Southern Ocean precipitation observed from satellite and ground instrumentation at Macquarie Island

Abstract

The seasonal and synoptic variability of Southern Ocean (SO) precipitation are studied using ground-based observations at Macquarie Island. Parsivel disdrometer and W-band radar measurements are blended to determine precipitation thermodynamic phase, hydrometeor size distributions and rain rates, enabling a more detailed examination of SO precipitation characteristics than has been previously possible. In particular, we find that small-particle precipitation occurs to 30 to 50% of the time, depending on the season. Glaciated precipitation is observed most often during fall and winter, and to the southeast of SO cyclonic systems. Comparisons of the Macquarie Island observations to precipitation estimates (retrievals) based on measurements from the CloudSat Cloud-Profiling Radar show good agreement in the distribution of rain rates for rates >0.5 mm/hour, which comprise the bulk of the total accumulated precipitation. However, CloudSat does miss much of the lighter precipitation that is comprised primarily of small particles (<0.5 mm) and occurs most frequently over the SO.