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  • 1
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    An assessment of the quality of aerosol retrievals over the Red Sea and evaluation of the climatological dust cloud-free direct radiative effect in the region (2015)
    Wiley
    Details
    Publication Date: 2015-09-26
    Description: Ground-based and satellite observations are used in conjunction with the RRTM radiative transfer model to assess climatological aerosol loading and the associated cloud-free aerosol direct radiative effect (DRE) over the Red Sea. Aerosol optical depth (AOD) retrievals from the MODIS and SEVIRI instruments are first evaluated via comparison with ship-based observations. Correlations are typically better than 0.9 with very small root-mean-square and bias differences. Calculations of the DRE along the ship cruises using RRTM also show good agreement with co-located estimates from the GERB instrument if the aerosol asymmetry parameter is adjusted to account for the presence of large particles. A monthly climatology of AOD over the Red Sea is then created from 5 yrs of SEVIRI retrievals. This shows enhanced aerosol loading and a distinct north to south gradient across the basin in the summer relative to the winter months. The climatology is used with RRTM to estimate the DRE at the top and bottom of the atmosphere and the atmospheric absorption due to dust aerosol. These climatological estimates indicate that although longwave effects can reach 10s of W m −2 , shortwave cooling typically dominates the net radiative effect over the Sea, being particularly pronounced in the summer, reaching 120 W m −2 at the surface. The spatial gradient in summer-time AOD is reflected in the radiative effect at the surface and in associated differential heating by aerosol within the atmosphere above the Sea. This asymmetric effect is expected to exert a significant influence on the regional atmospheric and oceanic circulation.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    Multiangle implementation of atmospheric correction (MAIAC): 2. Aerosol algorithm (2011)
    Wiley
    Details
    Publication Date: 2011-02-11
    Description: An aerosol component of a new multiangle implementation of atmospheric correction (MAIAC) algorithm is presented. MAIAC is a generic algorithm developed for the Moderate Resolution Imaging Spectroradiometer (MODIS), which performs aerosol retrievals and atmospheric correction over both dark vegetated surfaces and bright deserts based on a time series analysis and image-based processing. The MAIAC look-up tables explicitly include surface bidirectional reflectance. The aerosol algorithm derives the spectral regression coefficient (SRC) relating surface bidirectional reflectance in the blue (0.47 μm) and shortwave infrared (2.1 μm) bands; this quantity is prescribed in the MODIS operational Dark Target algorithm based on a parameterized formula. The MAIAC aerosol products include aerosol optical thickness and a fine-mode fraction at resolution of 1 km. This high resolution, required in many applications such as air quality, brings new information about aerosol sources and, potentially, their strength. AERONET validation shows that the MAIAC and MOD04 algorithms have similar accuracy over dark and vegetated surfaces and that MAIAC generally improves accuracy over brighter surfaces due to the SRC retrieval and explicit bidirectional reflectance factor characterization, as demonstrated for several U.S. West Coast AERONET sites. Due to its generic nature and developed angular correction, MAIAC performs aerosol retrievals over bright deserts, as demonstrated for the Solar Village Aerosol Robotic Network (AERONET) site in Saudi Arabia.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
    Electronic Resource
    Electronic Resource
    Carrier diffusion in porous silicon studied by transient laser-induced grating spectroscopy (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2481-2486 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report laser-induced transient grating experiments performed at room temperature on self-supporting p-type porous silicon films with different porosities. With this technique the diffusion of the photocarriers can be studied with a time resolution of some tens of picoseconds. The gratings were created by two interfering pulses of the second-harmonic radiation from an Nd3+:yttrium-aluminum-garnet YAG laser (2.3 eV) and their decay in time was studied by a time-delayed pulse of the fundamental YAG laser frequency (1.15 eV). The observed grating decay time is very fast (hundreds of picoseconds) and shortens with decreasing porosity. Diffusion constants D=45, 24, and 5 cm2 s−1 have been found for the porosities of 64%, 68%, and 73%, respectively. To explain these high values of D we consider a simple kinetic model which takes into account two different types of carriers, delocalized and trapped ones. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361177
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  • 4
    Electronic Resource
    Electronic Resource
    Degenerate four-wave mixing experiments on GaN in the quasistationary regime (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 1436-1438 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to determine the third order of the nonlinear susceptibility χ(3) of GaN, we perform degenerate four-wave mixing measurements in a two-beam configuration at low temperature on a GaN epilayer on sapphire substrate. We measure the excitation spectrum of χ(3) close to the exciton resonances. Besides the χ(3) contribution, higher orders of the nonlinear susceptibility show already up around 10 kW cm−2, leading to a saturation of the signal. Results are complemented by a study of the influence of a band-to-band excitation ((h-dash-bar)ωP=4.02 eV) on the nonlinear susceptibility. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123574
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  • 5
    Electronic Resource
    Electronic Resource
    Roughening kinetics of chemical vapor deposited copper films on Si(100) (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 1285-1287 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The roughening kinetics of copper films synthesized by low pressure chemical vapor deposition (LPCVD) on Si(100) substrates was investigated by scanning tunneling microscopy (STM). By applying the dynamic scaling theory to the STM images, a steady growth roughness exponent α=0.81±0.05 and a dynamic growth roughness exponent β=0.62±0.09 were determined. The value of α is consistent with growth model predictions incorporating surface diffusion. The value of β, while higher than expected from these models, can be related to LPCVD processing conditions favoring growth instabilities. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115954
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  • 6
    Electronic Resource
    Electronic Resource
    Tunable optical nonlinearities in Cd1−xZnxTe ternary alloys (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 1355-1358 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Bulk Cd1−xZnxTe ternary compounds are studied through nonlinear optical pump and probe experiments for different zinc concentrations x. These measurements, similar to excitation spectra, enable us to determine the frequency dependence of the optical nonlinearity. It is attributed to the presence of impurity levels in the material. The two-photon absorption through these states gives rise to a high induced absorption. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365910
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  • 7
    Electronic Resource
    Electronic Resource
    Structural characterization of boron nitride films (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 2990-2994 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The microstructure of amorphous hydrogenated boron nitride films, with nominal composition B3N:H, is characterized with respect to hydrogen bonding and distribution by combined application of nuclear-magnetic-resonance (NMR) spectroscopy, electron-spin-resonance spectroscopy, and evolved gas analysis. Previous infrared studies on annealed films suggest that hydrogen is present in multiple configurations; qualitatively, low-temperature anneals (∼600 °C) deplete N-H moieties whereas B-H configurations are depleted at higher temperatures (∼1050 °C). Gas analysis corroborates these results, showing H2 peaks at ∼570 and ∼950 °C. From an analysis of nuclear dipolar couplings extracted from the 1H NMR spectra, it is concluded that the hydrogen is essentially randomly distributed as monohydrides; other configurations, such as dihydrides and monohydride clusters, are estimated to be less than 20% total. Furthermore, the 1H NMR spectra show no evidence of molecular H2 trapped in the films. In a film exposed to a high x-ray dose (∼30 kJ cm−3), it was determined that the damage was equivalent to 1 unpaired electron spin per 175 B3N:H units. The 1H NMR linewidth did not change after irradiation, which suggests that the hydrogen spatial distribution was unaffected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342471
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  • 8
    Electronic Resource
    Electronic Resource
    Dynamics of beam defocusing and induced absorption in CdZnTe alloys (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 1720-1722 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We study the optical nonlinear properties of bulk Cd0.13Zn0.87Te monocrystals at room temperature near the band gap. In time-resolved test and pump experiments, they manifest themselves by a defocalization and an induced absorption of the test beam in the presence of the pump beam. By measuring the spatial intensity profile of the test pulse transmitted through the sample, we determine the real and the imaginary parts of the refractive index as functions of the photon energy and time delay between pump and test pulses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111790
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  • 9
    Electronic Resource
    Electronic Resource
    Picosecond excite and probe nonlinear absorption measurements in CuCl quantum dots (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 3378-3380 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report nonlinear absorption around the Z3 exciton in CuCl microcrystallites embedded in a glass matrix. Our experiments are performed in a test-pump configuration with picosecond pulses at low temperature. In addition to a shift and a bleaching of the excitonic resonance, induced absorption on the high-energy side is found. The nonlinear index changes induced per exciton per unit volume of CuCl quantum dot could be determined by Kramers–Kronig transformations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105680
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  • 10
    Electronic Resource
    Electronic Resource
    Hole-filling of persistent spectral holes in the excitonic absorption band of CuBr quantum dots (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 680-682 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Persistent spectral-holes (p-SH) are burned in the Z1,2 excitonic band of CuBr nanocrystals by a pulsed laser excitation. The annealing of p-SH is studied by three types of hole-filling (HF) experiments: (i) the spontaneous HF, (ii) thermally-induced HF, and (iii) the laser-induced HF. Results are compared to the well developed theory of the persistent spectral hole-burning (p-SHB) in the system of molecules in amorphous matrices. Both p-SHB and HF phenomena can be explained within the framework of a photochemical reaction like the photoionization of nanocrystals. The potential application of p-SHB to the frequency-domain optical data storage is discussed. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118273
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