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2m temperature is too low

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I run a case with WRF-BEP model(WRF version is in summertime, but the values of 2m temperature are 2-4deg lower than observation, especially between sunset and sunrise. Can you give me some advice to fix it?
By the way, I use the standard USGS classes which has only 1 type of urban surface. Is it right to reset the parameters of class 2(High density residential) in URBPARM.TBL if I'd like to modify the urban parameters?

I will appreciate for you warm help and following is the physics part of my namelist file.
mp_physics = 3, 3, 8,
ra_lw_physics = 4, 4, 4,
ra_sw_physics = 4, 4, 4,
radt = 30, 30, 30,
sf_sfclay_physics = 2, 2, 2,
sf_surface_physics = 2, 2, 2,
bl_pbl_physics = 2, 2, 2,
bldt = 0, 0, 0,
cu_physics = 1, 0, 0,
cudt = 30, 0, 0,
isfflx = 1,
ifsnow = 1,
icloud = 1,
surface_input_source = 1,
num_soil_layers = 4,
num_land_cat = 24,
sf_urban_physics = 0, 0, 2

Would you please look at other variables in your case, such as albedo, cloud fraction, short and long wave radiation, etc.? These information may give you some hints why the T2 is abnormally low. We need to know the reason why before we can fix the problem.
The WRF performance is highly case-dependent. It is hard for us to look into individual user's case and come up with a solution how to improve the simulation. Therefore, user feedback is important for us to get ideas about the model performance and possible methods to improve it.
Thank you Ming, I will check it and find out the problem. :)

And I have some another questions about the urban model:
1. There is a file named URBPARM.TBL in ../WRF/run, it defines some parameters such as albedo,emissivity and so on of built-up area. However, I found that in ../WRF/phys, some code file such as module_sf_noahdrv.F, also defines the values of albedo, emissivity and some other parameters. If I'd like to change surface albedo or emissivity, which file to modify will work?
2. In the code or TBL file I mentioned before, there are 3 values represent 3 different 3 types of urban classes, but I use the default USGS classes which only has 1 type of urban class. Is that right to modify the second value only?

Thanks again!

Best Regards,
Hi Tina,
I would like to apologize for the long delay in a response to your most recent questions. It seems this must have been overlooked. Were you able to figure out what you need to know?