The aerodynamic friction between air and sea is an important part of the momentum balance in the development of tropical cyclones. Measurements of the drag coefficient, relating the tangential stress (frictional drag) between wind and water to the wind speed and air density, have yielded reliable information in wind speeds less than 20 m/s (about 39 knots). In these moderate conditions it is generally accepted that the drag coefficient (or equivalently, the “aerodynamic roughness”) increases with the wind speed. Can one merely extrapolate this wind speed tendency to describe the aerodynamic roughness of the ocean in the extreme wind speeds that occur in hurricanes (wind speeds greater than 30 m/s)? This paper attempts to answer this question, guided by laboratory extreme wind experiments, and concludes that the aerodynamic roughness approaches a limiting value in high winds. A fluid mechanical explanation of this phenomenon is given.

The processing algorithms used for relating the apparent color of the ocean observed with the Coastal-Zone Color Scanner on Nimbus-7 to the concentration of phytoplankton pigments (principally the pigment responsible for photosynthesis, chlorophyll a) are developed and discussed in detail. These algorithms are applied to the shelf and slope waters of the Middle Atlantic Bight and also to Sargasso Sea waters. In all, four images are examined, and the resulting pigment concentrations are compared to continuous measurements made along ship tracks. The results suggest that over the 0.08–1.5-mg/m³ range the error in the retrieved pigment concentration is of the order of 30–40% for a variety of atmospheric turbidities. In three direct comparisons between ship-measured and satellite-retrieved values of the water-leaving radiance the atmospheric correction algorithm retrieved the water-leaving radiance with an average error of ~10%. This atmospheric correction algorithm does not require any surface measurements for its application.

Monte Carlo simulations of the transfer of radiation in the ocean are used to compute the apparent optical properties of a flat homogeneous ocean as a function of the inherent optical properties. The data are used to find general relationships between the inherent and apparent optical properties for optical depths τ ≤ 4. The results indicate that the apparent optical properties depend on the phase function only through the back scattering probability. It is shown that these relations can be used with measurements of the upwelling and downwelling irradiance, the beam attenuation coefficient, and the incident radiance distribution to determine the absorption coefficient, the scattering coefficient, and the backward and forward scattering probabilities.

Article appears in IEEE Transactions on Geoscience and Remote Sensing and is copyrighted by IEEE.The Moderate Resolution Imaging Spectroradiometer\ud (MODIS) will add a significant new capability for investigating\ud the 70% of the earth’s surface that is covered by\ud oceans, in addition to contributing to the continuation of a\ud decadal scale time series necessary for climate change assessment\ud in the oceans. Sensor capabilities of particular importance for\ud improving the accuracy of ocean products include high SNR and\ud high stability for narrower spectral bands, improved onboard\ud radiometric calibration and stability monitoring, and improved\ud science data product algorithms. Spectral bands for resolving\ud solar-stimulated chlorophyll fluorescence and a split window in\ud the 4-μm region for SST will result in important new global\ud ocean science products for biology and physics. MODIS will\ud return full global data at 1-km resolution. The complete suite\ud of Levels 2 and 3 ocean products is reviewed, and many areas\ud where MODIS data are expected to make significant, new contributions\ud to the enhanced understanding of the oceans’ role in\ud understanding climate change are discussed. In providing a highly\ud complementary and consistent set of observations of terrestrial,\ud atmospheric, and ocean observations, MODIS data will provide\ud important new information on the interactions between earth’s\ud major components