[Wrf-users] Question regarding determine some parameters in namelist.wps

[Zhixuan Cao]

Hi 
I feel confused on the exact meaning of some parameters in namelist.wps, following user manual can not solve my confusion. Could someone give me some advice on this? 

Here do these following parameters work together to determine the resolution of grids for nested domain simulation? 
parent_grid_ratio
i_parent_start 
j_parent_start
e_we
e_sn
geog_data_res

1) If geog_data_res gives resolution of grid, then it seems that I do not need e_we and  e_sn.
2) For nested domain simulation, should geog_data_res be consistent with parent_grid_ratio? For example, if parent_grid_ratio = 1, 3 then geog_data_res has to be something like geog_data_res = 9m, 3m.
3) In the tutorial, it says that ( e_we = n* parent_grid_ratio +1) and ( e_sn = n* parent_grid_ratio +1).  I guess I can use different n for e_we and  e_sn. Am I right? But is there any constrain on n besides that n has to be a positive integer? 

Thank you very much!

Zhixuan Cao