Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 19 of 19 for “"scatterometers"”.
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Satellite Scatterometers: Calibration Using a Ground Station and Statistical Measurement Theory
<p>Satellite scatterometers have recently gained popularity due to their unique ability to measure global geophysical data on a daily basis. Increased interest in scatterometry mandates improved design and calibration of these instruments. This dissertation presents new techniques for scatterometer …
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Melt Detection and Estimation in Greenland Using Tandem QuikSCAT and SeaWinds Scatterometers
… (QuikScat) and SeaWinds on ADEOS-2 (SeaWinds) scatterometers are used to classify the melt state and estimate melt severity in Greenland. Backscatter measurements are organized into high temporal and high spatial resolution images created using the Scatterometer Image Reconstruction (SIR) …
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A Methodology for the Design of Spaceborne Pencil-Beam Scatterometer Systems
… primary goal of measuring ocean winds, data from scatterometers have proven useful in the study of a variety of land and cryopshere processes as well. Several satellites carrying scatterometers have flown in the last two decades. These previous systems have been "fan-beam" scatterometers, where …
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A New Method for Melt Detection on Antarctic Ice-Shelves and Scatterometer Calibration Verification
… 2003 are analyzed and it is shown that Ku-band scatterometers are very useful for determining periods of melt in Antarctic ice-sheets and provide high temporal and spatial resolution ice-state estimates. These estimates can be important for long-term studies of the climatic effects of the …
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Calibration of and Attitude Error Estimation for a Spaceborne Scatterometer using Measurements Over Land
… estimates of ocean wind speed and direction. Scatterometers must be calibrated before their measurements are scientifically useful. However, the calibration of NSCAT must be done in orbit. A new methodology for selecting land regions for use in extended target spaceborne scatterometer …
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Monitoring the Antarctic Ice Sheet From Space
… thesis I use data from three Ku-band space-borne scatterometers to monitor changes in the backscatter signature of the Antarctic ice sheet from 1978 through 2007. Significant changes in backscatter, which result from geophysical changes in the ice sheet itself, are found over much of the Antarctic …
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An Analysis of SeaWinds Simultaneous Wind/Rain Retrieval in Severe Weather Events
Scatterometers, such as SeaWinds, can provide wide coverage of ocean surface winds. They estimate near-surface wind vectors by relating measured radar backscatter to a geophysical model function. However, SeaWinds measurements are also sensitive to rain, and conventional wind retrieval degrades in …
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Multisensor Microwave Remote Sensing in the Cryosphere
… glacial ice surface characteristics with both scatterometers and radiometers exhibiting high sensitivity to important ice properties. This dissertation presents an array of studies focused on extracting key surface features from multisensor microwave data sets. First, several enhanced …
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A Wind and Rain Backscatter Model Derived from AMSR and SeaWinds Data
The SeaWinds scatterometers aboard the QuikSCAT and ADEOS II satellites were originally designed to measure wind vectors over the ocean by exploiting the relationship between wind-induced surface roughening and the normalized radar backscatter cross-section. Recently, an algorithm for …
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Snowmelt Detection on Alpine Glaciers using Synthetic Aperture Radar Time Series
… into melt detection from passive microwave scatterometers over large ice sheets, this study detects melt characteristics from Sentinel-1 SAR backscatter intensity time series over glacier surfaces using a classification threshold based on a decrease in backscatter intensity relative to …
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Observational studies of scatterometer ocean vector winds in the presence of dynamic air-sea interactions
… vector wind measurements produced by satellite scatterometers are used in many applications across many disciplines, from forcing ocean circulation models and improving weather forecasts, to aiding in rescue operations and helping marine management services, and even mapping energy resources. …
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A Field-Wise Retrieval Algorithm for SeaWinds
… SeaWinds is different from previous spaceborne scatterometers in that it employs a rotating pencil-beam antenna as opposed to fixed fan-beam antennas. The scanning beam provides greater coverage but causes the wind retrieval accuracy to vary across the swath. This thesis develops a filed-wise …
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The effect of the Agulhas Current on synthetic aperture radar derived wind fields
… features in comparison to winds derived from Scatterometers. A combination of the current relative effect and SST-atmospheric heating for upcurrent wind directions results in a sharp increase in mean wind speeds over the inshore boundary of the current of between 5m/s and 7m/s (50−60%). …
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Annual and Interannual Variability in the Wind Field and the Hydrography Along the Seward Line in the Northern Gulf of Alaska
… resolution wind velocity data is from satellite scatterometers. Scatterometer wind data have spatial resolutions fine enough to calculate velocity shears across the shelf. On average the wind shears produce positive wind stress curls which promote upwelling due to Ekman pumping. Calculations show …
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Inter-Annual to Inter-Decadal Variability of Upwelling and Anchovy Population off Northern Chile
… wind field from ERS and QuikSCAT satellite radar scatterometers was analyzed.</p> <p>Variability occurred at four frequency bands: quasi-biennial (2–3 years), ENSO (3–8 years), decadal (9–12 years), and interdecadal (13–25 years). The origin of quasi-biennial variability could be explained by …
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Directional wavenumber characteristics of short sea waves
… (e.m.) scattering. Currently radars and scatterometers which use e.m. scattering to remotely examine the ocean can produce estimates of the surface wind field, surface currents, and other scientifically important ocean processes. These estimates are based on models which depend on a …
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Microwave Remote Sensing of Saharan Ergs and Amazon Vegetation
… incidence angle signatures of data combined from scatterometers and the precipitation radar depend upon vegetation density. The multi-frequency signatures of backscatter and Tb provide unique responses for different vegetation densities. Backscatter and Tb spatial inhomogeneity is related to …
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Using Space Borne Microwave Sensors to Track Large Antarctic Icebergs
<p>Studying Antarctic icebergs can provide insight into climatic changes of the Earth's frozen continent. Antarctic icebergs are regularly formed by the separations of massive sections of ice from ice shelves and glaciers. <p>The National Ice Center (NIC) is playing a major role in sea ice analysis …
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Tropical oceanic mesoscale cold pools in observations and models
… underlying scatterometry principles of both the scatterometers were similar, ASCAT GF methodology was effectively replicated on RapidScat ocean vector winds for the two-year period to identify diurnally-resolved cold pool properties. This similarity also allowed us to compare the tropical oceanic …