Precipitation Data

 

Format


Runoff simulations are driven by continuous hourly precipitation & daily air temperature time series.  Runoff results from rainfall and snowmelt.

Precipitation data are stored in an ASCII text file, one record per day in the following format:

   YYYY (or YY) = Year,  MM = Month,  D = Day, ( Pi = Hourly Precip in hundredths of an inch, I = 1 to 24 )

Values are separated by one or more spaces or commas. Days with no precipitation can be omitted from the file (no precipitation assumed).  Records must be sorted by date.  

There is no practical limit on the length of precipitation files.  However, the number of days used in a given simulation is limited by the program constraints. 

The sample precipitation files supplied with the program have an extension of ".pcp". 

The precipitation data file must be located in the same file directory as the case file.

Short storm sequences ("design storms") can be used in preliminary model runs.  An example file (type2.pcp) is provided.  This contains a 1-inch, 24-hr, SCS Type II design storm with a 72-hour interval between storm midpoints.   You can change the storm size by editing the 'Precipitation Scale Factor' parameter on the 'Edit General' screen.  To
initialize the simulation, more than one iteration should be specified by editing the 'number of passes through storm file' on the 'Edit General' screen.

External Data Sources  


Links to hourly precipitation and temperature data sources are listed below:

http://www.ncdc.noaa.gov/oa/ncdc.html

http://precip.fsl.noaa.gov/hpd/

http://www.earthinfo.com/databases/databases.htm

http://www.epa.gov/ceampubl/tools/metdata/us_met.htm 

The ' File Translate Precip' procedure will translate precipitation files in various formats.   Input formats are identified by the file extension:

File Extension Description Notes
*.prn NCDC Release B/ Condensed Handled by the 1997 P8 file conversion utility; apparently no longer supplied by NCDC
*.pre,*.txt,*.dat Earth Info ASCII format Available on CD from earthinfo.com
*.stm P8 Version 1.0 Storm File
*.xls Excel Workbook Use to compile data from any source for subsequent import to P8.

 

 

 

 

 

 

Additional information on the first three formats is contained in the documentation for the P8 File Conversion Utility (1997), which is posted at the P8 website .  


Excel File Translation


Excel can be used to import precipitation data from external sources in any format.  The translation utility reads the first worksheet in the specified workbook. 

The worksheet is of the following form:

Cell A1  =   Title

Cell A2  =   "DATE_HOUR" 

Cell B2 =    "PRECIP"

Cell An  =   Date/hour of measurement, in Excel date/time format; start of hour, i.e.  12/01/01 0 = midnight to 1 am,   12/01/01 23 = 11 pm to midnight

Cell Bn  =   Hourly precipitation (inches)

 

Rules are the following:

  • number of records (n) must be < 60,000
  • records in increasing order by date/hour
  • date/hour gaps are permitted (missing records will be assumed to have 0 precipitation)
  • the output file will exclude days with zero precipitation
  • see sample input file 'precipitation.xls'