Model biases in the atmosphere-ocean partitioning of poleward heat
transport are persistent across three CMIP generations
Abstract
The observed partitioning of poleward heat transport between atmospheric
and oceanic heat transports (AHT and OHT) is compared to that in coupled
climate models. Poleward OHT in the models is biased low in both
hemispheres, with the largest biases in the Southern Hemisphere
extratropics. Poleward AHT is biased high in the Northern Hemisphere,
especially in the vicinity of the peak AHT near
40$^\circ$N. The significant model biases are
persistent across three model generations (CMIP3, CMIP5, CMIP6) and are
insensitive to the satellite radiation and atmospheric reanalyses
products used to derive observational estimates of AHT and OHT. Model
biases in heat transport partitioning are consistent with biases in the
spatial structure of energy input to the ocean and atmosphere.
Specifically, larger than observed model evaporation in the tropics adds
excess energy to the atmosphere that drives enhanced poleward AHT at the
expense of weaker OHT