Changing compound rainfall events in Tasmania

While extreme weather and climate events have been studied for several decades, analysis of compound events has only begun in recent years. In this burgeoning field there are still many open questions around the optimal methodology and analysis tools for analysis. After consultation with state emergency services in Tasmania, Australia, we examined which compound events have the largest impacts on their organizations. Through this consultation process we found that many of the severe flooding events in the state do not coincide with the highest rainfall days. Flooding on intense rainfall days is well understood, but flooding can also occur on days where the rainfall is not particularly extreme, especially if catchments are already saturated. Using the Australian Gridded Climate Data and six dynamically downscaled, Representative Concentration Pathway 8.5, bias adjusted Coupled Model Intercomparison Project 5 models we developed a method to quantify such compounding events to examine how they are changing from 1961 to 2100. We optimized a pre‐existing technique to estimate the antecedent conditions in catchments, combined with daily rainfall. We found that during 1961–2017, the number of compound rainfall events has been decreasing in the four Tasmanian catchments we studied, although the trend was statistically significant in only one case. The intensity of compound rainfall events was found to have increased significantly in some areas. Many future projections place Tasmania at the boundary of a drying trend to the west and wetting trend to the east and the position of this boundary varies between models leading to contrasting projected changes for parts of Tasmania. However, there is projected to be a decline in rainfall to 2100 associated with the southward shift in the storm‐track. Compound rainfall events are projected to decline throughout Tasmania, except in the south which will remain stable to 2100. The intensities are projected to increase in the south and decrease in the west, related to the changing thermodynamics and dynamics of rainfall drivers in the region in a warmer climate.

[1]  Corinne Le Quéré,et al.  Climate Change 2013: The Physical Science Basis , 2013 .

[2]  Changchun Chen,et al.  Characteristics of concurrent precipitation and wind speed extremes in China , 2021 .

[3]  I. Simmonds,et al.  Global analysis of cyclone-induced compound precipitation and wind extreme events , 2021, Weather and Climate Extremes.

[4]  M. Rusticucci,et al.  Atmospheric circulation influence on temperature and precipitation individual and compound daily extreme events: Spatial variability and trends over southern South America , 2020 .

[5]  A. Ruane,et al.  Understanding and managing connected extreme events , 2020, Nature Climate Change.

[6]  Colin J. Carlson,et al.  Compound climate risks in the COVID-19 pandemic , 2020, Nature Climate Change.

[7]  J. Zscheischler,et al.  Climate change effects on hydrometeorological compound events over southern Norway , 2020, Weather and Climate Extremes.

[8]  R. Horton,et al.  A typology of compound weather and climate events , 2020, Nature Reviews Earth & Environment.

[9]  B. Merz,et al.  Trends in Compound Flooding in Northwestern Europe During 1901–2014 , 2019, Geophysical Research Letters.

[10]  D. Maraun,et al.  Higher probability of compound flooding from precipitation and storm surge in Europe under anthropogenic climate change , 2019, Science Advances.

[11]  R. Nathan,et al.  Influence of changes in rainfall and soil moisture on trends in flooding , 2019, Journal of Hydrology.

[12]  R. Wilby,et al.  An emerging tropical cyclone–deadly heat compound hazard , 2019, Nature Climate Change.

[13]  J. Kirchner,et al.  The Relative Importance of Different Flood‐Generating Mechanisms Across Europe , 2019, Water Resources Research.

[14]  B. Hurk,et al.  The Impact of Meteorological and Hydrological Memory on Compound Peak Flows in the Rhine River Basin , 2019, Atmosphere.

[15]  N. Gillett,et al.  Southern Hemisphere subtropical drying as a transient response to warming , 2019, Nature Climate Change.

[16]  S. Drijfhout,et al.  The role of atmospheric rivers in compound events consisting of heavy precipitation and high storm surges along the Dutch coast , 2018, Natural Hazards and Earth System Sciences.

[17]  T. O'Kane,et al.  The Relationship between Wave Trains in the Southern Hemisphere Storm Track and Rainfall Extremes over Tasmania , 2018, Monthly Weather Review.

[18]  I. Rudeva,et al.  Sub‐synoptic scale features associated with extreme surface gusts during the South Australia Storm of September 2016 – Part I: characteristics of the event , 2018, Weather.

[19]  I. Simmonds,et al.  Sub synoptic scale features of the South Australia Storm of September 2016 – Part II: analysis of mechanisms driving the gusts , 2018, Weather.

[20]  O. Martius,et al.  Rossby Wave Packets on the Midlatitude Waveguide—A Review , 2018, Monthly Weather Review.

[21]  S. Seneviratne,et al.  Future climate risk from compound events , 2018, Nature Climate Change.

[22]  Alex Hall,et al.  Increasing precipitation volatility in twenty-first-century California , 2018, Nature Climate Change.

[23]  B. van den Hurk,et al.  Storm Surge and Extreme River Discharge: A Compound Event Analysis Using Ensemble Impact Modeling , 2018, Front. Earth Sci..

[24]  E. Fischer,et al.  Understanding the regional pattern of projected future changes in extreme precipitation , 2017 .

[25]  Clément Chevalier,et al.  Clustering of Regional-Scale Extreme Precipitation Events in Southern Switzerland , 2016 .

[26]  T. Delworth,et al.  Regional rainfall decline in Australia attributed to anthropogenic greenhouse gases and ozone levels , 2014 .

[27]  Markus G. Donat,et al.  The efficacy of using gridded data to examine extreme rainfall characteristics: a case study for Australia , 2013 .

[28]  Lukas Gudmundsson,et al.  Technical Note: Downscaling RCM precipitation to the station scale using statistical transformations – a comparison of methods , 2012 .

[29]  Ashish Sharma,et al.  Why continuous simulation? The role of antecedent moisture in design flood estimation , 2012 .

[30]  Karl E. Taylor,et al.  An overview of CMIP5 and the experiment design , 2012 .

[31]  N. Nakicenovic,et al.  RCP 8.5—A scenario of comparatively high greenhouse gas emissions , 2011 .

[32]  A. Sharma,et al.  How does the Interdecadal Pacific Oscillation affect design floods in Australia? , 2011 .

[33]  F. Giorgi,et al.  Resolution effects on regional climate model simulations of seasonal precipitation over Europe , 2010 .

[34]  D. Jones,et al.  High-quality spatial climate data-sets for Australia , 2009 .

[35]  M. Wheeler,et al.  On the Remote Drivers of Rainfall Variability in Australia , 2009 .

[36]  J. Christensen,et al.  On the need for bias correction of regional climate change projections of temperature and precipitation , 2008 .

[37]  Lukas H. Meyer,et al.  Summary for Policymakers , 2022, The Ocean and Cryosphere in a Changing Climate.

[38]  K. Ridgway.  Long‐term trend and decadal variability of the southward penetration of the East Australian Current , 2007 .

[39]  G. Hegerl,et al.  Changes in temperature and precipitation extremes in the IPCC ensemble of global coupled model simulations , 2007 .

[40]  G. Meehl,et al.  Contributions of external forcings to Southern Annular Mode trends , 2006 .

[41]  Richard J. Heggen,et al.  Normalized Antecedent Precipitation Index , 2001 .

[42]  J. Wallace,et al.  Annular Modes in the Extratropical Circulation. Part I: Month-to-Month Variability* , 2000 .

[43]  J. Evans,et al.  The role of topography on projected rainfall change in mid-latitude mountain regions , 2019, Climate Dynamics.

[44]  M. Manton,et al.  Evaluation of the AWAP daily precipitation spatial analysis with an independent gauge network in the Snowy Mountains , 2016 .

[45]  C. Tebaldi,et al.  Long-term Climate Change: Projections, Commitments and Irreversibility , 2013 .

[46]  W. Cai,et al.  Severe heat waves in Southern Australia: synoptic climatology and large scale connections , 2011, Climate Dynamics.

[47]  N. Bindoff,et al.  Climate Futures for Tasmania: Climate Modelling Technical Report , 2010 .

[48]  J. McGregor,et al.  An Updated Description of the Conformal-Cubic Atmospheric Model , 2008 .

[49]  L. Minty,et al.  Rainfall Antecedent to Large and Extreme Design Rainfall Events over Southeast Australia , 1999 .