The session is addressed to experimentalists and modellers working on land surface fluxes from local to regional scales. The programme is open to a wide range of new studies in micrometeorology. The topics include the development of new devices, measurement techniques and experimental design methods, as well as novel findings on surface layer theory and parametrization at the local scale. The theoretical parts encompass soil-vegetation-atmosphere transport, internal boundary-layer theories and flux footprint analyses, etc.. Of special interest are comparisons of experimental data, parametrizations and models. This includes energy and trace gas fluxes (inert and reactive) as well as water, carbon dioxide and other GHG fluxes. Specific focus is given to outstanding problems in land surface boundary layer descriptions such as complex terrain, energy balance closure, stable stratification and night time fluxes, as well as to the dynamic interactions with atmosphere, plants (in canopy and above canopy) and soils including the scale problems in atmosphere and soil exchange processes.

Driven by atmospheric turbulence, and integrating surface processes to free atmospheric conditions, the Atmospheric Boundary Layer (ABL) plays a key role not only in weather and climate, but also in air quality and wind/solar energy. It is in this context that this session invites theoretical, numerical and observational studies ranging from fundamental aspects of atmospheric turbulence, to parameterizations of the boundary layer, and to renewable energy or air pollution applications. Below we propose a list of the topics included:

- Observational methods in the Atmospheric Boundary Layer
- Simulation and modelling of ABL: from turbulence to boundary layer schemes
- Stable Boundary Layers, gravity waves and intermittency
- Evening and morning transitions of the ABL
- Convective processes in the ABL
- Boundary Layer Clouds and turbulence-fog interactions
- Micro-Mesoscale interactions
- Micrometeorology in complex terrain
- Agricultural and Forest processes in the ABL
- Diffusion and transport of constituents in the ABL
- Turbulence and Air Quality applications
- Turbulence and Wind Energy applications

Solicited talk:

- "Revisiting Monin-Okukhov Similarity Theory",
by Jielun Sun, NorthWest Research Associates, Boulder, Colorado, USA.

Changes in the Arctic and Antarctic climate systems are strongly related to processes in the boundary layer and their feedbacks with the free troposphere. An adequate understanding and quantification of these processes is necessary to improve predictions of future changes in the polar regions and their teleconnections with mid-latitude weather and climate, including meridional transport of heat, moisture and air pollutants. Processes include atmosphere-ocean-ice (AOI) interactions, such as physical and chemical snow processes (e.g. snow photochemistry), exchange of chemical constituents, sources of aerosol, polynya formation processes, sea ice production and bottom water formation, and cloud formation, which represent key processes for the atmosphere, ocean and the cryosphere. AOI interactions are also triggered by and have feedbacks with synoptic systems and mesoscale weather phenomena such as cold air outbreaks, katabatic winds and polar lows. Associated processes also include the effect of warm air advection and clouds on the surface energy budget and related boundary layer exchanges. Of increasing interest is the study of extremes such as heat waves and storms, but also extreme meridional transport events that can disturb the physical and chemical state of the high latitudes and may have a large impact on ecosystem changes. In addition, Arctic boundary-layer processes play an important role for local Arctic air pollution and for the health and ecosystem impacts thereof. In addition, understanding natural processes including AOI interactions is essential to understand of the background atmosphere to quantify the anthropogenic impacts. Shallow inversions, mostly during winter-time, lead to high air pollutant concentrations. Even though severe air pollution episodes are frequently observed in the Arctic, knowledge on urban emission sources and atmospheric chemical processing of pollution, especially under cold and dark conditions, are poorly understood.

This session is intended to provide an interdisciplinary forum to bring together researchers working in the area of boundary layer processes and high-latitude weather and climate (including snow physics, air/snow chemistry, and oceanography). Cryosphere and atmospheric chemistry processes (the focus of the IGAC/SOLAS activity “CATCH” and the IGAC/IASC activity “PACES”) are highly relevant to this session. We invite contributions e.g. in the following areas:

1. Observations and research on the energy balance, physical and chemical exchange processes, and atmosphere-ocean-ice (AOI) interactions including particle sources.
2. Results from high-elevation sites where similar processes occur over snow and ice.
3. Field programs, laboratory studies and observational studies (including remote sensing).
4. Model studies and reanalyses.
5. Advances in observing technology.
6. External controls on the boundary layer such as clouds, aerosols, radiation.
7. Teleconnections between the polar regions and mid-latitudes resulting in effects related to atmosphere-ice-ocean interactions as well as insights provided by monitoring of water vapor isotopes that shed light on air mass origins.
8. High-latitude urban air quality studies.

Physical processes of Air-Sea Interaction and their representation

This session aims at fostering exchanges and discussions on the physical processes at work at the air-sea interface, their observation, and their representation in coupled numerical models.

Examples of such processes are sun-induced diurnal warming and rain-induced cool and fresh lenses, as well as gustiness associated with atmospheric boundary layer thermals or moist convection and cold pools induced by rain evaporation. Surface temperature and salinity fronts, oceanic meso- and sub-mesoscale dynamics are also of great interest.

This session is thus intended for (i) contributions presenting observational or theoretical aspects of the processes described above and their impact on energy and water exchanges at the interface, and (ii) contributions focusing on the mathematical and algorithmic methods used to represent these processes in coupled ocean-atmosphere models.

This session seeks observational studies based on recent campaigns such as (but not limited to) SPURS-2, YMC, or PISTON, or on satellite remote sensing. This session also aims to gather studies using numerical models of any level of complexity (from highly idealized to realistic) and any resolution from Large Eddy Simulation (LES) to global circulation models. Studies describing the impact of the air-sea interaction physical processes on the mean global or regional climates and variability representation are also welcome.

We invite presentations on ocean surface waves: their dynamics, modelling and applications. Wind-generated waves are a large topic of the physical oceanography in its own right, but it is also becoming clear that many large-scale geophysical processes are essentially coupled with the surface waves, and those include climate, weather, tropical cyclones, Marginal Ice Zone and other phenomena in the atmosphere and many issues of the upper-ocean mixing below the interface. This is a rapidly developing area of research and geophysical applications, and contributions on wave-coupled effects in the lower atmosphere and upper ocean are strongly encouraged.

The multitude of processes of various scales occurring simultaneously under strong winds in the air and sea boundary layers presents a true challenge for nonlinear science. We want to understand the physics of these processes, their specific role, their interactions and how they can be probed remotely, how these processes differ from their counterparts under moderate/weak winds. We welcome theoretical, experimental and numerical works on all aspects of processes in turbulent boundary layers above and below the ocean surface. Although we are particularly interested in the processes and phenomena occurring under strong wind conditions, the works concerned with similar processes under weaker winds which might provide an insight for rough seas are also welcomed. We are also very interested in works on remote sensing of these processes.
The areas of interest include the processes at and in the vicinity of the interface (nonlinear dynamics of surface water, wave-current-turbulence interactions, , including wave and current stability, wave breaking, generation and dynamics of spray and air bubbles, thermodynamics of the processes in the boundary layers, heat and gas exchange), all the processes above and below the air/water interface, as long as they are relevant for strong wind conditions (such as, e.g. inertial waves generated by changing winds). Relevant nonlinear biological phenomena are also welcomed.

The main aims of the session is to initiate discussion of the multitude of processes active under strong winds across the narrow specializations as a step towards creating an integrated picture. Theoretical, numerical, experimental and observational works are welcomed.

The energy of a closed system is steady. It is not lost but rather converted into other forms, such as when kinetic energy is transferred into thermal energy. However, this fundamental principle of natural science is often still a problem for climate research. For example, in case of the calculation of ocean currents and circulation, where small-scale vortices as well as diapycnal mixing and the deep convection processes they induce, need to be considered, to compute how heat content is redistributed along the entire water column and how such processes may change in the future. Similarly, in the atmosphere, the conversion of available potential energy into kinetic energy is the key driver of atmospheric dynamics at a variety of scales, from the zonal-mean general circulation to mesoscale convection. Local turbulent processes can drive larger movements and waves on a larger scale can disintegrate into small structures. All these processes are important for the Earth’s climate and determine its evolution in the future.

How exactly the energy transfers between waves, eddies, local turbulence and mixing in the ocean and the atmosphere works, often remains unclear. This session wants to discuss this by inviting contributions from oceanographers, meteorologists, climate modelers, and mathematicians. We are particularly interested in coupled atmosphere-ocean studies, we are also aiming at filling a knowledge gap on deep ocean processes, as well as novel subgrid-scale parameterizations, and studies of the energy budget of the complex Earth system, including the predictability of the global oceanic thermohaline circulation and thus climate variability.

Invited speakers:
Martin Wild, ETH, Zürich, Switzerland
Raffaele Ferrari, MIT, USA
Robert Weller, WHOI and OOI Research Infrastructures, USA