Modeling

Time series of the Niño-3.4 SST index (°C) in observations (black curves) and ensemble-mean forecasts (colored curves) composited for 10 1-yr El Niño, 5 2-yr El Niño, 4 1-yr La Niña, 8 2-yr La Niña, 4 2-yr La Niña following strong El Niño, and 4 2-yr La Niña following moderate El Niño events during 1954–2015.
April 23, 2021

A new study by Wu and co-authors shows that the duration of individual ENSO events during 1954-2015 can be predicted up to two years in advance using a suite of multiyear retrospective forecasts conducted with the Community Earth System Model version 1, a climate model that well simulates the statistical and dynamical features of the temporal evolution of ENSO events.

Dye tracer released from the Beaufort Gyre region of the western Artic Ocean indicates freshwater transport through the Canadian Arctic Archipelago into the western Labrador Sea, causing freshening there
April 8, 2021

The Beaufort Sea increased its freshwater content by 40% over the past two decades. How and where this water will flow into the Atlantic Ocean is important for local and global ocean conditions. Zhang and colleagues simulated ocean circulation and tracked the Beaufort Sea freshwater’s spread during a historical release episode from 1983 to 1995.

Contrasting recent and future changes  in the Intertropical Convergence Zone
January 28, 2021

Under global warming, the ITCZ is projected to shift towards the equator, leading to squeeze in the annual-mean tropical ascent and far-reaching impacts on global circulation. Zhou and coauthors researched the observed and projected ITCZ changes based on a variety of observation and reanalysis datasets and ensemble projections of climate models, and found that the observed ITCZ changes are largely opposite to the projected future changes.

Spatial distribution of two widespread precipitation events that occurred on 8 May 1995 and 13 September 1961 and geometric illustration of the extent of an SHPE on the ground.
December 30, 2020

Najibi, Devineni, and co-authors present a new idea defined as simultaneous heavy precipitation events (SHPEs) to quantify extreme regional precipitation considering the spatial structure of extreme events. Quantifying the characteristics of SHPEs and modeling their footprints can improve the projections of flood risk and understanding of damages to interconnected infrastructure systems.

The fraction of 1- to 96-day variability in 250-hPa geopotential height anomalies that is associated with the MJO, according to cross-spectral analysis
October 5, 2020

Research by Toms et al. estimates how much impact the QBO has on the global teleconnection signature of the MJO. The authors use a spectral decomposition approach to quantify the relationships between the MJO and upper-tropospheric geopotential separately for each season of the year and for westerly and easterly QBO phases. Similar to previous studies, the results suggest that the MJO is related to upper-tropospheric geopotential anomalies across the globe. The novel contribution of the results lies in the analysis of the impacts of the QBO.

Sources of uncertainty in climate projections and their relative importance for different variables, regions and seasons
June 29, 2020

A new collection of single model initial-condition large ensembles (SMILEs) can test statistical assumptions with a cleaner separation between sources of uncertainty in climate projections. In particular, the potential bias at regional scales or for variables with a lot of internal variability can be greatly reduced.

Time of emergence of the anthropogenic signal in storm-related extreme sea level at New York in the GFDL CM4 simulations.
June 1, 2020

Yin and coauthors use the new GFDL CM4 and CM4HR models to consider a series of climate change experiments under the CMIP6 protocol to study characteristics of extreme sea level events and their future evolution in a fully coupled weather, climate, sea level, and storm surge modeling system. They found that even in the absence of global warming, the Gulf Coast is most vulnerable to hurricane-induced storm surge.

A schematic of the transport structure across the Labrador Sea.
May 13, 2020

Zou and coauthors analyzed the transport and property fields across the Labrador Sea using OSNAP observations and an ocean reanalysis dataset GloSea5 to study why recent observations revealed minimal contribution of the Labrador Sea convection to the subpolar AMOC strength. They found that the density compensation has important consequences on the strength of the overturning circulation.

Efficacy of tropical width perturbations versus normalized extratropical static stability
April 14, 2020

Internal variability and anthropogenic forcing have contributed to the widening of the tropical belt during the last several decades. To better understand the effect of individual anthropogenic drivers (including aerosols) on the tropical belt, Zhao, Allen, and coauthors utilize idealized simulations with very large single forcing perturbations in comprehensive coupled ocean-atmosphere models from the PDRMIP.

Zonally averaged multi-model average shortwave low cloud feedbacks
March 25, 2020

Zelinka and coauthors compared ECS values derived from CO2 quadrupling experiments conducted with CMIP6 and CMIP5 models and found that the latest models warm more than their predecessors by about 0.5˚C. The primary culprit for the enhanced warming was shown to be clouds.

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