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Abstract. Turbulent fluxes have been measured in the atmospheric surface layer from a boom extending upwind from the Dutch offshore research platform Meetpost Noordwijk (MPN) during HEXMAX (Humidity Exchange over the Sea Main Experiment) in October-November, 1986. We started out to study eddy flux of water vapour, but discrepancies among simultaneous measurements made with three different anemometers led us to develop methods to correct eddy correlation measurements of wind stress for flow distortion by nearby objects. We then found excellent agreement among the corrected wind stress data sets from the three anemometers on the MPN boom and with eddy correlation measurements from a mast on a tripod. Inertial-dissipation techniques gave reliable estimates of wind stress from turbulence spectra, both at MPN and at a nearby ship. The data cover a range of wave ages and the results yield new insights into the variation of sea surface wind stress with sea state; two alternative formulas are given for the nondimensional surface roughness as a function of wave age.

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.

Low elevation aerosol spectra, ocean whitecap cover and 10m wind speeds measured during the 1978 JASIN experiment have been inter‐related and compared with previously published observations. The positive dependence of aerosol concentration upon whitecap cover was found to increase with droplet radius reflecting the expected higher correlation of the concentration of larger droplets, which have shorter effective residence time in the marine atmospheric boundary layer, with the immediate whitecap cover, which reflects the instantaneous rate of aerosol generation at the sea surface. The power‐law wind dependence, Uγ of the low elevation concentration of droplets larger than 8γm radius was determined to be similar to the wind dependence of whitecap cover, with γ values of 3.23 and 3.31 resulting from the respective application of the robust bi‐weight fitting technique. This observation is consonant with an aerosol generation model in which the instantaneous rate of production is simply proportional to the immediate whitecap cover. The large droplet end of the JASIN low elevation aerosol spectrum is seen to undergo a marked enhancement when the wind speed exceeds 10ms−1. This is a consequence of the onset at that speed of supplementary droplet production via the mechanical disruption of wave crests. The observed growth, with increasing wind speed, in the disparity in amplitude of near‐sea‐surface and near‐cloud‐base aerosol spectra is in part a consequence of the fact that the larger droplets, produced in relative abundance at the higher wind speeds, fall out before they can be mixed effectively through the boundary layer.

During the summer Marginal Ice Zone Experiment in Fram Strait in 1983 and 1984, fourteen mesoscale eddies, in both deep and shallow water, were studied between 78 ø and 81øN. Sampling combined satellite and aircraft remote sensing observations, conductivity-temperature-depth observations, drift of surface and subsurface floats and current meter measurements. Typical scales of these eddies were 20-40 km. Rotation was mainly cyclonic with a maximum speed, in several cases subsurface of up to 40 cm s-• Observations further suggest that the eddy lifetime was at least 20 to 30 days. Five generation sources are suggested for these eddies. Several of the eddies were topographically trapped, while others, primarily formed by combined baroclinic and barotropic instability, moved as much as 10-15 km d -• with the mean current. The vorticity balance in the nontrapped eddies is dominated by the stretching of isopycnals accompanied by a change in the radial shear. In the most completely observed eddy south of 79øN the available potential energy exceeded the kinetic energy by a factor of 2. Quantitative estimates suggest that the abundance of these eddies enhances the ice edge melt up to 1-2 km d-• !. INTRODUCTION The marginal ice zone (MIZ) is the transition region from open ocean to pack ice. Here strong mesoscale air-ice-ocean interactive processes occur which control the advance and retreat of the ice margin. To gain better understanding of these processes, the 1984 Marginal Ice Zone Experiment (MIZEX '84) was carried out in Fram Strait between Greenland and Svalbard from May 18 to July 30, !984, following a preliminary summer experiment in 1983 I-MIZEX Group, 1986]. One of the central objectives of MIZEX is to understand the physics of mesoscale eddies and their importance in the various exchange processes of mass, heat, and momentum which affect the position of the ice edge. Major investigations of mid-ocean eddies started in 1973 with the Mid-Ocean Dynamics Experiment (MODE) 1 program [Robinson, 1983]. Although it is now well established that eddies are present in all the world oceans with important implications for physical, biological, chemical, and geological oceanography and acoustics [Robinson, 1983; Maqaard et al., 1983], eddy features have not been extensively investigated in the MIZ. To qualitatively demonstrate the effect of eddies in the MIZ, a unique aerial photograph obtained on June 30, 1984 is shown in Plate 1, where the ice traces the cyclonic orbital motion of an eddy at the ice edge. (Plate 1 is shown here in black and white. The color version can be found in the separate color section in this issue.) Such motion advects large amounts of ice, Polar Water (PW), and Atlantic Water (AW) into closer contact, causing enhanced floe breakup and ice melting. While Plate 1 shows one ice edge eddy in detail, the National Oceanic and Atmospheric Administration (NOAA) satellite image from July 1, 1984 (Plate 2) establishes that eddies and meanders are the dominant features along the ice edge under moderate wind con...