the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Meteorological drought projections for Australia from downscaled high-resolution CMIP6 climate simulations
Abstract. Climate change is projected to lead to changes in rainfall patterns, which, when coupled with increasing evapotranspiration, has the potential to exacerbate future droughts. This study investigates the impacts of climate change on meteorological droughts in Australia using downscaled high-resolution CMIP6 climate models under three Shared Socioeconomic Pathway (SSP) scenarios. The Standardised Precipitation Index (SPI) and the Standardised Precipitation Evapotranspiration Index (SPEI) were used to assess changes to the frequency, duration, percent time, and spatial extent of droughts. There were consistent increases in droughts projected for south-west Western Australia, southern Victoria, southern South Australia, and western Tasmania using SPI and SPEI. There were significantly larger increases for SPEI derived droughts, with consistent increases projected for most of the country. The largest increases occurred at the end of the century and under the high emissions scenario (SSP370), demonstrating the influence of emissions on extreme droughts. For instance, if emissions reached high levels by the end of the century, the area subject to extreme drought in drought prone Southern Australia would be 2.8 greater than if they were kept to low levels using SPI, and 4 times greater if assessed using SPEI. The insights generated from these results and supplementary tailored datasets for Australian Local Government Areas and River Basins are essential to better inform decision making and future adaptation strategies at national, regional, and local scales.
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RC1: 'Comment on egusphere-2024-2341', Anonymous Referee #1, 12 Nov 2024
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The paper describes a set of drought projections for Australia developed by dynamically downscaling CMIP6 global climate models. A possible range of future drought conditions is considered that span multiple emissions pathways and model configurations. Future drought conditions are described through event frequency, duration, spatial extent and time spent in drought, in terms of changes in two commonly used drought metrics. The paper is well-structured, the information is clearly presented and the key results appropriately discussed. I recommend publication after minor revisions, which I describe below.
One key issue is the use of SPEI. This metric, being the difference between precipitation and potential evapotranspiration, is intended to reflect the atmospheric water balance and thereby give a complementary view to SPI-based drought. However, the use of potential evapotranspiration in the calculation of SPEI makes SPEI unrealistic in many water-limited parts of Australia, where actual evapotranspiration does not approach the potential upper limit. So, any projected worsening of PET-related conditions is merely an indication of an increase in atmospheric demand for moisture, rather than a conclusive reduction in water stores. I suggest this issue is more adequately discussed in the paper, including the implications in the interpretation of SPEI-based projections of drought.
The second key issue is the lack of attention given to the uncertainty of the projections. While using a multi-model ensemble and multiple emissions pathways goes some way to addressing uncertainty, the drought projections should be presented along with quantified uncertainty estimates. Moreover, the issue of uncertainty propagation from GCM through to downscaling technique to RCM was not addressed.
The final key issue is that one of the most crucial findings of the study needs to be made more prominent. The results show that more time is projected to be spent under extreme conditions, both wet and dry, and less time under ‘normal’ conditions, for some parts of Australia (Table 3). This result should be made more prominent, for example by featuring in the abstract. This result is important because it suggests that the combination of projected changes in the climate system is shifting the dial towards more extreme climatic conditions and motivates future research in understanding the physical processes responsible for the shift.
Minor comments:
- L84: this is a bit of a throw away line. I suggest turning this around by stating that since RCMs have been shown to estimate regional rainfall features with higher precision than GCMs, RCMs are more appropriate to study drought on the regional scale.
- Inter-model variability (Figure 11) is shown to be higher for SPEI and some drought characteristics. Can an explanation be offered for why this is? What are the implications of this variability on the interpretation of future drought changes?
Citation: https://doi.org/10.5194/egusphere-2024-2341-RC1 -
CC1: 'Comment on egusphere-2024-2341', Sivarajah Mylevaganam, 22 Nov 2024
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HESS is an open-access journal. For your review, I have included an excerpt from the journal office's official website(https://www.hydrology-and-earth-system-sciences.net/) below.
“Hydrology and Earth System Sciences (HESS) is a not-for-profit international two-stage open-access journal for the publication of original research in hydrology. HESS encourages and supports fundamental and applied research that advances the understanding of hydrological systems, their role in providing water for ecosystems and society, and the role of the water cycle in the functioning of the Earth system. A multi-disciplinary approach is encouraged that broadens the hydrological perspective and the advancement of hydrological science through integration with other cognate sciences and cross-fertilization across disciplinary boundaries.”
Why would the journal office entertain anonymous referees? If the journal is an open-access journal, how could the anonymous referees’ reviews fit into the journal’s statement of openness?
Do the authors have rights to request the journal office to disclose the names of the referees who are scared to disclose their names?
Do the readers of the journal have rights to request the journal office to disclose the names of the referees who are scared to disclose their names?
Could it be possible for the journal office to have clerical staff to post reviews as invited referees? Is this what we expect from EU and its official statements?
What is the relationship between the handling editor and the invited referees? Are the referees paying the handling editors to get them invited?
Why would an invited referee be scared to disclose his/her name in an open-access journal? Is it because he/she is unqualified and lacks potential and expertise in his/her field of specialization to demonstrate in an open-access journal?
I am requesting the handling editor to disclose the reason for promoting anonymity in an open-access journal. I am also requesting the journal office to disclose the rationale behind appointing the handling editors and referees. I request the journal office to disclose academic transcripts of the handling editors and referees. What did they do in their PhD work? Who were their supervisors? What were their GER scores in their postgraduate studies? How many billions have been invested in their PhD philosophies? These details are pertinent to showcase that the EU and the journal office don’t favor appointing handling editors and referees in an open-access journal.
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