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Running MM5 with 3D FDDA (no SFC FDDA)

If you are only doing FDDA on domain one, you already have all the input data (MMINPUT_DOMAIN1) needed to do this.

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

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 FDAEND=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, FDAEND=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

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=1440.,0.,0.,0.,0.,0.,0.,0.,0.,0.,  
        ! Dynamical Analysis, 24 hour run, one domain
I4D= 1,0,0,0,0,0,0,0,0,0,
     0,0,0,0,0,0,0,0,0,0,  
        ! 3D FDDA , NO 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 
       ! The 180. on line 2 has no meaning as SFC FDDA is off
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 
       ! 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  
       ! PBL nudging will be used for wind (it is not recommended to nudge T and Qv in PBL)
IDYNIN=0,  
       ! We are doing Dynamic Analysis - not used
DTRAMP=60.,
       ! We are doing Dynamic Analysis - not used
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