site map - email us - search  
 

Back to Example List

Running MM5 with 3D & SFC FDDA

Input data needed:

  • MMINPUT_DOMAIN1 created with INTERPF
  • SFC_FDDA_DOMAIN1 created with LITTLE_R

To do FDDA, the input file MMINPUT_DOMAIN1 is open twice with different unit numbers. Some computers cannot do this (i.e., Linux / IBM computers).

If you obtain an error:

Cannot open fort.31, you have run into this problem
To overcome this problem
cp MMINPUT_DOMAIN1 MMINPUT2_DOMAIN1
 

If you plan on doing FDDA for nested domains, you need to create MMINPUT_DOMAINx files for the nested domains as well.

  • You may do this with REGRID/INTERPF, same as you created MMINPUT_DOMAIN1
  • Recommended: Use NESTDOWN to create the extra files (set IFDATIM=-1 in the NESTDOWN namelist.input file)
  • Set IOVERW=1 for nested domains

3D FDDA can be run without SFC FDDA, but SFC FDDA CANNOT be run without 3D FDDA.

configure.user

FDDAGD = 1

make clean
make

mm5.deck

IOVERW

Set this parameter to 1 for ALL domains on which FDDA will be performed (need MMINPUT_DOMAINx files for all these domains as well)

FDASTA & FDAEND

  • Start and end times for analysis nudging
  • Time is in minutes relative to model initial time
  • Start time MUST always be 0
  • Columns represent different domains
  • For Dynamical Analysis, set FDEND=TIMAX (may do this to create input for an air quality model). In this case FDDA will be on for the duration of the model run.
     
     
  • For Dynamical Initialization, FDEND=x, where x is the length of the pre-forecast data assimilation. This is used to improve model initial conditions and to reduce model spin-up.
     
     

I4D

  • First row indicates whether 3D FDDA is on(1) / off(0)
  • Second row indicates whether SFC FDDA is on(1) / off(0)
  • Columns indicate domains
  • These settings overwrite any other settings

DIFTIM

  • First row indicates time interval for analysis input data (MMINPUT_DOMAINx)
  • Second row indicates time interval for surface input data (SFCFDDA_DOMAINx)
  • Columns indicate domains

IWIND & GV ; ITEMP & GT ; IMOIS & GQ

  • Whether to nudge wind (IWIND), temperature (ITEMP) and moisture (IMOIS)
  • Nudging terms for wind (GV), temperature (GT) and moisture (GQ)
  • For numerical stability:
  • Average:
  • Typical:
  • If G terms are too small, they will have little effect
  • If G terms are to big:
    • The models' ability to resolve mass—momentum imbalances will be decreased
    • The models' ability to generate its own mesoscale structure will be impaired

IROT & GR

  • Nudging of rotational component of wind
  • Typical:
  • Not commonly used, or recommended

INONBL

  • PBL fields will be nudge from 3D analysis when NOT using surface nudging
  • Include PBL nudging (0), exclude PBL nudging (1)
  • It is recommended to NOT temperature and moisture in the PBL

RINBLW

  • Radius of influence of SURFACE analysis nudging
  • Used to determine the horizontal variability of the surface-analysis nudging as a function of surface data density
  • The influence will be full strength up to RINBLW/2, thereafter it will linearly decrease from 1 to 0.2 at RINBLW
     

 

IDYNIN

  • To use (1), not use (0) ramping during dynamic initialization

DTRAMP

  • The time period in minutes over which the nudging (obs nudging and analysis nudging) is ramped down from one to zero.
  • Set dtramp negative if FDDA is to be ramped down BEFORE the end-of-data time (FDAEND),


     
  • Set dtramp positive if FDDA ramp-down period extends beyond the end-of-data time


     

IOVERW =    1, 2, 0, 0, 0, 0, 0, 0, 0, 0, ; 
        ! FDDA will only be used for domain1
FDASTA=0.,0.,0.,0.,0.,0.,0.,0.,0.,0.
FDAEND=720.,0.,0.,0.,0.,0.,0.,0.,0.,0.,  
        ! Dynamical Initialization, 36 hour run - FDDA active for first 12 hours, one domain
I4D= 1,0,0,0,0,0,0,0,0,0,
     1,0,0,0,0,0,0,0,0,0,  
        ! 3D & SFC FDDA
DIFTIM=360.,720.,0.,0.,0.,0.,0.,0.,0.,0.,
       180.,180.,0.,0.,0.,0.,0.,0.,0.,0., 
       ! MMINPUT_DOMAIN1 has analysis data available every 6 hours 
       ! Interval between dataset in SFCFDDA_DOMAIN1 is 180.
IWIND=1,1,0,0,0,0,0,0,0,0,
      1,1,0,0,0,0,0,0,0,0,
GV=2.5E-4,1.0E-4,0.,0.,0.,0.,0.,0.,0.,0.,
   2.5E-4,1.0E-4,0.,0.,0.,0.,0.,0.,0.,0.,
ITEMP=1,1,0,0,0,0,0,0,0,0,
      1,1,0,0,0,0,0,0,0,0,
GT=2.5E-4,1.0E-4,0.,0.,0.,0.,0.,0.,0.,0.,
   2.5E-4,1.0E-4,0.,0.,0.,0.,0.,0.,0.,0., ;
IMOIS=1,1,0,0,0,0,0,0,0,0,
      1,1,0,0,0,0,0,0,0,0,
GQ=1.E-5,1.E-5,0.,0.,0.,0.,0.,0.,0.,0.,
   1.E-5,1.E-5,0.,0.,0.,0.,0.,0.,0.,0.,  
       ! Wind, temperature and moisture nudging for domain1 is on (Both 3D and SFC)
       ! All other "1" settings are ignored as "I4D" settings will 
       ! take precedence
       ! Default nudging coefficients are used 
IROT=0,0,0,0,0,0,0,0,0,0, ; 3D ANALYSIS NUDGING 
GR=5.E6,5.E6,0.,0.,0.,0.,0.,0.,0.,0., ; 3D ANALYSIS NUDGING
       ! No rotational nudging is used
INONBL =0,0,0,0,0,0,0,0,0,0, ; U WIND
        0,0,0,0,0,0,0,0,0,0, ; V WIND
        1,1,1,1,1,1,1,1,1,1, ; TEMPERATURE
        1,1,1,1,1,1,1,1,1,1, ; MIXING RATIO  
       ! Not used as we are including SFC nudging
RINBLW=250.,
       ! Radius of surface nudging is 250km
IDYNIN=1,  
       ! Ramp FDDA down
DTRAMP=60.,
       ! FDDA will be active for first 13 hours of run. First 12 hours at full strength,
       ! after which FDDA will be ramp down from 1 to 0
       ! ramping will be complete at hour 13
UCAR Privacy Policy - Terms of Use - ©2004UCAR