Ocean surface circulation can be estimated by automated tracking of thermal infrared features in pairs of sequential satellite imagery. A 7-yr time series of velocity, extracted from thermal imagery of the East Australian Current using the maximum cross-correlation (MCC) technique, provides enough measurements for a more statistical evaluation of the method than has previously been possible. Excluding 1 yr with extensive cloud cover, the method produces about 8000 velocity estimates per month with some seasonal variation. Method precision is estimated to be between 0.08 and 0.2 m s Ϫ1 rms, the lower value with more restrictive compositing. Mean flow, time-dependent flow, and eddy kinetic energy from the time series are compared with values derived from a dynamic height climatology, altimeter analyses, and drifter datasets in the region. The observations reproduce similar features in the flow. The differences between the observations are discussed in relation to noise in the methods and differences in the types of velocities they measure.

The distribution of phytoplankton and the diversity of environmental conditions for their growth around the South Island, New Zealand, were examined in May 1989 by way of chlorophyll a fluorescence profiling in combination with discrete sample analysis of nutrients and particulates, CTDprofiles, and concurrent satellite images of sea surface temperature (SST). A composite of 7 overlaid SST images from the period of the cruise emphasised the strong north-south and east-west gradients in the oceanic environment. Water column sampling coupled with SST imagery was used to examine the frontal structure in Cook Strait, upwelling along the West Coast, gradients across the Solander Trough and through Foveaux Strait, and oceanographic features associated with the Subtropical Convergence off the East Coast and over Chatham Rise. A correlation analysis of the near-surface water properties showed the zonal relationships between nutrients, nutrient ratios, and temperature, but also underscored the strong local influence of freshwater inputs around the South Island coastline. An analysis of the in vivo fluorescence data revealed large site-to-site differences M90066Received 10 December 1990; accepted 8 February 1991 in the fluorescence yield per unit extracted chlorophyll a. The yield varied systematically with changes in the physical and biological environment across the Subtropical Convergence.

Data from the European Space Agency's ERS 1 satellite synthetic aperture radar (SAR) covering the region of the East Australian Current during late 1991 have been analyzed in conjunction with ship and airborne data and infrared imagery. Apart from wind effects, the largest differences in backscatter seem to be associated with different water masses, these differences probably being caused by wave damping due to natural surfactants. Slicklike features in the Tasman Sea are common, even in the deep ocean, when the winds are light. Ocean currents are often visible but as relatively subtle features. It is unlikely that changes in atmospheric boundary layer stability due to changing sea surface temperature are the dominant mechanism for radar imaging of ocean currents. It is suggested that C band radar backscatter will prove to be more directly correlated with biological activity (and ocean color) than with sea surface temperature, particularly at higher latitudes. Surfactants could cause errors of 20% or more in wind speeds derived from satellite scatterometers.

No abstract

Abstract. Some interesting cloud formations oV the west coast of Western Australia on NOAA AVHRR and GMS-5 images are described. The cloud structures shown here are rare and may be related to the 'Morning Glory' phenomenon. This Letter provides an observational study of these clouds which we are calling 'Concentric Ring Clouds'. A plausible mechanism for their generation is presented in terms of anomalous latent heat release, thunderstorm downdraught and out ow causing wave propagation in a low-level wave guide.