In CESM, coupler code has been improved in order to remove the need to change any coupler code when adding the exchange of new fields between model components. To accomplish this, a new standardized naming convention has been introduced for field names that are exchanged between model components. This is summarized below.
==================================================================== New standardized naming convention ==================================================================== --------- definitions: --------- state-prefix first 3 characters: Sx_, Sa_, Si_, Sl_, So_ one letter indices: x,a,l,i,o,s,g,r x => coupler (mapping, merging, atm/ocn flux calc done on coupler procs) a => atm l => lnd i => ice o => ocn g => glc s => snow (from clm to glc) r => rof state-name what follows state prefix flux-prefix first 5 characters: Flmn__ lm => between components l and m n => computed by component n example: Fioi => ice/ocn flux computed by ice example: Fall => atm/lnd flux computed by lnd If flux prefix has first letter of P (so first five characters are PFlmn_) then flux is passed straight through without scaling by the corresponding fraction) flux-name what follows flux-prefix --------- rules: --------- 1) states: a) atm attributes fields that HAVE a state-prefix of Sx_ in seq_flds_x2a_states rule: will merge all identical values of the state-names from seq_flds_i2x_states seq_flds_l2x_states seq_flds_o2x_states seq_flds_xao_states to obtain output state-name in seq_flds_x2a_states rule: to merge input states that originate in the lnd (l2x_a) will be scaled by the lndfrac ice (i2x_a) will be scaled by the icefrac cpl (xao_a) will be scaled by the ocnfrac ocn (o2x_a) will be scaled by the ocnfrac example: seq_flds_l2x_states = "Sl_t" seq_flds_i2x_states = "Si_t" seq_flds_o2x_states = "So_t" seq_flds_x2a_states = "Sx_t" attribute fields Sl_t, Si_t, So_t, in attribute vectors l2x_a, i2x_a, o2x_a will be merged to obtain attribute Sx_t in attribute vector x2a_a b) atm attribute fields that DO NOT HAVE a state-prefix of Sx_ in seq_flds_x2a_states rule: copy directly all variables that identical state-prefix AND state-name in seq_flds_i2x_states and seq_flds_x2a_states seq_flds_l2x_states and seq_flds_x2a_states seq_flds_o2x_states and seq_flds_x2a_states seq_flds_xao_states and seq_flds_x2a_states example seq_flds_i2x_states = ":Si_snowh" seq_flds_x2a_states = ":Si_snowh" attribute field of Si_snowh in i2x_a will be copied to attribute field Si_snowh in x2a_a 2) fluxes: rule: will merge all identical values of the flux-names from seq_flds_i2x_states seq_flds_l2x_states seq_flds_o2x_states seq_flds_xao_states to obtain output state-name in seq_flds_x2a_states rule: input flux fields that originate in the lnd (l2x_a) will be scaled by the lndfrac ice (i2x_a) will be scaled by the icefrac - ignore all fluxes that are ice/ocn fluxes (e.g. Fioi_) cpl (xao_a) will be scaled by the ocnfrac ocn (o2x_a) will be scaled by the ocnfrac+icefrac ==================================================================== New user specified fields ==================================================================== New fields that are user specidied can be added as namelist variables by the user in the cpl namelist seq_flds_user using the namelist variable array cplflds_customs. The user specified new fields must follow the above naming convention. As an example, say you want to add a new state 'foo' that is passed from the land to the atm - you would do this as follows apos;seq_flds_user cplflds_custom = 'Sa_foo->a2x', 'Sa_foo->x2a' / This would add the field 'Sa_foo' to the character strings defining the attribute vectors a2x and x2a. It is assumed that code would need to be introduced in the atm and land components to deal with this new attribute vector field. Currently, the only way to add this is to edit $CASEROOT/user_nl_cpl ==================================================================== Coupler fields use cases ==================================================================== Previously, new fields that were needed to be passed between components for certain compsets were specified by cpp-variables. This has been modified to now be use cases. The use cases are specified in the namelist cpl_flds_inparm and are currently triggered by the xml variables CCSM_VOC, CCSM_BGC and GLC_NEC. ====================================================================