Villarini Gabriele

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Last Name
Villarini
First Name
Gabriele
ORCID
0000-0001-9566-2370

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  • Preprint
    Extreme rainfall activity in the Australian tropics reflects changes in the El Niño/Southern Oscillation over the last two millennia
    ( 2015-03) Denniston, Rhawn F. ; Villarini, Gabriele ; Gonzales, Angelique N. ; Wyrwoll, Karl-Heinz ; Polyak, Victor J. ; Ummenhofer, Caroline C. ; Lachniet, Matthew S. ; Wanamaker, Alan D. ; Humphreys, William F. ; Woods, David ; Cugley, John
    Assessing temporal variability in extreme rainfall events prior to the historical era is complicated by the sparsity of long-term ‘direct’ storm proxies. Here we present a 2200-yr-long, accurate and precisely dated record of cave flooding events from the northwest Australian tropics that we interpret, based on an integrated analysis of meteorological data and sediment layers within stalagmites, as representing a proxy for extreme rainfall events derived primarily from tropical cyclones (TCs) and secondarily from the regional summer monsoon. This time series reveals substantial multi-centennial variability in extreme rainfall, with elevated occurrence rates characterizing the twentieth century, the period 850-1450 CE, and 50-400 CE; reduced activity marks 1450-1650 CE and 500-850 CE. These trends are similar to reconstructed numbers of TCs in the North Atlantic and Caribbean basins, and form temporal and spatial patterns best explained by secular changes in the dominant mode of the El Niño-Southern Oscillation (ENSO), the primary driver of modern TC variability. We thus attribute long-term shifts in cyclogenesis in both the central Australian and North Atlantic sectors over the past two millennia to entrenched El Niño or La Niña states of the tropical Pacific. The influence of ENSO on monsoon precipitation in this region of northwest Australia is muted, but ENSO-driven changes to the monsoon may have complemented changes to TC activity.
  • Article
    Expansion and contraction of the Indo-Pacific tropical rain belt over the last three millennia
    (Nature Publishing Group, 2016-09-29) Denniston, Rhawn ; Ummenhofer, Caroline C. ; Wanamaker, Alan D. ; Lachniet, Matthew S. ; Villarini, Gabriele ; Asmerom, Yemane ; Polyak, Victor J. ; Passaro, Kristian J. ; Cugley, John ; Woods, David ; Humphreys, William F.
    The seasonal north-south migration of the intertropical convergence zone (ITCZ) defines the tropical rain belt (TRB), a region of enormous terrestrial and marine biodiversity and home to 40% of people on Earth. The TRB is dynamic and has been shown to shift south as a coherent system during periods of Northern Hemisphere cooling. However, recent studies of Indo-Pacific hydroclimate suggest that during the Little Ice Age (LIA; AD 1400–1850), the TRB in this region contracted rather than being displaced uniformly southward. This behaviour is not well understood, particularly during climatic fluctuations less pronounced than those of the LIA, the largest centennial-scale cool period of the last millennium. Here we show that the Indo-Pacific TRB expanded and contracted numerous times over multi-decadal to centennial scales during the last 3,000 yr. By integrating precisely-dated stalagmite records of tropical hydroclimate from southern China with a newly enhanced stalagmite time series from northern Australia, our study reveals a previously unidentified coherence between the austral and boreal summer monsoon. State-of-the-art climate model simulations of the last millennium suggest these are linked to changes in the structure of the regional manifestation of the atmosphere’s meridional circulation.
  • Article
    Sensitivity of northwest Australian tropical cyclone activity to ITCZ migration since 500 CE
    (American Association for the Advancement of Science, 2023-01) Denniston, Rhawn F. ; Ummenhofer, Caroline C. ; Emanuel, Kerry ; Ingrosso, Roberto ; Pausata, Francesco S. R. ; Wanamaker, Alan D. ; Lachniet, Matthew S. ; Carr, Kenneth T. ; Asmerom, Yemane ; Polyak, Victor J. ; Nott, Jonathan ; Zhang, Wei ; Villarini, Gabriele ; Cugley, John ; Brooks, Darren ; Woods, David ; Humphreys, William F.
    Tropical cyclones (TCs) regularly form in association with the intertropical convergence zone (ITCZ), and thus, its positioning has implications for global TC activity. While the poleward extent of the ITCZ has varied markedly over past centuries, the sensitivity with which TCs responded remains poorly understood from the proxy record, particularly in the Southern Hemisphere. Here, we present a high-resolution, composite stalagmite record of ITCZ migrations over tropical Australia for the past 1500 years. When integrated with a TC reconstruction from the Australian subtropics, this time series, along with downscaled climate model simulations, provides an unprecedented examination of the dependence of subtropical TC activity on meridional shifts in the ITCZ. TCs tracked the ITCZ at multidecadal to centennial scales, with a more southward position enhancing TC-derived rainfall in the subtropics. TCs may play an increasingly important role in Western Australia's moisture budgets as subtropical aridity increases due to anthropogenic warming.