Hi Tewekel,
Do you have a Routelink? If you have a routelink setup, there is a function in rwrfhydro (https://github.com/NCAR/rwrfhydro) which creates the file for you. It is basically creating a netcdf file with all the parameters based on the gauges that are specified in the Routelink file. The number of gauges in this file should match the ones in the Routelink. Below is a short R code snippet to help you generate the file, note the values defined for G, R, Tau, gageExpCoeff1 and gageParamQThresh1 could be changed if you want. For more information, please refer to the documentation:
# read the list of gages from the Routelink file
library(rwrfhydro)
gageParams <- list()
rtlink <- rwrfhydro::ReadRouteLink("PATH_TO_ROUTLINK/RouteLink.nc")
gageParams$gageId <- subset(rtlink, trimws(gages) != "")$gages
gageParams$G <- rep(1, length(gageParams$gageId))
gageParams$R <- rep(0.25, length(gageParams$gageId))
gageParams$tau <- rep(15, length(gageParams$gageId))
gageExpCoeff1 <- array(rep(c(120),each=length(gageParams$gageId)*12),dim=c(length(gageParams$gageId),12,2))
gageParamQThresh1 <- array(rep(c(-100),each=length(gageParams$gageId)*12),dim=c(length(gageParams$gageId),12,1))
MkNudgingParams(gageId=gageParams$gageId, R=gageParams$R,
G=gageParams$G, tau=gageParams$tau,
qThresh=gageParamQThresh1,
expCoeff=gageExpCoeff1,
outFile=paste0("PATH_TO_OUTPUT_DIR/nudgeParam.nc"),
overwrite=TRUE, rmBlankGages=TRUE)
Hope this helps you!
Arezoo