Table 2 Perturbed parameters in sensitivity studies in ECHAM6.3-HAM2.3

REF

Default diagnostic scheme

REF-S1

Reducing autoconversion rate (ccraut) in stratiform clouds from 5 (default value) to 1 → Delayed rain formation in stratiform clouds

REF-S2

Reducing threshold RH \({{{{{\boldsymbol{\eta }}}}}}_{{{{{\boldsymbol{crit}}}}}}\) by applying a scaling factor of 0.8, only over the ocean → more marine clouds

REF-S3

Increasing evaporation of raindrops to 200% of default evaporation rate → Increase RH and therefore cloud cover

REF-S4

Reducing entrainment rate for shallow convective clouds (entrscv) from 0.003 to 0.001 → Drying the boundary layer and reducing cloud cover

REF-S5

Reducing fraction of overshooting of shallow convection (cmfctop) from 0.2 to 0.1 → Keeping more moisture in the planetary boundary layer

REF-S6

Reducing autoconversion rate for convective clouds (cprcon) from 0.0009 to 0.00002 → Delayed rain formation in convective clouds

PROG_CC

Default prognostic scheme

PROG_CC-S1

Reducing scaling factor for cloud formation by mixing of detrained air with environmental cloud-free air (tuningDetrainedMixing) from 0.8 (default value) to 0.6 → Reducing cloud formation

PROG_CC-S2

Reducing scaling factor for entrainment rate for shallow convection (tuningConvEntrShallow) from 0.003 (default value) to 0.0003 → Drying the boundary layer and reducing cloud cover

PROG_CC-S3

Increasing scaling factor for turbulent mixing (tuningTurbulentMixing) from 0.0 (default value) to 1.0 → Affect cloud formation

PROG_CC-S4

Reducing critical RH at the surface above which large-scale cloud cover can form (tuningRHcritSurface) from 0.9 (default value) to 0.8 everywhere → more clouds