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At least 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRS2011

A Record-High Ocean Bottom Pressure in the South Pacific Observed by GRACE

In late 2009 to early 2010, the Gravity Recovery and Climate Experiment (GRACE) satellite pair observed a record increase in ocean bottom pressure (OBP) over a large mid-latitude region of the South East Pacific. Its magnitude is substantially larger than other oceanic events in the Southern Hemisphere found in the entire GRACE data records (2003-2010) on multi-month time scales. The OBP data help to understand the nature of a similar signal in sea surface height (SSH) anomaly observed by altimetry: the SSH increase is mainly due to mass convergence. Analysis of the barotropic vorticity equation using scatterometer data, atmospheric reanalysis product, and GRACE and altimeter an atmospheric reanalysis product observations suggests that the observed OBP/SSH signal was primarily caused by wind stress curl associated with a strong and persistent anticyclone in late 2009 in combination with effects of planetary vorticity gradient, bottom topography, and friction

Gravity Recovery and Climate Experiment (GRACE)↗
NASA NTRSDate not supplied

PACE UV-VIS Polarimetric Remote Sensing of Atmosphere-Ocean Systems: Sensitivity to Variations in Brown Carbon

The NASA Plankton, Aerosol, Cloud, and ocean Ecosystem (PACE) mission, scheduled for launch in 2024, will carry two instruments that measure ultraviolet (UV) radiance emerging from the top of the atmosphere: the Ocean Color Instrument (OCI) and the Spectro-Polarimeter for Planetary Exploration (SPEXone) instrument. OCI will provide single-view, hyperspectral radiometric data, whereas SPEXone will provide multi-angle, multispectral polarimetric data. Together, these instruments will be the most advanced in NASA’s history for the combined observation of ocean color and atmospheric aerosols in the UV, and they will therefore provide unprecedented research opportunities for the ocean color and atmospheric aerosol communities. In particular, UV observations are best suited to retrieve properties of Colored Dissolved Organic Matter (CDOM) in the ocean, and of Brown Carbon (BrC) aerosols in the atmosphere. However, both CDOM and BrC exhibit very similar absorption spectra in the UV and the visible (VIS) spectrum; hence, care must be taken in accurately modeling these spectra for analyses of OCI and SPEXone measurements. In this presentation, we summarize a simple but highly accurate three-parameter model for complex refractive index spectra of BrC in the UV and VIS. We apply this model to simulations of PACE-like total and polarized multiangle radiance in the UV, and demonstrate that the impact of BrC and CDOM variations can be similar in total radiance, but is easy to distinguish in polarized radiance.

PACE↗
NASA NTRS2012

Sensitivity of Multiangle, Multispectral Polarimetric Remote Sensing Over Open Oceans to Water-Leaving Radiance: Analyses of RSP Data Acquired During the MILAGRO Campaign

For remote sensing of aerosol over the ocean, there is a contribution from light scattered underwater. The brightness and spectrum of this light depends on the biomass content of the ocean, such that variations in the color of the ocean can be observed even from space. Rayleigh scattering by pure sea water, and Rayleigh-Gans type scattering by plankton, causes this light to be polarized with a distinctive angular distribution. To study the contribution of this underwater light polarization to multiangle, multispectral observations of polarized reflectance over ocean, we previously developed a hydrosol model for use in underwater light scattering computations that produces realistic variations of the ocean color and the underwater light polarization signature of pure sea water. In this work we review this hydrosol model, include a correction for the spectrum of the particulate scattering coefficient and backscattering efficiency, and discuss its sensitivity to variations in colored dissolved organic matter (CDOM) and in the scattering function of marine particulates. We then apply this model to measurements of total and polarized reflectance that were acquired over open ocean during the MILAGRO field campaign by the airborne Research Scanning Polarimeter (RSP). Analyses show that our hydrosol model faithfully reproduces the water-leaving contributions to RSP reflectance, and that the sensitivity of these contributions to Chlorophyll a concentration [Chl] in the ocean varies with the azimuth, height, and wavelength of observations. We also show that the impact of variations in CDOM on the polarized reflectance observed by the RSP at low altitude is comparable to or much less than the standard error of this reflectance whereas their effects in total reflectance may be substantial (i.e. up to >30%). Finally, we extend our study of polarized reflectance variations with [Chl] and CDOM to include results for simulated spaceborne observations.

Chowdhary, Jacek↗
NASA NTRS1999

Singular Plasma Disturbance in the Low-Latitude F Region

We describe here a new phenomenon characterized by unusual patterns of ion drifts inside ion density depletion regions observed by the AE-E satellite in the low-latitude F region. In about 30 depletions, vertical ion drift relative to the background was upward on the western sides, downward on the eastern sides, and zero near the middle where the density depletion was greatest. These drift characteristics are distinct from those observed in plasma bubble depletions. The structures reported here were observed on circular orbits below 300 km altitude and had density depletions of up to 2 orders of magnitude or more below the ambient ion density. The upward and downward drift excursions were up to 200 m/s relative to the background. Almost all these structures were observed over oceans or near coasts and largely between +/- 10 deg and +/- 30 deg clip latitude. The structures were observed mostly as isolated, single depletion regions with the majority of them about 250 km wide in the east-west direction. They occurred during quiet magnetic conditions with near-equal occurrence frequencies in the premidnight and postmidnight periods. The characteristic density and drift signatures indicate westward propagating disturbances in which the bottomside F layer is first lifted and then returned back to its original position, leaving the ionosphere undisturbed after the disturbance passes by. The estimated speed of these disturbances is of the order of 200 m/s. These unique solitary plasma disturbances, which we designate as singular plasma disturbances, are associated with a propagating source of E x B drift, not driven by neutral perturbations at the altitude of observation.

Singh, Sardul↗
NASA NTRS2002

Convection and Easterly Waves Observed in the Eastern Pacific ITCZ During EPIC2001

During the last three weeks of September 2001, the East Pacific Investigation of Climate Processes in the Coupled Ocean-Atmosphere System (EPIC2001) intensive field campaign focused on studies of deep convection in the ITCZ-cold tongue complex over the Mexican warm-pool region (10 deg. N 95 deg. W) of the eastern Pacific Ocean. Major observational platforms deployed during this phase of EPIC2001 included two ships, the NOAA R/V Ronald H. Brown and the NSF R/V Horizon, and two research aircraft including a NOAA P-3 and the NCAR C-130. This study utilizes new C-band Doppler radar and sounding observations collected aboard the R/V Ronald Brown to describe the 4-D structure of ITCZ convection as a function of the environmental forcing and phase of 3-5 day easterly wave passages. Three distinct easterly wave passages occurred during EPIC2001. Each wave originated in the eastern Atlantic Ocean and after moving over Central America and into the eastern Pacific, were easily identified in time-height profiles of wind and thermodynamic data collected at the position of the R/V Brown. In all cases, the wave trough axes (as defined by changes in the meridional and zonal wind direction and changes in pressure altitude) exhibited relatively weak shear at low to mid-levels and tilted westward with height. The humidity profile in each wave did not exhibit as great a tilt in the vertical as the trough axes. Consistent with previous studies of westward tilting waves over the western Pacific Ocean, peaks in radar diagnosed rainfall tended to lead the passage of the surface wave trough by 0-2 days.

Petersen, Walter A.↗
NASA NTRS2002

MODIS Observations of Smoke and Fires

The MODIS (Moderate Resolution Imaging Spectroradiometer) instruments collect daily measurements of our planet since early 2000 from the Terra spaceborne polar platform. It has unique channels to observe smoke over land and ocean and to observe fires. Using unsaturated channels at 3.9 micron MODIS detects the fires and estimates the fire radiative energy. Using solar channels in the visible (0.47 and 0.66 micron) and in the mid IR (2.1 micron) MODIS measures the smoke optical thickness distribution and evolution over the land. Seven Channels in the solar spectrum are used to detect the smoke properties and distribution over the oceans. Data from the Aerosol Robotic Network, are used to validate the MODIS observations. The MODIS aerosol data presented in a movie form is used to observe the generation of smoke plumes and their dispersion around the globe. For example a key conclusion is that smoke in particular from Southern Africa can pollute significantly the 'pristine' Southern Hemisphere zonal range of 45'S-60'S, and the Northern Pacific.

Kaufman, Yoram↗
NASA NTRS1998

SeaWiFS Postlaunch Technical Report Series: AMT-5 Cruise Report - Volume 2

This report documents the scientific activities on board the Royal Research Ship (RRS) James Clark Ross (JCR) during the fifth Atlantic Meridional Transect (AMT-5), 14 September to 17 October 1997. There are three objectives of the AMT Program. The first is to derive an improved understanding of the links between biogeochemical processes, biogenic gas exchange, air-sea interactions, and the effects on, and responses of, oceanic ecosystems to climate change. The second is to investigate the functional roles of biological particles and processes that influence ocean color in ecosystem dynamics. The Program relates directly to algorithm development and the validation of remotely-sensed observations of ocean color. Because the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) instrument achieved operational status during the cruise (on 18 September), AMT-5 was designated the SeaWiFS Atlantic Characterization Experiment (SeaACE) and was the only major research cruise involved in the validation of SeaWiFS data during the first 100 days of operations. The third objective involved the near-real time reporting of in situ light and pigment observations to the SeaWiFS Project, so the performance of the satellite sensor could be determined.

Hooker, Stanford B.↗
DOE OSTI2021

Mixed-phase clouds and precipitation in Southern Ocean cyclones and cloud systems observed poleward of 64°S by ship-based cloud radar and lidar

Mixed-phase clouds (MPCs), composed of both liquid and ice, are prevalent in Southern Ocean cyclones. A characterisation of these clouds on fine vertical scales is required in order to understand the microphysical processes within these clouds, and for model and satellite evaluations over this region. We investigated three examples of cloud systems collected by ship-mounted remote sensing instruments adjacent to East Antarctica at latitudes between 64°S and 69°S. These cases allow us to examine the properties of mid-level MPCs, with cloud tops between 2 and 6 km. Mid-level MPCs contain multiple layers of supercooled liquid water (SLW) embedded within ice during the passage of cyclones. SLW layers are capped by strong temperature inversions and are observed at temperatures as low as - 31°C. Convective generating cells (GCs) are present inside supercooled liquid-topped mid-level MPCs. The horizontal extent, vertical extent and maximum upward Doppler velocity of these GCs were 0.6 – 3.6 km, 0.7 – 1.0 km and 0.5 – 1.0 m s -1 , respectively, and are consistent with observations from previous lower-latitude studies. Ice precipitation is nearly ubiquitous, except in the thinnest clouds at the trailing end of the observed systems. Seeding of lower SLW layers from above leads to periods with either larger ice particles or greater ice precipitation rates. Additionally, periods of supercooled drizzle lasting up to two hours were observed toward the end of two of the three cyclone systems. This supercooled drizzle turns into predominantly ice precipitation as the result of seeding by ice clouds located above the precipitating SLW layer.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS2001

The New MODIS-Terra, and the Proposed COBRA Mission: First Global Aerosol Distribution and Properties Over Land and Ocean, and Plans to Measure Global Black Carbon Absorption Over the Ocean Glint

The MODIS instrument was launched on the NASA Terra satellite in Dec. 1999. Since last Oct, the sensor and the aerosol algorithm reached maturity and provide global daily retrievals of aerosol optical thickness and properties. MODIS has 36 spectral channels in the visible to IR with resolution down to 250 m. This allows accurate cloud screening and multi-spectral aerosol retrievals. We derive the aerosol optical thickness over the ocean and most of the land areas, distinguishing between fine (mainly man-made aerosol) and coarse (mainly natural) aerosol particles. New methods to derive the aerosol absorption of sunlight are also being developed. These measurements are use to track different aerosol sources, transport and the radiative forcing at the top and bottom of the atmosphere. However MODIS or any present satellite sensor cannot measure absorption by Black Carbon over the oceans, a critical component in studying climate change and human health. For this purpose we propose the COBRA mission that observes the ocean at glint and off glint simultaneously measuring the spectral polarized light and deriving precisely the aerosol absorption.

Kaufman, Yoram J.↗
NASA NTRS2009

The Hurricane Imaging Radiometer (HIRAD): Instrument Status and Performance Predictions

The Hurricane Imaging Radiometer (HIRAD) is an innovative radiometer which offers new and unique remotely sensed observations of both extreme oceanic wind events and strong precipitation. It is based on the airborne Stepped Frequency Microwave Radiometer (SFMR) [Uhlhorn and Black, 2004]. The HIRAD instrument advances beyond the current nadir viewing SFMR to an equivalent wide-swath SFMR imager using passive microwave synthetic thinned aperture radiometer (STAR) technology [Ruf et al., 1988]. This sensor operates over 4-7 GHz, where the required tropical cyclone remote sensing physics has been validated by both SFMR and WindSat radiometer [Bettenhausen et al., 2006; Brown et al., 2006]. HIRAD incorporates a new and unique array antenna design along with several technologies successfully demonstrated by the Lightweight Rain Radiometer instrument [Ruf et al., 2002; Ruf and Principe, 2003]. HIRAD will be a compact, lightweight, low-power instrument with no moving parts that will produce wide-swath imagery of ocean winds and rain in hurricane conditions. Accurate observations of surface ocean vector winds (OVW) with high spatial and temporal resolution are required for understanding and predicting tropical cyclones. The Hurricane Imaging Radiometer (HIRAD) is an innovative architecture which offers new and unique remotely sensed observations of both extreme oceanic wind events and strong precipitation. It is based on the airborne Stepped Frequency Microwave Radiometer (SFMR), which is a proven remote sensing technique for observing tropical cyclone (TC) ocean surface wind speeds and rain rates. The proposed HIRAD instrument advances beyond the current nadir viewing SFMR to an equivalent wide-swath SFMR imager using passive microwave synthetic thinned aperture radiometer (STAR) technology combined with a a unique array antenna design. The overarching design concept of HIRAD is to combine the multi-frequency C-band observing strategy of the SFMR with STAR technology to produce a wide-swath imager. Single frequency STAR technology The Hurricane Imaging Radiometer (HIRAD) is an innovative radiometer which offers new and unique remotely sensed observations of both extreme oceanic wind events and strong precipitation. It is based on the airborne Stepped Frequency Microwave Radiometer (SFMR) [Uhlhorn and Black, 2004]. The HIRAD instrument advances beyond the current nadir viewing SFMR to an equivalent wide-swath SFMR imager using passive microwave synthetic thinned aperture radiometer (STAR) technology [Ruf et al., 1988]. This sensor operates over 4-7 GHz, where the required tropical cyclone remote sensing physics has been validated by both SFMR and WindSat radiometer [Bettenhausen et al., 2006; Brown et al., 2006]. HIRAD incorporates a new and unique array antenna design along with several technologies successfully demonstrated by the Lightweight Rain Radiometer instrument [Ruf et al., 2002; Ruf and Principe, 2003]. HIRAD will be a compact, lightweight, low-power instrument with no moving parts that will produce wide-swath imagery of ocean winds and rain in hurricane conditions. Accurate observations of surface ocean vector winds (OVW) with high spatial and temporal resolution are required for understanding and predicting tropical cyclones. The Hurricane Imaging Radiometer (HIRAD) is an innovative architecture which offers new and unique remotely sensed observations of both extreme oceanic wind events and strong precipitation. It is based on the airborne Stepped Frequency Microwave Radiometer (SFMR), which is a proven remote sensing technique for observing tropical cyclone (TC) ocean surface wind speeds and rain rates. The proposed HIRAD instrument advances beyond the current nadir viewing SFMR to an equivalent wide-swath SFMR imager using passive microwave synthetic thinned aperture radiometer (STAR) technology combined with a a unique array antenna design. The overarching design concept of HIRAD is to combine the multi-frequency C-banbserving strategy of the SFMR with STAR technology to produce a wide-swath imager. Single frequency STAR technology

Ruf, Christopher↗
NASA NTRS2004

Evaluation and Validation of Case 2 Algorithms in Chesapeake Bay

The high temporal and spatial resolution of satellite ocean color observations will prove invaluable for monitoring the health of coastal ecosystems where physical and biological variability demands sampling scales beyond that possible by ship. However, ocean color remote sensing of Case 2 waters is a challenging undertaking due to the optical complexity of the water. The focus of this SIMBIOS support has been to provide in situ optical measurements form Chesapeake Bay (CB) and adjacent mid-Atlantic bight (MAB) waters for use in algorithm development and validation efforts to improve the satellite retrieval of chlorophyll (chl a) in Case 2 waters. CB provides a valuable site for validation of data from ocean color sensors for a number of reasons. First, the physical dimensions of the Bay (greater than 6,500 square kilometers) make retrievals from satellites with a spatial resolution of approximately 1 kilometer (i.e., SeaWiFS) or less (i.e., MODIS) reasonable for most of the ecosystem. Second, CB is highly influenced by freshwater flow from major rivers, making it a classic Case 2 water body with significant concentrations of chlorophyll, particulates and chromophoric dissolved organic matter (CDOM) that highly impact the shape of reflectance spectra. Finally, past and ongoing research efforts provided an expensive data set of optical observations that support the goal of this project.

Harding, Lawrence W., Jr.↗
DOE OSTI2024

Quantifying the Role of Ocean Dynamics in SST Variability across GCMs and Observations

Abstract Midlatitude SSTs forced by mesoscale oceanic processes can affect the large-scale atmosphere, pointing to the ocean’s crucial role outside the tropics. Previous studies have shown oceanic mesoscale processes’ effect on global and regional climate variability. This study quantifies the local contribution of ocean dynamics to mixed-layer temperature across the globe by directly estimating the ocean heat flux divergence resolved by state-of-the-art ocean reanalysis, eddy-resolving, and eddy-parameterized versions of two U.S. national climate models and indirectly from air–sea flux satellite-based estimates. Our results show that the eddy-resolving climate simulations resolve mixed-layer temperature variances that are larger and closer to those inferred from observations than both their eddy-parameterized counterparts and ECCO over much of the extratropics. The observations and the eddy-resolving models indicate a more significant role of ocean dynamics in the mixed-layer temperature variability than the surface fluxes over most extratropics compared to their eddy-parameterized versions. A frequency domain analysis shows that the better-resolved ocean mesoscale and thermal gradients enhance the variance over a time scale from 2 months to 30 years. Results show agreement in the ocean’s contribution among satellite-based estimates, ocean reanalysis products, and ocean eddy-resolving simulations. At the same time, differences emerge for ECCO and the eddy-parameterized models, suggesting that surface fluxes account for a larger fraction of the mixed-layer temperature variability in most of the extratropics.

Siqueira, L.↗
NASA NTRS2018

The Diurnal Cycle of Cloud Profiles over Land and Ocean Between 51degS and 51degN, Seen by the CATS Spaceborne Lidar from the International Space Station

We document, for the first time, how detailed vertical profiles of cloud fraction (CF) change diurnally between 51 deg S and 51 deg N, by taking advantage of 15 months of measurements from the Cloud-Aerosol Transport System (CATS) lidar on the non-sun-synchronous International Space Station (ISS). Over the tropical ocean in summer, we find few high clouds during daytime. At night they become frequent over a large altitude range (11-16 km between 22:00 and 04:00 LT). Over the summer tropical continents, but not over ocean, CATS observations reveal mid-level clouds (4-8 km above sea level or a.s.l.) persisting all day long, with a weak diurnal cycle (minimum at noon). Over the Southern Ocean, diurnal cycles appear for the omnipresent low-level clouds (minimum between noon and 15:00) and high-altitude clouds (minimum between 08:00 and 14:00). Both cycles are time shifted, with high-altitude clouds following the changes in low-altitude clouds by several hours. Over all continents at all latitudes during summer, the low-level clouds develop upwards and reach a maximum occurrence at about 2.5 km a.s.l. in the early afternoon (around 14:00). Our work also shows that (1) the diurnal cycles of vertical profiles derived from CATS are consistent with those from ground-based active sensors on a local scale, (2) the cloud profiles derived from CATS measurements at local times of 01:30 and 13:30 are consistent with those observed from CALIPSO at similar times, and (3) the diurnal cycles of low and high cloud amounts (CAs) derived from CATS are in general in phase with those derived from geostationary imagery but less pronounced. Finally, the diurnal variability of cloud profiles revealed by CATS strongly suggests that CALIPSO measurements at 01:30 and 13:30 document the daily extremes of the cloud fraction profiles over ocean and are more representative of daily averages over land, except at altitudes above 10 km where they capture part of the diurnal variability. These findings are applicable to other instruments with local overpass times similar to CALIPSO's, such as all the other A-Train instruments and the future Earth-CARE mission.

Noel, Vincent↗
NASA NTRS1980

Remote sensing and spectral analysis of plumes from ocean dumping in the New York Bight Apex

The application of the remote sensing techniques of aerial photography and multispectral scanning in the qualitative and quantitative analysis of plumes from ocean dumping of waste materials is investigated in the New York Bight Apex. Plumes resulting from the dumping of acid waste and sewage sludge were observed by Ocean Color Scanner at an altitude of 19.7 km and by Modular Multispectral Scanner and mapping camera at an altitude of 3.0 km. Results of the qualitative analysis of multispectral and photographic data for the mapping, location, and identification of pollution features without concurrent sea truth measurements are presented which demonstrate the usefulness of in-scene calibration. Quantitative distributions of the suspended solids in sewage sludge released in spot and line dumps are also determined by a multiple regression analysis of multispectral and sea truth data.

Johnson, R. W.↗
NASA NTRS1987

Arctic Sea ice, 1973-1976: Satellite passive-microwave observations

The Arctic region plays a key role in the climate of the earth. The sea ice cover affects the radiative balance of the earth and radically changes the fluxes of heat between the atmosphere and the ocean. The observations of the Arctic made by the Electrically Scanning Microwave Radiometer (ESMR) on board the Nimbus 5 research satellite are summarized for the period 1973 through 1976.

Parkinson, Claire L.↗
NASA NTRS1985

Ocean color measurements

Ocean color observations by the Coastal Zone color scanner (CZCS) aboard the Nimbus-7 satellite are discussed, together with the factors contributing to the 'apparent' color of the ocean. The CZCS optical systems and the tecniques for extraction of the phytoplankton pigment concentration and the diffuse attenuation coefficient K from the 'apparent' water color are described in detail. Special consideration is given to the use of biooptical algorithms and the development of the K algorithm for the CZCS imagery. It is shown that under typical atmospheric conditions, the pigment concentration can be extracted from the satellite imagery to within + or - 30 percent over concentration ranges from 0 to 5 mg/cu m for the Morel case 1 water (Morel and Prieur, 1977), to which the oceanic waters belong as a rule.

Gordon, H. R.↗