7,456 research outputs found
Improving the altimetric rain record from Jason-1 & Jason-2
Full text linkDual-frequency rain-flagging has long been a standard part of altimetric data analysis, both for quality control of the data and for the study of rain itself, because altimeters can provide a finer spatial sampling of rain than can passive microwave instruments. However, there have been many varied implementations, using different records of the surface backscatter and different thresholds. This paper compares four different measures available for the recently-launched Jason-2. The evaluation compares these measures against clearly desired properties, finding that in most cases the adjusted backscatter and that from the ice retracker perform much better than that recommended in the users' handbook. The adjusted backscatter measure also provides a much better link to observations from Jason-1, opening up a much longer period for consistent rain investigations, and enabling greatly improved analysis of the short-scale variability of precipitation. Initial analysis shows that although the spatial and temporal gradients of backscatter increase at very low winds, the spatial gradients in rain attenuation are concentrated where rainfall is greatest, whilst the temporal changes have a simple broad latitudinal pattern
Sea state and rain: a second take on dual-frequency altimetry
Full text linkTOPEX and Jason were the first two dual-frequency altimeters in space, with both operating at Ku- and C-band. Each thus gives two measurements of the normalized backscatter, sigma0, (from which wind speed is calculated) and two estimates of wave height. Departures from a well-defined relationship between the Ku- and C-band sigma0 values give an indication of rain.This paper investigates differences between the two instruments using data from Jason's verification phase. Jason's Ku-band estimates of wave height are ~1.8% less than TOPEX's, whereas its sigma0 values are higher. When these effects have been removed the root mean square (r.m.s.) mismatch between TOPEX and Jason's Ku-band observations is close to that for TOPEX's observations at its two frequencies, and the changes in sigma0 with varying wave height conditions are the same for the two altimeters. Rain flagging and quantitative estimates of rain rate are both based on the atmospheric attenuation derived from the sigma0 measurements at the two frequencies. The attenuation estimates of TOPEX and Jason agree very well, and a threshold of -0.5 dB is effective at removing the majority of spurious data records from the Jason GDRs. In the high sigma0 regime, anomalous data can be cause by processes other than rain. Consequently, for these low wind conditions, neither can reliable rain detection be based on altimetry alone, nor can a generic rain flag be expected to remove all suspect data
CRISP: coarse-grained reconfigurable image stream processor for digital still cameras and camcorders
No full textCoarse-grained reconfigurable image stream processor for digital still cameras and camcorders
No full textRETRACTED – See Author Note - Validation of Crawford’s Postulate: Quantum Collapse Dynamics (v1.51)
No full textUpdated Author Note – May 2025
This paper represents an early attempt to model quantum collapse within the EiG (Energy–information Gradient) framework. While the formulation was internally consistent, I have since identified key flaws in the simulation methodology—particularly in how photon dynamics were represented across discernibility gradients.
As a result, the core conclusion of this manuscript is no longer considered valid. However, the process of developing and testing this model directly led to several foundational insights now informing an updated field theory of light, discernibility, and time—Now available here: https://osf.io/uwn2e
I’ve chosen to leave this paper online as part of an open research process. Future readers should interpret it as an early step in an ongoing effort to model physical reality from first principles under the EiG framework.
— Jason Crawfor
Coarse-Grained Reconfigurable Image Stream Processor Architecture for Embedded Image/Video Processing and Analysis
No full textCoarse-grained reconfigurable image stream processor architecture for high-definition cameras and camcorders
No full textCRISP-DS: dual-stream coarse-grained reconfigurable image stream processor for HD digital camcorders and digital still cameras
No full textIonosphere redistribution during strong geomagnetic storms as detected by the CHAMP, SAC-C, TOPEX and Jason-1 satellites
Full text linkIonosphere response to severe geomagnetic storms that occurred in 2001-2003 was analyzed using data of global ionosphere maps (GIM), altimeter data from the Jason-1 and TOPEX satellites, and data of GPS receivers onboard CHAMP and SAC-C satellites. This allowed us to study in detail ionosphere redistribution due to geomagnetic storms, dayside ionospheric uplift and overall dayside TEC increase. It is shown that after the interplanetary magnetic field turns southward and intensifies, the crests of the equatorial ionization anomaly (EIA) travel poleward and the TEC value within the EIA area increases significantly (up to ～50%). GPS data from the SAC-C satellite show that during the main phase of geomagnetic storms TEC values above the altitude of 715 km are 2-3 times higher than during undisturbed conditions. These effects of dayside ionospheric uplift occur owing to the > and last few hours while the enhanced interplanetary electric field impinged on the magnetopause
Towards finding a population biomarker for wastewater epidemiology studies
No full textHighlights • We suggested five criteria for choosing a population biomarker in wastewater. • We evaluated seven potential population biomarkers. • 5-Hydroxyindoleacetic acid (5-HIAA) and cotinine satisfy the criteria.Chang Chen, Chris Kostakis, Jacobus P. Gerber, Ben J. Tscharke, Rodney J. Irvine, Jason M. Whit
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