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305 results on '"ARBLASTER, JULIE M."'

9. Processes that Contribute to Future South Asian Monsoon Differences in E3SMv2 and CESM2.

Author

Meehl, Gerald A., Shields, Christine A., Arblaster, Julie M., Fasullo, John, Rosenbloom, Nan, Hu, Aixue, Neale, Richard, Capotondi, Antonietta, Golaz, Jean‐Christophe, Van Roekel, Luke, and Annamalai, H.

Subjects
WALKER circulation, ATMOSPHERIC circulation, MONSOONS, EL Nino
Abstract

Two Earth system models are analyzed to gain insight into the processes that govern projected changes in the South Asian monsoon. Warmer present‐day base state tropical SSTs contribute to coupled processes that produce greater future tropical Pacific warming in CESM2 with less of an increase in season‐mean monsoon precipitation compared to E3SMv2. This is attributed to changes in the large‐scale east‐west atmospheric Walker circulation, with relatively larger increases in precipitation and upper‐level divergence over the tropical Pacific and increases in upper‐level convergence over South Asia in CESM2. The stronger El Niño‐like response in CESM2, which increases Pacific precipitation and upper‐level divergence farther to the east, and larger future ENSO amplitude in E3SMv2, produce a greater relative increase in future monsoon‐ENSO connections in E3SMv2 compared to CESM2. This analysis indicates that the key processes that affect future monsoon‐ENSO connections are ENSO amplitude and size of the future tropical Pacific El Niño‐like response. Plain Language Summary: Two different Earth system models are analyzed to investigate processes that contribute to possible future changes of South Asian monsoon precipitation and connections to ENSO. The stronger increase of precipitation in CESM2 over the tropical Pacific, due in part to a larger El Niño‐like response of Pacific SSTs, produces less of an increase in future monsoon precipitation in CESM2 compared to E3SMv2. The eastward shift of precipitation in CESM2, along with the larger increase of ENSO amplitude in E3SMv2, produce a stronger future monsoon‐ENSO connection in E3SMv2 compared to CESM2. Key Points: Warmer future tropical Pacific SSTs in CESM2 compared to E3SMv2 produce less of an increase in South Asian monsoon precipitation through the Walker CirculationFuture monsoon‐ENSO connections are stronger in E3SMv2 compared to CESM2 due to larger increases in future ENSO amplitude and shifts in the Walker CirculationKey processes that affect future monsoon‐ENSO connections are ENSO amplitude and the size of the future tropical Pacific El Niño‐like response [ABSTRACT FROM AUTHOR]

Published
2024
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15. Identifying human influences on atmospheric temperature

Author

Santer, Benjamin D, Painter, Jeffrey F, Mears, Carl A, Doutriaux, Charles, Caldwell, Peter, Arblaster, Julie M, Cameron-Smith, Philip J, Gillett, Nathan P, Gleckler, Peter J, Lanzante, John, Perlwitz, Judith, Solomon, Susan, Stott, Peter A, Taylor, Karl E, Terray, Laurent, Thorne, Peter W, Wehner, Michael F, Wentz, Frank J, Wigley, Tom ML, Wilcox, Laura J, and Zou, Cheng-Zhi

Subjects
Earth Sciences, Atmospheric Sciences, Climate Action, Atmosphere, Climate Change, Computer Simulation, Geography, Human Activities, Humans, Models, Theoretical, Signal-To-Noise Ratio, Temperature, climate change detection and attribution, climate modeling, multimodel analysis
Abstract

We perform a multimodel detection and attribution study with climate model simulation output and satellite-based measurements of tropospheric and stratospheric temperature change. We use simulation output from 20 climate models participating in phase 5 of the Coupled Model Intercomparison Project. This multimodel archive provides estimates of the signal pattern in response to combined anthropogenic and natural external forcing (the fingerprint) and the noise of internally generated variability. Using these estimates, we calculate signal-to-noise (S/N) ratios to quantify the strength of the fingerprint in the observations relative to fingerprint strength in natural climate noise. For changes in lower stratospheric temperature between 1979 and 2011, S/N ratios vary from 26 to 36, depending on the choice of observational dataset. In the lower troposphere, the fingerprint strength in observations is smaller, but S/N ratios are still significant at the 1% level or better, and range from three to eight. We find no evidence that these ratios are spuriously inflated by model variability errors. After removing all global mean signals, model fingerprints remain identifiable in 70% of the tests involving tropospheric temperature changes. Despite such agreement in the large-scale features of model and observed geographical patterns of atmospheric temperature change, most models do not replicate the size of the observed changes. On average, the models analyzed underestimate the observed cooling of the lower stratosphere and overestimate the warming of the troposphere. Although the precise causes of such differences are unclear, model biases in lower stratospheric temperature trends are likely to be reduced by more realistic treatment of stratospheric ozone depletion and volcanic aerosol forcing.

Published
2013

40. Monsoon Regimes in the CCSM3

Author

Meehl, Gerald A., Arblaster, Julie M., Lawrence, David M., Seth, Anji, Schneider, Edwin K., Kirtman, Ben P., and Min, Dughong

Published
2006

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