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Built-in aliases

EAMxx recognises certain diagnostic name patterns as built-in aliases. A built-in alias is expanded to a canonical composable expression before any other regex is tested. The expansion recurses, so the resulting name is itself parsed normally.

Reference table

User request Expands to Meaning
X_atm_backtend X_minus_X_prev_over_dt Atmospheric backward tendency of X: (X − X_prev) / dt

Example

field_names:
  - T_mid_atm_backtend   # expands to T_mid_minus_T_mid_prev_over_dt

This is equivalent to requesting:

field_names:
  - T_mid_minus_T_mid_prev_over_dt

which in turn chains:

  • FieldPrevDiag(T_mid) → T_mid_prev
  • BinaryOpsDiag(T_mid, minus, T_mid_prev) → T_mid_minus_T_mid_prev
  • FieldOverDtDiag(T_mid_minus_T_mid_prev) → T_mid_minus_T_mid_prev_over_dt

Notes

  • Built-in aliases are checked before all other pattern rules (including suffix operators and binary ops), so they always take precedence.
  • The match is greedy on the field-name part, so T_mid_at_500hPa_atm_backtend expands to T_mid_at_500hPa_minus_T_mid_at_500hPa_prev_over_dt.
  • Additional built-in aliases may be added in eamxx_io_utils.cpp in the dedicated block at the top of create_diagnostic().