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CPC Hourly US Precipitation

Note, 1998 and onward files have small values over the oceans and small values over land which are likely incorrect and may be due to smoothing of some sort on the original dataset. You may wish to exlcude 1998 onwards data or you can set very small values to missing (ocean) and 0 (land).

One-Line Description:

  • NOAA's CPC (Climate Prediction Center) Hourly US Precipitation, gridded and smoothed

Temporal Coverage:

  • Hourly values for 1948/01 - 2002/09

Spatial Coverage:

  • 2.0 degree latitude x 2.5 degree longitude US grid (33x21).
  • 20N - 60.0N, 220.0E - 297.5E


  • Surface

Update Schedule:

  • Static

Download/Plot Data: (FTP Access)

Variable Statistic Level Download File Create Plot/Subset
Precipitation Hourly Total Surface precip.hour.yyyy.nc (see list) plot

Usage Restrictions:

  • None

Detailed Description:

  • (This section is excerpted in part from the description at CPC)
    Dataset is derived from US station reports which were obtained from the NWS/Techniques Development Laboratory. About one-third of the stations analyzed are first order NWS stations and the remaining ones are climatic substations (observations from cooperative observers). The precipitation gauges used at the climatic substations are of either the Universal or Fisher/Porter type. Precipitation amounts from the Fisher/Porter gauges (which are used at slightly less than half of the stations) are accurate only to the nearest one-tenth of an inch. The accuracy of the Universal gauges is one-hundredth of an inch.
    Users of the data may also notice occasional "bulls eyes" along the southeast coast of Alaska. This is due to the fact that two Alaskan stations (lat,lon)=(131.57 W, 55.03 N) and (139.67 W, 59.52 N) with relatively high separation distance were inadvertently analyzed. Also, since the data were subjected to objective analysis, precipitation amounts have been interpolated to grids for which no gauge observations exist. This is readily seen over the oceanic parts of the domain. We recommend using the analyzed data only at gridpoints over the conterminous U.S.
    For the discussion of daily mean statistics, measurable precipitation is defined as more than 1.0 mm/day. A relatively high threshold for measurable precipitation is used compared to studies based exclusively on station data (e.g. Barnston 1993) because the observations have been analyzed at a coarser resolution than the average station spacing (roughly 70 km) which can lead to an overabundance of trace amounts. A trace is defined as nonzero, but less than a measurable amount of precipitation. Because the observations are available only over land, a mask (available with the data set) is used over the oceans. Finally, throughout the CPC atlas the term "rainfall" is equivalent to measurable precipitation.
    The hour assigned to a precipitation amount is that which begins the hourly period. For example, an amount for 00Z represents an accumulation over the period 00Z-01Z, an amount for 01Z is for the period 01Z-02Z, etc. The units in the netCDF files distributed by PSL are inches, but please note if you wish to compare these data to the CPC atlas they have converted the data to metric units expressed as a rate (i.e. mm/day).
    Stations were gridded into 2.0x2.5 boxes that extended over the region, 140W-60W, 20N-60N using a modified Cressman Scheme.


  • None

Related File Naming & Structure Information:

File Names:

  • precip.yyyy.nc   (In directory: /Datasets/cpc_us_hour_precip/)

OpenDap File Names:

  • /dodsC//Datasets/cpc_us_hour_precip/precip.yyyy.nc   

Dataset Format and Size:

  • PSL standard NetCDF 12.2 Mbyte file for each monthly file.

Missing Data:

  • Missing data is flagged with a value of -9.96921e+36.
  • A list of times can be found at CPC.


  • Please note: If you acquire CPC Hourly US Precipitation data products from PSL, we ask that you acknowledge us in your use of the data. This may be done by including text such as CPC Hourly US Precipitation data provided by the NOAA/OAR/ESRL PSL, Boulder, Colorado, USA, from their Web site at / in any documents or publications using these data. We would also appreciate receiving a copy of the relevant publications. This will help PSL to justify keeping the CPC Hourly US Precipitation data set freely available online in the future. Thank you!


  • Higgins, R.W., W. Shi, E. Yarosh and R. Joyce, 2000: Improved United States Precipitation Quality Control System and Analysis. NCEP/Climate Prediction Center ATLAS No. 7, 40 pp., Camp Springs, MD 20746, USA.
  • Higgins, R. W., J. E. Janowiak, and Y.-P. Yao, 1996: A gridded hourly precipitation data base for the United States (1963-1993). NCEP/Climate Prediction Center Atlas 1, national Centers for Environmental Prediction, 46pp.
  • Online CPC writeup.

Original Source:

  • NCEP/Climate Prediction Center (Wayne Higgins, Evgeney Yarosh, Wei Shi)


  • Physical Sciences Laboratory: Data Management
    325 Broadway
    Boulder, CO 80305-3328