CableUserGuide_CBL3_Introduction
CABLE is a community land-surface model. Users of CABLE are encouraged to actively participate as members of this community. It is the community of users and developers that will guide the future direction of CABLE.
Like most land surface models (LSMs), CABLE simulates the exchanges of radiation, moisture, heat and momentum between the land-surface and the atmosphere. Coupled to our biogeochemical model (CASA-CNP), CABLE-CASA-CNP can also simulate the exchange(s) of carbon (C) Nitrogen (N) and Phosphorus (P) between the land-surface and the atmosphere, and simulate the evolution of CNP pools at the surface. This "exchange" is of course dependent on particular characteristics of the patch of land relevant to the simulation. In particular, characteristics of the vegetation cover and the underlying ground surface. These characteristics are parametrised in CABLE and generally remain constant throughout the simulation.
Altogether CABLE considers 17 distinct types of land cover, however two of these are generally
unoccupied.
Accounting for this, CABLE considers 15 different types of land cover.
Eleven of these are vegetation types (or Plant Functional Types [PFTs]).
The remaining four are not vegetated.
CABLE considers 9 different types of ground or soil.
In CABLE each land "patch" or "tile" must have it's soil type and vegetation type defined.
A list of CABLE surface types can be reviewed here.
Having defined the soil and vegetation characteristics of the patch of land relevant to the simulation, CABLE can be forced with meteorological conditions and compute the exchanges discussed above. These meteorological conditions comprise of the downward radiation (short-wave and long-wave), the air temperature and pressure at the defined inter-section of the atmosphere and land-surface based on these inputs, predicts fluxes (its outputs, e.g. latent heat flux, upward long-wave radiation, net ecosystem exchange of CO2, runoff or drainage through deep soil).
Variables which CABLE stores in memory from one time step to the next, known as model states, include soil moisture content, soil and vegetation temperatures, and carbon stored in the vegetation and soil. An abstract schematic representation of these model components is shown in Figure 1.
Figure 1: A schematic representation of a model, with real number inputs, outputs, states and time- independent parameters
CABLE can be used as a single component of a larger global climate model (GCM). In this situation, CABLE receives meteorological data from, and passes flux information to, the boundary layer of an atmospheric model. When coupled to such a model, CABLE is said to be running online. Alternatively, meteorological data from observational sites or saved from an atmospheric model can be used to force CABLE and its output simply saved to file, in which case it is operating offline.
Although various versions of CABLE have been successfully hosted by a number of GCMs, the previous release of CABLE was for offline applications only. This release of CABLE-2.0 supports both offline CABLE and one online application. The supported online model is the Australian Community Climate and Earth System Simulator (ACCESS). The atmospheric component of ACCESS is the UK Met Office Unified Model (UM). In the implementation described here, CABLE replaces the Met Office Surface Exchange Scheme (MOSES). In Sections 3 and 4 respectively, we describe in detail the offline and online implementations of CABLE. It is anticipated that future CABLE releases will support CABLE coupled to additional climate models.