BISMG:SarahS/jules model description

OLD JULES-glacier model description
Ice layers sit underneath the snowpack. The maximum number of ice levels and thickness of each level is prescribed by the used (similar to the way the snowpack levels work). Snow from the bottom level of the snow pack is converted into ice if the density is greater than firn-ice transition density and the bottom level is really deep(in snowpack.F90)

$$ firn flux(i)=MIN(sice(i,n)/timestep,0.5*dz ice(1)*ice rho/timestep) $$ where sice is the ice content of the snow layer. The value of 0.5 is tuneable and means that 50% of the bottom snow layer is converted into ice in one time step. The bottom snow layer depth ds is then reduced

$$ ds(i,n) = ( 1.0 - (firn flux(i)*timestep)/sice(i,n) ) * ds(i,n) $$

Long wave down radiation is put into elevation tiles (in control.F90) using the equation

$$LW down tile= \sigma T^{4} $$ where T has been adjusted for elevation.

Snowfall is put onto elevation tiles (in control.F90). The wet bulb temperature is calculated using the elevated temperature humidity. If the wet bulb temp is < 0oC then rain is converted into snow. snow = snowfall + rainfall (which is now snow)

The albedo of snow and ice is changed in tile_albedo.F90. For ice the code came from Jeff Ridley. If the tile temp is 1 deg warmer than the melt temp and snowdepth is less than 0.1m and we have an ice type then adjust the albedo from the default values (which are set in the .jin file)

Input files
1) 59_glacier_elev_tiles_n192.pp: Elevation relative to the grid box mean. You can have fixed elevation band or bands that extend to the maximum observed elevation ~4500m. Also you can cluster the levels at particular elevations. In this file there are 59 maps of elevations. Maps 1-9 have no elevation because these correspond to vegetation types (which are not elevated), 10-59 are the elevations of the ice type. 2) 50_glacier_tiles_n192.nc:     59 maps of fraction of surface types. 1-9 are the fraction of each non ice type and 10-59 is the fraction of ice. Note that 10-59 is the same data repeated

3) ajkkga.da60c10.JULES.soil.pp: 1 map of soil parameters for several variables