Description - Introduction
Photo courtesy Grant Goodge/NCDC
GHCN (Global Historical Climatology Network)-Daily is an integrated database of daily climate summaries from land surface stations across the globe. Like its monthly counterpart (GHCN-Monthly) , GHCN-Daily is comprised of daily climate records from numerous sources that have been integrated and subjected to a common suite of quality assurance reviews.
GHCN-Daily now contains records from over 75000 stations in 180 countries and territories. Numerous daily variables are provided, including maximum and minimum temperature, total daily precipitation, snowfall, and snow depth; however, about two thirds of the stations report precipitation only. Both the record length and period of record vary by station and cover intervals ranging from less than year to more than 175 years.
The dataset is regularly reconstructed (usually every weekend) from its 20-plus data source components to ensure that GHCN-Daily is generally in sync with its growing list of constituent sources. During this process, quality assurance checks are applied to the full dataset. On most weekdays, GHCN-Daily station data are updated when possible from a variety of data streams, which also undergo a suite of quality checks.
Each updated and fully reprocessed copy of the GHCN-Daily dataset is assigned a unique version number , and each dataset version is then archived at NOAA/NCDC for potential future retrieval. GHCN-Daily and its processing system also serve as the official archive and processing system for U.S. Cooperative Observer data, which have been comprehensively integrated into the dataset along with other U.S. daily data sources.
Users of U.S. data are encouraged to see further notes on the Source Data page regarding real-time versus time-delayed, archive quality updates. In general, real-time, update data streams are replaced by archive-quality sources 45 to 60 days after the close of a data month.
Major changes to the processing system as well as announcements of significant data additions to GHCN-Daily are provided via an RSS feed and in the GHCN-Daily status reports . GHCN-Daily data documentation is provided in the readme.txt file, which includes a definition of the data quality and data source flags that accompany each datum.