GENIE:EMBM

Summary

 * Name of model: EMBM (Enegry-Moisture Balance Model)


 * Authors/Constructors: Bob Marsh (NOCS) & Neil Edwards (OU)


 * Reference and description: Edwards and Marsh (2005)


 * Original version: Part of UVic Earth System Model (Weaver et al. 2001)


 * Units: SI (vertical EMBM) & non-dimensional (horizontal transport)


 * Sign convention: positive into atmosphere (fluxes of heat & moisture)


 * Grid: As ocean (preferrred meshes at present are 36x36s and 64x32)


 * Timestep: default 5 per ocean timestep (500-1000/year, depending on horizontal resolution)


 * Checks to ensure continuity: n/a


 * Dynamical variables: Atmospheric temperature and specific humidity referenced to surface values

Processes modelled

 * Horizontal transport of heat and moisture in atmosphere
 * Surface exchange of heat with ocean, sea ice and land, according to balance of incoming shortwave radiation, sensible and latent heat fluxes, and outgoing long-wave radiation, as a function of planetary albedo and radiative gases (CO2, water vapour)
 * Surface exchange of moisture with ocean, sea ice and land, according to balance of precipitation, evaporation and, when land module not coupled, runoff

Key parameters commonly used for tuning / model configuration

 * Atmospheric heat diffusivity (T diff. amp.)
 * Shape of the meridional profile for heat diffusivity: width dimension (T diff. Width); south-to-north slope (T. diff slope)
 * Atmospheric moisture diffusivity (q diff.)
 * Coefficient for heat advection by prescribed winds (T adv. coeff.)
 * Coefficient for moisture advection by prescribed winds (T adv. coeff.)
 * Adjustment to the surface freshwater flux in Atlantic & Pacific sectors (FWF adjust.)
 * Threshold relative humidity, for precipitation (RH threshold)
 * Relaxation timescale, delaying precipitation (P timescale) – coming soon

Tuned values for key parameters
These are ensemble-mean values based on parameter tuning through data assimilation with the Ensemble Kalman Filter (Hargreaves et al. 2004). For further tuned parameter sets see Price et al. (2006)


 * {| border="1" cellpadding="3"

!Parameter !Value !Units
 * T diff. amp.
 * 3.75x106
 * m2s-1
 * T diff. width
 * 1.31
 * Radians
 * T diff. slope
 * 0.07
 * unitless
 * q diff.
 * 1.75x106
 * m2s-1
 * T adv. coeff.
 * 0.06
 * unitless
 * q adv. coeff.
 * 0.14
 * unitless
 * FWF adjust.
 * 0.28
 * Sv
 * RH threshold
 * 0.85
 * unitless
 * P timescale
 * 3.65
 * days
 * }
 * RH threshold
 * 0.85
 * unitless
 * P timescale
 * 3.65
 * days
 * }
 * days
 * }
 * }

Couplings to other modules

 * Atmosphere-Land (ENTS) – pending further code development
 * Atmosphere-Ocean (GOLDSTEIN)
 * Atmosphere-Sea Ice (N.B. thermodynamics embedded in surface exchange scheme)
 * Atmosphere-Atmospheric Chemistry (ATCHEM)

Atmosphere-Ocean I/O

 * Inputs:
 * Ocean surface temperature (deg. C)


 * Outputs:
 * Air temperature (deg. C)
 * Specific humidity (g/kg)

Atmosphere-Land I/O

 * Inputs:
 * Surface temperature (deg. C)
 * Soil Moisture (m water equivalent)


 * Outputs:
 * Runoff (m s-1 equivalent at coastal gridboxes, according to simple catchment areas) – optional (if not coupled to Land)

Atmosphere-Atmospheric Chemistry I/O

 * Inputs:
 * CO2 (ppt) - optional


 * Outputs:
 * none

Prescribed inputs

 * Wind field (m s-1), annual or monthly-mean NCEP reanalysis interpolated to model grid
 * Climatological Albedo, as function of latitude