<p>The presence of inherent systematic biases in global Earth System Climate models limit their ability to accurately represent oceanic and atmospheric processes at regional scales. Therefore, the available estimates of future changes in air temperature (T2M) and precipitation (PR) from these models, are subject to high uncertainty. This study evaluates the performance of five widely used bias-correction methods using two reanalysis datasets. Among them, Quantile Mapping (QM) and Time-varying Delta (TVD) show comparable performance, with TVD marginally outperforming QM. An ensemble approach combining TVD and QM (ETQM) leverages the strengths of both methods, outperforming other methods. It is then applied to correct biases in T2M and PR from three selected Coupled Model Intercomparison Project Phase 6 (CMIP6) models over the Indian Ocean region. The upper T2M extremes in the historical period (1980–2014) are corrected by approximately 1.5<InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="382_2025_7685_Article_IEq1.gif" Format="GIF" Height="13" Rendition="HTML" Resolution="72" Type="Linedraw" Width="19" /> </InlineMediaObject> <EquationSource Format="TEX">\(-\)</EquationSource> <EquationSource Format="MATHML"><math> <mo>-</mo> </math></EquationSource> </InlineEquation>4.5%. A persistent positive bias in PR extremes over the west-central Indian Ocean is reduced by 30–40%. In future projections, the upper T2M extremes decrease by approximately 4.0<InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="382_2025_7685_Article_IEq2.gif" Format="GIF" Height="13" Rendition="HTML" Resolution="72" Type="Linedraw" Width="19" /> </InlineMediaObject> <EquationSource Format="TEX">\(-\)</EquationSource> <EquationSource Format="MATHML"><math> <mo>-</mo> </math></EquationSource> </InlineEquation>5.0% across most of the study region. The variance in T2M anomalies (relative to the historical period) show a decline of 4.0<InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="382_2025_7685_Article_IEq3.gif" Format="GIF" Height="13" Rendition="HTML" Resolution="72" Type="Linedraw" Width="19" /> </InlineMediaObject> <EquationSource Format="TEX">\(-\)</EquationSource> <EquationSource Format="MATHML"><math> <mo>-</mo> </math></EquationSource> </InlineEquation>7.0% between 2015–2040, which further increases to 16.0<InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="382_2025_7685_Article_IEq4.gif" Format="GIF" Height="13" Rendition="HTML" Resolution="72" Type="Linedraw" Width="19" /> </InlineMediaObject> <EquationSource Format="TEX">\(-\)</EquationSource> <EquationSource Format="MATHML"><math> <mo>-</mo> </math></EquationSource> </InlineEquation>22.0% by 2071–2100. The difference in PR anomaly variance before and after bias correction are significant but do not show a substantial change in future periods. Overall, the bias correction suggests a future that is cooler than original CMIP6 model projections. Finally, the bias-corrected T2M and PR will be valuable for driving regional ocean-climate models in climate change studies.</p>

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Future changes in bias-corrected CMIP6 earth system model’s air temperature and precipitation over the Indian Ocean Region

  • Prasanna Kanti Ghoshal,
  • A. P. Joshi,
  • Kunal Chakraborty,
  • Riccardo Farneti,
  • Vinu Valsala

摘要

The presence of inherent systematic biases in global Earth System Climate models limit their ability to accurately represent oceanic and atmospheric processes at regional scales. Therefore, the available estimates of future changes in air temperature (T2M) and precipitation (PR) from these models, are subject to high uncertainty. This study evaluates the performance of five widely used bias-correction methods using two reanalysis datasets. Among them, Quantile Mapping (QM) and Time-varying Delta (TVD) show comparable performance, with TVD marginally outperforming QM. An ensemble approach combining TVD and QM (ETQM) leverages the strengths of both methods, outperforming other methods. It is then applied to correct biases in T2M and PR from three selected Coupled Model Intercomparison Project Phase 6 (CMIP6) models over the Indian Ocean region. The upper T2M extremes in the historical period (1980–2014) are corrected by approximately 1.5 \(-\) - 4.5%. A persistent positive bias in PR extremes over the west-central Indian Ocean is reduced by 30–40%. In future projections, the upper T2M extremes decrease by approximately 4.0 \(-\) - 5.0% across most of the study region. The variance in T2M anomalies (relative to the historical period) show a decline of 4.0 \(-\) - 7.0% between 2015–2040, which further increases to 16.0 \(-\) - 22.0% by 2071–2100. The difference in PR anomaly variance before and after bias correction are significant but do not show a substantial change in future periods. Overall, the bias correction suggests a future that is cooler than original CMIP6 model projections. Finally, the bias-corrected T2M and PR will be valuable for driving regional ocean-climate models in climate change studies.