Diurnal Ocean Surface Warming Drives Convective Turbulence and Clouds in the Atmosphere

Szoeke, Simon P. de; Marke, Tobias

doi:10.1029/2020gl091299

Cited by 11 publications

(9 citation statements)

References 62 publications

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“…Our results are in agreement with the observations of de Szoeke et al. (2021). They find that, in the tropical Indian ocean, the SST forcing is responsible for the enhanced vertical mixing in the maritime ABL when the wind is weak, and a strong SST diurnal warming occurs.…”

Section: Resultssupporting

confidence: 94%

Fast Atmospheric Response to a Cold Oceanic Mesoscale Patch in the North‐Western Tropical Atlantic

et al. 2022

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Low clouds over tropical oceans have a cooling impact on the Earth's radiation budget. They strongly reflect the incoming solar radiation (high albedo) and slightly reduce the terrestrial emission (Scott et al., 2020). They also impact the temperature and moisture of the marine boundary layer (Bretherton et al., 2013) and are crucial in modulating the air-sea interactions that influence the sea surface temperature (SST) patterns (Yuan et al., 2018). Stratocumulus clouds prevail where free tropospheric subsidence reinforces the atmospheric boundary layer (ABL) stability, while shallow cumuliform clouds develop where subsidence and ABL inversion are weaker, typically over warmer surfaces with a deeper ABL (Mieslinger et al., 2019). Bony and Dufresne (2005) identify such clouds as the largest source of uncertainty in climate model predictions. Most climate models cannot realistically simulate low cloud processes and strongly diverge in the feedback to global warming (Zelinka et al., 2020). Recent observational studies show that in response to surface warming,

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Section: Resultssupporting

confidence: 94%

Fast Atmospheric Response to a Cold Oceanic Mesoscale Patch in the North‐Western Tropical Atlantic

et al. 2022

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“…The spatially broad and temporally regular nature of DWLs has allowed for extensive study of these phenomena, and their impact upon atmospheric convection is well‐documented (Bellenger & Duvel, 2009 ; Bellenger et al., 2010 ; de Szoeke et al., 2021 ). Increased SST within DWLs deepens the atmospheric boundary layer and helps regulate the diurnal cycle of convection in the tropics, and inclusion of DWL parameterizations in atmospheric models has improved forecasting of the MJO (Woolnough et al., 2007 ; Zhao & Nasuno, 2020 ) and ENSO (Masson et al., 2012 ; Terray et al., 2012 ), indicating that DWLs contribute to climate variability on the intraseasonal and interannual time scales.…”

Section: Introductionmentioning

confidence: 99%

Rain‐Induced Stratification of the Equatorial Indian Ocean and Its Potential Feedback to the Atmosphere

et al. 2022

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Surface freshening through precipitation can act to stably stratify the upper ocean, forming a rain layer (RL). RLs inhibit subsurface vertical mixing, isolating deeper ocean layers from the atmosphere. This process has been studied using observations and idealized simulations. The present ocean modeling study builds upon this body of work by incorporating spatially resolved and realistic atmospheric forcing. Fine‐scale observations of the upper ocean collected during the Dynamics of the Madden‐Julian Oscillation field campaign are used to verify the General Ocean Turbulence Model (GOTM). Spatiotemporal characteristics of equatorial Indian Ocean RLs are then investigated by forcing a 2D array of GOTM columns with realistic and well‐resolved output from an existing regional atmospheric simulation. RL influence on the ocean‐atmosphere system is evaluated through analysis of RL‐induced modification to surface fluxes and sea surface temperature (SST). This analysis demonstrates that RLs cool the ocean surface on time scales longer than the associated precipitation event. A second simulation with identical atmospheric forcing to that in the first, but with rainfall set to zero, is performed to investigate the role of rain temperature and salinity stratification in maintaining cold SST anomalies within RLs. Approximately one third, or 0.1°C, of the SST reduction within RLs can be attributed to rain effects, while the remainder is attributed to changes in atmospheric temperature and humidity. The prolonged RL‐induced SST anomalies enhance SST gradients that have been shown to favor the initiation of atmospheric convection. These findings encourage continued research of RL feedbacks to the atmosphere.

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“…In contrast, de Szoeke et al. (2021) argued that in the observations from the DYNAMO data set, convection is enhanced on days with large SST differences. Finally, Voldoire et al.…”

Section: Introductionmentioning

confidence: 87%

“…Voldoire et al (2022) showed that the impact of DWLs on the boundary layer depth, atmospheric moisture and precipitation seems to be small. In contrast, de Szoeke et al (2021) argued that in the observations from the DYNAMO data set, convection is enhanced on days with large SST differences. Finally, Voldoire et al (2022) conjectured that a single column model cannot capture horizontal interactions that might lead to a larger impact.…”

mentioning

confidence: 91%

Impact of Diurnal Warm Layers on Atmospheric Convection

2023

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Diurnal sea surface temperature (SST) anomalies and their interplay with the atmosphere and in particular with the diurnal cycle of convection have been an object of study for many decades. In this study, we investigate this connection for the first time using simulations that can explicitly resolve both the diurnal temperature variations in the ocean and convection in the atmosphere on a global scale.Diurnal variations in SST have already been described in Sverdrup et al. (1942). Since then, there have been numerous studies describing the physics and the conditions of appearance of diurnal SST variations, the seminal work by Price et al. (1986) being the first detailed description of this phenomenon. Under low-wind conditions and with sufficient insolation, a stable near-surface layer forms during the day in the upper layers of the ocean (until the depth of O(10 m)) that leads to a surface warming of up to 5 K (see Wick and Castro (2020)). In the absence of solar radiation during the night, the stratification dissolves as vertical turbulent mixing takes overhand, until a homogeneous mixed layer is restored. The physics of this phenomenon is described in detail in a monograph by Soloviev and Lukas (2013). This stratified, warm layer is known as diurnal warm layer (DWL) and it is ubiquitous in all latitudes, causing SST fluctuations of 0.2 K or more in the entire Northern hemisphere and beyond during boreal summer (see Gentemann et al. (2003)). A comprehensive discussion of its definition and properties can be found in a review by Kawai and Wada (2007). In particular, the authors of the review point out that the presence of DWLs in observations as well as in single column simulations leads to stronger latent and sensible heat fluxes. As surface fluxes connect the surface to the atmospheric boundary layer and since changes in boundary layer properties affect the development of convection, the question of the impacts of DWLs on atmospheric convection arises.Investigating this question in models requires both fine enough vertical resolution in the ocean, to resolve DWLs, and fine enough horizontal grid spacing in the atmosphere, to resolve atmospheric convection. With the development of deca-to kilometer scale simulations in a coupled configuration (Hohenegger et al. ( 2023)) such investigations are becoming possible. Prominent among the newest studies are the papers by Voldoire et al. (2022) and Brilouet et al. (2021). In Voldoire et al. (2022), a single column coupled model has been considered, while

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Diurnal Ocean Surface Warming Drives Convective Turbulence and Clouds in the Atmosphere

Cited by 11 publications

References 62 publications

Fast Atmospheric Response to a Cold Oceanic Mesoscale Patch in the North‐Western Tropical Atlantic

Fast Atmospheric Response to a Cold Oceanic Mesoscale Patch in the North‐Western Tropical Atlantic

Rain‐Induced Stratification of the Equatorial Indian Ocean and Its Potential Feedback to the Atmosphere

Impact of Diurnal Warm Layers on Atmospheric Convection

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