# README file for HadCRUT.5.0.0.0 # 14 December 2020 Directory structure: analysis/ diagnostics/ [hadcrut_version]_analysis_component-series_[region]_[time_resolution].nc [hadcrut_version]_analysis_ensemble-series_[region]_[time_resolution].nc [hadcrut_version]_analysis_summary-series_[region]_[time_resolution].nc grids/ ensemble/ [hadcrut_version]_analysis_anomalies_[member_index].nc summary-statistics/ [hadcrut_version]_analysis_anomalies_ensemble-mean.nc [hadcrut_version]_analysis_anomalies_ensemble-median.nc [hadcrut_version]_analysis_anomalies_ensemble-deviation.nc weights/ [hadcrut_version]_analysis_weights.nc non-infilled/ diagnostics/ [hadcrut_version]_component-series_[region]_[time_resolution].nc [hadcrut_version]_ensemble-series_[region]_[time_resolution].nc [hadcrut_version]_summary-series_[region]_[time_resolution].nc grids/ ensemble/ [hadcrut_version]_anomalies_[member_index].nc error-covariance/ [YYYY]/ [hadcrut_version]_error-covariance_[YYYY][MM].nc summary-statistics/ [hadcrut_version]_anomalies_ensemble-mean.nc [hadcrut_version]_anomalies_ensemble-median.nc uncorrelated/ [hadcrut_version]_uncorrelated.nc weights/ [hadcrut_version]_weights.nc File name terms: [hadcrut_version] - The HadCRUT version number (e.g. HadCRUT.5.0.0.0). [region] - A string describing the geographic region represented. [time_resolution] - Either 'monthly' or 'annual'. [YYYY] - The year that the file corresponds to. [MM] - The month that the file corresponds to. HadCRUT5 Analysis Files The HadCRUT5 analysis is recommend as the primary version of the HadCRUT5 data set use for climate monitoring purposes. Analysis Diagnostics Regional average time series are provided for selected regions. Three varieties of time series files are provided. Component series files - Regional average temperature anomaly series with each uncertainty component provided separately. Two uncertainty components are provided: ensemble spread (1 sigma) and coverage uncertainty that arises from the presence of missing data regions (1 sigma). Provided as monthly average or annual average time series. Example: HadCRUT.5.0.0.0_analysis_component-series_global_annual.nc Ensemble series files - Regional average temperature anomaly series with information provided for individual ensemble members. Two uncertainty components are provided: the full set of 200 ensemble member time series (ensemble series) and coverage uncertainty that arises from the presence of missing data regions (1 sigma). Provided as monthly average or annual average time series. Example: HadCRUT.5.0.0.0_analysis_ensemble-series_global_annual.nc Summary series files - Regional average temperature anomaly series with combined uncertainty information describing lower and upper bounds on total uncertainty. Provided as monthly average or annual average time series. Example: HadCRUT.5.0.0.0_analysis_summary-series_global_annual.nc Analysis Grids Ensemble member files - Gridded temperature anomalies, numbered by ensemble member index [member_index] in the range (1-200). All uncertainties in the gridded data for the HadCRUT5 analysis are encoded into the 200 ensemble members. Example: HadCRUT.5.0.0.0_analysis_anomalies_1.nc Pre-computed analysis ensemble summary statistics Grids of summary statistics derived from the gridded ensemble. Ensemble mean, median and standard deviation grids are provided. Examples: [hadcrut_version]_analysis_anomalies_ensemble-mean.nc - Grids of the ensemble mean of the 200 ensemble members. [hadcrut_version]_analysis_anomalies_ensemble-median.nc - Grids ensemble median of the 200 ensemble members. [hadcrut_version]_analysis_anomalies_ensemble-deviation.nc - Grids of the standard deviation of the 200 ensemble members. Weights - HadCRUT5 analysis grids are produced as a weighted average of two analyses: one based on sea-surface temperature observations and one based on land meteorological station observations. Grids are provided for the fractional weighting of the land analysis when combining land and marine analyses. This weighting is based on fractional area of land in a grid cell, availability of observations and the presence of sea-ice. Regions of sea-ice are weighted as if they are land regions, based on sea ice concentration. Example: HadCRUT.5.0.0.0_analysis_weights.nc HadCRUT5 Non-Infilled Files The HadCRUT5 non-infilled dataset is recommend for use in application where there are scientific reasons to not use the HadCRUT5 analysis. Such applications include those where downstream application of the HadCRUT5 will use methods that account for uneven observation sampling or where the data will be analysed using other methods (e.g. data assimilation). Non-infilled Diagnostics Regional average time series are provided for selected regions. Three varieties of time series files are provided. Component series files - Regional average temperature anomaly series with each uncertainty component provided separately. Four uncertainty components are provided: ensemble spread (1 sigma), uncertainty from uncorrelated errors (1 sigma), uncertainty for correlated errors (1 sigma) and coverage uncertainty that arises from the presence of missing data regions (1 sigma). Provided as monthly average or annual average time series. Example: HadCRUT.5.0.0.0_component-series_global_annual.nc Ensemble series files - Regional average temperature anomaly series with information provided for individual ensemble members. Provided as the component series, but with the individual time series provided for each of the 200-members. Four uncertainty components are provided: the full set of 200 ensemble member time series (ensemble series), uncertainty for correlated errors (1 sigma) and coverage uncertainty that arises from the presence of missing data regions (1 sigma). Provided as monthly average or annual average time series. Example: HadCRUT.5.0.0.0_ensemble-series_global_annual.nc Summary series files - Regional average temperature anomaly series with combined uncertainty information describing lower and upper bounds on total uncertainty. Provided as monthly average or annual average time series. Example: HadCRUT.5.0.0.0_analysis_summary-series_global_annual.nc Non-infilled Grids In addition to a 200-member ensemble of gridded temperature anomalies, the uncertainty model for the HadCRUT5 non-infilled grids includes two additional components. The first are provided as fields of uncertainty associated with uncorrelated measurement and sampling errors. The second are provided in monthly error covariance matrices for correlated errors arising from marine platform biases. Combined with the 200-member ensemble, these three terms fully describe the uncertainty model for the non-infilled grids. Ensemble member files - Gridded temperature anomalies, numbered by ensemble member index [member_index] in the range (1-200). Represents residual uncertainty for observational biases with large-scale structure in space and/or time. These uncertainties are independent from uncertainties described by the uncorrelated error and error covariances files. Example: HadCRUT.5.0.0.0_anomalies_1.nc Monthly error covariance matrices - One error covariance per month describing the error covariance between grid cells for partially correlated errors. These uncertainties are independent from uncertainties described by the ensemble and the uncorrelated. Example: HadCRUT.5.0.0.0_error-covariance_185001.nc Uncorrelated uncertainties - Uncertainty associated with uncorrelated measurement and sampling errors in gridded anomalies (1 sigma uncertainty). These uncertainties are independent from those described by the ensemble and the error covariances files. Provided as per-grid-cell values in HadCRUT.5.0.0.0_uncorrelated.nc. Pre-computed non-infilled ensemble summary statistics Grids of summary statistics derived from the gridded ensemble. Ensemble mean, median and standard deviation grids are provided. Examples: [hadcrut_version]_anomalies_ensemble-mean.nc - Grids of the ensemble mean of the 200 non-infilled ensemble member grids. [hadcrut_version]_anomalies_ensemble-median.nc - Grids ensemble median of the 200 non-infilled ensemble members grids. Weights - HadCRUT5 non-infilled grids are produced as a weighted average of sea-surface temperature grids and land air temperature grids. Grids are provided for the fractional weighting of the land analysis when combining land and marine data. This weighting is based on fractional area of land in a grid cell and availability of observations. Sea-ice concentration information is not used in weight computation for the non-infilled dataset. Example: HadCRUT.5.0.0.0_weights.nc