Predictions of our future climate vary greatly, with detailed forecasts still subject to debate. One key uncertainty is caused by the lack of our present knowledge of transport processes in the air-water interface, which poses the main transfer resistance between the oceans and atmosphere. Modeling and predictions of our global climate can only be improved by gaining a more complete understanding of the mechanisms involved in transporting energy, mass and momentum across the phase boundary.

This monograph contains selected, peer-reviewed post-conference contributions of the International Workshop on Transport at the Air-Sea Interface, which took place at Heidelberg University from September 6-8, 2006. The workshop brought together leading scientists from around the world, bridged the gap between modeling and measurements, and sparked new ideas for novel simulation and experimental efforts. The focus of the monograph is on small scale processes directly at the interface and includes the topics:

- Small-scale transport processes at the air-sea interface: surface divergence, microscale and largescale wave breaking, intermittency and rain-induced gas exchange

- Novel measurement techniques including eddy correlation measurements, active and passive thermography, visualization of concentration fields by fluorescent dyes, profile measurements and visualization of flow fields by particle imaging velocimetry (PIV)

- Modeling of the transport across the air-water interface and simulation of flow fields as well as concentration fields in the boundary layer

- Parameterizations of the transfer process for global modeling

The Impact of Different Gas Exchange Formulations and Wind Speed Products on Global Air-Sea CO2 Fluxes.- Turbulent Gas Flux Measurements near the Air-Water Interface in a Grid-Stirred Tank.- Quantitative Imaging of CO2 Transfer at an Unsheared Free Surface.- Visualisation of Oxygen Concentration Fields in the Mass Boundary Layer by Fluorescence Quenching.- Visualization of 2-D Divergence on the Free Surface and its Relation to Gas Transfer.- The Air-Water Interface: Turbulence and Scalar Exchange.- Turbulence Generation in the Wind-Driven Subsurface Water Flow.- Defining the Enhancement of Air-Water Interfacial Oxygen Exchange Rate due to Wind-Forced Microscale Waves.- Momentum Flux and Energy Dissipation Associated with Breaking Waves.- The Interaction of Ocean Surface Processes, Waves, and Turbulence in the Adjacent Boundary Layers.- A Numerical Study on the Characteristic Flow Structures of a Micro-Breaking Wind Wave.- The Effect of Raindrops on Interfacial Turbulence and Air-Water Gas Transfer.- Air-Water Flux Reconciliation Between the Atmospheric CO2 Profile and Mass Balance Techniques.- Air-Water Interfacial Temperature Measurements.- Observations of the Structure of the Surface Temperature Field at an Air-Water Interface for Stable and Unstable Cases.- Estimating the Viscous Shear Stress at the Water Surface from Active Thermography.- Estimation of Air-Sea Gas and Heat Fluxes from Infrared Imagery Based on Near Surface Turbulence Models.- The Influence of Intermittency on Air-Water Gas Transfer Measurements.- Micrometeorological Approaches to Measure Air-Water CO2 Fluxes.- Bias of CO2 Surface Fluxes Estimated by Eddy Covariance due to Adjustment Fluxes..- Eddy Correlation Measurements of Sea Spray Aerosol Fluxes.