On the Spatial and Temporal Variability of Atmospheric Heat Transport in a Hierarchy of Models

Abstract

he present study analyses the spatial and temporal variability of zonally integrated meridional atmospheric heat transport due to transient eddies in a hierarchy of datasets. These are a highly idealised two-layer model seeded with point geostrophic vortices, an intermediate complexity GCM and the European Centre for Medium Range Weather Forecasts ERA-Interim reanalysis data. The domain of interest is the extratropics. Both the two-layer model and the GCM display a pronounced temporal variability in the zonally integrated meridional transport, with the largest values (or pulses) of zonally integrated transport being associated with extended regions of anomalously strong local heat transport. In the two-layer model these large-scale coherent transport regions, which we term heat transport bands, are linked to densely packed baroclinic vortex pairs and can be diagnosed as low wavenumber streamfunction anomalies. In the GCM they are associated with both the warm and cold sectors of mid-latitude weather systems. Both these features are also found in ERA-Interim: the heat transport bands match weather systems and occur primarily in the storm track regions, which in turn correspond to planetary-scale climatological streamfunction anomalies. We hypothesise that the temporal variability of the zonally integrated heat transport is partly linked to oscillatory variations in the storm track activity, but also contains a background rednoise component. The existence of a pronounced variability in the zonally integrated meridional heat transport can have important consequences for the interplay between mid-latitude dynamics and the energy balance of the high latitudes.