Evidence of a diurnal cycle in precipitation over the southern ocean as observed at macquarie Island

• Published in: Atmosphere
• Main Authors: Lang, Francisco, Huang, Yi, Siems, Steven T., Manton, Michael J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2020
• Subjects: Diurnal cycle; Macquarie island; Marine boundary layer clouds; Precipitation; Southern ocean; Southern Ocean; Macquarie Island
• Online Access: https://research.monash.edu/en/publications/269c7dea-5d9a-4914-91de-08067a251f97; https://doi.org/10.3390/atmos11020181; https://researchmgt.monash.edu/ws/files/312394952/301436462_oa.pdf; http://www.scopus.com/inward/record.url?scp=85081156297&partnerID=8YFLogxK

Due to a lack of observations, relatively large discrepancies exist between precipitation products over the Southern Ocean. In this manuscript, surface hourly precipitation observations from Macquarie Island (54.62° S, 158.85° E) are analysed (1998-2016) to reveal a diurnal cycle. The precipitation rate is at a maximum during night/early morning and a minimum in the afternoon at Macquarie Island station. Seasonally, the diurnal cycle is strongest in summer and negligible over winter. Such a cycle is consistent with precipitation arising from marine boundary layer clouds, suggesting that such clouds are making a substantial contribution to total precipitation over Macquarie Island and the Southern Ocean. Using twice daily upper air soundings (1995-2011), lower troposphere stability parameters show a stronger inversion at night, again consistent with precipitation arising from marine boundary layer clouds. The ERA-Interim precipitation is dominated by a 12 hourly cycle, year around, which is likely to be a consequence of the twice-daily initialisation. The implication of a diurnal cycle in boundary layer clouds over the Southern Ocean to derived A-Train satellite precipitation products is also discussed.