Questions about ROMS surface forcing files

[qwdy]

Hello, everyone!

I'm a COAWST user and working on a ROMS-only application.When I try to create surface forcing files by 'ncei_2roms.m' using NARR and GFS dataset respectively, I can obtain two forcing files R1 and R2 successfully. But lwrad, swrad and rain are all 0 value in R2 due to GFS is lack of these variables while R1 has complete variables.I wonder know if I use R1 and R2 to run ROMS respectively, does their difference matter much to the model output? I attach the ncei_2roms.m file below.

Also about ncei_2roms.m, I was unable to create surface forcing file using NAM dataset correctly which all variables were assigned to 0. Though in line 14 it writes "NAM seems to be from 2017 to present", But I could find ealier data in it include 2012. I checked the url and variable names in the script but after running I got many messages like this: could not get that data at https://www.ncei.noaa.gov/thredds...Do you have any suggestion about this?

I tried to use ECMWF tools distributed by wilkin to create surface forcing file today. When I set up bbox fluxopt, year, month etc, I could get a E containing variables I need,but after I try to run roms_write_era5_NCARds633_frcfile.m, my matlab crashed down in the middle without any error. I guess it's my computer issue, but if it's possible to specify the date I need rather than whole month in the roms_get_era5_NCARds633_bulkflux.m?

I noticed ECMWF tools also include 2 scripts using GFS dataset. But I couldn't understand the input keywords ''romsvname'',''outcoords'' very well. Could somebody give me an example of how to use it?（The GFS dataset url in ncei_2roms.m between roms_get_gfs_NCARds083_bulkflux.m are different and cover different time periods）

Last, I have a confusion for some description about these dataset.For example:
Dataset: 20200508/gfsanl_4_20200508_0000_000.grb2,Dataset: 20200508/gfsanl_4_20200508_0000_003.grb2,Dataset: 20200508/gfsanl_4_20200508_0000_006.grb2
Dataset: 20200508/gfsanl_4_20200508_0600_000.grb2,Dataset: 20200508/gfsanl_4_20200508_0600_003.grb2,Dataset: 20200508/gfsanl_4_20200508_0600_006.grb2
I don't know what does the last 3 number mean? This maybe a question beyond ROMS field, but I don't know where to ask either.

So many questions in one time,I want to express my gratitude in advance for anyone help me.