Anthropogenic aerosol forcing of Atlantic tropical storms

Dunstone, Nick; Smith, Douglas M.; Booth, Ben B. B.; Hermanson, Leon; Eade, Rosie

doi:10.1038/ngeo1854

Cited by 154 publications

(138 citation statements)

References 28 publications

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“…9f) is not well predicted by the DePreSys. However, further examination of the 20th Century reanalysis (Compo et al 2011) reveals a significant drying over the tropical North Atlantic ocean in this period (not shown, but see Dunstone et al (2013) for rainfall anomalies in the main hurricane development region). Although there is uncertainty related to precipitation in the 20th Century reanalysis, the similarity with DePreSys suggests that the 1960s cooling of the North Atlantic may have contributed to a southward shift of the ITCZ.…”

Section: Climate Impactsmentioning

confidence: 99%

Decadal predictions of the cooling and freshening of the North Atlantic in the 1960s and the role of ocean circulation

2014

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In the 1960s North Atlantic sea surface temperatures (SST) cooled rapidly. The magnitude of the cooling was largest in the North Atlantic subpolar gyre (SPG), and was coincident with a rapid freshening of the SPG. Here we analyze hindcasts of the 1960s North Atlantic cooling made with the UK Met Office's decadal prediction system (DePreSys), which is initialised using observations. It is shown that DePreSys captures-with a lead time of several years-the observed cooling and freshening of the North Atlantic SPG. DePreSys also captures changes in SST over the wider North Atlantic and surface climate impacts over the wider region, such as changes in atmospheric circulation in winter and sea ice extent. We show that initialisation of an anomalously weak Atlantic Meridional Overturning Circulation (AMOC), and hence weak northward heat transport, is crucial for DePreSys to predict the magnitude of the observed cooling. Such an anomalously weak AMOC is not captured when ocean observations are not assimilated (i.e. it is not a forced response in this model). The freshening of the SPG is also dominated by ocean salt transport changes in DePreSys; in particular, the simulation of advective freshwater anomalies analogous to the Great Salinity Anomaly were key. Therefore, DePreSys suggests that ocean dynamics played an important role in the cooling of the North Atlantic in the 1960s, and that this event was predictable.

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Section: Climate Impactsmentioning

confidence: 99%

Decadal predictions of the cooling and freshening of the North Atlantic in the 1960s and the role of ocean circulation

2014

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“…HadGEM2-ES (~200 km equatorial resolution) cannot adequately represent the central pressure of hurricanes, but metrics for coarse resolution models as indicators of hurricane frequency have been developed that may be compared against suitably averaged observations focused on the Maximum Development Region Smith et al, 2010;Knutson et al, 2010;Dunstone et al, 2013]. Equilibrating the hemispheric albedos in STRAT reduces biases in MDR wind shear (owing to the reduction in the westerly bias in the tropical upper troposphere shown in Figure 4), precipitation (owing to the increase in the precipitation shown in Figure 1b), and the tropical storm index (see supporting information Figure S6), by 58%, 82%, and 52%, respectively, when compared to the observational/reanalysis products, indicating a significant improvement in model performance.…”

Section: 1002/2015gl066903mentioning

confidence: 99%

The impact of equilibrating hemispheric albedos on tropical performance in the HadGEM2‐ES coupled climate model

Haywood

Jones

Dunstone

et al. 2016

Geophysical Research Letters

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The Earth's hemispheric reflectances are equivalent to within ± 0.2 Wm−2, even though the Northern Hemisphere contains a greater proportion of higher reflectance land areas, because of greater cloud cover in the Southern Hemisphere. This equivalence is unlikely to be by chance, but the reasons are open to debate. Here we show that equilibrating hemispheric albedos in the Hadley Centre Global Environment Model version 2‐Earth System coupled climate model significantly improves what have been considered longstanding and apparently intractable model biases. Monsoon precipitation biases over all continental land areas, the penetration of monsoon rainfall across the Sahel, the West African monsoon “jump”, and indicators of hurricane frequency are all significantly improved. Mechanistically, equilibrating hemispheric albedos improves the atmospheric cross‐equatorial energy transport and increases the supply of tropical atmospheric moisture to the Hadley cell. We conclude that an accurate representation of the cross‐equatorial energy transport appears to be critical if tropical performance is to be improved.

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“…Applications are numerous, and include corrections for radiance assimilation systems for the NWP modeling systems themselves (Wang and Niu, 2013;Weaver et al, 2007). There is further mounting evidence that for heavily burdened atmospheres, inclusion of the radiative effects of aerosol particles improves overall NWP forecasts (e.g., Haywood et al, 2005;Pérez et al, 2006;Wang et al, 2010;Mulcahy et al, 2014) and is even hypothesized to impact tropical cyclone (TC) development (e.g., from Karyampudi and Carlson, 1988;Karyampudi and Pierce, 2002;Dunion and Velden, 2004; to most recently Dunstone et al, 2013;Reale et al, 2011Reale et al, , 2014. Direct and indirect radiative effects have also been found to impact common NWP parameters such as temperature.…”

Section: Introductionmentioning

confidence: 99%

Development towards a global operational aerosol consensus: basic climatological characteristics of the International Cooperative for Aerosol Prediction Multi-Model Ensemble (ICAP-MME)

Reid²,

et al. 2015

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Anthropogenic aerosol forcing of Atlantic tropical storms

Cited by 154 publications

References 28 publications

Decadal predictions of the cooling and freshening of the North Atlantic in the 1960s and the role of ocean circulation

Decadal predictions of the cooling and freshening of the North Atlantic in the 1960s and the role of ocean circulation

The impact of equilibrating hemispheric albedos on tropical performance in the HadGEM2‐ES coupled climate model

Development towards a global operational aerosol consensus: basic climatological characteristics of the International Cooperative for Aerosol Prediction Multi-Model Ensemble (ICAP-MME)

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