Dynamics in the Equatorial
OceansOcean Mixed-Layer
StructureUpper Ocean Thermal
ResponseSea-Surface Microwave
ScatterUsing Satellite Imagery
Time Series to Infer Surface DynamicsApplied Space Shuttle
PhotographyMicrowave and Oceanic
WindsOcean Feature RecognitionOceanic upper mixed-layer structure, ocean heat storage, and sea surface temperature (SST) play important roles in the evolution of atmospheric events. In turn, these parameters are driven by processes responsible for surface energy fluxes. We seek to improve remote sensing methods in studies of mixed-layer dynamics, air-sea interactions, meso- to large-scale circulation, and internal waves. We are also working on improving our understanding of the ocean's role in the global climate changes.
Dynamics in the Equatorial Oceans
As a part of NOAA, NASA and NSF's Global Change Program, we are using satellite infrared imagery and altimeter data to study the Western Pacific Warm Pool, a huge water mass with SSTs higher than 28 degrees C. The warm pool significantly influences global heat balance and large-scale processes such as sea surface height anomaly, circulation, and wave motion. The results will reveal the characteristics and mechanisms of these phenomena and provide new understanding of the relationships between ocean variabilities, El Nino Southern Oscillation, and global change.
Ocean Mixed-Layer Structure
Algorithms have been developed to use visible, infrared and microwave techniques to record SST, wind stress, and heat flux and to simulate diurnal and seasonal mixing processes in the Sargasso Sea and the Pacific Ocean. Mixed-layer depths predicted by remote sensing agree well with observational data, suggesting that remote sensing is a promising tool for studying the upper ocean mixed layer and locating pools of warm water and fronts, knowledge that can aid both fishermen and meteorologists.
Upper Ocean Thermal Response
The transport of heat, accomplished mainly by the upper layers of the oceans, is an important link in the seasonal cycle of the ocean-atmosphere system. Using a 14-year record of expendable bathythermograph data and simultaneous wind and heat- flux data, we are studying upper ocean heat storage in the North Pacific. A correlation analysis is being performed to determine temporal and spatial relationships between mixed-layer depth variability and oceanic and meteorological parameters.
Sea-Surface Microwave Scatter
We are analyzing the relationships between X-band normalized radar cross section (NRCS) data and coincidently measured wind speed, wind direction, SST, air temperature, and surface waves, emphasizing the relationships at low wind velocities. We are also examining the response of NRCS to the wave-number spectra of capillary or capillary-gravity waves and the effects of SST on NRCS measurements.
Using Satellite Imagery Time Series to Infer Surface Dynamics
Remote sensing data bases go back about two decades and are expanding rapidly while the quality of the data keeps increasing. We can now conduct long-term analyses to extract seasonal, annual, or climatic information. Our aim is to extract temporal and spatial variability in the temperature and turbidity signals from an historical time series of imagery. The resulting variability modes will be correlated with concurrent time series of wind forcing and river runoff. The spatial patterns of variability will be compared to modeled surface currents. Good correlations should encourage more ambitious quantitative analyses of existing and future remote sensing data sets.
Applied Space Shuttle Photography
We are using time-series photographs taken aboard the space shuttles to examine an internal wave field that occurred on the continental shelf of the North Atlantic Bight and in other ocean areas. We can calculate and analyze dynamical parameters and solitary characteristics based on the statistical features and measured data of the internal wave field. The tidal parameters of Delaware Bay can be measured and calculated using the same data.
Microwave and Oceanic Winds
We are developing a physical model to calculate oceanic winds from backscatter data measured by scatterometer. The tilt modulation from the dominant wave and the interaction between radar microwaves and Bragg resonant waves from various directions are being considered. Another model applying to synthetic aperture radar is also being derived. The research may give direction to the modification of relevant statistical models.
Ocean Feature Recognition
Pattern-recognition methods to measure ocean surface movement using sequential satellite images have been developed. An ordered, statistical edge-detection algorithm is used to select ocean thermal patterns by detecting and mapping gradients. The computer then locates the best match to the pattern in a subsequent image, and surface displacement direction and distance are calculated for each selected point. The results of this project will improve our ability to determine real velocity fields (translational and rotational), to plot the trajectory of oil spills, to carry out effective search-and-rescue efforts, and to perform other environmental analyses.