Unforced interannual to decadal variability of global radiation imbalance: Role of low clouds.
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| Title: | Unforced interannual to decadal variability of global radiation imbalance: Role of low clouds. |
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| Authors: | Miyamoto, Ayumu1 (AUTHOR) aymiyamoto@ucsd.edu, Xie, Shang-Ping1 (AUTHOR), Deser, Clara2 (AUTHOR) |
| Source: | Journal of Climate. May2026, Vol. 39 Issue 10, p1-15. 15p. |
| Subjects: | El Niño, Stratus clouds, Ocean temperature, Climate feedbacks, Climate change, Radiative forcing |
| Geographic Terms: | Pacific Ocean |
| Abstract: | The global-mean radiation imbalance at the top of the atmosphere (GMTOA) is an important indicator of the climate response to anthropogenic greenhouse forcing. Natural variability perturbs this radiation imbalance on interannual and decadal timescales, confounding the externally forced signal. However, limited observations hinder efforts to understand the mechanisms of internally generated radiation imbalance. This study investigates the natural variability of global TOA radiation using a 500-year preindustrial coupled simulation with the Community Earth System Model version 2, and a corresponding atmospheric model simulation forced with daily sea surface temperature (SST) and sea ice from the coupled run. GMTOA variations lead those in tropical Pacific SST and global-mean surface temperature by 90° in phase, and are attributed to timescale-dependent SST patterns and associated low-cloud radiative effects. Interannual GMTOA peaks are driven by the development and decay of El Niño-Southern Oscillation (ENSO), which induce low-cloud anomalies that are maximized over the equatorial northeast Pacific. In contrast, decadal GMTOA variability stems from variations in eastern subtropical low cloud decks coupled with underlying SST anomalies. These low cloud-SST co-variations are triggered by stochastic extratropical atmospheric variability. This timescale dependence reflects the characteristics of these drivers: the amplitude of ENSO peaks at interannual timescales due to tropical ocean dynamics, whereas extratropical stochastic forcing on SST becomes increasingly important on decadal and longer timescales. Recent satellite observations of GMTOA corroborate both mechanisms. This study underscores the importance of subtropical low cloud-SST co-variations driven by extratropical atmospheric forcing in unforced variability of global energy imbalance. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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| Abstract: | The global-mean radiation imbalance at the top of the atmosphere (GMTOA) is an important indicator of the climate response to anthropogenic greenhouse forcing. Natural variability perturbs this radiation imbalance on interannual and decadal timescales, confounding the externally forced signal. However, limited observations hinder efforts to understand the mechanisms of internally generated radiation imbalance. This study investigates the natural variability of global TOA radiation using a 500-year preindustrial coupled simulation with the Community Earth System Model version 2, and a corresponding atmospheric model simulation forced with daily sea surface temperature (SST) and sea ice from the coupled run. GMTOA variations lead those in tropical Pacific SST and global-mean surface temperature by 90° in phase, and are attributed to timescale-dependent SST patterns and associated low-cloud radiative effects. Interannual GMTOA peaks are driven by the development and decay of El Niño-Southern Oscillation (ENSO), which induce low-cloud anomalies that are maximized over the equatorial northeast Pacific. In contrast, decadal GMTOA variability stems from variations in eastern subtropical low cloud decks coupled with underlying SST anomalies. These low cloud-SST co-variations are triggered by stochastic extratropical atmospheric variability. This timescale dependence reflects the characteristics of these drivers: the amplitude of ENSO peaks at interannual timescales due to tropical ocean dynamics, whereas extratropical stochastic forcing on SST becomes increasingly important on decadal and longer timescales. Recent satellite observations of GMTOA corroborate both mechanisms. This study underscores the importance of subtropical low cloud-SST co-variations driven by extratropical atmospheric forcing in unforced variability of global energy imbalance. [ABSTRACT FROM AUTHOR] |
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| ISSN: | 08948755 |
| DOI: | 10.1175/JCLI-D-25-0320.1 |
