Modeling the GABLS4 strongly-stable boundary layer with a GCM
parameterization: parametric sensitivity or intrinsic limits?
Abstract
The representation of stable boundary layers (SBLs) still challenges
turbulence parameterizations implemented in current weather or climate
models. The present work assesses whether these model deficiencies
reflect calibration choices or intrinsic limits in currently-used
turbulence parameterization formulations and implementations. This
question is addressed for the ARPEGE-Climat 6.3 CNRM atmospheric model
in a single-column model/large-eddy simulation (SCM/LES) comparison
framework, using the history matching with iterative refocusing
statistical approach. The GABLS4 case, which samples a nocturnal strong
SBL observed at Dome C, Antarctic Plateau, is used. The standard
calibration of the ARPEGE-Climat 6.3 turbulence parameterization leads
to a too deep SBL, a too high low-level jet and misses the nocturnal
wind rotation. This behavior is found for low and high vertical
resolution model configurations. The statistical tool then proves that
these model deficiencies reflect a poor parameterization calibration
rather than intrinsic limits of the parameterization formulation itself.
In particular, the role of two lower bounds that were heuristically
introduced during the parameterization implementation to increase mixing
in the free troposphere and to avoid runaway cooling in snow- or
ice-covered region is emphasized. The statistical tool identifies the
space of the parameterization free parameters compatible with the LES
reference, accounting for the various sources of uncertainty. This space
is non-empty, thus proving that the ARPEGE-Climat 6.3 turbulence
parameterization contains the required physics to capture the GABLS4
SBL. The SCM framework is also used to validate the statistical
framework and a few guidelines for its use in parameterization
development and calibration are discussed.