Research

The zonal inhomogeneities of the land surface are known to strongly modulate the large-scale atmospheric circulation, especially in the northern hemisphere. The impacts of an enhanced summer land-sea contrast in a future climate are still poorly constrained.

By combining CMIP6 model, satellite and EMIC (Earth model of intermediate complexity) simulation data, the goal is to assess the links between soil moisture distribution, land-sea summer contrast and planetary circulation.

In parallel, we have looked at how removing the mantle-induced dynamic topography influence atmospheric dynamics and, thus, our climate system.

Ocean and atmosphere interact in a very wide range of scales. We studied the fast (hourly-daily) and small scale (1-10 km) atmospheric response to Sea Surface Temperature (SST) spatial structures in the Mediterranean region. With a range of numerical simulations we found out that the Downward Momentum Mixing (DMM) mechanism is important over sub-mesoscale SST features (Meroni et al., JGRA, 2018). 

The Sea Surface Temperature (SST) affects the development of heavy rain events through the control of the air column stability. From semi-idealized numerical simulations of a Mediterranean case study, we found that if the Oceanic Mixed Layer (OML) is shallow, the winds associated with the intense rains mix up the cold water below the OML and reduce the SST, that subsequently controls the amount of rain (Meroni et al., PAAG, 2018).

With observational data over the entire Mediterranean Sea, then, we discovered that the DMM is statistically significant in determining the atmospheric response and its influence is strongest when an atmospheric front crosses a SST gradient (Meroni et al., QJRMS, 2020). These results are confirmed and extended to the wind response in the entire Marine Atmospheric Boundary Layer (MABL) and to the cloud cover and rainfall fields using ERA5 reanalysis data in Desbiolles et al., GRL, (2021).  

A new metric to measure the PA mechanism is introduced in Meroni et al., JGRA (2022). The rationale of this new metric is to evaluate the wind divergence response in the direction perpendicular to the background wind, to avoid the distortion of advection. 

Exploiting some of the in-situ data collected during the EUREC4A field campaign (Stevens et al.,  ESSD, 2021), we analyse the atmospheric response to the forcing of a cold mesoscale patch in the north-western Atlantic (Acquistapace et al., JGRA, 2022). We find that the stronger vertical atmospheric mixing over the warm SST can be responsible for a larger export of water vapour above the lifting condensation level (LCL), enhancing low-level cloud cover. By exploiting high-resolution numerical simulations we verify that this mechanism is associated with a statistically significant response (Borgnino et al., GRL, 2025).

At the global scale, we analyzed the control that some environmental variables have on the air-sea coupling. In particular we found nonlinear dependence on the wind speed and the air-sea temperature difference (Desbiolles et al., JCli, 2023).  This large-scale modulation is useful to interpret the seasonal variability of the instantaneous coupling observed over the major western boundary current systems with satellite data (Meroni et al., QJRMS, 2023).

Do large iceberg know that the Earth spins? This was the core question that we tried to answer to with my project during the summer 2017 at the GFD-WHOI summer program. Through laboratory experiments using cylindrical icebergs in a spinning tank, we found a significant effect of the background rotation on the basal melting of flat icebergs. This can be interpreted with the formation of partial Taylor columns underneath the icebergs that alter the flow and the turbulent heat transfer (Meroni et al., JFM, 2019). 

The atmosphere inputs energy in the ocean in various forms. The strong forcing of tropical cyclones, in particular, is known to mix the upper ocean and trigger a three-dimensional internal wave wake. By thinking of the advective terms in the equations of motion as a forcing of super-inertial waves, nonlinear interactions of internal waves can be quantified in an analytical way. We found out that energy is transferred to super-inertial waves that are characterized by small vertical scales, contributing to the energy cascade in the interior of the ocean (Meroni et al., JPO, 2017).

An accurate knowledge of the water vapor spatial distribution is critical in the challenge of correctly forecasting heavy rains. The assimilation of GNSS- and SAR- derived water vapor observations in Numerical Weather Prediction (NWP) models has been shown to improve the forecast skills of heavy precipitation events (Lagasio et al., RS, 2019). 

New GNSS networks, a new SAR algorithm (with an appropriate procedure for its calibration, Meroni et al., F, 2020) and new NWP assimilation experiments are being carried out in the framework of the TWIGA-h2020 project, with a focus on sub-Saharan Africa. 

Assimilating observations from the Hydroterra 10th ESA Earth Explorer candidate mission has positive impacts on the forecast of convective rainfalls (Lagasio et al., RS, 2020).