly rainfall on a 2.5-degree global grid from 1979 to the present. The careful combination of satellite-based rainfall estimates provides the most …