Abstract. This paper describes the various physical processes relating near-surface atmospheric and oceanographic bulk variables; their relationship to the surface fluxes of momentum, sensible heat, and latent heat; and their expression in a bulk flux algorithm.The algorithm follows the standard Monin-Obukhov similarity approach for near-surface meteorological measurements but includes separate models for the ocean's cool skin and the diurnal warm layer, which are used to derive true skin temperature from the bulk temperature measured at some depth near the surface.

The response of the lower marine atmospheric boundary layer to sharp changes in sea surface temperature was studied in the Frontal Air‐Sea Interaction Experiment (FASINEX) with aircraft and ships measuring mean and turbulence quantities, sea surface temperature, and wave state. Changing synoptic weather on 3 successive days provided cases of wind direction both approximately parallel and perpendicular to a surface temperature front. For the wind perpendicular to the front, both wind over cold‐to‐warm and warm‐to‐cold surface temperatures occurred. For the cold‐to‐warm case, the unstable boundary layer was observed to thicken, with increased convective activity on the warm side. For the warm‐to‐cold case, the surface layer buoyant stability changed from unstable to neutral or slightly stable, and the sea state and turbulence structure in the lower 100 m were immediately altered, with a large decrease in stress and slowing of the wind. Measurements for this case with two aircraft in formation at 30 and 100 m show a slightly increased stress divergence on the cold side. The turbulent velocity variances changed anisotropically across the front: the streamwise variance was practically unchanged, whereas the vertical and cross‐stream variances decreased. Model results, consistent with the observations, suggest that an internal boundary layer forms at the sea surface temperature front. The ocean wave, swell, and microwave radar backscatter fields were measured from several aircraft which flew simultaneously with the low‐level turbulence aircraft. Significant reductions in backscatter and wave height were observed on the cold side of the front.

| iv) Utilization of subseasonal and seasonal predictions for social and economic benefits.These are particularly promising areas of research that will greatly accelerate realizing the common goals of WWRP and WCRP and in turn any Earthsystem prediction initiative that would embrace our research (Nobre 2010;Shapiro et al. 2010;Shukla et al. 2010). The advance of predictive skill of weather/ climate EPSs, promoted by the first of the four areas of collaboration, will depend crucially on progress in the other three areas. These are the most pressing issues to solve before achieving optimal utilization of EPSs and their applications. Because they lie at the intersection of weather and climate, these research priorities require the multidisciplinary, collaborative approach promoted by an Earth-system prediction initiative. SEAMLESS WEATHER/CLIMATE EPSS.A fundamental principle of seamless prediction is that the Earth system 1 exhibits a wide range of dynamical, physical, biological, and chemical interactions involving spatial and temporal variability continuously spanning all weather/climate scales. The traditional boundaries between weather and climate are artificial (Shapiro et al. 2010).As explained in Hurrell et al. (2009), for example, the slowly varying planetary-scale circulation preconditions the environment for the "fast acting" microscale and mesoscale processes of daily highimpact weather and regional climate. As an example, there is evidence that natural climate variations, such as ENSO and the North Atlantic Oscillation (NAO)/ northern annular mode, significantly alter the intensity, track, and frequency of extratropical and tropical cyclones and also affect decadal variability in tropical cyclones and the multidecadal drought in the Sahel region. Conversely, small-scale processes have significant upscale effects on large-scale circulation and on the interactions among the components of the global climate system.The challenge facing our scientific community is to improve the prediction of the spatial-temporal continuum of the interactions among weather, climate, and the Earth system. The most important aspect of the challenge is the chaotic nature of weather and climate predictability that needs to be characterized with probabilistic information.EPSs are widely used for weather and environmental (e.g., hydrological) prediction by operational services. Ensemble forecasts offer not only an estimate of the most probable future state of a system, but also a range of possible outcomes. Assessing how climate subseasonal-to-seasonal variations may alter the frequencies, intensities, and locations of highimpact events is a high priority for decision making. Many users are risk averse-more concerned with the probability of high-impact events than with the most probable future mean state. This makes the AFFILIATIONS: brunet-meteorological research division, environment Canada, dorval, Quebec, Canada; Shapiro-national Center for atmospheric research, boulder, Colorado, and Geophysical institute, university of berge...

No abstract

Some of the highlights of an experiment designed to study coastal atmospheric phenomena along the California coast (Coastal Waves 1996 experiment) are described. This study was designed to address several problems, including the cross-shore variability and turbulent structure of the marine boundary layer, the influence of the coast on the development of the marine layer and clouds, the ageostrophy of the flow, the dynamics of trapped events, the parameterization of surface fluxes, and the supercriticality of the marine layer.Based in Monterey, California, the National Center for Atmospheric Research (NCAR) C-130 Hercules and the University of North Carolina Piper Seneca obtained a comprehensive set of measurements on the structure of the marine layer. The study focused on the effects of prominent topographic features on the wind. Downstream of capes and points, narrow bands of high winds are frequently encountered. The NCAR-designed Scanning Aerosol Backscatter Lidar (SABL) provided a unique opportunity to connect changes in the depth of the boundary layer with specific features in the dynamics of the flow field.An integral part of the experiment was the use of numerical models as forecast and diagnostic tools. The Naval Research Laboratory's Coupled Ocean Atmosphere Model System (COAMPS) provided high-resolution forecasts of the wind field in the vicinity of capes and points, which aided the deployment of the aircraft. Subsequently, this model and the MIUU (University of Uppsala) numerical model were used to support the analysis of the field data.These are some of the most comprehensive measurements of the topographically forced marine layer that have been collected. SABL proved to be an exceptionally useful tool to resolve the small-scale structure of the boundary layer and, combined with in situ turbulence measurements, provides new insight into the structure of the marine atmosphere. Measurements were made sufficiently far offshore to distinguish between the coastal and open ocean effects. COAMPS proved to be an excellent forecast tool and both it and the MIUU model are integral parts of the ongoing analysis. The results highlight the large spatial variability that occurs directly in response to topographic effects. Routine measurements are insufficient to resolve this variability. Numerical weather prediction model boundary conditions cannot properly define the forecast system and often underestimate the wind speed and surface wave conditions in the nearshore region.