**Please note, this dataset has been superseded by a newer version (see below). New version is only used starting from the last date this version was updated.** National Weather Service (NWS) Station Information System (SIS) contains observing station metadata from November 2014 to present. These are renditions are used to update the Historical Observing Metadata Repository (HOMR) daily. Within this dataset will be embedded PDFs which will be loaded into Environmental Document Access and Display System (EDADS) Version 2 (EV2) and JSON machine readable version of the information on the PDFs which will be integrated into Historical Observing Metadata Repository (HOMR). Currently only Cooperative ObserverProgram (COOP) (www.nws.noaa.gov/os/coop) station metadata are being submitted. NWS plans to add additional types of stations to this dataset which will may require additional data elements.

**Please note, this dataset has been superseded by a newer version (see below). New version is only used starting from the last date this version was updated.** National Weather Service (NWS) Station Information System (SIS) contains observing station metadata from November 2014 to present. These are renditions are used to update the Historical Observing Metadata Repository (HOMR) daily. Within this dataset will be embedded PDFs which will be loaded into Environmental Document Access and Display System (EDADS) Version 2 (EV2) and JSON machine readable version of the information on the PDFs which will be integrated into Historical Observing Metadata Repository (HOMR). Currently only Cooperative ObserverProgram (COOP) (www.nws.noaa.gov/os/coop) station metadata are being submitted. NWS plans to add additional types of stations to this dataset which will may require additional data elements.

A G-AIRMET is a graphical advisory of weather that may be hazardous to aircraft, but are less severe than SIGMETs. They are valid at specific time "snapshots". The G-AIRMET forecasts are distributed in XML (USWX) format. The USWX XML files contain forecaster-created graphical objects which depict hazard areas and attributes. G-AIRMETs are issued at discrete times 3 hours apart for a period of up to 12 hours into the future (00, 03, 06, 09, and 12 hours). They are issued at 03:00, 09:00, 15:00 and 21:00 UTC (with updates issued as necessary). G-AIRMETs are issued by the AWC for the lower 48 states and adjacent coastal waters. The G-AIRMET USWX XML files are currently disseminated from AWC to the operational NGITWS system, and from AWC to the NWSTG for dissemination over NOAAPort. AWC provides the legacy AIRMET information via traditional alphanumeric code (TAC), which is currently archived at NCEI. The G-AIRMET data in BUFR format was operational from 2010 to 2022 and was not archived. This data archive includes the USWX XML formatted products starting on January 1, 2023.

The Service Records Retention System (SRRS) was developed to store weather observations, summaries, forecasts, warnings, and advisories provided by the U.S. National Weather Service (NWS) for public use, and are retained by the National Centers for Environmental Information (NCEI) [formerly the National Climatic Data Center (NCDC)]. Service products issued by the NWS offices are transmitted on the Advanced Weather Interactive Processing System (AWIPS) or Federal Aviation Administration (FAA) communications to an NWS Gateway (NWSTG) server. The products are then electronically transferred to the NCEI and ingested into the Hierarchal Data Storage System (HDSS) for records retention. The three basic groupings of NWS Service Products (SP) are: 1) Observations: reports originated by NWS, Federal Aviation Administration, or Department of Defense facilities and transmitted through the NWS Telecommunication Gateway, NOAAPORT, or equivalent. These reports include, but are not limited to, surface observations (including Automated Surface Observing System and Automated Weather Observing System reports), pilot reports, upper air reports, marine reports, and automated buoy observations; 2) Forecasts: all official routine and non-routine disseminated products related to, or derived from, NWS forecast and warning programs (alphanumeric and graphic format), regardless of dissemination method; and 3) Graphics: all routine and non-routine environmental data analysis graphics, such as surface analysis, standard layer upper air analyses, weather depiction, radar summary, etc.; and all routine and non-routine graphics represented as official NWS forecasts including aviation prognostic graphics (e.g., Low Level and High Level Significant Weather Prognosis) produced by the National Centers for Environmental Prediction and other NWS facilities (e.g., Alaska Aviation Weather Unit).

The Global Hourly Summaries are simple indicators of observational normals which include climatic data summarizations and frequency distributions. These typically are statistical analyses of station data over 5-, 10-, 20-, 30-year or longer time periods. In a GIS map service, the results of these calculations are represented by a given symbology set for different statistical criteria and observation type. Having the ability to modify the symbology "on-the-fly" is a useful tool in the analysis of station trends, accuracy, and regional or localized variances. The summaries are computed from the global surface hourly dataset. This dataset totaling over 350 gigabytes is comprised of 40 different types of weather observations with 20,000 stations worldwide. NCDC and the U.S. Navy have developed these value added products in the form of hourly summaries from many of these observations. These data are a subset of the Integrated Surface Hourly dataset (DSI-3505) (C00532).

The Global Hourly Summaries are simple indicators of observational normals which include climatic data summarizations and frequency distributions. These typically are statistical analyses of station data over 5-, 10-, 20-, 30-year or longer time periods. In a GIS map service, the results of these calculations are represented by a given symbology set for different statistical criteria and observation type. Having the ability to modify the symbology "on-the-fly" is a useful tool in the analysis of station trends, accuracy, and regional or localized variances. The summaries are computed from the global surface hourly dataset. This dataset totaling over 350 gigabytes is comprised of 40 different types of weather observations with 20,000 stations worldwide. NCDC and the U.S. Navy have developed these value added products in the form of hourly summaries from many of these observations. These data are a subset of the Integrated Surface Hourly dataset (DSI-3505) (C00532).

**Please note, this dataset has been superseded by a newer version (see below). Users should not use this version except in rare cases (e.g., when reproducing previous studies that used this version).** The Global Historical Climatology Network (GHCN) Version 1 is a comprehensive, global, surface, baseline, climate data set designed for monitoring and detecting climate change. Comprised of surface station observations of temperature, precipitation, and pressure, all GHCN data are monthly. GHCN was produced jointly by the NCDC, Arizona State University, and the Carbon Dioxide Information Analysis Center (CDIAC) at Oak Ridge National Laboratory (ORNL). GHCN version 1 was released in August of 1992 and has data from ~6,000 Temperature stations ~7,500 Precipitation stations ~2,000 Pressure stations The earliest station data was from 1697. The most recent is from 1990. Version 1 was created from 15 source data sets. Quality Control includes visual inspection of graphs of all station time series, tests for precipitation digitized 6 months out of phase, tests for different stations having identical data, and other tests.

**Please note, this dataset has been superseded by a newer version (see below). Users should not use this version except in rare cases (e.g., when reproducing previous studies that used this version).** The Global Historical Climatology Network (GHCN) Version 1 is a comprehensive, global, surface, baseline, climate data set designed for monitoring and detecting climate change. Comprised of surface station observations of temperature, precipitation, and pressure, all GHCN data are monthly. GHCN was produced jointly by the NCDC, Arizona State University, and the Carbon Dioxide Information Analysis Center (CDIAC) at Oak Ridge National Laboratory (ORNL). GHCN version 1 was released in August of 1992 and has data from ~6,000 Temperature stations ~7,500 Precipitation stations ~2,000 Pressure stations The earliest station data was from 1697. The most recent is from 1990. Version 1 was created from 15 source data sets. Quality Control includes visual inspection of graphs of all station time series, tests for precipitation digitized 6 months out of phase, tests for different stations having identical data, and other tests.

The Regional Snowfall Index (RSI) is an index of significant snowstorms that impact the eastern two thirds of the U.S. The RSI ranks snowstorm impacts on a scale from 1 to 5, similar to the Fujita scale for tornadoes or the Saffir-Simpson scale for hurricanes. NCEI has analyzed and assigned RSI values to over 500 storms going as far back as 1900. New storms are added operationally. As such, RSI puts the regional impacts of snowstorms into a century-scale historical perspective. The RSI differs from other indices because it includes population. RSI is based on the spatial extent of the storm, the amount of snowfall, and the juxtaposition of these elements with population. The area and population are cumulative values above regional specific thresholds. For example, the thresholds for the Southeast are 2", 5", 10", and 15" of snowfall while the thresholds for the Northeast are 4", 10", 20", and 30" of snowfall. Population information ties the index to societal impacts. Currently, the index uses population based on the 2000 Census. The RSI is an evolution of the Northeast Snowfall Impact Scale (NESIS) which NCDC (the precursor to NCEI) began producing operationally in 2005. While NESIS was developed for storms that had a major impact in the Northeast, it includes the impact of snow on other regions as well. It can be thought of as a quasi-national index that is calibrated to Northeast snowstorms. By contrast, the RSI is a regional index; a separate index is produced for each of the six NCDC climate regions in the eastern two-thirds of the nation. The indices are calculated in a similar fashion to NESIS, but our experience has led us to propose a change in the methodology. The new indices require region-specific parameters and thresholds for the calculations. For details on how RSI is calculated, see Squires et al. 2011.