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The diurnal cycle of rainfall and cloud properties from Himawari-8 during the austral summer (2016-2020).
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  • Clemente Lopez-Bravo,
  • Claire Vincent,
  • Yi Huang,
  • Todd Lane
Clemente Lopez-Bravo
The University of Melbourne, ARC Centre of Excellence for Climate Extremes

Corresponding Author:llopezbravo@student.unimelb.edu.au

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Claire Vincent
The University of Melbourne
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Yi Huang
The University of Melbourne
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Todd Lane
The University of Melbourne, ARC Centre of Excellence for Climate Extremes
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Abstract

In this work, the characteristics of the diurnal cycle around Sumatra are examined with unprecedented detail using high-resolution satellite-derived cloud properties from the Himawari-8 Advanced Himawari Imager (AHI) data. Offshore propagation is resolved into multiple local propagation directions of cloud cells, and the interaction between propagations is shown to result in forced convection over the Strait of Malacca, Java Sea, and the Indian Ocean. The diurnal cycle of rainfall and deep convection over Sumatra show complex interactions between the land-sea-breeze system, the seasonal background wind, the local topography, and the influence of surrounding islands. We used high-resolution satellite-derived products from Himawari-8 AHI, the Geostationary Cloud Algorithm Testbed Geocat, and Integrated Multi-satellitE Retrievals for Global Precipitation Measurement (IMERG) to investigate the cloud properties of deep convection and the signatures of the diurnal cycle of rainfall and cloudiness over Sumatra. Previous studies have shown evidence of the variability of diurnally forced convection in the Maritime Continent, including the diurnal signal over land in the late afternoon and the offshore propagation of Sumatra at night (Yang and Slingo 2001). The role of gravity waves has explained the night-time propagation (e.g., Mapes 2003; Love et al. 2011; Vincent and Lane 2016; Sakaeda et al. 2020). This propagation can be modified by the influence of small islands and the interconnection of diurnal cycles between Sumatra, Malay Peninsula, Java, and Borneo (Ruppert and Zhang 2019; Ruppert and Chen 2020). In this work, we present evidence of the cloudiness and rainfall patterns propagating offshore/onshore Sumatra during five austral summers from 2016 to 2020, employing cloud properties from Himawari-8 and IMERG collections. By combining detailed satellite-based cloud properties and rainfall estimates, we highlight the strong dependency of the diurnal cycle on local modulators.