How strong are the Southern Hemisphere storm tracks?

Abstract

The real strength of the Southern Hemisphere (SH) storm tracks is poorly known, as the NCEP‐NCAR and ECMWF reanalyses differ significantly in this measure. In this work, the COSMIC GPS radio occultation dataset is used to investigate this issue. The ratio of the strength of the SH storm tracks to that in the Northern Hemisphere (NH) based on the COSMIC dataset can be regarded as close to the true inter‐hemisphere ratio since the dataset has similar biases and errors in both hemispheres. Comparing this ratio with that based on the reanalysis, it is found that the strength of the SH storm tracks in the NCEP‐NCAR reanalysis is significantly biased low by at least 25% at 300 hPa, while those in the ECMWF reanalyses are much closer to that inferred from COSMIC observations but ERA40 may be biased low by 5–10%.