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Skylab S-193 Radscat microwave measurements of sea surface winds
The S-193 Radscat made extensive measurements of many sea conditions. Measurements were taken in a tropical hurricane (Ava), a tropical storm (Christine), and in portions of extratropical cyclones. Approximately 200 scans of ocean data at 105 kilometer spacings were taken during the first two Skylab missions and another 200 during the final mission when the characteristics of the measurements changed due to damage of the antenna. Backscatter with four transmit/receive polarization combinations and emissions with horizontal and vertical receive polarizations were measured. Other surface parameters investigated for correlation with the measurements included sea temperature, air/sea temperature difference, and gravity-wave spectrum. Methods were developed to correct the microwave measurements for atmospheric effects. The radiometric data were corrected accurately for clear sky and light cloud conditions only. The radiometer measurements were used to recover the surface scattering characteristics for all atmospheric conditions excluding rain. The radiometer measurements also detected the presence of rain which signaled when the scattering measurement should not be used for surface wind estimation. Regression analysis was used to determine empirically the relation between surface parameters and the microwave measurements, after correction for atmospheric effects. Results indicate a relationship approaching square-law at 50 deg between differential scattering coefficient and wind speed with horizontally polarized scattering data showing slightly more sensitivity to wind speed than vertically polarized data.
Effect of Rain-Adjusted Satellite Sea Surface Salinity on ENSO Predictions from the GMAO S2S Forecast System
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Polarimetric Brightness Temperatures of Sea Surfaces Measured
Dual-frequency (19 and 37 GHz) multi-incidence measurements of.
AIRS radiance validation over ocean from sea surface temperature measurements
The objective of this paper is to demonstrate the accuracy of methods and in situ data for early validation of calibrated Earth scene radiances measured by the Atmospheric InfraRed Sounder (AIRS) on the Aqua spacecraft.
Improving the Sea Surface Wind Retrieval Algorithm for NASA Scatterometers Using Atmospheric Boundary Layer Models
The use of an atmospheric boundary layer (ABL) model is investigated to improve wind retrieval algorithms for NASA scatterometer projects.
Sea Surface Temperature Imagery Elucidates Spatiotemporal Nutrient Patterns for Offshore Kelp Aquaculture Siting in the Southern California Bight
Not Available
Coupled Poleward Propagation of Sea Surface Temperature and Atmospheric Angular Momentum Anomalies: Results From AMIP
The purpose of the present study is to investigate the robustness of this phenomenon by examining interannual AAM variations in an ensemble of nine GCM simulations, performed for the decade 1979-1988 as part of the Atmospheric Model Intercomparison Project.
Satellite Data Product and Data Dissemination Updates for the SPoRT Sea Surface Temperature Composite Product
The SPoRT SST composite is a reliable and robust high-resolution product generated twice per day in near real time. It incorporates highest quality data satellite data from infrared imagers and global analysis from NESDIS and UKMO. Recent updates to the product include the inclusion of VIIRS data to extend the life of the product beyond the MODIS era. It is used by a number of users in their DSS.
A novel algorithm for sea surface height estimation using complex SAR data
A method of extracting sea height information from Synthetic Aperture Radar (SAR) complex data was studied. A fundamental SAR ocean imaging model for gravity waves showed that information about the long wave is present in the SAR complex data, especially its phase. Phase demodulation algorithm followed by linear regression and filtering was employed. Only the latter two steps incorporated a priori information that might be available. A relatively simplified simulation indicated that the finite bandwidth of the SAR system imposed the apparently most serious limitation. A preliminary application to SEASAT-SAR complex imagery was encouraging. Information about the long wave, if incorporated into a more sophisticated phase demodulation structure, i.e., at an earlier point in the algorithm, could conceivably mitigate this bandwidth limitation.
On the Influence of Water Vapor on the Retrieval of Satellite Sea Surface Temperatures
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Experimental measurements of 2.25-cm backscatter from sea surfaces.
Airborne 2.25-cm wavelength radar backscatter measurements of low-wind-speed sea conditions were obtained off the coast of Texas in January 1971. These data are compared with unpublished NASA 2.25-cm backscatter measurements recorded over the Atlantic in 1970. The two data sets were in general agreement and supported results previously reported by other authors which showed the absence of a saturation effect at this wavelength. Analyses of these data using computerized clustering techniques indicated that a wind speed measurement accuracy of 5-7 knots is an operational potential.
Fractal properties of the sea surface manifested in microwave remote sensing signatures
The wave spectrum of a well developed sea is discussed. It includes a broad range of wavenumbers where the spectral density is governed by a power law of the form k sup-p. When p is less than or = 4, the surface exhibits properties, such as an increased surface number density of steep and breaking wavelet events and an increased number of specular points for vertical incidence, due to the cascade (fractal) pattern in its geometry. These properties manifest themselves in error trends in wind speed measurements by scatterometer and altimeter.
Fractal features of sea surface manifested in microwave remote sensing signatures
The wave number spectrum of a well developed sea includes a broad range of wavenumbers (the equilibrium range) where the spectral density is governed by a power law, k exp p. In the approximation of a Gaussian surface, the exponent p is related to the Hausdorff dimension. For p less than 4 the Hausdorff dimension is greater than 2 and the surface is characterized by an increased number of steep and breaking wavelets and by an increased number of specular points at near vertical incidence. The former results in the so-called spike component in the total return at oblique incidence, whereas the latter leads to an increased backscatter at nadir and near-nadir angles. Theory for both cases is reviewed and implications for satellite scatterometer and altimeter measurements of surface winds are discussed.
Mapping sea-surface roughness using microwave radiometry.
Microwave radiometry data (1.55 cm) taken by aircraft over the Salton Sea have been corrected for viewing angle and atmospheric effects, rectified, and mapped. No fetch-limited conditions are observed along the upwind shore despite a 15 m/sec wind, which indicates that the radiometer is sensitive to the short wavelength surface roughness but not to the longer wavelengths. The brightness temperature field can be represented as a nearly linear function of the surface wind speed.
Slow and Steady: Ocean Circulation. The Influence of Sea Surface Height on Ocean Currents
The study of ocean circulation is vital to understanding how our climate works. The movement of the ocean is closely linked to the progression of atmospheric motion. Winds close to sea level add momentum to ocean surface currents. At the same time, heat that is stored and transported by the ocean warms the atmosphere above and alters air pressure distribution. Therefore, any attempt to model climate variation accurately must include reliable calculations of ocean circulation. Unlike movement of the atmosphere, movement of the ocean's waters takes place mostly near the surface. The major patterns of surface circulation form gigantic circular cells known as gyres. They are categorized according to their general location-equatorial, subtropical, subpolar, and polar-and may run across an entire ocean. The smaller-scale cell of ocean circulation is known' as an eddy. Eddies are much more common than gyres and much more difficult to track in computer simulations of ocean currents.
Microwave radiometric observations of simulated sea surface conditions.
Review of the results of an experimental investigation of various factors affecting the surface properties of the ocean as seen by a passive microwave radiometer operating at 2.66 GHz. The principal uncertainties in the absolute measurements of the thermal emissions from the sea in terms of molecular temperature are shown to stem from (1) surface contaminations, such as oil slicks, (2) spray and foam, (3) salinity variation, and (4) surface waves. The results of a variety of experiments conducted so far indicate that the direct contribution of surface films and spray to the thermal emission from the sea is considerably less significant than that of foam and waves.
The relationship among sea surface roughness variations, oceanographic analyses, and airborne remote sensing analyses
The synthetic aperture radar (SAR) was studied to determine whether it could image large scale estuaries and oceanic features such as fronts and to explain the electromagnetic interaction between SAR and the individual surface front features. Fronts were observed to occur at the entrance to the Chesapeake Bay. The airborne measurements consisted of data collection by SAR onboard an F-4 aircraft and real aperture side looking radar (SLAR) in Mohawk aircraft. A total of 89 transects were flown. Surface roughness and color as well as temperature and salinity were evaluated. Cross-frontal surveys were made. Frontal shear and convergence flow were obtained. Surface active organic materials, it was indicated, are present at the air-sea interface. In all, 2000 analyses were conducted to characterize the spatial and temporal variabilities associated with water mass boundaries.