The Ocean Color CAL/VAL team is evaluating the VIIRS bio-optical products for real-time operations. VIIRS ocean data are being processed using standard government algorithms, and channel calibration and product validation evaluation activities are ongoing. A network of 27 global "Golden Regions" has been established to evaluate and validate bio-optical products. Satellite inter-comparison for data consistency with current ocean color products, and real time vicarious adjustment calculation are performed using in situ water leaving radiance propagated to Top of Atmosphere in coastal and open ocean regions. In addition, routine matchups with VIIRS and MODIS-Aqua are done with in situ data collection from ships and real time coastal AERONET-OC sites. The above activities, product evaluation and tracking of channel stability, are being contributed to the JPSS Team to evaluate the overall mission, including calibration and inter-satellite product consistency. Initial NPP VIIRS ocean bio-optical products are demonstrated with other ocean color satellites.
The southward propagation of cold-air frontal boundaries into the Gulf of Mexico region initiates a cascade of coupled air–sea processes that manifests along the coastlines as an apparent brightness anomaly in the ocean color signals. Our hypothesis is that the color anomaly is largely due to the turbulent resuspension of sedimentary particles. Initially, there is significant wind-driven ocean turbulence as the frontal boundary passes, followed by the potential for sustained convective instability due to significant heat losses from the ocean surface. These cold front events occur during boreal autumn, winter, and into early spring, and the latter episodes occur in the context of the seasonally recurring thermal stratification of shelf waters. Here, we show that as stratification reasserts thermal stability in the waning days of a cold front episode, daily to hourly ocean color patterns are temporally coherent with the air–sea heat flux changes and the resulting impact on water column stability. Concomitant results from a nested, data-assimilative, and two-way coupled ocean-atmosphere numerical modeling system provides both corroboration and insight into how surface air–sea fluxes and in-water turbulent mixing manifest as hourly changes in apparent surface water turbidity due to the potential excitation and settling of reflective particles. A simple model of particle mixing and settling driven by the simulated turbulence mimics patterns seen in the satellite image sequences. This study offers a preview of potential application areas that may emerge following the launch of a dedicated ocean color geostationary sensor.
The Planet SuperDove sensors produce eight-band, three-meter resolution images covering the blue, green, red, red-edge, and NIR spectral bands. Variations in spectral response in the data used to perform atmospheric correction combined with low signal-to-noise over ocean waters can lead to visible striping artifacts in the downstream ocean-color products. It was determined that the striping artifacts could be removed from these products by filtering the top of the atmosphere radiance in the red and NIR bands prior to selecting the aerosol models, without sacrificing high-resolution features in the imagery. This paper examines an approach that applies this filtering to the respective bands as a preprocessing step. The outcome and performance of this filtering technique are examined to assess the success of removing the striping effect in atmospherically corrected Planet SuperDove data.
The SAtellite VAlidation Navy Tool (SAVANT) was developed by the Navy to help facilitate the assessment of the stability and accuracy of ocean color satellites using ground truth (insitu) platform and buoy stations positioned around the globe and support methods for match-up protocols. This automated, continuous monitoring system for satellite ocean color sensors employs a website interface to extract and graph coincident satellite and insitu data in near-real-time. Available satellite sensors include MODerate resolution Imaging Spectrometer (MODIS) onboard the Aqua satellite, Visible Infrared Imaging Radiometer Suite (VIIRS) onboard Suomi National Polar-orbitting Partnership (SNPP) & Joint Polar Satellite Sensor (JPSS), Ocean and Land Colour Instrument (OLCI) onboard the Sentinel 3A and Geostationary Ocean Color Imager (GOCI) onboard the Communication, Ocean and Meteorological Satellite (COMS). SAVANT houses an extensive match-up data set covering nineteen plus years (2000- 2019) of coincident global satellite and ground truth spectral Normalized Water Leaving Radiance (nLw) data allowing users to evaluate the accuracy of ocean color sensors spectral water leaving radiance at specific ground truth sites that provide continuous data. The tool permits changing different match-up constraints and evaluating the effects on the match-up uncertainty. Results include: a) the effects of spatial selection (using single satellite pixel versus 3x3 and 5x5 boxes, all centered around the insitu location), b) time difference between satellite overpass and ground truth observations, c) and satellite and solar zenith angles. Match-up uncertainty analyses was performed on VIIRS SNPP at the AErosol RObotic NETwork Ocean Color (AeroNET-OC) Wave Current surge Information System (WavCIS) site, maintained by NRL and the Louisiana State University (LSU) in the North Central Gulf of Mexico onboard the Chevron platform CSI-06. The VIIRS SNPP and AeroNET-OC assessment determined optimal satellite ocean color cal/val match-up protocols that reduced uncertainty in the derived satellite products.
In those patients who are not a candidate for liver transplantation or TIPSS, managing refractory ascites is challenging. Repeated large volume paracentesis (LVP) is effective but requires hospitalization. Long term abdominal drains (LTAD) have been considered as an alternative to minimize the need for admission and improve quality of life.
Methods
A retrospective review of all patients treated with LTAD(Rocket ®) between 2009 and 2019 in Royal Derby Hospital was undertaken and included the indication, frequency of hospital admission for LVP prior to and after LTAD insertion, MELD score, SBP prior to insertion, complications encountered following insertion, the need for re-insertion and duration of the drain.
Results
24(7 female) patients had LTAD inserted under ultrasound guidance by experienced interventional radiologists. Ascites was secondary to liver cirrhosis in 22 patients (NASH 10; ALD 7; HCV 3; HFE 1; PBC 1) and heart failure/cardiac cirrhosis in 2 patients. The median MELD score was 14(6–32). Median number of LVP in 6 months prior to LTAD insertion was 5 (0–15), with median interval of 2 weeks. Following LTAD insertion, median LVP in 6 months fell to 0(0–5). SBP was diagnosed and treated in 7 patients before LTAD,6 of whom remained on prophylaxis. No immediate complications were reported. Following LTAD, 15 patients (5/15 had pre-LTAD diagnosis) developed SBP at median 60(20–425) days. Post-LTAD SBP was treated with antibiotics but 5 died. In 10 patients LTAD was removed after median 10 days of antibiotics and only 4 were replaced. For those who had replacement, 2 of 3 patients given prophylaxis suffered recurrent SBP. Other indications for removal were (leak 2; blockage 2). Patients needed hospitalization for median 19 (2–40) days in the 6 months prior to LTAD, and 12(0–34) days in the following 6 months. In 11 of 20 patients with MELD score less than 21 (figure 1), the drain remained for 90 or more days while the median lifespan of LTAD in the whole cohort was 67(6–465).
Conclusions
In some patients, LTAD achieved long term palliation without hospital admission but many developed SBP post-insertion. Nevertheless, there was still a reduction in hospital stay. It was not possible to identify factors which might predict a successful outcome from this small cohort. Further research should focus on the impact of LTAD on quality of life measures, the role of antibiotic prophylaxis and better defining when LTAD is best employed in the natural history of patient's with ascites.
The Joint Polar Satellite System (JPSS) launched the Suomi National Polar-Orbiting Partnership (NPP) satellite including the Visible Infrared Imager Radiometer Suite (VIIRS) on October 28, 2011 which has the capability to monitor ocean color properties. Four months after launch, we present an initial assessment of the VIIRS ocean color products including inter-comparisons with satellite and in situ observations. Satellite ocean color is used to characterize water quality properties, however, this requires that the sensor is well characterized and calibrated, and that processing addresses atmospheric correction to derive radiometric water leaving radiance (nLw ). These radiometric properties are used to retrieve products such as chlorophyll, optical backscattering and absorption. The JPSS ocean calibration and validation program for VIIRS establishes methods and procedures to insure the accuracy of the retrieved ocean satellite products and to provide methods to improve algorithms and characterize the product uncertainty. A global monitoring network was established to integrate in situ data collection with satellite retrieved water leaving radiance values from ocean color satellites including Moderate Resolution Imaging Spectroradiometer (MODIS), MEdium Resolution Imaging Spectrometer (MERIS) and VIIRS. The global network provides a monitoring capability to evaluate the quality of the VIIRS nLw in different areas around the world and enables an evaluation and validation of the products using in situ data and other satellites. Monitoring of ocean color satellite retrievals is performed by tracking the "gain" at the Top of the Atmosphere (TOA) and then performing a vicarious adjustment fo reach site. VIIRS ocean color products are compared with MODIS and MERIS retrieved nLw and chlorophyll, and have been shown to provide similar quality. We believe that VIIRS can provide a follow-on to MODIS and MERIS equivalent ocean color products for operational monitoring of water quality. Additional research, including an assessment of stability, a full characterization of the sensor and algorithm comparisons is underway. Weekly sensor calibration tables (look up tables) are produced by JPSS and an evaluation of their impact on ocean color products is ongoing.
The Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project (NPP) (SNPP) was launched in October 2011 to continue monitoring the globe in a similar fashion as the heritage sensors, such as the MODerate resolution Imaging Spectroradiometer (MODIS). This paper applies a scene-based technique to examine in-orbit radiometric stability of VIIRS relative to Aqua MODIS. The cross-comparison is made over global deep ocean waters. This cross-comparison allows for a comprehensive examination of the sensors' radiometric responsivity at relatively low signal levels (over oceanic waters). The study is further extended to L2/L3 products, including remote sensing reflectance and the inherent optical properties (IOPs) of waters under investigation, derived from the top-of-atmosphere (TOA) radiance (L1B). The temporal analyses give insights into the trends in the relative radiometric stability and the resulting discrepancies in the corresponding products.
Abstract : This document describes the testing and evaluation of the Automated Optical Processing System (AOPS) version 4.10 for the Moderate Resolution Imaging Spectrometers (MODIS-Aqua), Visible Infrared Imager Radiometer Suite (VIIRS), and the Geostationary Ocean Color Imager (GOCI) sensors. AOPS enables exploitation of multiple space-borne ocean color satellite sensors to provide optical conditions for operational Navy products supporting Mine Warfare (MIW), Naval Special Warfare (NSW), Expeditionary Warfare (EXW), and Anti-Submarine Warfare (ASW). Ocean optical products are used to predict the impact of the environment on diver operations, communications, mine detection, and target detection. As part of this evaluation, inter-sensor satellite-derived ocean color properties (nLw,IOPs) comparisons are made. In addition, all sensors-derived ocean color properties are evaluated against in situ data from ocean cruises and comparison with the Aerosol Robotic Network- Ocean Color (AERONET-OC) SeaPrism sensors. These comparisons show that MODIS, VIIRS, and GOCI generate high quality ocean color products and should provide a continued data stream to support operational products.
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