Recent trends in extratropical lows and their rainfall over Australia
Acacia Pepler A *A
Abstract
Low pressure systems are an important source of rainfall in southern Australia, particularly deep lows that extend from the surface to at least 500 hPa. This paper uses multiple reanalyses to assess long-term trends in lows over the period 1959–2023, and identifies statistically significant decreasing trends in the number of surface low pressure systems near southern Australia during May–October, linked to a decrease in cyclogenesis near south-western Western Australia. Trends in lows at 500 hPa are also negative but weaker than at the surface, and are less consistent between reanalyses owing to less consistent observations through time. The spatial pattern of observed declines during the cool season is consistent with trends using eight CMIP6 models, but global climate models systematically underestimate the magnitude of the observed decline in surface lows. Trends in rainfall associated with lows are also shown, including assessing the sensitivity of trends to the specific years used. Despite well above average numbers of lows and enhanced rainfall during recent La Niña years 2020–2022, total rainfall from low pressure systems is declining during the cool season in south-east Australia. Trends in rainfall from lows are largest on the east coast, where they explain more than 70% of observed rainfall changes since the 1960s.
Keywords: Australia, climate change, CMIP6, cyclone, extratropical low, extreme precipitation, rainfall, reanalysis, trend.
References
Abram NJ, Wright NM, Ellis B, Dixon BC, Wurtzel JB, England MH, et al. (2020) Coupling of Indo-Pacific climate variability over the last millennium. Nature 579(7799), 385-392.
| Crossref | Google Scholar | PubMed |
Abram NJ, Henley BJ, Sen Gupta A, Lippmann TJR, Clarke H, Dowdy AJ, et al. (2021) Connections of climate change and variability to large and extreme forest fires in southeast Australia. Communications Earth & Environment 2(1), 8.
| Crossref | Google Scholar |
Barnes MA, King M, Reeder M, Jakob C (2023) The dynamics of slow‐moving coherent cyclonic potential vorticity anomalies and their links to heavy rainfall over the eastern seaboard of Australia. Quarterly Journal of the Royal Meteorological Society 149, 2233-2251.
| Crossref | Google Scholar |
Bell B, Hersbach H, Simmons A, Berrisford P, Dahlgren P, Horányi A, et al. (2021) The ERA5 global reanalysis: preliminary extension to 1950. Quarterly Journal of the Royal Meteorological Society 147(741), 4186-4227.
| Crossref | Google Scholar |
Bentsen M, Oliviè DJL, Seland Ø, Toniazzo T, et al. (2019) NCC NorESM2-MM model output prepared for CMIP6 CMIP historical. Version 20190514. (Earth System Grid Federation) [Dataset] doi:10.22033/ESGF/CMIP6.8040
Booth JF, Naud CM, Jeyaratnam J (2018) Extratropical cyclone precipitation life cycles: a satellite-based analysis. Geophysical Research Letters 2009, 8647-8654.
| Crossref | Google Scholar |
Browning SA, Goodwin ID (2013) Large-scale influences on the evolution of winter subtropical maritime cyclones affecting Australia’s east coast. Monthly Weather Review 141(7), 2416-2431.
| Crossref | Google Scholar |
Catto JL (2016) Extratropical cyclone classification and its use in climate studies. Reviews of Geophysics 54(2), 486-520.
| Crossref | Google Scholar |
Cavicchia L, Pepler A, Dowdy A, Walsh K (2019) A physically based climatology of the occurrence and intensification of Australian east coast lows. Journal of Climate 32(10), 2823-2841.
| Crossref | Google Scholar |
Chand SS, Dowdy AJ, Ramsay HA, Walsh KJE, Tory KJ, Power SB, et al. (2019) Review of tropical cyclones in the Australian region: Climatology, variability, predictability, and trends. Wiley Interdisciplinary Reviews: Climate Change 10(5), 1-17.
| Crossref | Google Scholar |
Chand SS, Walsh KJE, Camargo SJ, Kossin JP, Tory KJ, Wehner MF, et al. (2022) Declining tropical cyclone frequency under global warming. Nature Climate Change 12(7), 655-661.
| Crossref | Google Scholar |
CSIRO, Bureau of Meteorology (2015) Climate change in Australia: projections for Australia’s NRM regions. Technical report. (CSIRO and Bureau of Meteorology) Available at https://www.climatechangeinaustralia.gov.au/media/ccia/2.2/cms_page_media/168/CCIA_2015_NRM_TechnicalReport_WEB.pdf
Dey R, Lewis SC, Arblaster JM, Abram NJ (2019) A review of past and projected changes in Australia’s rainfall. Wiley Interdisciplinary Reviews: Climate Change 10(3), e577.
| Crossref | Google Scholar |
Dey R, Gallant AJE, Lewis SC (2020) Evidence of a continent-wide shift of episodic rainfall in Australia. Weather and Climate Extremes 29, 100274.
| Crossref | Google Scholar |
Dix M, Bi D, Dobrohotoff P, Fiedler R, et al. (2019) CSIRO-ARCCSS ACCESS-CM2 model output prepared for CMIP6 CMIP historical. Version 20210607. (Earth System Grid Federation) [Dataset] doi:10.22033/ESGF/CMIP6.4271
Dowdy AJ (2020) Climatology of thunderstorms, convective rainfall and dry lightning environments in Australia. Climate Dynamics 54(5), 3041-3052.
| Crossref | Google Scholar |
Dowdy AJ, Catto JL (2017) Extreme weather caused by concurrent cyclone, front and thunderstorm occurrences. Scientific Reports 7, srep40359.
| Crossref | Google Scholar |
Dowdy AJ, Mills GA, Timbal B, Wang Y (2013) Changes in the risk of extratropical cyclones in eastern Australia. Journal of Climate 26(4), 1403-1417.
| Crossref | Google Scholar |
Dowdy AJ, Pepler A, Di Luca A, Cavicchia L, Mills G, Evans J, et al. (2019) Review of Australian east coast low pressure systems and associated extremes. Climate Dynamics 53, 4887.
| Crossref | Google Scholar |
EC-Earth Consortium (2019) EC-Earth-Consortium EC-Earth3 model output prepared for CMIP6 CMIP historical. Version 20200310. (Earth System Grid Federation) [Dataset] doi:10.22033/ESGF/CMIP6.4700
Eyring V, Bony S, Meehl GA, Senior CA, Stevens B, Stouffer RJ, Taylor KE (2016) Overview of the Coupled Model Intercomparison Project Phase 6 (CMIP6) experimental design and organization. Geoscientific Model Development 9(5), 1937-1958.
| Crossref | Google Scholar |
Fogt RL, Marshall GJ (2020) The Southern Annular Mode: variability, trends, and climate impacts across the Southern Hemisphere. Wiley Interdisciplinary Reviews: Climate Change 11(4), e652.
| Crossref | Google Scholar |
Frederiksen CS, Frederiksen JS, Sisson JM, Osbrough SL (2016) Trends and projections of Southern Hemisphere baroclinicity: the role of external forcing and impact on Australian rainfall. Climate Dynamics 48(9–10), 3261-3282.
| Crossref | Google Scholar |
Freund MB, Henley BJ, Karoly DJ, McGregor HV, Abram NJ, Dommenget D (2019) Higher frequency of Central Pacific El Niño events in recent decades relative to past centuries. Nature Geoscience 12(6), 450-455.
| Crossref | Google Scholar |
Grieger J, Leckebusch GC, Donat MG, Schuster M, Ulbrich U (2014) Southern Hemisphere winter cyclone activity under recent and future climate conditions in multi-model AOGCM simulations. International Journal of Climatology 34(12), 3400-3416.
| Crossref | Google Scholar |
Grose MR, Narsey S, Delage FP, Dowdy AJ, Bador M, Boschat G, et al. (2020) Insights from CMIP6 for Australia’s future climate. Earth’s Future 8, e2019EF001469.
| Crossref | Google Scholar |
Grose MR, Michael R, Narsey S, Trancoso R, Mackallah C, Delage F, Dowdy A, et al. (2023) A CMIP6-based multi-model downscaling ensemble to underpin climate change services in Australia. Climate Services 30, 100368.
| Crossref | Google Scholar |
Hawcroft MK, Shaffrey LC, Hodges KI, Dacre HF (2012) How much Northern Hemisphere precipitation is associated with extratropical cyclones? Geophysical Research Letters 39, L24809.
| Crossref | Google Scholar |
Hersbach H, Bell B, Berrisford P, Hirahara S, Horányi A, Muñoz‐Sabater J, et al. (2020) The ERA5 global reanalysis. Quarterly Journal of the Royal Meteorological Society 146(730), 1999-2049.
| Crossref | Google Scholar |
Hope PK, Drosdowsky W, Nicholls N (2006) Shifts in the synoptic systems influencing southwest Western Australia. Climate Dynamics 26(7), 751-764.
| Crossref | Google Scholar |
Hopkins LC, Holland GJ (1997) Australian heavy-rain days and associated east coast cyclones: 1958–92. Journal of Climate 10(4), 621-634.
| Crossref | Google Scholar |
Hurley JV, Boos WR (2015) A global climatology of monsoon low-pressure systems. Quarterly Journal of the Royal Meteorological Society 141(689), 1049-1064.
| Crossref | Google Scholar |
Ji F, Pepler AS, Browning S, Evans JP, Di Luca A (2018) Trends and low frequency variability of east coast lows in the twentieth century. Journal of Southern Hemisphere Earth System Science 68, 1-15.
| Crossref | Google Scholar |
Jones DA, Wang W, Fawcett R (2009) High-quality spatial climate data-sets for Australia. Australian Meteorological and Oceanographic Journal 58(4), 233-248.
| Crossref | Google Scholar |
Jungclaus J, Bittner M, Wieners K, Wachsmann F, et al. (2019) MPI-M MPI-ESM1.2-HR model output prepared for CMIP6 CMIP historical. Version 20190815. (Earth System Grid Federation) [Dataset] doi:10.22033/ESGF/CMIP6.6594
Kalnay E, Kanamitsu M, Kistler R, Collins W, Deaven D, Gandin L, et al. (1996) The NCEP/NCAR 40-Year Reanalysis Project. Bulletin of the American Meteorological Society 77(3), 437-471.
| Crossref | Google Scholar |
Kobayashi S, Ota Y, Harada Y, Ebita A, Moriya M, Onoda H, et al. (2015) The JRA-55 reanalysis: general specifications and basic characteristics. Journal of the Meteorological Society of Japan. Ser. II 93(1), 5-48.
| Crossref | Google Scholar |
Lavender SL, Abbs DJ (2013) Trends in Australian rainfall: contribution of tropical cyclones and closed lows. Climate Dynamics 40(1–2), 317-326.
| Crossref | Google Scholar |
Lim EP, Hendon HH, Butler AH, Thompson DWJ, Lawrence ZD, Scaife AA, et al. (2021) The 2019 southern hemisphere stratospheric polar vortex weakening and its impacts. Bulletin of the American Meteorological Society 102(6), E1150-E1171.
| Crossref | Google Scholar |
Lovato T, Peano D, Butenschön M (2021) CMCC CMCC-ESM2 model output prepared for CMIP6 CMIP historical. Version 20210114. (Earth System Grid Federation) [Dataset] doi:10.22033/ESGF/CMIP6.13195
McKay RC, Boschat G, Rudeva I, Pepler A, Purich A, Dowdy A, et al. (2023) Can southern Australian rainfall decline be explained? A review of possible drivers. WIREs Climate Change 14, e820.
| Crossref | Google Scholar |
Murray RJ, Simmonds I (1991) A numerical scheme for tracking cyclone centres from digital data. Part I: development and operation of the scheme. Australian Meteorological Magazine 39(3), 155-166.
| Google Scholar |
Neu U, Akperov MG, Bellenbaum N, Benestad R, Blender R, Caballero R, et al. (2013) Imilast: A community effort to intercompare extratropical cyclone detection and tracking algorithms. Bulletin of the American Meteorological Society 94(4), 529-547.
| Crossref | Google Scholar |
Pepler A (2020) Record lack of cyclones in southern Australia during 2019. Geophysical Research Letters 47(13), e2020GL088488.
| Crossref | Google Scholar |
Pepler A, Dowdy A (2020) A three-dimensional perspective on extratropical cyclone impacts. Journal of Climate 33(13), 5635-5649.
| Crossref | Google Scholar |
Pepler A, Dowdy A (2021a) Fewer deep cyclones projected for the midlatitudes in a warming climate, but with more intense rainfall. Environmental Research Letters 16(5),.
| Crossref | Google Scholar |
Pepler A, Dowdy A (2021b) Intense east coast lows and associated rainfall in eastern Australia. Journal of Southern Hemisphere Earth Systems Science 71, 110-122.
| Crossref | Google Scholar |
Pepler AS, Dowdy AJ (2022) Australia’s future extratropical cyclones. Journal of Climate 35, 7795-7810.
| Crossref | Google Scholar |
Pepler AS, Rakich CS (2010) Extreme inflow events and synoptic forcing in Sydney catchments. IOP Conference Series: Earth and Environmental Science 11(1), 12010.
| Crossref | Google Scholar |
Pepler AS, Rudeva I (2023) Anomalous subtropical zonal winds drive decreases in southern Australian frontal rain. Weather and Climate Dynamics 4(1), 175-188.
| Crossref | Google Scholar |
Pepler AS, Di Luca A, Ji F, Alexander LV, Evans JP, Sherwood SC (2015) Impact of identification method on the inferred characteristics and variability of Australian east coast lows. Monthly Weather Review 143(3), 864-877.
| Crossref | Google Scholar |
Pepler AS, Fong J, Alexander LV (2017) Australian east coast mid-latitude cyclones in the 20th Century reanalysis ensemble. International Journal of Climatology 37(4), 2187-2192.
| Crossref | Google Scholar |
Pepler A, Dowdy A, Hope P (2019) A global climatology of surface anticyclones, their variability, associated drivers and long-term trends. Climate Dynamics 52, 5397.
| Crossref | Google Scholar |
Pepler AS, Dowdy AJ, van Rensch P, Rudeva I, Catto JL, Hope P (2020) The contributions of fronts, lows and thunderstorms to southern Australian rainfall. Climate Dynamics 55(5–6), 1489-1505.
| Crossref | Google Scholar |
Pepler AS, Dowdy AJ, Hope P (2021) The differing role of weather systems in southern Australian rainfall between 1979–1996 and 1997–2015. Climate Dynamics 56(7–8), 2289-2302.
| Crossref | Google Scholar |
Priestley MDK, Catto JL (2022) Future changes in the extratropical storm tracks and cyclone intensity, wind speed, and structure. Weather and Climate Dynamics 3(1), 337-360.
| Crossref | Google Scholar |
Priestley MDK, Ackerley D, Catto JL, Hodges KI, McDonald RE, Lee RW (2020) An overview of the extratropical storm tracks in CMIP6 historical simulations. Journal of Climate 33(15), 6315-6343.
| Crossref | Google Scholar |
Rauniyar SP, Power SB (2020) The impact of anthropogenic forcing and natural processes on past, present, and future rainfall over Victoria, Australia. Journal of Climate 33(18), 8087-8106.
| Crossref | Google Scholar |
Rauniyar SP, Hope P, Power SB, Grose M, Jones D (2023) The role of internal variability and external forcing on southwestern Australian rainfall: prospects for very wet or dry years. Scientific Reports 13(1), 21578.
| Crossref | Google Scholar | PubMed |
Risbey JS, Pook MJ, McIntosh PC, Wheeler MC, Hendon HH (2009) On the remote drivers of rainfall variability in Australia. Monthly Weather Review 137(10), 3233-3253.
| Crossref | Google Scholar |
Risbey JS, Mcintosh PC, Pook MJ (2013a) Synoptic components of rainfall variability and trends in southeast Australia. International Journal of Climatology 33(11), 2459-2472.
| Crossref | Google Scholar |
Risbey JS, Pook MJ, McIntosh PC (2013b) Spatial trends in synoptic rainfall in southern Australia. Geophysical Research Letters 40(14), 3781-3785.
| Crossref | Google Scholar |
Seferian R (2018) CNRM-CERFACS CNRM-ESM2-1 model output prepared for CMIP6 CMIP historical. Version 20181206. (Earth System Grid Federation) [Dataset] doi:10.22033/ESGF/CMIP6.4068
Simmonds I, Murray RJ, Leighton RM (1999) A refinement of cyclone tracking methods with data from FROST. Australian Meteorological Magazine SP, 35-49.
| Google Scholar |
Slivinski LC, Compo GP, Whitaker JS, Sardeshmukh PD, Giese BS, McColl C, Allan R, Yin X, Vose R, Titchner H, Kennedy J, Spencer LJ, Ashcroft L, Brönnimann S, Brunet M, Camuffo D, Cornes R, Cram TA, Crouthamel R, Domínguez‐Castro F, Freeman JE, Gergis J, Hawkins E, Jones PD, Jourdain S, Kaplan A, Kubota H, Blancq FL, Lee T, Lorrey A, Luterbacher J, Maugeri M, Mock CJ, Moore GWK, Przybylak R, Pudmenzky C, Reason C, Slonosky VC, Smith CA, Tinz B, Trewin B, Valente MA, Wang XL, Wilkinson C, Wood K, Wyszyński P (2019) Towards a more reliable historical reanalysis: improvements for version 3 of the Twentieth Century reanalysis system. Quarterly Journal of the Royal Meteorological Society 145(724), 2876-2908.
| Crossref | Google Scholar |
Speer M, Wiles P, Pepler A (2009) Low pressure systems off the New South Wales coast and associated hazardous weather: establishment of a database. Australian Meteorological and Oceanographic Journal 58(01), 29-39.
| Crossref | Google Scholar |
Timbal B, Drosdowsky W (2013) The relationship between the decline of southeastern Australian rainfall and the strengthening of the subtropical ridge. International Journal of Climatology 33(4), 1021-1034.
| Crossref | Google Scholar |
Timbal B, Arblaster J, Braganza K, Fernandez E, Hendon H, Murphy B, et al. (2010) Understanding the anthropogenic nature of the observed rainfall decline across south eastern Australia. CAWCR Technical Report Number 26, July 2010. (CSIRO and Bureau of Meteorology: Melbourne, Vic., Australia) Available at http://www.bom.gov.au/research/publications/cawcrreports/CTR_026.pdf
Utsumi N, Kim H, Kanae S, Oki T (2017) Relative contributions of weather systems to mean and extreme global precipitation. Journal of Geophysical Research: Atmospheres 122, 152-167.
| Crossref | Google Scholar |
Wang XL, Feng Y, Chan R, Isaac V (2016) Inter-comparison of extra-tropical cyclone activity in nine reanalysis datasets. Atmospheric Research 181, 133-153.
| Crossref | Google Scholar |
Wasko C, Westra S, Nathan R, Pepler A, Raupach TH, Dowdy A, Johnson F, Ho M, McInnes KL, Jakob D, Evans J, Villarini G, Fowler HJ (2024) A systematic review of climate change science relevant to Australian design flood estimation. Hydrology and Earth System Sciences 28(5), 1251-1285.
| Crossref | Google Scholar |
Yukimoto S, Koshiro T, Kawai H, Oshima N, et al. (2019) MRI MRI-ESM2.0 model output prepared for CMIP6 CMIP historical, Version 20190722. (Earth System Grid Federation) [Dataset] doi:10.22033/ESGF/CMIP6.6842
Ziehn T, Chamberlain M, Lenton A, Law R (2019) CSIRO ACCESS-ESM1.5 model output prepared for CMIP6 CMIP historical, Version 20200529. (Earth System Grid Federation) [Dataset] doi:10.22033/ESGF/CMIP6.4272