Submesoscale oceanic fronts (SFs), which typically occur on a spatial scale of 0.1-10 km, may have a large influence on the atmospheric surface layer (ASL). However, due to their short temporal-spatial scales, evaluating their direct impact on this layer remains challenging and characterizing the nature of SF-ASL interaction has not been done in the field. To address this, a study of the air-sea response to SFs was conducted using observations collected during the Lagrangian Submesoscale Experiment, which took place in the northern Gulf of Mexico. This manuscript focuses on the meteorological measurements made from a pair of masts installed on the bow of the R/V Walton Smith. This work represents one of the first observation-based investigations into the potential influence that SFs have on the ASL. Contemporaneous measurements from an X-band marine radar, moving vessel profiler, and Lagrangian drifters were also used to analyze the SF dynamics. Systematic surface wind velocity changes over several cross-frontal transects were observed, a process previously associated with mesoscale fronts. A comparison between the eddy covariance and parameterized (COARE 3.5) air-sea fluxes revealed that the directly observed heat flux was 1.5 times larger than the bulk value in the vicinity of the SFs. This suggests that the hydrodynamic processes near the front enhance the local exchange of sensible and latent heat. Given the prevalence of SF over the global upper ocean, these findings suggest that these features may have a widely distributed and cumulative impact on air-sea interactions. Plain Language SummaryThe atmosphere responds to the ocean over all scales-from microscopic to planetary scales. Previous studies showed that surface wind and even the entire atmospheric boundary layer could be affected by the relatively large-scale (10-1,000 km) temperature variations across the open ocean, for example, the Gulf Stream. However, the impacts of relatively small-scale (100 m to 10 km) and rapidly (hours to days) evolving fronts are largely unknown due to the difficulty in actually observing the physical processes. As part of an ongoing effort to better understand surface material dispersion across the northern Gulf of Mexico, we conducted ship-based measurements of air-sea fluxes across near small-scale fronts. The observations showed that the physical mechanism used to explain the interaction between the atmosphere and large-scale ocean temperature gradients readily downscales to these smaller fronts, which have a direct impact of wind directly above the ocean surface. These small-scale fronts were also observed to locally enhance the air-sea heat flux, and the conventional model used to predict this underestimates the observed value by as much as 50%. These small-scale frontal features are common across the global ocean, and our findings suggest that they could cumulatively impact the global energy budget.

Offshore wind and wave energy potentials are commonly simulated by atmosphere and wave stand-alone models, in which the Atmosphere–Wave–Ocean (AWO) dynamical coupling processes are neglected. Based on four experiments (simulated by UU-CM, Uppsala University-Coupled model) with four different coupling configurations between atmosphere, waves, and ocean, we found that the simulations of the wind power density (WPD) and wave potential energy (WPE) are sensitive to the AWO interaction processes over the North and Baltic Seas; in particular, to the atmosphere–ocean coupling processes. Adding all coupling processes can change more than 25% of the WPE but only less than 5% of the WPD in four chosen coastal areas. The impact of the AWO coupling processes on the WPE and WPD changes significantly with the distance off the shoreline, and the influences vary with regions. From the simulations used in this study, we conclude that the AWO coupling processes should be considered in the simulation of WPE and WPD.

Here we have determined the nature of turbulent flow associated with oceanic nonbreaking waves, which are on average much more prevalent than breaking waves in most wind conditions. We found this flow to be characterized by a low turbulence microscale Reynolds number of 30 < Re < 100. We observed that the turbulent kinetic energy dissipation rate associated with nonbreaking waves , ranged to 3 • 10 −4 W/kg for a wave amplitude 50 cm. The , under nonbreaking waves, was consistent with = 2 T (S i) 2 ; S ij is the large-scale (energy-containing scales) wave-induced mean flow stress tensor. The turbulent Reynolds stress associated with nonbreaking waves was consistent with experimental data when parameterized by an amplitude independent constant turbulent eddy viscosity, 10 times larger than the molecular value. Given that nonbreaking waves typically cover a much larger fraction of the ocean surface (90-100%) than breaking waves, this result shows that their contribution to wave dissipation can be significant. Plain Language Summary Considering that surface waves cover most of the ocean, the precise determination of the rate at which surface waves dissipate energy is necessary to properly quantify climate, weather, or ocean dynamic processes at the air-sea interface and within the upper layer of the ocean. The upper-ocean mixing intensity is often related to breaking surface waves, while the turbulence generated by nonbreaking surface waves is poorly understood and thus not well represented. Our laboratory experiments used microstructure and optical measurements to observe micro velocity shears and temperature fluctuations associated with passing nonbreaking solitary surface waves. Here we report measurements of the energy dissipation associated with these nonbreaking surface waves. We present an analytical approach to quantify the nonbreaking wave turbulence strength from large-scale (energy-containing) flow measurements. The analysis by Teixeira and Belcher (2002) demonstrated that the main mechanism responsible for NBSW turbulence is associated with Stokes drift tilting the small-scale vortex structures, followed by their RESEARCH LETTER

Short range infrared (IR) observations of ocean surface reveal complicated spatially varying and evolving structures. Here we present an approach to use spatially correlated time-series IR images, over a time scale of one tenth of a second, of the water surface to derive underlying surface velocity and turbulence fields. The approach here was tested in a laboratory using grid-generated turbulence and a heater assembly. The technique was compared with in situ measurements to validate our IR derived remote measurements. The IR measured turbulent kinetic energy (TKE) dissipation rates were consistent with in situ measured dissipation using a microstructure profiler (VMP). We used measurements of the gradient of the velocity field to calculate TKE dissipation rates at the surface. Based on theoretical and experimental considerations, we have proposed two models of IR TKE dissipation rate retrievals and designed an approach for oceanic field IR applications.

Abstract. We performed MAX-DOAS measurements during the PRiDe-PRD2006 campaign in the Pearl River Delta region 50 km north of Guangzhou, China, for 4 weeks in June 2006. We used an instrument which simultaneously sampled the wavelength range from 292 nm to 443 nm at 7 different elevation angles between 3° and 90°. Here we show that the O4 (O2 dimer) absorption at 360 nm can be used to retrieve the aerosol extinction and the height of the boundary layer. A comparison with simultaneously recorded, ground based nephelometer data shows an excellent agreement.