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

Acquistapace, Claudia; Meroni, Agostino N.; Labbri, Giacomo; Lange, Diego; Späth, Florian; Abbas, Syed Saqlain

doi:10.1029/2022jd036799

Cited by 10 publications

(32 citation statements)

References 64 publications

(99 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…SST and q 2m present the same southwestern-northeastern gradient, both showing larger values towards the coast (Figure 1A). An exception to the SST general pattern is the presence of a cold patch close to the South American coast (Figure 1A) which likely corresponds to a coastal upwelling system (Acquistapace et al, 2022).…”

Section: Resultsmentioning

confidence: 94%

“…This configuration enhances vertical mixing within the MABL, entrainment at the MABL top and a subsequent MABL thickening. Hence, at least two mechanisms contribute to the decrease of a q : (1) the thickening of the MABL that dilutes the air water content, and (2) the mixing at the top of the MABL which entrains dryer air from the free atmosphere (Neggers et al, 2006;Acquistapace et al, 2022;Albright et al, 2022).…”

Section: Sst-mabl Coupling At Different Spatial Scalesmentioning

confidence: 99%

“…In particular, EUREC 4 A-OA constitutes the ocean component of EUREC 4 A. It investigates heat, momentum, freshwater and CO 2 transport in the ocean (Reverdin et al, 2021), their exchanges across the air-sea interface (Olivier et al, 2022) and the related atmospheric boundary layer processes (Acquistapace et al, 2022). In particular, EUREC 4 A-OA focuses on small-scale ocean dynamics (0.1-100 km).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

On the importance of the atmospheric coupling to the small-scale ocean in the modulation of latent heat flux

Fernández

Speich²,

Borgnino³

et al. 2023

Front. Mar. Sci.

View full text Add to dashboard Cite

In this study, ocean and atmosphere satellite observations, an atmospheric reanalysis and a set of regional numerical simulations of the lower atmosphere are used to assess the coupling between the sea-surface temperature (SST) and the marine atmospheric boundary layer (MABL) as well as the latent heat flux (LHF) sensitivity to SST in the north-west tropical Atlantic Ocean. The results suggest that the SST-MABL coupling depends on the spatial scale of interest. At scales larger than the ocean mesoscale (larger than 150 km), negative correlations are observed between near-surface wind speed (U10m) and SST and positive correlations between near-surface specific humidity (q2m) and SST. However, when smaller scales (1 – 150 km, i.e., encompassing the ocean mesoscale and a portion of the submesoscale) are considered, U10m-SST correlate inversely and the q2m-SST relation significantly differs from what is expected using the Clausius-Clapeyron equation. This is interpreted in terms of an active ocean modifying the near-surface atmospheric state, driving convection, mixing and entrainment of air from the free troposphere into the MABL. The estimated values of the ocean-atmosphere coupling at the ocean small-scale are then used to develop a linear and SST-based downscaling method aiming to include and further investigate the impact of these fine-scale SST features into an available low-resolution latent heat flux (LHF) data set. The results show that they induce a significant increase of LHF (30% to 40% per °C of SST). We identify two mechanisms causing such a large increase of LHF: (1) the thermodynamic contribution that only includes the increase in LHF with larger SSTs associated with the Clausius-Clapeyron dependence of saturating water vapor pressure on SST and (2) the dynamical contribution related to the change in vertical stratification of the MABL as a consequence of SST anomalies. Using different downscaling setups, we conclude that largest contribution comes from the dynamic mode (28% against 5% for the thermodynamic mode). To validate our approach and results, we have implemented a set of high-resolution WRF numerical simulations forced by high-resolution satellite SST that we have analyzed in terms of LHF using the same algorithm. The LHF estimate biases are reduced by a factor of 2 when the downscaling is applied, providing confidence in our results.

show abstract

Section: Resultsmentioning

confidence: 94%

Section: Sst-mabl Coupling At Different Spatial Scalesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

On the importance of the atmospheric coupling to the small-scale ocean in the modulation of latent heat flux

Fernández

Speich²,

Borgnino³

et al. 2023

Front. Mar. Sci.

View full text Add to dashboard Cite

show abstract

“…A possible reason for this is that DWLs develop in windstill areas, and their impact on the LHF therefore remains small, in contrast to the observational study in Acquistapace et al. (2022) showing a large atmospheric effect of a 1 K SST anomaly under high wind (10 m s −1 ). In view of this crucial difference, we conclude that it is important to resolve (sub)mesoscale oceanic structures such as eddies that result in large SST anomalies even under strong wind conditions.…”

Section: Discussionmentioning

confidence: 64%

“…The difference between the two studies could come from the different height use to compute the LHF, at the surface versus in the subcloud in Acquistapace et al. (2022). This is nevertheless unlikely as LHF only slightly increases with height (see Siebesma et al.…”

Section: Effect Of Dwls On Convectionmentioning

confidence: 99%

Impact of Diurnal Warm Layers on Atmospheric Convection

2023

View full text Add to dashboard Cite

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

show abstract

Satellite signature of the instantaneous wind response to mesoscale oceanic thermal structures

Meroni,

Desbiolles,

Pasquero

2023

Quart J Royal Meteoro Soc

Self Cite

View full text Add to dashboard Cite

The thermal air‐sea interaction mechanism that modulates the atmospheric mixing by the sea surface temperature (SST) variability is studied with long‐term consistent satellite records. Statistical analyses of daily and instantaneous wind and SST data are performed over the major western boundary currents (WBCs). This wind‐SST coupling, that is mediated by the atmospheric mixing, is found to be very relevant on daily, and even shorter, time scales. Co‐located and simultaneous SST and surface wind fields (from Advanced Very High Resolution Radiometer and Advanced Scatterometer data) reveal that the atmosphere responds instantaneously to the presence of SST structures with a larger coupling coefficient with respect to daily and monthly time averaged fields. The coupling strength varies seasonally over the WBCs in the Northern Hemisphere, with the winter‐time coupling being the lowest. Reanalysis data show that this behaviour is related to the seasonality of the air‐sea temperature difference over the region of interest. Over the Northern Hemisphere WBCs, dry and cold continental air masses drive very unstable conditions, associated with a very weak thermal air‐sea coupling.This article is protected by copyright. All rights reserved.

show abstract

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

Cited by 10 publications

References 64 publications

On the importance of the atmospheric coupling to the small-scale ocean in the modulation of latent heat flux

On the importance of the atmospheric coupling to the small-scale ocean in the modulation of latent heat flux

Impact of Diurnal Warm Layers on Atmospheric Convection

Satellite signature of the instantaneous wind response to mesoscale oceanic thermal structures

Contact Info

Product

Resources

About