Problem with CLDFRA when progn=1

[Rui Pedro Silva]

Dear all,

I am running WRF-Chem v4.1.3 to study aerosol-radiation-cloud interactions using chem_opt=10 (i.e., CBMZ-MOSAIC 8-bin AQ) and with icloud=1 (i.e., cloud fraction calculated based on Xu and Randall 1996). 

When running the model with aerosol indirect effects turned on (i.e., progn=1) CLDFRA values are either 0 or 1. However, with icloud=1 I should get CLDFRA values that are between 0 and 1.

I did several tests, including running the model with only direct effects using chem_opt=8  (i.e., CBMZ-MOSAIC 8-bin), and running WRF model without chemistry. In all the tests, I get continuous CLDFRA values. It is only when I turn on progn that I get binary values.

Why is this happening?

Here are my &physics and &chem options:

 &physics                                
 mp_physics           = 10, 10, 10,     ! (max_dom) Morrison double-moment
 ra_lw_physics        = 4, 4, 4,        ! (max_dom) RRTMG LW
 ra_sw_physics        = 4, 4, 4,        ! (max_dom) RRTMG SW
 radt                 = 36, 36, 36,     ! (max_dom) 1 minute per dx in km. Use the same value for   all nests
 slope_rad       = 1, 1, 1,
 topo_shading       = 1, 1, 1,
 swint_opt       = 1,
 sf_sfclay_physics    = 1, 1, 1,        ! (max_dom) Revised MM5
 sf_surface_physics   = 2, 2, 2,        ! (max_dom) Noah LSM
 bl_pbl_physics       = 5, 5, 5,        ! (max_dom) MYNN 2.5        
 bldt                 = 0, 0, 0,   ! (max_dom) Call every time_step    
 cu_physics           = 5, 5, 0,        ! (max_dom) Grell 3D
 cugd_avedx       = 1,              ! only works with Grell 3D cumulus scheme      
 cudt                 = 0, 0, 0,     ! (max_dom) Call every time_step  
 do_radar_ref         = 1,
 isfflx               = 1,
 ifsnow               = 0,
 surface_input_source = 1,
 num_soil_layers      = 4,
 sf_urban_physics     = 0,    
 seaice_threshold     = 0.0,
 fractional_seaice    = 1,
 sst_update       = 1,
 num_land_cat       = 33,
 cu_rad_feedback      = .true., .true., .false.,
 cu_diag              = 1, 1, 0,

 icloud = 1,  
 progn                = 1, 1, 1, 

/

 &chem
 chem_opt = 10, 10, 10,  
 chem_in_opt = 1, 1, 1,
 io_style_emissions = 2,
 chemdt = 0, 0, 0,
 bioemdt = 30, 30, 30, 
 kemit = 1,
 photdt = 30, 30, 30, 
 phot_opt = 2, 2, 2, 
 emiss_opt = 3, 3, 3,  
 gas_drydep_opt = 1, 1, 1,
 aer_drydep_opt = 1, 1, 1, 
 bio_emiss_opt = 3, 3, 3,
 ne_area = 300, 
 emiss_inpt_opt = 101, 101, 101,  
 biomass_burn_opt = 2, 2, 2,  
 plumerisefire_frq = 30, 30, 30, 
 dust_opt = 13, 
 seas_opt = 2,
 aer_op_opt = 1, 1, 1,  
 opt_pars_out = 1, 
 gas_bc_opt = 16, 16, 16,  
 gas_ic_opt = 16, 16, 16, 
 aer_bc_opt = 1, 1, 1,
 aer_ic_opt     = 1, 1, 1,
 gaschem_onoff = 1, 1, 1, 
 aerchem_onoff = 1, 1, 1, 
 wetscav_onoff = 1, 1, 1, 
 cldchem_onoff = 1, 1, 1, 
 chem_conv_tr = 1, 1, 0,   
 vertmix_onoff = 1, 1, 1, 
 conv_tr_wetscav = 1, 1, 1,
 conv_tr_aqchem   = 1, 1, 1,
 have_bcs_chem   = .true., .false., .false., 
 aer_ra_feedback = 1, 1, 1, 
 /

Kind regards,

Rui Silva