Dr Chiara Holgate
I am a hydroclimatologist, which means I study the water cycle and how it interacts with other parts of the climate system. I study the way moisture moves from the ocean through the atmosphere to the land, and how changes in that movement affect climate extremes like droughts and floods.
My PhD research focused on the role of land-atmosphere feedbacks and their impact on Australian rainfall and drought.
After completing my doctorate, I held a Research Scientist position at the Australian Bureau of Meteorology where I worked to understand how well Australia’s climate models represent land-atmosphere feedbacks.
Prior to my PhD I worked as a Hydrologist and Water Resources Engineer. I provided technical advice to the Australian federal, state and local governments, as well as resource companies and transport authorities. I collaborated on, helped develop and executed a variety of hydrological projects, including the areas of: groundwater and surface water field investigation, hydraulic and hydrologic analysis and modelling, environmental assessment of major projects, groundwater-surface water connectivity studies and water balance assessment.
My research focuses on understanding the processes driving hydrological extremes, like droughts, extreme rainfall and floods. Some of my research highlights are shown below.
Australian rainfall recycling and evaporative source regions
Where does Australia’s rainfall come from? To answer this seemingly simple question, we traced the path of moisture from where it rained, backward in time through the atmosphere to see where it originally evaporated from. We identified important moisture supply regions, showing the reliance of Australia’s rainfall on moisture sourced from the ocean and some land areas. By tracking moisture every day between 1979 and 2013, we created a long-term time series of the sources of moisture supplying rainfall in different parts of the country. Identifying the long-term average moisture sources enabled subsequent investigation into changes in rainfall during extreme periods, providing insight into the processes driving Australia’s highly variable rainfall. Read more on this study in the Journal of Climate.
Local and remote drivers of southeast Australian drought
Extreme drought has devastated many communities in southeast Australia time and again, but the processes driving drought in Australia are not well understood. Our study helped to change this by disentangling the roles of atmospheric circulation, weather systems and land surface processes in recurring Australian droughts. We found the leading cause for southeast Australian drought was that normal amounts of moisture from the oceans failed to reach the region and produced less rainfall when it did. The drying landscape made low rainfall conditions worse, but tended to have a smaller impact than the ocean. Read commentary on this in The Conversation or the full study in Geophysical Research Letters.
The impact of interacting climate modes on east Australian rainfall
Australian rainfall is known to be impacted by El Niño and La Niña, opposing phases of the El Niño-Southern Oscillation (ENSO). ENSO is a form of climate variability that represents changes in sea surface temperatures in the tropical Pacific Ocean. But exactly how do distant changes in the ocean lead to changes in rainfall in east Australia? This study provides a new perspective on the links between modes of climate variability and rainfall by examining changes in the atmospheric moisture supplying rainfall. During La Niña, more moisture is transported from the ocean, through the atmosphere to the land, and is more easily converted into rainfall when it arrives. Conversely, on average, El Niño results in little change to moisture availability, but atmospheric conditions make it much harder for that moisture to be converted to rainfall. Other modes of climate variability, like the Indian Ocean Dipole and Southern Annular Mode, modify the El Niño- and La Niña-related rainfall impact and its moisture supply in east Australia. Read commentary on this in The Conversation or the full study in the Journal of Climate.
My research is supported by the ARC Centre of Excellence for Climate Extremes.
Many of these publications require an academic library subscription to read the full content. Please email me if you would like me to send you a PDF copy of any of these papers. You can also access my publication history through Google Scholar.
Holgate, C.M., J. P. Evans, A. S. Taschetto, A. S. Gupta, and A. Santoso, 2022: The impact of interacting climate modes on east Australian precipitation moisture sources. Journal of Climate, 1, 1–31, https://doi.org/10.1175/JCLI-D-21-0750.1.
Gallant, A.J.E, Power, S., Henley, B.J., Verdon-Kidd, D.C., Pitman, A.J., Kirono, D.G.C., Adamu, M., Holgate, C.M., Ashcroft, L., Allen, K., Hope, P., Kiem, A.S., King, A., Lehner, F., Pendergrass, A., Taschetto, A.S., Ukkola, A.M., Vance, T.R. and Wright, N., 2022: Multi-year droughts through an Australian lens. Weather and Climate Extremes, under review.
Holgate, C. M., A. I. J. M. Van Dijk, J. P. Evans, and A. J. Pitman, 2020: Local and Remote Drivers of Southeast Australian Drought. Geophysical Research Letters, 47, e2020GL090238, https://doi.org/10.1029/2020GL090238.
Holgate, C. M., J. P. Evans, A. I. J. M. van Dijk, A. J. Pitman, and G. D. Virgilio, 2020: Australian Precipitation Recycling and Evaporative Source Regions. Journal of Climate, 33, 8721–8735, https://doi.org/10.1175/JCLI-D-19-0926.1.
Holgate, C. M., A. I. J. M. V. Dijk, J. P. Evans, and A. J. Pitman, 2019: The Importance of the One-Dimensional Assumption in Soil Moisture - Rainfall Depth Correlation at Varying Spatial Scales. Journal of Geophysical Research: Atmospheres, 124, 2964–2975, https://doi.org/10.1029/2018JD029762.
Holgate, C. M., A. I. J. M. Van DIjk, G. J. Cary, and M. Yebra, 2017: Using alternative soil moisture estimates in the McArthur Forest Fire Danger Index. International Journal of Wildland Fire, 26, 806–819, https://doi.org/10.1071/WF16217.
Vogel, E., Holgate, C.M., Cairns, J., Ramchurn, A., Frost, A.J., and van Dijk, A.I.J.M., 2017: Seasonal soil moisture forecasting using the AWRA landscape water balance model. 22nd International Congress on Modelling and Simulation, Hobart, Australia, 3-8 December 2017.
Holgate, C. M., and Coauthors, 2016: Comparison of Remotely Sensed and Modelled Soil Moisture Data Sets across Australia. Remote Sensing of Environment, 186, 479–500, https://doi.org/10.1016/j.rse.2016.09.015.
Holgate, C.M., A.S., Sen Gupta, A., Santoso, A., (2022). The east coast rain seems endless. Where on earth is all the water coming from? The Conversation (link).
Holgate, C.M., Evans, J.P. and van Dijk, A. I. J. M (2020). We looked at 35 years of rainfall and learnt how droughts start in the Murray-Darling Basin. The Conversation (link).