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Global Change Master Directory (GCMD)
Fifth-Generation NCAR / Penn State Mesoscale Model (MM5)

Abstract: The PSU/NCAR mesoscale model is a limited-area, nonhydrostatic or hydrostatic
(Version 2 only), terrain-following sigma-coordinate model designed to simulate
or predict mesoscale and regional-scale atmospheric circulation. It has been
developed at Penn State and NCAR as a community mesoscale model and is
continuously being improved by contributions from users at several universities
and government laboratories.

The Fifth-Generation NCAR / Penn State Mesoscale Model (MM5) is the latest in a
series that developed from a mesoscale model used by Anthes at Penn State in
the early 70's that was later documented by Anthes and Warner (1978). Since
that time, it has undergone many changes designed to broaden its usage. These
include (i) a multiple-nest capability, (ii) nonhydrostatic dynamics, which
allows the model to be used at a few-kilometer scale, (iii) multitasking
capability on shared- and distributed-memory machines, (iv) a four-dimensional
data-assimilation capability, and (v) more physics options.

The model (known as MM5) is supported by several auxiliary programs, which are
referred to collectively as the MM5 modeling system.

A schematic diagram (a pdf file, to be opened by Adobe Acrobat Reader) is
provided to facilitate discussion of the complete modeling system. It is
intended to show the order of the programs and the flow of the data, and to
briefly describe their primary functions. Documentation for various programs in
the modeling system is available online.

Terrestrial and isobaric meteorological data are horizontally interpolated
(programs TERRAIN and REGRID) from a latitude-longitude mesh to a variable
high-resolution domain on either a Mercator, Lambert conformal, or polar
stereographic projection. Since the interpolation does not provide mesoscale
detail, the interpolated data may be enhanced (program RAWINS or little_r) with
observations from the standard network of surface and rawinsonde stations using
either a successive-scan Cressman technique or multiquadric scheme. Program
INTERPF performs the vertical interpolation from pressure levels to the sigma
coordinate system of MM5. Sigma surfaces near the ground closely follow the
terrain, and the higher-level sigma surfaces tend to approximate isobaric
surfaces. Since the vertical and horizontal resolution and domain size are
variable, the modeling package programs employ parameterized dimensions
requiring a variable amount of core memory. Some peripheral storage devices are
also used.

Since MM5 is a regional model, it requires an initial condition as well as
lateral boundary condition to run. To produce lateral boundary condition for a
model run, one needs gridded data to cover the entire time period that the
model is integrated.

MM5 has been used for a broad spectrum of theoretical and real-time studies,
including applications of both predictive simulation and four-dimensional data
assimilation to monsoons, hurricanes, and cyclones. On the smaller meso-beta
and meso-gamma scales (2-200 km), MM5 has been used for studies involving
mesoscale convective systems, fronts, land-sea breezes, mountain-valley
circulations, and urban heat islands. The model allows for multiple levels of
nesting for cases involving scale interaction. Since the model is designed
primarily for research applications, modification and development will

(Summary adapted from: "".)

Related URL
Description: The SPoRT real-time mesoscale modeling system web site. High-resolution
meteorological forecasts are produced twelve times daily by the Pennsylvania
State University/National center for Atmospheric Research (PSU/NCAR) mesoscale
model (MM5v3.4).

ISO Topic Category

atmospheric circulation
Polar stereographic
Lambert conformal

Extended Metadata Properties
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Creation and Review Dates
SERF Creation Date: 2003-01-07
SERF Last Revision Date: 2018-08-06