1:1.3.1 Daily Air Temperature

Daily Air Temperature SWAT+ requires daily maximum and minimum air temperature. This data may be read from an input file or generated by the model. The user is strongly recommended to obtain measured daily temperature records from gages in or near the watershed if at all possible. The accuracy of model results is significantly improved by the use of measured temperature data.

The variable TMPSIM in the master watershed (file.cio) file identifies the method used to obtain air temperature data. To read in daily maximum and minimum air temperature data, the variable is set to 1 and the name of the temperature data file(s) and the number of temperature records stored in the file are set. To generate daily air temperature values, TMPSIM is set to 2. The equations used to generate air temperature data in SWAT+ are reviewed in Chapter 1:3. SWAT+ input variables that pertain to air temperature are summarized in Table 1:1-5.

Table 1:1-5: SWAT+ input variables that pertain to daily air temperature.

Variable Name	Definition	File Name
TMPSIM	Air temperature input code: 1-measured, 2-generated	file.cio
NTGAGE	Number of temperature gage (.tmp) files used in simulation file (required if TMPSIM = 1)	file.cio
NTTOT	Number of temperature records used in simulation (required if TMPSIM = 1)	file.cio
NTFIL	Number of temperature records within each .tmp file file (required if TMPSIM = 1)	file.cio
TFILE	Name of measured temperature input file (.tmp) Up to 18 files may be used. (required if TMPSIM = 1)	file.cio
ITGAGE	Number of temperature record used within the subbasin (required if TMPSIM = 1)	.sub

See description of .tmp file in the User’s Manual for input and format requirements if measured temperature data is being used.