Initial albedo values

General
1

Hi, yet another question - or rather flagging a potential issue with albedo values in SUEWS 2026.5 vs UMEP’s Database Prepare. In its reference table we have:

  • Helsinki deciduous trees: alb_min = alb_max = 0.16 (ref ID 41240027), while the initial alb_id is 0.12
  • Helsinki grass: alb_min = alb_max = 0.19 (ref ID 41240029), while the initial alb_id is 0.18

These therefore fall outside the allowed initial albedo range in 2026.5. All works fine with UK values.

Any tips on how to proceed (other than using UK albedo values:)?

Thanks in advance! /Janka

2

Thanks for flagging this.

The Helsinki values themselves are fine: SUEWS allows alb_min == alb_max for a constant albedo, and only objects when alb_min > alb_max. The sample config does this for evergreen trees (both 0.1).

The error comes from alb_id, the initial albedo. In the sample config each surface’s alb_id is set to its alb_min, 0.12 for deciduous and 0.18 for grass. When you change alb_min and alb_max, alb_id is left pointing at the old range, and that is a hard error at config load rather than a warning.

The fix is to set alb_id to null on those two surfaces:

initial_states:
  dectr:
    alb_id:
      value: null
  grass:
    alb_id:
      value: null

SUEWS then derives it from lai_id and the alb_min/alb_max pair, giving exactly 0.16 and 0.19, and the validation report lists it under NO ACTION NEEDED as auto-calculated. Setting it explicitly to 0.16 and 0.19 works too, since the check is inclusive. The field is documented on the vegetation initial state page.

One thing to avoid: do not delete the alb_id key altogether. The config itself is still valid, but the updated YAML that suews validate writes puts the key back at the wrong indentation, nested inside decidcap_id, and that file then fails to load. I have reproduced it and will get it fixed.

Worth noting separately that alb_min == alb_max switches off the seasonal albedo cycle for that surface, because the daily update scales the change by (alb_max - alb_min). If 0.16 is a growing-season value, you may prefer it as alb_max with a lower leaf-off alb_min.

Your wider point is tracked in #1007, and the auto-initialisation came out of that discussion (#1132). Useful evidence for that thread.

Did the 0.12 and 0.18 come from Database Prepare itself, or from the sample config you started from?