The Twentieth Century Reanalysis Project, produced by the Earth System Research Laboratory Physical Sciences Division from NOAA and the University of Colorado Cooperative Institute for Research in Environmental Sciences using resources from Department of Energy supercomputers, is an effort to produce a global reanalysis dataset spanning a portion of the nineteenth century and the entire twentieth century (1836 - 2015), assimilating only surface observations of synoptic pressure into an 80-member ensemble of estimates of the Earth system. Boundary conditions of pentad sea surface temperature and monthly sea ice concentration and time-varying solar, volcanic, and carbon dioxide radiative forcings are prescribed. Products include 3 and 6-hourly ensemble mean and spread analysis fields and 6-hourly ensemble mean and spread forecast (first guess) fields on a global Gaussian T254 grid. Fields are accessible in yearly time series (1 file per parameter). The NOAA-CIRES-DOE Twentieth Century Reanalysis Version 3 uses the NCEP Global Forecast Model that was operational in autumn 2017, with differences as described in (Slivinski et al. 2019). Sea ice boundary conditions are specified from HadISST 2.3 (Slivinski et al. 2019). Sea surface temperature fields prior to 1981 are prescribed from the 8-member ensemble of pentad Simple Ocean Data Assimilation with sparse input (SODAsi.3, Giese et al. 2016) and from the 8-member ensemble of pentad HadISST 2.2 for 1981 to 2015. Observations from ISPD version 4.7 are assimilated using an ensemble Kalman filter. The Twentieth Century Reanalysis Project version 3 used resources of the National Energy Research Scientific Computing Center managed by Lawrence Berkeley National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 and used resources of NOAA's Remote Deployed High Performance Computing Systems. Version 3 is a contribution to the international Atmospheric...

16 potential temperature levels

the Twentieth Century Reanalysis Project is generating a six-hourly

The 20th Century Reanalysis version 2c (20CRV2c)is an effort led by PSL and the CIRES at the University of Colorado to produce a reanalysis dataset spanning the entire twentieth century, assimilating only surface observations of synoptic pressure, monthly sea surface temperature and sea ice distribution. V1 was initially completed as a test from 1950-1958. V2 covers the period from 1871-2012 . The model used is a 2008 experimental, reduced-resolution version of the NCEP Global Forecast System (GFS2008ex). Briefly, that model has a spatial resolution of nearly 200-km on an irregular Gaussian grid in the horizontal (corresponding to a spherical harmonic representation of model fields truncated at total wavenumber 62, T62). In the vertical, we use finite differencing of 28 levels. The model has a complete suite of physical parameterizations as described in Kanamitsu et al. (1991) with updates detailed in Moorthi et al. (2001). Additional updates to these parameterizations are described in Saha et al. [Need YEAR] and include revised solar radiation transfer, boundary layer vertical diffusion, cumulus convection, and gravity wave drag parameterizations. In addition, the cloud liquid water is a prognostic quantity with a simple cloud microphysics parameterization. The radiation interacts with a fractional cloud cover that is diagnostically determined by the predicted cloud liquid water. The radiation also interacts with stratospheric ozone that is determined prognostically. The GFS2008ex also includes the radiative effects of historical time-varying CO2 concentrations, volcanic aerosol and solar variations using the longwave radiation model of Mlawer et al. (1997) and shortwave radiation model of Hou et al. (2002). Pressure observations are from the International Surface Pressure Databank station component version 3. It is run as an 56 member forecast ensemble. The boundary forcing is taken from the Soda C (time-evolving sea-surface temperature and sea-ice). The model is run using 9 hour integrations of the ensemble members. A subset of the model variables are output every 6 hours. Additional variables are available every 3 hours. In addition to the subdaily values, the dataset also includes daily and monthly average values. In addition to the mean values, standard deviations of the 56 ensemble members are also provided for the subdaily and monthly average output. Subdaily, daily, and monthly long terms means of both the model means and standard deviations are also provided (1981-2010). Output includes 2D and 3D variables. The 3D atmospheric variables are on 24 pressure levels extending from 1000mb to 10mb. Soil moisture is provided on 4 levels. The horizontal resolution of the 2D and 3D variables are about 2 degrees latitude by 2 degrees longitude. Individual ensemble members are available via the NERSC interface. All data are in netCDF4 format. Total 20CRV2 data volume at PSL is approximately 4TB. In general, data is divided into annual files (except for monthly values). The files are available via FTP and OPEnDAP (THREDDS) and a selection of plotting and analysis tools.

Various input data were used by the 20th Century Reanalysis project team including surface pressure observations from the International Surface Pressure Databank version 2. The original observations from the International Surface Pressure Databank version 2 used in the project are archived with associated original metadata and model quality control information. These are the only records which have the original station metadata and source information and model quality control information on the same record. The 20th Century Reanalysis dataset provides 6 hourly analyses on a Global 2.0 degree latitude x 2.0 degree longitude global grid from 1871 to present produced from a series of 56-member ensemble runs. For each output time step ensemble means and associated spreads have been calculated and form a continuous dataset over the entire timespan of the dataset. The data contain fields at the surface and on pressure levels from 1000 hPa to 10 hPa and are also available as part of the copy held by the British Atmospheric Data Centre. The dataset authors request that the following acknowledgment be included in all papers using the dataset: 'Support for the Twentieth Century Reanalysis Project dataset is provided by the U.S. Department of Energy, Office of Science Innovative and Novel Computational Impact on Theory and Experiment (DOE INCITE - http://www.doeleadershipcomputing.org/incite-program/ ) program, and Office of Biological and Environmental Research (BER - http://science.energy.gov/ber/ ), and by the National Oceanic and Atmospheric Administration Climate Program Office (http://www.climate.noaa.gov/).'

The 20th Century Reanalysis dataset provides 6 hourly analyses on a global grid from 1870 to present produced from a series of 56-member ensemble runs. These data are the from each of the 56 ensemble members from the run covering 1981 to 1985. These data were produced on a 2 degree latitude-longitude (180x91) global grid and include data both at the surface and on pressure levels. The dataset authors request that the following acknowledgment be included in all papers using the dataset: 'Support for the Twentieth Century Reanalysis Project dataset is provided by the U.S. Department of Energy, Office of Science Innovative and Novel Computational Impact on Theory and Experiment (DOE INCITE - http://www.doeleadershipcomputing.org/incite-program/ ) program, and Office of Biological and Environmental Research (BER - http://science.energy.gov/ber/ ), and by the National Oceanic and Atmospheric Administration Climate Program Office (http://www.climate.noaa.gov/).'

The 20th Century Reanalysis dataset provides 6 hourly analyses on a global grid from 1870 to present produced from a series of 56-member ensemble runs. These data are the from each of the 56 ensemble members from the run covering 1871 to 1875. These data were produced on a 2 degree latitude-longitude (180x91) global grid and include data both at the surface and on pressure levels. The dataset authors request that the following acknowledgment be included in all papers using the dataset: 'Support for the Twentieth Century Reanalysis Project dataset is provided by the U.S. Department of Energy, Office of Science Innovative and Novel Computational Impact on Theory and Experiment (DOE INCITE - http://www.doeleadershipcomputing.org/incite-program/ ) program, and Office of Biological and Environmental Research (BER - http://science.energy.gov/ber/ ), and by the National Oceanic and Atmospheric Administration Climate Program Office (http://www.climate.noaa.gov/).'

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The 20th Century Reanalysis dataset provides 6 hourly analyses on a global grid from 1870 to present produced from a series of 56-member ensemble runs. These data are the from each of the 56 ensemble members from the run covering 1901 to 1905. These data were produced on a 2 degree latitude-longitude (180x91) global grid and include data both at the surface and on pressure levels. The dataset authors request that the following acknowledgment be included in all papers using the dataset: 'Support for the Twentieth Century Reanalysis Project dataset is provided by the U.S. Department of Energy, Office of Science Innovative and Novel Computational Impact on Theory and Experiment (DOE INCITE - http://www.doeleadershipcomputing.org/incite-program/ ) program, and Office of Biological and Environmental Research (BER - http://science.energy.gov/ber/ ), and by the National Oceanic and Atmospheric Administration Climate Program Office (http://www.climate.noaa.gov/).'

ERA-20CL is ECMWF's land surface reanalysis of the 20th century

The 20th Century Reanalysis dataset provides 6 hourly analyses on a global grid from 1870 to present produced from a series of 56-member ensemble runs. These data are the from each of the 56 ensemble members from the run covering 1886 to 1890. These data were produced on a 2 degree latitude-longitude (180x91) global grid and include data both at the surface and on pressure levels. The dataset authors request that the following acknowledgment be included in all papers using the dataset: 'Support for the Twentieth Century Reanalysis Project dataset is provided by the U.S. Department of Energy, Office of Science Innovative and Novel Computational Impact on Theory and Experiment (DOE INCITE - http://www.doeleadershipcomputing.org/incite-program/ ) program, and Office of Biological and Environmental Research (BER - http://science.energy.gov/ber/ ), and by the National Oceanic and Atmospheric Administration Climate Program Office (http://www.climate.noaa.gov/).'

The 20th Century Reanalysis dataset provides 6 hourly analyses on a global grid from 1870 to present produced from a series of 56-member ensemble runs. These data are the from each of the 56 ensemble members from the run covering 1911 to 1915. These data were produced on a 2 degree latitude-longitude (180x91) global grid and include data both at the surface and on pressure levels. The dataset authors request that the following acknowledgment be included in all papers using the dataset: 'Support for the Twentieth Century Reanalysis Project dataset is provided by the U.S. Department of Energy, Office of Science Innovative and Novel Computational Impact on Theory and Experiment (DOE INCITE - http://www.doeleadershipcomputing.org/incite-program/ ) program, and Office of Biological and Environmental Research (BER - http://science.energy.gov/ber/ ), and by the National Oceanic and Atmospheric Administration Climate Program Office (http://www.climate.noaa.gov/).'

An ensemble of ten atmospheric model integrations for the years 1899 to 2009/2010. There are two versions of the ERA-20CM atmospheric model integrations. Each is comprised of a 10-member ensemble using: Radiative forcing from CMIP5 Sea-surface

The data consist of 4 frozen gridded estimates as described in Gillespie et al, 2022. The data are presented as 5 degree resolution global fields over 1850-2014. Station data arising from the International Surface Temperature Initiative (ISTI) global databank of monthly holdings have been homogenised using 20CRv3 to identify breakpoints. Four distinct approaches to adjustment have been undertaken resulting in 4 separate estimates of the resulting series. The gridding is a simple gridbox average of any observations available within each 5 degree gridbox. Data is available for those global land areas for which underlying station data are available in teh ISTI holdings.

Historical reanalyses have become a widely used resource for analyzing weather and climate processes and their changes over time. In this article I explore how further historical observations could support reanalyses and lead to products that reach further back in time or have a better quality. Using an off-line Ensemble Kalman Filter I estimate improvements arising from assimilating additional observations into the ensemble of the “Twentieth Century Reanalysis” Version 3 (20CRv3). I demonstrate this for three case studies and evaluate them using independent data and a leave-one-out approach. For Europe in 1807, assimilating additional pressure data improves the skill for pressure but slightly decreases it for temperature, while assimilating temperature data, a variable that is not assimilated in 20CRv3, improves the skill for temperature but slightly decreases it for pressure. Assimilating both leads to substantially increased skill in a leave-one-out approach. For Sub-Saharan Africa in 1877/78, assimilating ship-based pressure observations as well as land station data, albeit extremely sparse, leads to a slight improvement over the entire domain. Finally, for Europe in 1926/27, assimilating upper air and total column ozone observations both lead to improvements in geopotential height and wind in the middle troposphere and in total column ozone, but with little or no effect in the lower troposphere. This is because 20CRv3 is already close to perfect over Europe in this period. The article shows how additional observations could improve historical reanalyses. A backward extension to the 1780s seems possible, but further data rescue efforts are necessary. For some applications, improved fields as generated by the offline assimilation presented in this study could be useful.

Gridded historical climate data over China, spanning 1851 to 2010. Dynamically downscaled to 25km resolution using the PRECIS2.0 (HadRM3P) Met Office regional climate model, driven by 20th century reanalysis (20CRv2c, NOAA/ESRL PSD 20th Century Reanalysis version 2c, ensemble member 37). This data has been un-rotated to true latitude longitude coordinates from its original rotate pole frame of reference. For more information on the PRECIS regional climate model, visit www.metoffice.gov.uk/precis. Data near the boundaries should be used with caution due to model configuration aspects of regional climate modelling, and the interpolation method applied. Domain: 17N to 58.84N, 73E to 135.7E Countries covered: China, Nepal, Bhutan, Bangladesh, Taiwan, Mongolia, North Korea, South Korea, Kyrgzstan, and northern parts of India, Myanmar, Lao PDR & Vietnam. Variables: pr (mean precipitation flux), tm (mean surface temperature), tn (minimum surface temperature) & tx (maximum surface temperature) Time averaging: monthly This data set supplements the equivalent downscaled ERA-Interim data set: Downscaled ERA-Interim gridded historical climate data over China (1980-2010) doi: 10.5281/zenodo.2600192 {"references": ["Amato, R., Steptoe, H., Buonomo, E., & Jones, R. (2019). High-Resolution History: Downscaling China's Climate from the 20CRv2c Reanalysis, Journal of Applied Meteorology and Climatology, 58(10), 2141-2157"]} This work and its authors were supported by the UK-China Research & Innovation Partnership Fund through the Met Office Climate Science for Service Partnership (CSSP) China as part of the Newton Fund.

This dataset contains selected variables as monthly means, extracted from the original The Community Earth System Model 2 (CESM2) Large Ensemble Community Project (LENS2) dataset. Additionally, it contains observational reference datasets for the respective variables. The data in this bucket is lossy compressed with zfp. We provide full ensembles with 100 members for the variables listed in the table below. The 3d winds and temperature (ua, va, ta) are provided at preassure levels 200 and 850 hPa. Specific humidity is provided at levels 300 and 850 hPa. The full set comprises 4 repositories:

• LENS2 data repository (1960-1990) (DOI: 10.5281/zenodo.15049672)
• LENS2 data repository (1990-2014) (DOI: 10.5281/zenodo.15045356)
• LENS2 data repository (1859-1880) (DOI: 10.5281/zenodo.15049720)
• Script repository (DOI: 10.5281/zenodo.15052431)

How to extract and use the data is described in the README of the script repository. For questions, please email to kai.keller@bsc.es and marta.alerany@bsc.es.

The LENS2 project provides open access to multi-decadal climate simulation data at 1-degree horizontal resolution, conducted with a large ensemble comprising 100
members (Rodgers et al., 2021). The simulation covers a historical period (1850-2014) and a future projection (2015-2100), following the Shared Socioeconomic Pathways (SSP) scenario SSP3-7.0.

For a full description of the dataset, we refer to the webpage of the LENS2 project: https://www.cesm.ucar.edu/community-projects/lens2, and to the article from Rodgers et al., 2021 (DOI: 10.5194/esd-12-1393-2021).

Reanalysis-Based Global Tropical Cyclone Tracks Dataset for the Twentieth Century (RGTracks-20C), which provides a long-term historical proxy record of global TCs spanning from 1850 to 2014. The provided TC data is reconstructed from the National Oceanic and Atmospheric Administration (NOAA) Twentieth Century Reanalysis (20CRv3) with two TC tracking algorithms.

Much of the uncertainty in the pre-satellite sea ice record stems from the difficulty establishing a consistent record of sea ice variability that covers the entire Arctic from historical observations such as ship logs, reconnaissance flights, etc. These observations are scattered in space and time and the primary challenge in constructing a representative picture of sea ice variability from these records is to adequately sample the strong seasonal cycle and high spatial variability of sea ice in the Arctic. Sea ice reconstructions must therefore rely on interpolation in time and space, which is made difficult by the dynamic nature of sea ice. For some critically important climate variables, such as sea ice thickness and total arctic sea ice volume, no historical data exist. The PIs will conduct a Century-scale Arctic Sea Ice Reanalysis (CASIR) that synthesizes observations and models from 1872 to the present to produce a long-term record of arctic sea ice extent, concentration, thickness, and volume. Advances in atmospheric reanalysis, sea ice modeling, and recovery of historical data make CASIR possible. To construct CASIR, they will recover and collect new and existing historical sea ice observations as far back as the late 1800s and integrate them into a model validation and assimilation framework based on the Pan-arctic Ice-Ocean Modeling and Assimilation System (PIOMAS). This will include the extraction of sea ice variables from historical Revenue Service/Coast Guard ship logs that are now being transcribed and promise to fill important gaps in the Pacific sector of the Arctic. Through data assimilation and model calibration and validation, the observational record will be integrated into PIOMAS to generate CASIR. An ensemble of atmospheric forcing data for CASIR will be extracted from atmospheric reanalysis projects for the 20th century that are completed or currently underway. This ensemble, in addition to comparisons with observations, will be used to determine uncertainties in CASIR sea ice variables. The PIs will analyze CASIR ice extent, concentration, thickness, and volume, to characterize 20th century temporal and spatial variability, improve understanding of the mechanisms driving this variability, and place the recent sea ice decline in a longer term context. This project will conduct a Century-scale Arctic Sea Ice Reanalysis (CASIR) that synthesizes observations and models from 1872 to the present to produce a long-term record of arctic sea ice extent, concentration, thickness, and volume. To construct CASIR, researchers plan to recover and collect new and existing historical sea ice observations as far back as the late 1800s and integrate them into a model validation and assimilation framework based on the Pan-arctic Ice-Ocean Modeling and Assimilation System (PIOMAS). This will include the extraction of sea ice variables from historical Revenue Service/Coast Guard ship logs that are now being transcribed and promise to fill important gaps in the Pacific sector of the Arctic. Through data assimilation and model calibration and validation, the observational record will be integrated into PIOMAS to generate CASIR. An ensemble of atmospheric forcing data for CASIR will be extracted from atmospheric reanalysis projects for the 20th cent...

We make available the daily discharge dataset of the Hydrological Reanalysis across the 20th Century for the Amazon Basin in its v1.0 version, which correspond to the HRXX_Amz.nc file. The matrix of daily discharge contains 36890 columns (one per day, starting at 01Jan/1910) and 12466 rows (one per catchment).

Authors: Sly Wongchuig Correa Rodrigo Cauduro Dias de Paiva Vinícius Siqueira Walter Collischonn

Institute of Hydraulic Research - (IPH/UFRGS) Brazil - November 2018

Citation: When using these data, please refer to the following paper: Wongchuig, C.S.; Paiva, R.C.D.; Siqueira, V.; Collischonn, W. 2019. Hydrological Reanalysis Across the 20th Century: A Case Study of the Amazon Basin. Journal of Hydrology, vol. 570, p. 755-773. https://doi.org/10.1016/j.jhydrol.2019.01.025