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.

ISMRD	0	set initial soil moisture according to MAVAIL (no soil moisture data needed)
	1	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.
	2	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.
note that for ISMRD = 0 or 2 soil temperature is initialized in the same way as SLAB
NUDGE	0	no soil moisture nudging
	1	do soil moisture nudging. This requires surface FDDA grid analyses.
IFGROW	0	interpolate LAI and vegetation fraction between maximum and minimum values for each grid cell from monthly VEGFRC data (from Terrain)
	1	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).
	2	same as IFGROW=1 except no planting dates are input. Emergence dates are estimated from VEGFRC.
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.
Default settings are ISMRD = 0, NUDGE = 0, IFGROW = 0

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.