Aerosol effect on the distribution of solar radiation over the clear-sky global oceans derived from four years of MODIS retrievals

Abstract. A four year record of MODIS spaceborne data provides a new measurement tool to assess the aerosol direct radiative effect at the top of the atmosphere. MODIS derives the aerosol optical thickness and microphysical properties from the scattered sunlight at 0.55–2.1 μm. The monthly MODIS data used here are accumulated measurements across a wide range of view and scattering angles and represent the aerosol's spectrally resolved angular properties. We use these data consistently to compute with estimated accuracy of ±0.3 Wm−2 the reflected sunlight by the aerosol over global oceans in cloud free conditions. The MODIS high spatial resolution (0.5 km) allows observation of the aerosol impact between clouds that can be missed by other sensors with larger footprints. We found that over the clear-sky global ocean the aerosol reflected 5.0±0.3Wm−2 with an average radiative efficiency of 46±2 Wm−2 per unit optical thickness. The seasonal and regional distribution of the aerosol radiative effects are discussed. The analysis adds a new measurement perspective to a climate change problem dominated so far by models.

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Aerosol direct radiative effect at the top of the atmosphere over cloud free ocean derived from four years of MODIS data

Atmospheric Chemistry and Physics ◽

10.5194/acp-6-237-2006 ◽

2006 ◽

Vol 6 (1) ◽

pp. 237-253 ◽

Cited By ~ 100

Author(s):

L. A. Remer ◽

Y. J. Kaufman

Keyword(s):

Optical Thickness ◽

Regional Distribution ◽

Global Ocean ◽

Measurement Tool ◽

Radiative Effect ◽

Modis Data ◽

Microphysical Properties ◽

Wide Range ◽

Spectrally Resolved ◽

Aerosol Radiative Effects

Abstract. A four year record of MODIS spaceborne data provides a new measurement tool to assess the aerosol direct radiative effect at the top of the atmosphere. MODIS derives the aerosol optical thickness and microphysical properties from the scattered sunlight at 0.55–2.1 μm. The monthly MODIS data used here are accumulated measurements across a wide range of view and scattering angles and represent the aerosol's spectrally resolved angular properties. We use these data consistently to compute with estimated accuracy of ±0.6 Wm−2 the reflected sunlight by the aerosol over global oceans in cloud free conditions. The MODIS high spatial resolution (0.5 km) allows observation of the aerosol impact between clouds that can be missed by other sensors with larger footprints. We found that over the clear-sky global ocean the aerosol reflected 5.3±0.6 Wm−2 with an average radiative efficiency of −49±2 Wm−2 per unit optical thickness. The seasonal and regional distribution of the aerosol radiative effects are discussed. The analysis adds a new measurement perspective to a climate change problem dominated so far by models.

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Long-Term Aerosol Climate Data Record Derived from Operational AVHRR Satellite Observations

Dataset Papers in Geosciences ◽

10.7167/2013/140791 ◽

2013 ◽

Vol 2013 ◽

pp. 1-5 ◽

Cited By ~ 10

Author(s):

P. K. Chan ◽

X.-P. Zhao ◽

A. K. Heidinger

Keyword(s):

Climate Forcing ◽

Global Ocean ◽

Climatic Data ◽

Climate Data ◽

Clear Sky ◽

National Climatic Data Center ◽

Data Record ◽

Climate Data Record ◽

Global Oceans

Aerosol optical thickness (AOT) was retrieved using the Advanced Very High Resolution Radiometer (AVHRR) PATMOS-x Level-2b gridded radiances and the two-channel algorithm of the National Climatic Data Center (NCDC). The primary retrieval product is AOT at 0.63 μm channel. AOT is also retrieved at 0.83 μm or 1.61 μm channel for consistent check. The retrieval was made during day time, under clear sky and snow-free conditions, and over the global oceans. The spatial resolution is 0.1×0.1 degree grid and the temporal resolution is both daily and monthly. The resultant AVHRR AOT climate data record (CDR) spans from August 1981 to December 2009 and provides the longest aerosol CDR currently available from operational satellites. This dataset is useful in studying aerosol climate forcing, monitoring long-term aerosol trends, and evaluating global air pollution and aerosol transport models over the global ocean.

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Retrieval of Aerosol Optical Thickness with Custom Aerosol Model Using SKYNET Data over the Chiba Area

Atmosphere ◽

10.3390/atmos12091144 ◽

2021 ◽

Vol 12 (9) ◽

pp. 1144

Author(s):

Zixuan Xue ◽

Hiroaki Kuze ◽

Hitoshi Irie

Keyword(s):

Radiative Transfer ◽

Optical Thickness ◽

Surface Albedo ◽

Spectral Response ◽

Aerosol Optical Thickness ◽

Observation Data ◽

Aerosol Model ◽

Clear Sky ◽

Wide Range ◽

Sky Conditions

The retrieval of the aerosol optical thickness (AOT) from remotely-sensed data relies on the adopted aerosol model. However, the method of this technique has been rather limited because of the high variability of the surface albedo, in addition to the spatial variability in the aerosol properties over the land surfaces. To overcome unsolved problems, we proposed a method for the visibility-derived AOT estimation from SKYNET-based measurement and daytime satellite images with a custom aerosol model over the Chiba area (35.62° N, 140.10° E), which is located in the greater Tokyo metropolitan area in Japan. Different from conventionally-used aerosol models for the boundary layer, we created a custom aerosol model by using sky-radiometer observation data of aerosol volume size distribution and refractive indices, coupled with spectral response functions (SPFs) of satellite visible bands to alleviate the wide range of path-scattered radiance. We utilized the radiative transfer code 6S to implement the radiative transfer calculation based on the created custom aerosol model. The concurrent data from ground-based measurement are used in the radiative analysis, namely the temporal variation of AOT from SKYNET. The radiative estimation conducted under clear-sky conditions with minimum aerosol loading is used for the determination of the surface albedo, so that the 6S simulation yields a well-defined relation between total radiance and surface albedo. We made look-up tables (LUTs) pixel-by-pixel over the Chiba area for the custom aerosol model to retrieve the satellite AOT distribution based on the surface albedo. Therefore, such a reference of surface albedo generated from clear-sky conditions, in turn, can be employed to retrieve the spatial distribution of AOT on both clear and relatively turbid days. The value for the AOTs retrieved using the custom aerosol model is found to be stable than conventionally-used typical aerosol models, indicating that our method yields substantially better performance.

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Colloidal Plasmonic Nanostar Antennas with Wide Range Resonance Tunability

10.26434/chemrxiv.6552743 ◽

2019 ◽

Cited By ~ 1

Author(s):

Theodoros Tsoulos ◽

Supriya Atta ◽

Maureen Lagos ◽

Michael Beetz ◽

Philip Batson ◽

...

Keyword(s):

Single Particle ◽

Structural Complexity ◽

Field Enhancement ◽

Hot Electron ◽

Structure Property ◽

Plasmon Band ◽

Gold Nanostars ◽

Wide Range ◽

Particle Level ◽

Spectrally Resolved

<div>Gold nanostars display exceptional field enhancement properties and tunable resonant modes that can be leveraged to create effective imaging tags or phototherapeutic agents, or to design novel hot-electron based photocatalysts. From a fundamental standpoint, they represent important tunable platforms to study the dependence of hot carrier energy and dynamics on plasmon band intensity and position. Toward the realization of these platforms, holistic approaches taking into account both theory and experiments to study the fundamental behavior of these</div><div>particles are needed. Arguably, the intrinsic difficulties underlying this goal stem from the inability to rationally design and effectively synthesize nanoparticles that are sufficiently monodispersed to be employed for corroborations of the theoretical results without the need of single particle experiments. Herein, we report on our concerted computational and experimental effort to design, synthesize, and explain the origin and morphology-dependence of the plasmon modes of a novel gold nanostar system, with an approach that builds upon the well-known plasmon hybridization model. We have synthesized monodispersed samples of gold nanostars with finely tunable morphology employing seed-mediated colloidal protocols, and experimentally observed narrow and spectrally resolved harmonics of the primary surface plasmon resonance mode both at the single particle level (via electron energy loss spectroscopy) and in ensemble (by UV-Vis and ATR-FTIR spectroscopies). Computational results on complex anisotropic gold nanostructures are validated experimentally on samples prepared colloidally, underscoring their importance as ideal testbeds for the study of structure-property relationships in colloidal nanostructures of high structural complexity.</div>

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FAME-C: cloud property retrieval using synergistic AATSR and MERIS observations

Atmospheric Measurement Techniques ◽

10.5194/amt-7-3873-2014 ◽

2014 ◽

Vol 7 (11) ◽

pp. 3873-3890 ◽

Cited By ~ 6

Author(s):

C. K. Carbajal Henken ◽

R. Lindstrot ◽

R. Preusker ◽

J. Fischer

Keyword(s):

Optical Thickness ◽

Single Layer ◽

Cloud Water ◽

Effective Radius ◽

Cloud Property ◽

Microphysical Properties ◽

Microphysical Property ◽

Resolution Imaging ◽

Cloud Optical Thickness ◽

Cloud Water Path

Abstract. A newly developed daytime cloud property retrieval algorithm, FAME-C (Freie Universität Berlin AATSR MERIS Cloud), is presented. Synergistic observations from the Advanced Along-Track Scanning Radiometer (AATSR) and the Medium Resolution Imaging Spectrometer (MERIS), both mounted on the polar-orbiting Environmental Satellite (Envisat), are used for cloud screening. For cloudy pixels two main steps are carried out in a sequential form. First, a cloud optical and microphysical property retrieval is performed using an AATSR near-infrared and visible channel. Cloud phase, cloud optical thickness, and effective radius are retrieved, and subsequently cloud water path is computed. Second, two cloud top height products are retrieved based on independent techniques. For cloud top temperature, measurements in the AATSR infrared channels are used, while for cloud top pressure, measurements in the MERIS oxygen-A absorption channel are used. Results from the cloud optical and microphysical property retrieval serve as input for the two cloud top height retrievals. Introduced here are the AATSR and MERIS forward models and auxiliary data needed in FAME-C. Also, the optimal estimation method, which provides uncertainty estimates of the retrieved property on a pixel basis, is presented. Within the frame of the European Space Agency (ESA) Climate Change Initiative (CCI) project, the first global cloud property retrievals have been conducted for the years 2007–2009. For this time period, verification efforts are presented, comparing, for four selected regions around the globe, FAME-C cloud optical and microphysical properties to cloud optical and microphysical properties derived from measurements of the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra satellite. The results show a reasonable agreement between the cloud optical and microphysical property retrievals. Biases are generally smallest for marine stratocumulus clouds: −0.28, 0.41 μm and −0.18 g m−2 for cloud optical thickness, effective radius and cloud water path, respectively. This is also true for the root-mean-square deviation. Furthermore, both cloud top height products are compared to cloud top heights derived from ground-based cloud radars located at several Atmospheric Radiation Measurement (ARM) sites. FAME-C mostly shows an underestimation of cloud top heights when compared to radar observations. The lowest bias of −0.3 km is found for AATSR cloud top heights for single-layer clouds, while the highest bias of −3.0 km is found for AATSR cloud top heights for multilayer clouds. Variability is low for MERIS cloud top heights for low-level clouds, and high for MERIS cloud top heights for mid-level and high-level single-layer clouds, as well as for both AATSR and MERIS cloud top heights for multilayer clouds.

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China's Navy and the exit 0f his marine ships to the global ocean: political aspects

BULLETIN Series of Sociological and Political sciences ◽

10.51889/2020-2.1728-8940.13 ◽

2020 ◽

Vol 70 (2) ◽

pp. 84-98

Author(s):

R.B. Absattarov ◽

◽

I.A. Rau ◽

Keyword(s):

Political Science ◽

Global Ocean ◽

The Political ◽

Global Oceans

This essay discusses the political aspects of the development of the Chinese navy , and release of its submarine fleet into the global oceans , which have not yet been sufficiently studied in socio-political science. This article discusses in detail the problems encountered in achieving the goals set for the development of the Chinese navy.

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Version 4 CALIPSO IIR ice and liquid water cloud microphysical properties, Part I: the retrieval algorithms

10.5194/amt-2020-387 ◽

2020 ◽

Author(s):

Anne Garnier ◽

Jacques Pelon ◽

Nicolas Pascal ◽

Mark A. Vaughan ◽

Philippe Dubuisson ◽

...

Keyword(s):

Liquid Water ◽

Cloud Base ◽

Transfer Model ◽

Effective Diameter ◽

Ice Clouds ◽

Clear Sky ◽

Brightness Temperatures ◽

Microphysical Properties ◽

Data Products ◽

Level 2

Abstract. Following the release of the Version 4 Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) data products from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission, a new version 4 (V4) of the CALIPSO Imaging Infrared Radiometer (IIR) Level 2 data products has been developed. The IIR Level 2 data products include cloud effective emissivities and cloud microphysical properties such as effective diameter and ice or liquid water path estimates. Dedicated retrievals for water clouds were added in V4, taking advantage of the high sensitivity of the IIR retrieval technique to small particle sizes. This paper (Part I) describes the improvements in the V4 algorithms compared to those used in the version 3 (V3) release, while results will be presented in a companion (Part II) paper. To reduce biases at very small emissivities that were made evident in V3, the radiative transfer model used to compute clear sky brightness temperatures over oceans has been updated and tuned for the simulations using MERRA-2 data to match IIR observations in clear sky conditions. Furthermore, the clear-sky mask has been refined compared to V3 by taking advantage of additional information now available in the V4 CALIOP 5-km layer products used as an input to the IIR algorithm. After sea surface emissivity adjustments, observed and computed brightness temperatures differ by less than ± 0.2 K at night for the three IIR channels centered at 08.65, 10.6, and 12.05 µm, and inter-channel biases are reduced from several tens of Kelvin in V3 to less than 0.1 K in V4. We have also aimed at improving retrievals in ice clouds having large optical depths by refining the determination of the radiative temperature needed for emissivity computation. The initial V3 estimate, namely the cloud centroid temperature derived from CALIOP, is corrected using a parameterized function of temperature difference between cloud base and top altitudes, cloud absorption optical depth, and the CALIOP multiple scattering correction factor. As shown in Part II, this improvement reduces the low biases at large optical depths that were seen in V3, and increases the number of retrievals in dense ice clouds. As in V3, the IIR microphysical retrievals use the concept of microphysical indices applied to the pairs of IIR channels at 12.05 μm and 10.6 μm and at 12.05 μm and 08.65 μm. The V4 algorithm uses ice look-up tables (LUTs) built using two ice crystal models from the recent TAMUice 2016 database, namely the single hexagonal column model and the 8-element column aggregate model, from which bulk properties are synthesized using a gamma size distribution. Four sets of effective diameters derived from a second approach are also reported in V4. Here, the LUTs are analytical functions relating microphysical index applied to IIR channels 12.05 µm and 10.6 µm and effective diameter as derived from in situ measurements at tropical and mid-latitudes during the TC4 and SPARTICUS field experiments.

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Atmospheric aerosol characterization with a ground-based SPEX spectropolarimetric instrument

Atmospheric Measurement Techniques ◽

10.5194/amt-7-4341-2014 ◽

2014 ◽

Vol 7 (12) ◽

pp. 4341-4351 ◽

Cited By ~ 29

Author(s):

G. van Harten ◽

J. de Boer ◽

J. H. H. Rietjens ◽

A. Di Noia ◽

F. Snik ◽

...

Keyword(s):

Optical Thickness ◽

Atmospheric Aerosols ◽

Complex Refractive Index ◽

Random Noise ◽

Aerosol Optical Thickness ◽

Clear Sky ◽

Field Deployment ◽

Scattering Phase Function ◽

Aerosol Parameters ◽

Low Degrees

Abstract. Characterization of atmospheric aerosols is important for understanding their impact on health and climate. A wealth of aerosol parameters can be retrieved from multi-angle, multi-wavelength radiance and polarization measurements of the clear sky. We developed a ground-based SPEX instrument (groundSPEX) for accurate spectropolarimetry, based on the passive, robust, athermal, and snapshot spectral polarization modulation technique, and is hence ideal for field deployment. It samples the scattering phase function in the principal plane in an automated fashion, using a motorized pan/tilt unit and automatic exposure time detection. Extensive radiometric and polarimetric calibrations were performed, yielding values for both random noise and systematic uncertainties. The absolute polarimetric accuracy at low degrees of polarization is established to be ~5 × 10−3. About 70 measurement sequences have been performed throughout four clear-sky days at Cabauw, the Netherlands. Several aerosol parameters were retrieved: aerosol optical thickness, effective radius, and complex refractive index for fine and coarse mode. The results are in good agreement with the colocated AERONET products, with a correlation coefficient of ρ = 0.932 for the total aerosol optical thickness at 550 nm.

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Intercomparison of Phytoplankton functional types dynamics from satellite observations

10.5194/egusphere-egu21-9855 ◽

2021 ◽

Author(s):

Marine Bretagnon ◽

Séverine Alvain ◽

Astrid Bracher ◽

Philippe Garnesson ◽

Svetlana losa ◽

...

Keyword(s):

Remote Sensing ◽

Marine Environment ◽

Model Simulation ◽

Chlorophyll Concentration ◽

Satellite Observations ◽

Global Ocean ◽

Ocean Colour ◽

Marginal Seas ◽

Functional Types ◽

Wide Range

Copernicus marine environment monitoring service (CMEMS) gives users access to a wide range of ocean descriptors. Both physics and biogeochemistry of the marine environment can be studied with complementary source of data, such as in situ data, modelling output and satellite observations at global scale and/or for European marginal seas. Among the ocean descriptors supplied as part of CMEMS, phytoplankton functional types (PFTs) describe the phytoplanktonic composition at global level or over European marginal seas. Studied phytoplankton assemblage is particularly important as it is the basis of the marine food-web. Composition of the first trophic level is a valuable indicator to infer the structure of the ecosystem and its health. Over the last decades, ocean colour remote sensing has been used to estimate the phytoplanktonic composition. The algorithms developed to estimate PFTs composition based on ocean colour observation can be classified in three categories: the spectral approaches, the abundance-based approaches (derived from the chlorophyll concentration) and the ecological approaches. The three approaches can lead to differences or, conversely, to similar patterns. Difference and similarity in PFTs estimation from remote sensing is a useful information for data assimilation or model simulation, as it provides indications on the uncertainties/variability associated to the PFT estimates. Indeed, PFT estimates from satellite observations are increasingly assimilated into ecological models to improve biogeochemical simulations, what highlights the importance to get an index or at least information describing the validity range of such PFTs estimates.In this study, four algorithms (two abundance-based, and two spectral approaches) are compared. The aim of this study is to compare the related PFT products spatially and temporally, and to study the agreement of their derived PFT phenology. This study proposes also to compare PFT algorithms developed for the global ocean with those developed for specific regions in order to assess the potential strength and weakness of the different approaches. Once similarities and discrepancies between the different approaches are assessed, this information could be used by model to give an interval of confidence in model simulation.

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The Southern Ocean carbon sink 1985-2018: first results of the RECCAP2 project

10.5194/egusphere-egu21-1834 ◽

2021 ◽

Author(s):

Judith Hauck ◽

Luke Gregor ◽

Cara Nissen ◽

Eric Mortenson ◽

Seth Bushinsky ◽

...

Keyword(s):

Southern Ocean ◽

Seasonal Cycle ◽

Carbon Sink ◽

Global Ocean ◽

Biogeochemical Models ◽

Wide Range ◽

Data Products ◽

First Results ◽

Ocean Carbon ◽

Indian Sector

The Southern Ocean is the main gateway for anthropogenic CO2 into the ocean owing to the upwelling of old water masses with low anthropogenic CO2 concentration, and the transport of the newly equilibrated surface waters into the ocean interior through intermediate, deep and bottom water formation. Here we present first results of the Southern Ocean chapter of RECCAP2, which is the Global Carbon Project&#8217;s second systematic study on Regional Carbon Cycle Assessment and Processes. In the Southern Ocean chapter, we aim to assess the Southern Ocean carbon sink 1985-2018 from a wide range of available models and data sets, and to identify patterns of regional and temporal variability, model limitations and future challenges.We gathered global and regional estimates of the air-sea CO2 flux over the period 1985-2018 from global ocean biogeochemical models, surface pCO2-based data products, and data-assimilated models. The analysis on the Southern Ocean quantified geographical patterns in the annual mean and seasonal amplitude of air-sea CO2 flux, with results presented here aggregated to the level of large-scale ocean biomes.Considering the suite of observed and modelled estimates, we found that the subtropical seasonally stratified (STSS) biome stands out with the largest air-sea CO2 flux per area and a seasonal cycle with largest ocean uptake of CO2 in winter, whereas the ice (ICE) biome is characterized by a large ensemble spread and a pronounced seasonal cycle with the largest ocean uptake of CO2 in summer. Connecting these two, the subpolar seasonally stratified (SPSS) biome has intermediate flux densities (flux per area), and most models have difficulties simulating the seasonal cycle with strongest uptake during the summer months.Our analysis also reveals distinct differences between the Atlantic, Pacific and Indian sectors of the aforementioned biomes. In the STSS, the Indian sector contributes most to the ocean carbon sink, followed by the Atlantic and then Pacific sectors. This hierarchy is less pronounced in the models than in the data-products. In the SPSS, only the Atlantic sector exhibits net CO2 uptake in all years, likely linked to strong biological production. In the ICE biome, the Atlantic and Pacific sectors take up more CO2 than the Indian sector, suggesting a potential role of the Weddell and Ross Gyres.These first results confirm the global relevance of the Southern Ocean carbon sink and highlight the strong regional and interannual variability of the Southern Ocean carbon uptake in connection to physical and biogeochemical processes.

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