This variable is used to calculate values for pcp_hhr.

This value is calculated by summing the maximum air temperature for every day in the month for all years of record and dividing the sum by the number of days:

where $μmx_{mon}$is the mean daily maximum temperature for the month $mon$ (ºC), $T_{mx,mon}$ is the daily maximum temperature on day $d$ in month $mon$ (ºC), and $N$is the total number of daily maximum temperature records for month $mon$.

The name of the weather generator station is a primary key referenced by wgn in weather-sta.cli.

This parameter is calculated as

where $d_{wet,i}$ is the average number of days of precipitation in month $i$, $days_{wet,i}$ is the number of wet days in month $i$ during the entire period of record, and $yrs$ is the number of years of record.

This parameter quantifies the variability in maximum temperature for each month. The standard deviation is calculated as

where $σmx_{mon}$is the standard deviation for daily maximum temperature in month $mon$ (ºC), $T_{mx,mon}$ is the daily maximum temperature on day $d$ in month $mon$ (ºC), $μmx_{mon}$ is the average daily maximum temperature for the month $mon$ (ºC), and $N$ is the total number of daily maximum temperature records for month $mon$.

The weather generator file contains weather generator data for any number of stations. For each weather generator station, there will be one line specifying the name of the station, its latitude, longitude, and elevation, and the number of years of maximum monthly 0.5 h rainfall data used to define values for pcp_hhr. There are no headers for this line. These variables are listed in the first table below. The second line for each weather generator station contains the headers for the following 12 lines, which list the weather generator data for each month of the year. An overview of the weather generator data variables is given in the second table below.

This value is calculated by summing the minimum air temperature for every day in the month for all years of record and dividing the sum by the number of days:

where $μmn_{mon}$is the mean daily minimum temperature for the month $mon$ (ºC), $T_{mn,mon}$ is the daily minimum temperature on day $d$ in month $mon$ (ºC), and $N$is the total number of daily minimum temperature records for month $mon$.

The probability is calculated as

where $P_i(W⁄W)$ is the probability of a wet day following a wet day in month $i$, $days_{W⁄W,i}$ is the number of times a wet day followed a wet day in month $i$ for the entire period of record, and $days_{wet,i}$ is the number of wet days in month $i$ during the entire period of record. A wet day is a day with > 0 mm precipitation.

This parameter quantifies the variability in minimum temperature for each month. The standard deviation is calculated as

where $σmn_{mon}$is the standard deviation for daily minimum temperature in month $mon$ (ºC), $T_{mn,mon}$ is the daily minimum temperature on day $d$ in month $mon$ (ºC), $μmn_{mon}$ is the average daily minimum temperature for the month $mon$ (ºC), and $N$ is the total number of daily minimum temperature records for month $mon$.

This value is calculated by summing the total solar radiation for every day in the month for all years of record and dividing the sum by the number of days:

where $μrad_{mon}$ is the mean daily solar radiation for the month (MJ/m2/day), $H_{day,mon}$ is the total solar radiation reaching the earth’s surface on day $d$ in month $mon$ (MJ/m2/day), and $N$ is the total number of daily solar radiation records for month $mon$.

The probability is calculated as

where $P_i(W⁄D)$ is the probability of a wet day following a dry day in month $i$, $days_{W⁄D,i}$ is the number of times a wet day followed a dry day in month $i$ for the entire period of record, and $days_{dry,i}$ is the number of dry days in month $i$ during the entire period of record. A dry day is a day with 0 mm of precipitation. A wet day is a day with > 0 mm precipitation.

This value represents the most extreme 30-minute rainfall intensity recorded in the entire period of record.

The average or mean total monthly precipitation is calculated as

where $R_{mon}$ is the mean monthly precipitation (mm H2O), $R_{day,mon}$ is the daily precipitation for day $d$ in month $mon$ (mm H2O), $N$ is the total number of records in month $mon$ used to calculate the average, and $yrs$ is the number of years of daily precipitation records used in calculation.

This parameter quantifies the symmetry of the precipitation distribution around the monthly mean. The skew coefficient is calculated as

where $g_{mon}$ is the skew coefficient for precipitation in the month, $N$ is the total number of daily precipitation records for month $mon$, $R_{day,mon}$ is the amount of precipitation for day $d$ in month $mon$ (mm H2O), $R_{mon}$ is the average precipitation for the month (mm H2O), and $σ_{mon}$ is the standard deviation for daily precipitation in month $mon$ (mm H2O). Daily precipitation values of 0 mm are included in the skew coefficient calculation.

This value is calculated by summing the average or mean wind speed values for every day in the month for all years of record and dividing the sum by the number of days:

where $μwnd_{mon}$ is the mean daily wind speed for the month (m/s), $T_{wnd,mon}$ is the average wind speed for day $d$ in month $mon$ (ºC), and N is the total number of daily wind speed records for month $mon$.

This parameter quantifies the variability in precipitation for each month. The standard deviation is calculated as

where $σ_{mon}$ is the standard deviation for daily precipitation in month $mon$ (mm H2O), $R_{day,mon}$ is the amount of precipitation for day $d$ in month $mon$ (mm H2O), $R_{mon}$ is the average precipitation for the month (mm H2O), and $N$ is the total number of daily precipitation records for month $mon$. Daily precipitation values of 0 mm are included in the standard deviation calculation.

If all twelve months are < 1.0, the model assumes the data provided is relative humidity. Relative humidity is defined as the amount of water vapor in the air as a fraction of saturation humidity. If any month has a value > 1.0, the model assumes the data provided is dewpoint temperature.

Dew point temperature is the temperature at which the actual vapor pressure present in the atmosphere is equal to the saturation vapor pressure. This value is calculated by summing the dew point temperature for every day in the month for all years of record and dividing the sum by the number of days:

where $μdew_{mon}$ is the mean daily dew point temperature for the month (ºC), $T_{dew,mon}$ is the dew point temperature for day $d$ in month $mon$ (ºC), and $N$is the total number of daily dew point records for month $mon$. Please refer to the SWAT+ Theoretical Documentation for the equations used to convert dew point to relative humidity.