Land-Surface Models in MM5 Version 3
How to run PX LSM (provided by J. Pleim)
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).
To run the PX LSM/PBL certain switches need to be set in Terrain
and MM5. Also, there is an additional preprocessor (Interppx) which
may be used to initialize soil moisture and temperature from a previous
run.
TERRAIN
In terrain.deck, set script variables:
LSMDATA = .TRUE.
VEGTYPE = 1
IEXTRA = .TRUE.
INTERPPX (optional)
Interppx is a new preprocessor used to initialize soil moisture,
canopy moisture, and soil temperature from a previous run when simulation
time periods overlap. This can be use to create a continuous simulation
of these parameters across a series of runs. Interppx
is only needed when the switch ISMRD=1 (see below). It should be
run after Interp and before MM5. Interppx reads an MMOUT file from
a previous run and the MMINPUT file for the current run. The canopy
moisture content and soil moisture and temperature in the two model
soil layers (SMCA and STCA arrays) for the current run's initial
date and time are read from the previous MMOUT and the MMINPUT file
is rewritten with these arrays added.
MM5
To use the PX LSM set ISOIL=3 and IBLTYP=7 in configure.user prior
to compilation. Currently the PX LSM model includes it's own PBL
scheme (ACM), therefore IBLTYP=7 must be selected too.
Also, at this release (V3.4), the nest initialization is only limitted
to IOVERW=1 option. That means one must prepare MMINPUT files for
all the nest. One can do so by either running REGRID and then INTERPF
for the nest domains without running an objective package (such
as RAWINS or LITTLE_R). Or one can use NESTDOWN with MMINPUT_DOMAIN1
and nest TERRAIN file to generate nest MMINPUT files. (mesouser's
note)
There are three new namelist switches for the PX LSM:
1. ISMRD: select option for soil moisture initialization
2. NUDGE: activate soil moisture nudging
3. IFGROW: select vegetation growth option.
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ISMRD
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0
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set initial soil moisture according to MAVAIL (no soil moisture
data needed)
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1
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initialize soil moisture and temperature from MMINPUT. This
option is used to create continuos soil moisture and soil
temperature across a
series of runs. The soil moisture and temperature data must
be added to MMINPUT in the SMCA and STCA arrays by running
the preprocessor Interppx.
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2
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interpolate initial soil moisture from Eta or NNRP. This
option initializes soil moisture only in a way similar to
the OSU LSM. Follow the
instructions in Appendix D of the Tutorial notes to run Regrid
to produce the SOILMnnn arrays.
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note that for ISMRD = 0 or 2 soil temperature is initialized
in the same way as SLAB
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NUDGE
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0
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no soil moisture nudging
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1
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do soil moisture nudging. This requires surface FDDA grid
analyses.
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IFGROW
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0
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interpolate LAI and vegetation fraction between maximum and
minimum values for each grid cell from monthly VEGFRC data
(from Terrain)
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1
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read planting dates for every grid cell and use growth curves
for crops. State of natural vegetation is estimated according
to deep soil
temp in the PX model. Note that this option requires an additional
ASCII input file for planting dates (user provided).
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2
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same as IFGROW=1 except no planting dates are input. Emergence
dates are estimated from VEGFRC.
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Note that the IFGROW = 1 or 2 options are intended
for more realistic treatment of crop emergence and growth
in the spring and summer. Currently, there is no provision
for the autumn harvest.
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Default settings are ISMRD = 0, NUDGE = 0, IFGROW
= 0
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Note that the PX LSM conditionally uses a maximum internal time
step of 40s (depending on heat flux and friction velocity). Therefore,
for coarse resolution runs (greater than about 15 km) where the
model time step is longer than 40s, the PX LSM will be significantly
slower than other options. However, at finer resolutions, run times
should be comparable.
References
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, 2000, Development of a land surface model
part I: Application in a mesoscale meteorology model. Accepted by
J. Appl. Meteor.
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