Influences of atmospheric blocking on North American summer heatwaves in a changing climate: a comparison of two Canadian Earth system model large ensembles
Bibliographic record
Abstract
Abstract As summer heatwaves have severe adverse impacts on human society and ecosystems, there is need to better understand their meteorological drivers and future projections under climate change. This study investigates the linkage between atmospheric blocking and summer (June–August) heatwaves over North America using two reanalysis datasets (ERA-Interim and NCEP-DOE-R2) and two large-ensembles of Canadian Earth System Models (CanESM2 and CanESM5) for the 1981–2010 baseline period as well as projected changes under high-emission scenarios out to 2071–2100. Compared to NCEP-DOE-R2, both ensembles underestimate summer blocking frequency in the north Pacific, Alaska, and western Canada (by − 37%), while CanESM2 ensemble also underestimates blocking frequency in central and eastern Canada (by − 36%). CanESM5 generally shows better performance than CanESM2 in its reproduction of blocking frequency over central and eastern Canada, which is consistent with its overall improvements in simulating large-scale climate patterns. The two ensembles, however, agree with the reanalyses in their blocking-heatwave linkages. Above-normal heatwave frequency occurs in the blocking core and its surroundings due to positive heat flux anomalies, while below-normal frequency occurs at remote locations on the eastern and/or southern flanks of the blocking core due to cold air temperature advection anomalies. Future projections in central Canada differ between the models, largely due to the significant under-representation of blocking frequency by CanESM2. However, the two ensembles generally project similar behavior between the baseline and future period for spatial distributions of blocking-heatwave linkages, indicating blocking will continue to play an important role in the development of summer heatwaves in the future.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".