Oral Presentation AMOS Annual Meeting and International Conference on Tropical Meteorology and Oceanography

Roles of diurnal mixing in the development of the 2013 marine heat wave off the northwest coast of Australia (#161)

Anna Maggiorano 1 2 , Ming Feng 2 , Xiao Hua Wang 1 , Elizabeth Ritchie-Tyo 1 , Jim Greenwood 2 , Frank Colberg 3
  1. UNSW Canberra, DIckson, ACT, Australia
  2. CSIRO, Perth, WA, Australia
  3. Bureau of Metereology, Melbourne, VIC, Australia

Anomalous warm conditions in the ocean off the Western Australia coast, referred to as Ningaloo Niño or marine heat wave, usually start to develop in the tropical region of the southeast Indian Ocean in September-October, peak along the west coast of Australia in austral summer in January-February and decay in March (Feng et al., 2015). An unusual Ningaloo Niño event has been observed in 2012/2013 austral summer, which peaked on the North Western Shelf of Australia in February 2013 (Feng et al., 2015; Xu et al., 2018). The aim of this study is to analyze the development of this event and calculate the mixed layer heat budget of the region with taking into account the role of the diurnal mixing processes to better understand the dynamics of this event.

A numerical model based on ROMS (Marchesiello et al., 2003) has been implemented to simulate the ocean circulation dynamics of the region. The model has been forced with hourly data from ECMWF ERA5 air-sea fluxes (Copernicus Climate Change Service (C3S), 2017) and is able to simulate the diurnal cycles of the heat fluxes and the sea surface temperature. In this presentation, the model simulation of the 2012/2013 marine heat wave event will be assessed against satellite observations. A mixed layer heat budget will be used to quantify the roles of air-sea heat fluxes and ocean circulation in the development of the peak temperature anomalies in the region. The roles of the diurnal mixing in developing the peak anomalous temperature will be evaluated. The connection of this marine heatwave and the large scale climate variability in the region will also be assessed.

  1. Copernicus Climate Change Service (C3S) (2017): ERA5: Fifth generation of ECMWF atmospheric reanalyses of the global climate . Copernicus Climate Change Service Climate Data Store (CDS), 2018. https://cds.climate.copernicus.eu/cdsapp#!/home
  2. Feng, Ming, Harry H Hendon, Shang-Ping Xie, Andrew G Marshall, Andreas Schiller, Yu Kosaka, Nick Caputi, and Alan Pearce (2015). “Decadal increase in Ningaloo Niño since the late 1990s”. In: Geophysical Research Letters 42.1, pp. 104–112.
  3. Marchesiello, Patrick, James C McWilliams, and Alexander Shchepetkin (2003). “Equilibrium structure and dynamics of the California Current System”. In: Journal of Physical Oceanography 33.4, pp. 753–783.
  4. Xu, Jiangtao, Ryan J Lowe, Gregory N Ivey, Nicole L Jones, and Zhenling Zhang (2018). “Contrasting heat budget dynamics during two La Nina marine heat wave events along Northwestern Australia”. In: Journal of Geophysical Research: Oceans 123.2, pp. 1563–1581.