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ItemNo Preview AvailableRevisiting the 1888 centennial droughtRitman, MEH ; Ashcroft, LC (Royal Society of Victoria, 2020-01-01)Droughts are a key feature of Australia's climate and can lead to water shortages, crop failure and economic instability. Historical droughts are an important source of information to better understand recent droughts and how they might be managed. However, the majority of studies into Australian drought only consider dry periods in the 20th and 21st centuries. Here, a newly developed gridded rainfall dataset from the Bureau of Meteorology and a network of historical rainfall stations are used to re-examine the short but sharp Centennial Drought of 1888. The Centennial Drought is explored on a monthly scale, highlighting key periods of rainfall deficiency, and identifying the impacts of relevant atmospheric circulation patterns. The most significant rainfall declines occur in autumn and spring and are likely to be the result of an El Niño event, a positive Sub-Tropical Ridge intensity anomaly, and seasonal fluctuations of the Southern Annular Mode. Comparing the Centennial Drought to other short droughts of 1914-15, 1982-83 and 2017~ indicates that the magnitude of the rainfall deficiencies and widespread spatial extent are comparable, placing the Centennial Drought alongside some of the most severe short droughts in Australia's colonial climate history.
ItemClimate indices in historical climate reconstructions: a global state of the artNash, DJ ; Adamson, GCD ; Ashcroft, L ; Bauch, M ; Camenisch, C ; Degroot, D ; Gergis, J ; Jusopovic, A ; Labbe, T ; Lin, K-HE ; Nicholson, SD ; Pei, Q ; Prieto, MDR ; Rack, U ; Rojas, F ; White, S (COPERNICUS GESELLSCHAFT MBH, 2021-06-17)Abstract. Narrative evidence contained within historical documents and inscriptions provides an important record of climate variability for periods prior to the onset of systematic meteorological data collection. A common approach used by historical climatologists to convert such qualitative information into continuous quantitative proxy data is through the generation of ordinal-scale climate indices. There is, however, considerable variability in the types of phenomena reconstructed using an index approach and the practice of index development in different parts of the world. This review, written by members of the PAGES (Past Global Changes) CRIAS working group – a collective of climate historians and historical climatologists researching Climate Reconstructions and Impacts from the Archives of Societies – provides the first global synthesis of the use of the index approach in climate reconstruction. We begin by summarising the range of studies that have used indices for climate reconstruction across six continents (Europe, Asia, Africa, the Americas, and Australia) as well as the world's oceans. We then outline the different methods by which indices are developed in each of these regions, including a discussion of the processes adopted to verify and calibrate index series, and the measures used to express confidence and uncertainty. We conclude with a series of recommendations to guide the development of future index-based climate reconstructions to maximise their effectiveness for use by climate modellers and in multiproxy climate reconstructions.
ItemAn Evaluation of the Performance of the Twentieth Century Reanalysis Version 3Slivinski, LC ; Compo, GP ; Sardeshmukh, PD ; Whitaker, JS ; McColl, C ; Allan, RJ ; Brohan, P ; Yin, X ; Smith, CA ; Spencer, LJ ; Vose, RS ; Rohrer, M ; Conroy, RP ; Schuster, DC ; Kennedy, JJ ; Ashcroft, L ; Broennimann, S ; Brunet, M ; Camuffo, D ; Cornes, R ; Cram, TA ; Dominguez-Castro, F ; Freeman, JE ; Gergis, J ; Hawkins, E ; Jones, PD ; Kubota, H ; Lee, TC ; Lorrey, AM ; Luterbacher, J ; Mock, CJ ; Przybylak, RK ; Pudmenzky, C ; Slonosky, VC ; Tinz, B ; Trewin, B ; Wang, XL ; Wilkinson, C ; Wood, K (AMER METEOROLOGICAL SOC, 2021-02-01)Abstract The performance of a new historical reanalysis, the NOAA–CIRES–DOE Twentieth Century Reanalysis version 3 (20CRv3), is evaluated via comparisons with other reanalyses and independent observations. This dataset provides global, 3-hourly estimates of the atmosphere from 1806 to 2015 by assimilating only surface pressure observations and prescribing sea surface temperature, sea ice concentration, and radiative forcings. Comparisons with independent observations, other reanalyses, and satellite products suggest that 20CRv3 can reliably produce atmospheric estimates on scales ranging from weather events to long-term climatic trends. Not only does 20CRv3 recreate a “best estimate” of the weather, including extreme events, it also provides an estimate of its confidence through the use of an ensemble. Surface pressure statistics suggest that these confidence estimates are reliable. Comparisons with independent upper-air observations in the Northern Hemisphere demonstrate that 20CRv3 has skill throughout the twentieth century. Upper-air fields from 20CRv3 in the late twentieth century and early twenty-first century correlate well with full-input reanalyses, and the correlation is predicted by the confidence fields from 20CRv3. The skill of analyzed 500-hPa geopotential heights from 20CRv3 for 1979–2015 is comparable to that of modern operational 3–4-day forecasts. Finally, 20CRv3 performs well on climate time scales. Long time series and multidecadal averages of mass, circulation, and precipitation fields agree well with modern reanalyses and station- and satellite-based products. 20CRv3 is also able to capture trends in tropospheric-layer temperatures that correlate well with independent products in the twentieth century, placing recent trends in a longer historical context.
ItemThe Australian Science Communicators conference 2020Ashcroft, L ; Cobb, M ; Bailey, L ; Martin, J ; Daniel, S (SCUOLA INT SUPERIORE STUDI AVANZATI-S I S S A-INT SCH ADVANCED STUDIES, 2020-01-01)This special issue of JCOM features six commentary articles from the research stream of the Australian Science Communicators conference, held in February 2020. These opportunistic assessments and deliberate analyses explore important themes of trust, engagement, and communication strategy across a diverse range of scientific contexts. Together, they demonstrate the importance of opportunities to come together and share the research that underpins our practice. The conference and these commentaries enable us to engage in professional development during these exceptional times when successful evidence-based science communication is of critical significance.
ItemThe world's longest known parallel temperature dataset: A comparison between daily Glaisher and Stevenson screen temperature data at Adelaide, Australia, 1887-1947Ashcroft, L ; Trewin, B ; Benoy, M ; Ray, D ; Courtney, C (WILEY, 2021-10-04)
ItemA historical climate dataset for southwestern Australia, 1830-1875Gergis, J ; Baillie, Z ; Ingallina, S ; Ashcroft, L ; Ellwood, T (WILEY, 2021-03-28)