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MM5 Modeling System Version 3

WHAT'S NEW IN MM5 VERSION 3 SINCE ITS RELEASE IN JULY 1999?

release-3-7 (12/23/04)

ITPDIFF = 2

Horizontal diffusion modifications. This allows for diffusion to be calculated truly horizontal.

TDKORR

This option is only active if the new horizontal diffusion option (ITPDIFF=2) is switched on.
Temperature gradient correction for horizontal diffusion at ground level uses:
=1; ground temperature, or
=2; one-sided difference of air temperature.

LEVSLP & OROSHAW

Solar slope and topography shadowing effects are included with two new switches, LEVSLP and OROSHAW. LEVSLP indicates the nest level at which solar radiation start accounting for orography. (This will correspond to LEVIDN). This is only recommended for very high resolution model runs. To switch this off, set LEVSLP equals to a large number like 9. OROSHAW include the effect of orography shadowing. This only has an effect if LEVSLP is also set. OROSHAW is NOT included in the MPP version of the code.

ISOIL = 2

The Noah LSM now has urban effect, and considers emissivity in computing surface temperature. The second change generally increases the amplitude of the diurnal cycle.

IPOLAR = 1

The polar physics, which has been available in the code since version 3-6, was added to the MRF PBL scheme (previously only available with the Eta PBL).

ISFMTHD = 1

New switch to allow for a different way to diagnose 2 m temperature/moisture and 10 m winds in stable regime. The general impact in a stable regime would be cooler temperature and weaker winds.

IFRSFA

A new logical flag was added that works in conjunction with the existing variable CDATEST. This was added to ensure the correct start time during a restart run, which makes use of multiple input files, and FDDA switched ON.

Example: If you have 2 sets of input files,
MMINPUT_DOMAIN1_01 ; BDYOUT_DOMAIN1_01 ; LOWBDY_DOMAIN1_01 and
MMINPUT_DOMAIN1_02 ; BDYOUT_DOMAIN1_02 ; LOWBDY_DOMAIN1_02,
the first set is for January 2005 and the second set is for February 2005.
You plan on running the model initially for the month of January , then do a restart and run for the month of February.

If you do NOT use FDDA:
you will need MMINPUT_DOMAIN1_01 ; BDYOUT_DOMAIN1_01 ; LOWBDY_DOMAIN1_01 for your initial run, and
MMINPUT_DOMAIN1_01 ; BDYOUT_DOMAIN1_02 ; LOWBDY_DOMAIN1_02, for the restart run - in this case, you do NOT need to set the flag IFRSFA.

If however, you DO USE FDDA:
you will need MMINPUT_DOMAIN1_01 ; BDYOUT_DOMAIN1_01 ; LOWBDY_DOMAIN1_01 for your initial run, and
MMINPUT_DOMAIN1_02 ; BDYOUT_DOMAIN1_02 ; LOWBDY_DOMAIN1_02, for the restart run - in this case, you NEED to set the flag IFRSFA, AND set CDATEST to correspond to the start date of your INITIAL run (i.e., in this case 2005-01-01).

ITADVM & IQADVM = 1

This allows for the use of an instability limiter when calculating advection. ITADVM, switches the temperature advection code on, and IQADVM switches the moisture advection code on. This may have a benefit when using the new diffusion scheme (ITPDIFF=2) and in high-resolution, complex terrain domain.

IMPHYS=7

Updates to the Reisner 2 include:

• Bug fix to the Berry/Reinhardt autoconversion. The required minimum diameter of ice is set to greater than 100 microns before riming ice. This is based on Pruppacher and Klett (1997).
   
• Modifications were made to the rain y-intercept value, RONV, (parameters in paramr.F) to eliminate "rain-gush" effect.
   
• Added parameter xnu calculated from CNP to make maritime CCN use broad drop spectra but narrow the distribution (decrease dispersion) as CNP increases to continental values. Net effect: increase autoconversion for maritime CNP values; little change for continental.
   
• Assigned min fallspeed of cloud ice to 0.3 m/s, and changed aggregation of cloud ice according to new fallspeed.
   
• With the new Berry & Reinhardt autoconversion, users may need to adjust the value of the CNP parameter (in paramf.F) to a value appropriate for their simulation conditions.
  If one has a very maritime or continental CCN distribution, this value is meant to be tuned. It is currently set to a value of 100.E6 (100 per cc) which is a compromise. Values could range from of 25 to 250 per cc, depending on the cloud drop concentrations of the case.

Optimized routines to ensure faster run times.

Some routines have been optimized to improve model runs times. The new routines especially improve run times on IBM computers.

In order to give users a choice, both the optimized and original code are available. To switch to the optimized code, "-DIBMopt" needs to be added to the compiler flags in configure.user. Users must also use the "massv" library to compile. If this library is not available, a second flag "-DvsLIB" needs to be added to the compiler flags. During tests runs on the IBM, most of these changes reduced run times by approximately 2%.

The optimization to the exmoisr routine reduced run times by up to 20%. This routine can be switched on separately from the other optimization routines, by setting MPHYSTBL=2 in the configure.user file. If this option is used, users must either include the "massv" library or add the compiler flag "-DvsLIB".

New compiler flags.

Compiler flags for the Cray X1 and INTEL compilers were added.

release-3-6 (12/19/02)

ISOIL=2

The OSU LSM model before V3.6 is replaced in this new release with an updated version which unifies the codes between AFWA AGRMET, NCEP Eta/LDAS, and NCAR MM5. This version is referred to as Noah LSM. The new features include:

• Frozen soil physics,
• Snow pack upgrade:
  • Fractional snow cover,
  • Time-varying snow density,
  • Roughness length calculation over snow covered area,
  • Snow albedo calculation.
• Ground heat flux upgrades:
  • New soil thermal conductivity,
  • Under snow pack,
  • Vegetation reduction of thermal condition.
• Vegetation model upgrade:
  • Rooting depth dependent on vegetation types.
• Soil model upgrade:
  • Lower boundary condition for soil temperature at 8 meters.

The new Noah LSM may use two types of new data (ingested through REGRID):

• Monthly 0.15 degree global background albedo based on 5-year climatology AVHRR/NDVI data;
• 1-degree global maximum snow albedo.

These data may be read in by the model using new namelist variables:

• RDBRDALB: set it to .TRUE. if you want to use the monthly albedo data;
• RDMAXALB: set it to .TRUE. if you want to use the maximum snow albedo data;

IPOLAR=1

This switch in configure.user activates polar physics modifications from Ohio State University. The polar physics modifications will allow for effects of sea-ice fraction, fluxes within sea-ice and snow/ice in slab, surface fluxes over ice in the Eta PBL, Meyers ice nuclei conc in the simple and Reisner1 microphysics schemes, and modified permanent ice properties in LANDUSE.TBL. Sea-ice can be diagnosed from SST (namelist variable IEXSI=1), or fraction data is read in (IEXSI=2) from LOWBDY file.

Note: At this time, the polar physics modification can not be used in combination with the updated Noah LSM.

Click here to see information on how to obtain fractional sea ice data from National Snow and Ice Data Center.

IMPHYS=7

The Reisner 2 scheme has been updated to

• Change snow-to-graupel conversion;
• Change Kessler autoconversoin for Berry and Reinhardt scheme implemented as in Walko et al. (1995);
• Include Schmidt number to one-third power (0.84) in PREI, PRE, PMLTEV.
• With some simple change, the scheme may be called at every 2 or 3 time steps. (Information coming soon.)

IFSNOW=2

Account for the melting of snow in the simple snow model added to MM5 in V3.5.

release-3-5 (12/5/01)

ICUPA=8

A new Kain-Fritsch scheme is available in this release. This scheme has several improvements over the previous one:

• shallow (non-precipitating) convection is allowed for any updraft that does not reach minimum cloud depth for precipitating clouds;  this minimum depth varies as a function of cloud-base temperature;
• A minimum entrainment rate is imposed to suppress widespread convection in marginally unstable, relatively dry environments;
• Entrainment rate is allowed to vary as a function of low-level convergence;
• Downdraft changes:
  • source layer is entire 150 - 200 mb deep layer just above cloud base;
  • mass flux is specified as a fraction of updraft mass flux at cloud base; fraction is a function of source layer RH rather  than wind shear or other parameters, i.e., old precipitation efficiency relationship not used;
  • detrainment is specified to occur in updraft source layer and below.

Click here for a paper by Kain that describes the details of the changes.

IFSNOW=2

A simple snow model is implemented. This option is controlled by IFSNOW=2, and can be used when a land-surface model is not used. This option requires water equivalent snow depth (or WEASD) as input, and output snow depth in the output (SNODPTH). This scheme is an additional capability in slab.F, and hence applicable to all PBL schemes that call slab.F (which are Blackadar, Eta, MRF, Gayno-Seaman and bulk PBL). It also requires explicit prediction of snow and it is implemented with microphysics options of simple ice, Reisner I and II schemes. The scheme uses heat and moisture budget to update the snow amount based on precipitation, melting and sublimation. It assumes melted snow runs off, and allows albedo and moisture availability to change with snow cover. It still uses 5-layer soil model beneath the snow.

IFSNOW=1

If the input to MM5 contains time-varying snow cover data, then the model will allow direct update of the field at the time frequecy the data are available.

ICLOUD=1 for CCM2

An option to use CCM2 radiation scheme that interacts directly with model predicted clouds is included. This option is controlled by ICLOUD = 1. Set ICLOUD =2, if one wants to use the old option of using CCM2 scheme with relative humidity.

IZ0TOPT

This is a new namelist option that controls how thermal roughness is computed in the Blackadar and MRF PBL schemes.
IZ0TOPT = 0: old Carlson-Boland method. It also uses different thermal roughness for heat and moisture. It uses same formula for land and water.
IZ0TOPT = 1: Garratt formula. It uses the same thermal roughness for heat and moisture. It uses different formula for land and water.
IZ0TOPT = 2: Zilitinkevich formula. It too uses the same thermal roughness for heat and moisture. It also uses different formula for land and water.

Time-Varying Green Vegetation Fraction

This is implemented to allow green vegetation fraction to be updated every day. This is for land-surface model option only.

Coupling OSU LSM with Eta PBL

This means ISOIL=2 works with IBLTYP=4 options.

Outputing 2 m temperature, mixing ration and 10 m winds

This is implemented in MRF (release-3-4), Blackadar, and Eta PBL.

release-3-4 (10/6/2000)

IFTSOUT, ITSN, JTSN

IFTSOUT = .FALSE.,	;	TRUE = output time series; FALSE = do not output time series
TSLAT   = 39.75, 35.33,	;	latitude values of time series points
TSLON  = -104.87, -97.47,	;	longitude values of time series points

Output option to write out time series of a number of surface fields to Fortran units (25 + inest). The default maximum number of points is 30. But a user may modify parameter ITSDIM in include/parame to increase that number. The user specified input include an on/off switch, IFTSOUT, and latitudes (TSLAT) and longitudes (TSLON) of the time-series output points. All are added to namelist section OPARAM. The model turns them into closest (x,y) location on the model grid. Note that western longitudes are negative.

The currect time-series output include:

forecast time (in minutes),

Nth time series,

I and J locations of the time series,

'surface' temperature (K),

2-m or lowest sigma level's mixing ratio (kg/kg),

10-m or lowest sigma level u and v wind component (m/sec) (Note: the wind components have been rotated to earth-coordinate since V3.6 released in Dec. 2002),

reference p* (cb or 10xhPa),

perturbation pressure (Pa),

accumulative convective and non-convective precipititation (cm),

column-integrated cloud water (mm),

surface downward long-wave radiation (W/m^2),

surface sensible heat flux (W/m^2) and moisture flux (x 2.5E6 -> latent heat flux in unit of W/m^2),

surface downward short-wave radiation (W/m^2),

and ground temperature (K).

If you choose MRF, Blackadar or Eta PBL, then the time series output 2 m temperature and mixing ratio, and 10 m u and v.

Two simple plotting routines, time-series.f and time-series-rad.f, can be found from the ftp site. Sample plots from these programs can be found from MM5 real-time forecast page.

ISSTVAR

ISSTVAR = 0,

This namelist switch (under namelist section LPARAM) controls whether a user wants the SST (sea-surface temperature), sea ice and snow cover (if they are available) to vary during a long model integration. This requires the user to use INTERPF version 3.4 which produces the time-varying fields in LOWBDY file. A user must use this option with caution. True SST field must be used here in order to define the land-water boundary correctly in the model. (A field that varies abruptly across land-water boundary may not be considered as an SST, since if the land-water boundary is different in the incoming dataset and in MM5, it will cause ill-defined water temperature near land-water boundary.)

IMOIAV

IMOIAV = 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,     ;

This is old namelist switch (under namelist section LPARAM) reactivated to control the use of a simple soil moisture bucket scheme. This scheme considers rainfall, evaporation and runoff from the surface, and modifies the model's moisture availablity parameter. The bucket model may be used with PBL options 1, 2, 4, 5 and 6, or bulk, Blackadar, Eta PBL, MRF PBL, and Gayno-Seaman PBL. It takes values 0, 1 and 2.

IMOIAV=0: the bucket model is not used.

IMOIAV=1: the bucket model is used, but the moisture availability from LANDUSE.TBL is used to start the model

IMOIAV=2: the bucket model is used, and the initial moisture availability is estimated from the 10 cm-layer volumetric soil moisture (as required to initialize LSM option in MM5). The conversion equation (in rdinit.F) is empirical and based on experience working with RUC data over US. It may not be applicable everywhere.

SOILFAC

SOILFAC = 1.0,  ; a factor to control sub-soil time step when ISOIL=1

This switch is added (under namelist section PPARAM) to allow a user to adjust sub-soil time step used in the 5-layer soil model (ISOIL=1). To make the soil time-step smaller, set SOILFAC greater than 1.

Pleim-Xiu LSM ( ISOIL=3 and IBLTYP=7):

This is a new addition to MM5, and is developed by J. Pleim and A.-J. Xiu of EPA. The PX PBL is a combined land-surface and PBL model with indirect soil moisture nudging (Pleim and Xiu 1995; Xiu and Pleim, 2000).  Development and evaluation have focused on realistic surface heat and moisture fluxes and PBL development responding to spatial and temporal variations in moisture and vegetation conditions. It is particularly well suited for extended (weeks to months) retrospective simulations where the data assimilation scheme provides realistic tracking of moisture and vegetation trends.  The PX LSM includes explicit simulation of soil moisture and temperature in two layers (surface - 1 cm and root zone - 1 m) as well as canopy moisture.  There are three pathways for evaporation: soil surface, canopy, and evapotranspiration.  Grid cell aggregate surface parameters are derived from fractional land use and soil texture data provided by Terrain.  The PBL scheme is a derivative of the Blackadar model called the Asymmetric Convective Model (ACM) (Pleim and Chang, 1992). (Provided by J. Pleim)There are additional namelist variables used with this scheme. They are defined under namelist section LPARAM and are: ISMRD (=0, 1, 2 for soil moisture initialization), NUDGE (=0, 1), and IFGROW (=0, 1).

Pleim, J. E. and A. Xiu, 1995.  Development and testing of a surface flux and planetary boundary layer model for application in mesoscale models. J. Applied Meteorology, 34, 16-32.

Pleim, J. E., J. S. Chang, 1992.  A non-local closure model for vertical mixing in the convective boundary layer. Atm. Env., 26A, 965-981.

Xiu, A. and J. E. Pleim, 2001, Development of a land surface model part I: Application in a mesoscale meteorology model.  J. Appl. Meteor., 40, 192-209.

release-3-3 (1/25/2000)

FRAD = 4

A new and more accurate longwave radiation scheme is available in this release - it may be referred to as RRTM which stands for Rapid Radiative Transfer Model (Mlawer et al. 1997). It uses the same shortwave radiation scheme as in the cloud radiation option (FRAD=2). This new option is listed as FRAD=4. It is roughly 5% more expensive to run. 

release-3-2 (9/27/99)

ISTLYR and ISMLYR

The model is modified to be flexible in reading input soil temperature and moisture data. This is done through namelist variables ISTLYR and ISMLYR (currently hidden). It was fixed to read only 3-level soil temperature and 2-level soil moisture. If a user has soil temperature and moisture data at different layers than those MM5 expects (these are 10, 200 and 400 cm soil temp, and 10 and 200 cm soil moisture fields), the layers can be specified using these two namelist variables. For example, if one only has two-layer soil temperature at 10 and 200 cm, you can add ISTLYR under namelist section LPARAM like this,

ISTLYR = 10, 200, 0, 0,    ;

Similar format may be used to define new soil moisture layer.

A list of hidden namelist parameters that may be set in PPARAM

SOLSET = -999.,

This allows setting solar constant. A value < 0 means to use standard formula.

CZO = .0032,	;	Charnock constant
OZO = 1.E-4,	;	background value for roughness value over water
IFDTSET=.FALSE.,	;	=.T. ALLOWS SETTING DTIME USED IN CALCULATING LARGE-SCALE FORCING
DTIMSET=900.,
PBCMAX=50.,	;	PBCMAX IS MAX ALLOWED DEPTH (MB) OF STABLE LAYER BETWEEN LCL AND LFC
IFCDZ=.FALSE.,	;	WHETHER TO LIMIT CLOUD DEPTH IN TERMS OF HEIGHT
CDMINZ=1000.,	;	MINIMUM CLOUD DEPTH IN METERS USED IF IFCDZ=.TRUE.
CDMINP=150.,	;	MINIMUM CLOUD DEPTH IN PRESSURE (MB) USED IF IFCDZ=.FALSE.
EDTMIN=0.2, EDTMAX=0.8,	;	LIMITS OF PRECIP EFFICIENCY
EDTSMN=0.3, EDTSMX=0.9,	;	LIMITS FOR SHEAR DEPENDENCE (SETTING SAME WILL REMOVE EFFECT)
TCRIT=273.15,	;	FREEZING IN UPDRAFT BELOW THIS TEMPERATURE
SIGCBHI=0.7,	;	MAXIMUM CLOUD BASE HEIGHT ALLOWED IN TERMS OF SIGMA
PKDCUT=75.,	;	DEPTH OF DOWNDRAFT DETRAINMENT (MB)
CUQMAX=500., CUQMIN=-250.,	;	LIMITS ON CONVECTIVE HEATING/COOLING
TREL = 3000.,	;	Relaxation time used in Betts-Miller scheme.
RAD  = 1500.,	;	Cloud radius assumed in Kain-Fritsch scheme.
BFAC = 2.,	;	Constant used in computing b parameter in Anthes-Kuo scheme.
VCONVC = 2.,	;	Constant used in computing convective velocity in PBL options 1,2 and 5.