If the user wishes to use RTTOV, download and install the RTTOV v11 library before compiling WRFDA. This library can be downloaded from http://nwpsaf.eu/deliverables/rtm/index.html. The RTTOV libraries must be compiled with the “emis_atlas†option in order to work with WRFDA; see the RTTOV “readme.txt†for instructions on how to do this. After compiling RTTOV (see the RTTOV documentation for detailed instructions), set the “RTTOV†environment variable to the path where the lib directory resides. For example, if the library files can be found in /usr/local/rttov11/gfortran/lib/librttov11.*.a, you should set RTTOV as: