Climatic Data

Minimum required climatic data are daily precipitation and monthly mean daily potential evaporation. Daily data are most often obtained as historic files, which usually contain measured precipitation and maximum-minimum air temperature, and less often have evaporation by various methods. Supplemental evaporation data estimates are described as "default" values for use when daily data are not available in the climatic file. The selection of the specific climatic data file, default file and adjustments for each study site are described in the "location climate" screen.

The model accommodates many combinations of available and estimated climatic data and provides adjustments for data sources being a distance from the study field and thus somewhat different. Climatic data are available from several sources such as the NOAA National Climatic Data Center or USDA/National Water and Climate Center. Climatic files generally include daily precipitation and max/min air temperature, but may also include evaporation, snow depth, etc. The climate files, labeled "xxx.txt", are manually copied into the SPAW directory at: "SPAW Hydrology/SPAW/Database/Climates/Data".

If potential evaporation methods, such as the Penman-Monteith or Thornthwaite equations, are to be used, these calculations would be made separately before the simulation and the values placed in a climatic data file column with a corresponding heading "evap". The values may be entered using the CLIMATE DATA screen editor or any common spreadsheet program saved in text format with proper headings and order with tab delimiters between columns, then copied into the "Data" directory.

The "*.txt" climatic files must be in a specific format for access by the SPAW model and its CLIMATE DATA editor. The first line must be of the exact format and wording as follows: "XXXXXX-date ^ tmax ^ tmin ^ prcp ^ evap", where the XX is a six digit station identification, "^" symbol denotes a single tab either side, and the designators must be spelled exactly as shown, although the order can be varied if the data are in another column arrangement. Additional data can be included, tab delimited, and will be ignored by the read routine. The date is in the format "mo-da-yr", e.g. 021598 for Feb. 15, 1998.

An example first three lines of a climatic data file (xxx.txt) would be as follows:
WA6789-date tmax tmin tavg prcp snwd snow stn1 stn2 stn3 stx1
100160 73.00 38.00 55.50 0.00 0.00 0.00
100260 78.00 39.00 58.50 0.00 0.00 0.00

The file finder of "climatic data" shows all pre-loaded climatic data files. Opening a file initiates a climatic data editor to assist in modifying or checking the file data. The daily data are displayed in spreadsheet form and a checking routine provides identifying missing and out-of-range values. The data check routine generates a report file that can be saved or printed. Any edited changes in the climate data screen will by saved into the file if the "save & exit" button is used to close the screen.