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Convective and stratiform rain: Multichannel microwave sensing over oceans
Measurements made by the Special Sensor Microwave/Imager (SSM/I) radiometer over the oceans, at 19, 37, and 85 GHz in dual polarization, are used to develop a model to classify rain into light-stratiform, moderately convective, and heavy convective types in the mesoscale convective systems (MCS). It is observed that the bulk of the 19- and 37-GHz data are linearly correlated with respect to one another, and generally increase together in brightness as the mean rain rate in the field of view (FOV) of the radiometer increases. However, a significant fraction of the data from these channels departs from this linear relationship, reflecting the nonuniform rain that is convective vs. the relatively light stratiform rain. It is inferred from the SSM/I data, in a MCS, when the slope dT sub 3/dT sub 19 is greater than unity there are optically thin clouds which produce light uniform rain. On the other hand, when dT sub 3/dT sub 19 is close to unity, the rain cells have an open structure and correspond to the convective type of rain. The openings between the cells are apparently a result of the downdrafts and/or entrainment. Relatively low values of 85-GHz brightness temperatures that are present when dT sub 37/dT sub 19 is close to unity support these views and, in addition, leads us to conclude that when the convection is heavy this brightness temperature decreases due to scattering by hydrometeors. On the basis of this explanation of the SSM/I data, an empirical rain retrieval algorithm is developed. Radar backscatter observations over the Atlantic Ocean next to Florida are used to demonstrate the applicability of this method. Three monthly mean maps of rainfall over the oceans from 50 degrees N to 50 degrees S, are presented to illustrate the ability of this method to sense seasonal and interannual variations of rain.
The remote sensing of oceanic primary productivity - A review
The ocean is a major sink for atmospheric carbon dioxide. This paper assesses the correctness of the present estimates of the marine primary productivity, obtained by remote sensing techniques, by modeling the physiological mechanisms of carbon assimilation by phytoplankton. The model uses, as the input, measurements of the ocean-surface pigments and data on the incident solar irradiance, and incorporates a description of the photosynthetically available and usable irradiance in the ocean, to describe the light field required for photosynthesis. A comparison of measured and estimated values of the water-column integrated primary marine productivity over large ocean regions yielded favorable results. These estimates do not appear to depend on regional or seasonal factors.
Remote sensing of ocean currents using ERTS imagery
Major ocean currents such as the Loop Current in the eastern Gulf of Mexico have surface manifestations which can be exploited for remote sensing. Surface chlorophyll-a concentrations, which contribute to the shift in color from blue to green in the open sea, were found to have high spatial variability; significantly lower concentrations were observed in the current. The cyclonic edge of the current is an accumulation zone which causes a peak in chlorophyll concentration. The dynamics also cause surface concentrations of algae, which have a high reflectance in the near infrared. Combining these observations gives rise to an edge effect which can show up as a bright lineation on multispectral imagery delimiting the current's boundary under certain environmental conditions. When high seas introduce bubbles, white caps, and foam, the reflectance is dominated by scattering rather than absorption. This has been detected in ERTS imagery and used for current location.
Remote sensing of ocean color in the Arctic
The main objectives of the research are: to increase the understanding of biological production (and carbon fluxes) along the ice edge, in frontal regions, and in open water areas of the Arctic and the physical factors controlling that production through the use of satellite and aircraft remote sensing techniques; and to develop relationships between measured radiances from the Multichannel Aircraft Radiometer System (MARS) and the bio-optical properties of the water in the Arctic and adjacent seas. Several recent Coastal Zone Color Scanner (CZCS) studies in the Arctic have shown that, despite constraints imposed by cloud cover, satellite ocean color is a useful means of studying mesoscale physical and biological oceanographic phenomena at high latitudes. The imagery has provided detailed information on ice edge and frontal processes such as spring breakup and retreat of the ice edge, influence of ice on ice effects of stratification on phytoplankton production, river sediment transport, effects of spring runoff, water mass boundaries, circulation patterns, and eddy formation in Icelandic waters and in the Greenland, Barents, Norwegian, and Bering Seas.
Polarimetric radar remote sensing of ocean surface wind
Experimental data are presented to support the development of a new concept for ocean wind velocity measurement with the polarimetric microwave radar technology.
Wide Bandwidth Radiometer Sensitivity for Remote Sensing of Ocean Salinity
Modern microwave radiometers have demonstrated the feasibility of monitoring surface salinity from space and also the need for better accuracy in cold water. Accuracy could be improved by adding measurements at lower frequencies (lower than the measurement at 1.4 GHz currently used) and closer to the peak in sensitivity of brightness temperature to changes in salinity. Proposals to accomplish this have focused on wide bandwidth receivers which include at the low end frequencies close to the peak in sensitivity. This strategy involves trade-offs, some obvious such as radio frequency interference (RFI) when operating outside the protected band at 1.4 GHz and the loss of spatial resolution at lower frequencies. Others stemming from the interdependence of the retrieval of salinity on water temperature and surface roughness are more subtle. The objective of this manuscript is to examine this interdependence and its implications to future wide bandwidth instruments for remote sensing of salinity from space.
Use of Ocean Remote Sensing Data to Enhance Predictions with a Coupled General Circulation Model
Surface height, sea surface temperature and surface wind observations from satellites have given a detailed time sequence of the initiation and evolution of the 1997/98 El Nino. The data have beet complementary to the subsurface TAO moored data in their spatial resolution and extent. The impact of satellite observations on seasonal prediction in the tropical Pacific using a coupled ocean-atmosphere general circulation model will be presented.
Remote sensing of ocean color from aircraft
Over 3000 ocean spectra of sunlight backscattered from the upper layers of the sea have been obtained at flight altitudes to 10,000 feet together with detailed ground truth. These spectra are from stations which include a wide range of water masses differing as to biological and physical condition. This data bank and the analysis already performed demonstrates the probable feasibility of using ocean color as a parameter to locate areas of special significance to physical oceanographers and marine biologists from aircraft and satellites.
Remote sensing of ocean currents
There are no author-identified significant results in this report.
Remote sensing of ocean currents
The author has identified the following significant results. Monthly field experiments in support of the NOAA investigation of ocean color boundary determination using ERTS data have been conducted since June 1972. The color boundary between the Loop Current and coastal water has been detected by airborne cameras with ERTS type bandpass filters, at altitudes of 7300 meters. Ship and aircraft data hint that the boundary may be enhanced due to increased phytoplankton populations caused by convergence of the surface waters. The term edge effect has been coined to describe this phenomenon.
Remote sensing of ocean currents
There are no author-identified significant results in this report.
Remote sensing of ocean currents using ERTS imagery
ERTS-1 imagery of ocean currents in Gulf of Mexico
Remote sensing of ocean currents
There are no author-identified significant results in this report.
Remote sensing of ocean currents
The author has identified the following significant results. Monthly field experiments in support of the NOAA investigation of ocean color boundary determination using ERTS-1 data have been conducted since June 1972. The boundary between coastal waters and the Loop Current has been detected by ERTS-1 as a result of sea state changes as well as color differences. Ocean information is contained in all 24 channels of the Bendix MSS flown on the C-130 in June 1972; this includes UV, visible, reflected IR, and emitted IR. Computer enhancement of MSS data is revealing many features not shown in the NDPF product.
Remote sensing of ocean currents
The author has identified the following significant results. Sea ice is detectable in all of the MSS bands and can be distinguished from clouds through a number of interpretive keys. Overall, MSS-4 and 5 appear to be better for mapping the ice edge, whereas MSS-7 provides greater detail in the ice features.
Remote sensing of ocean current boundary layer
There are no author-identified significant results in this report.