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  • 1
    Electronic Resource
    Electronic Resource
    Valence bond corrected single reference coupled cluster approach (1994)
    Springer
    Theoretical chemistry accounts 89 (1994), S. 33-57 
    Details
    ISSN: 1432-2234
    Keywords: Coupled cluster method ; Valence bond (VB) wave functions ; VB corrected CCSD method ; Cluster analysis ; Correlation effects ; PPP Hamiltonian
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The recently proposed valence bond (VB) corrected single reference (SR) coupled cluster method with singly and doubly excited cluster components (CCSD) [Paldus and Planelles, Theor Chim Acta 89, 13–31 (1994)] is tested using a number of simple yet typical Pariser-Parr-Pople (PPP) π-electron model systems, including both cyclic and linear polyenes. The cluster analysis of various approximate VB wave functions, obtained with the PPP-VB approach [Li and Paldus, J Mol Struct (Theochem) 229, 249 (1991)], is carried out and the resulting three- and four-body connected cluster components are employed in the VB corrected CCSD method. The cluster structure and the correlation energies obtained are compared to full configuration interaction (FCI) or full VB (FVB) results, representing the exact solutions for these models, and the performance and potential of the CCSD-VB approach are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01123869
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  • 2
    Electronic Resource
    Electronic Resource
    Valence bond corrected single reference coupled cluster approach (1994)
    Springer
    Theoretical chemistry accounts 89 (1994), S. 59-76 
    Details
    ISSN: 1432-2234
    Keywords: Coupled cluster methods ; Valence bond (VB) wave functions ; VB corrected CCSD method ; Cluster analysis ; Correlation effects ; PPP Hamiltonians ; Dissociation ; Bond formation ; Potential energy surfaces
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The valence bond (VB) corrected single reference (SR) coupled cluster (CC) method [J. Paldus and J. Planelles, Theor. Chim. Acta 89, 13–31 (1994)] with Singly and Doubly excited cluster components (CCSD-VB) is applied to simple Parise-Parr-Pople (PPP) model systems that are capable of simulating chemical bond breaking or formation. Dissociation into both closed and open shell type subsystems is considered. The 3- and 4-body connected cluster components are first determined by cluster analyzing simple PPP-VB wave functions [X. Li and J. Paldus, J. Mol. Structure (Theochem) 229, 249 (1991)] involving only covalent-type structures, and are subsequently employed in the CCSD-VB approach. The results are compared with the full configuration interaction (FCI) or full valence bond (FVB) solutions, representing the exact result for these models, and the potential of the CCSD-VB approach is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01167281
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Valence bond corrected single reference coupled cluster approach (1994)
    Springer
    Theoretical chemistry accounts 89 (1994), S. 59-76 
    Details
    ISSN: 1432-2234
    Keywords: Coupled cluster methods ; Valence bond (VB) wave functions ; VB corrected CCSD method ; Cluster analysis ; Correlation effects ; PPP Hamiltonians ; Dissociation ; Bond formation ; Potential energy surfaces
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The valence bond (VB) corrected single reference (SR) coupled cluster (CC) method [J. Paldus and J. Planelles, Theor. Chim. Acta 89, 13–31 (1994)] with Singly and Doubly excited cluster components (CCSD-VB) is applied to simple Parise-Parr-Pople (PPP) model systems that are capable of simulating chemical bond breaking or formation. Dissociation into both closed and open shell type subsystems is considered. The 3- and 4-body connected cluster components are first determined by cluster analyzing simple PPP-VB wave functions [X. Li and J. Paldus, J. Mol. Structure (Theochem) 229, 249 (1991)] involving only covalent-type structures, and are subsequently employed in the CCSD-VB approach. The results are compared with the full configuration interaction (FCI) or full valence bond (FVB) solutions, representing the exact result for these models, and the potential of the CCSD-VB approach is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01123870
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Valence bond corrected single reference coupled cluster approach (1994)
    Springer
    Theoretical chemistry accounts 89 (1994), S. 33-57 
    Details
    ISSN: 1432-2234
    Keywords: Coupled cluster method ; Valence bond (VB) wave functions ; VB corrected CCSD method ; Cluster analysis ; Correlation effects ; PPP Hamiltonian
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The recently proposed valence bond (VB) corrected single reference (SR) coupled cluster method with singly and doubly excited cluster components (CCSD) [Paldus and Planelles, Theor Chim Acta 89, 13–31 (1994)] is tested using a number of simple yet typical Pariser-Parr-Pople (PPP) π-electron model systems, including both cyclic and linear polyenes. The cluster analysis of various approximate VB wave functions, obtained with the PPP-VB approach [Li and Paldus, J Mol Struct (Theochem) 229, 249 (1991)], is carried out and the resulting three- and four-body connected cluster components are employed in the VB corrected CCSD method. The cluster structure and the correlation energies obtained are compared to full configuration interaction (FCI) or full VB (FVB) results, representing the exact solutions for these models, and the performance and potential of the CCSD-VB approach are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01167280
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  • 5
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    The Role of Atmospheric Aerosol Concentration on Deep Convective Precipitation: Cloud-resolving Model Simulations (2007)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: Aerosols and especially their effect on clouds are one of the key components of the climate system and the hydrological cycle [Ramanathan et al., 20011. Yet, the aerosol effect on clouds remains largely unknown and the processes involved not well understood. A recent report published by the National Academy of Science states "The greatest uncertainty about the aerosol climate forcing - indeed, the largest of all the uncertainties about global climate forcing - is probably the indirect effect of aerosols on clouds NRC [2001]." The aerosol effect on clouds is often categorized into the traditional "first indirect (i.e., Twomey)" effect on the cloud droplet sizes for a constant liquid water path and the "semi-direct" effect on cloud coverage. The aerosol effect on precipitation processes, also known as the second type of aerosol indirect effect, is even more complex, especially for mixed-phase convective clouds. ln this paper, a cloud-resolving model (CRM) with detailed spectral-bin microphysics was used to examine the effect of aerosols on three different deep convective cloud systems that developed in different geographic locations: South Florida, Oklahoma and the Central Pacific. In all three cases, rain reaches the ground earlier for the low CCN (clean) case. Rain suppression is also evident in all three cases with high CCN (dirty) case. However, this suppression only occurs during the first hour of the simulations. During the mature stages of the simulations, the effects of increasing aerosol concentration range from rain suppression in the Oklahoma case, to almost no effect in the Florida case, to rain enhancement in the Pacific case. These results show the complexity of aerosol interactions with convection.
    Keywords: Meteorology and Climatology
    Format: application/pdf
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  • 6
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    Cloud-Resolving Model and GPM (2003)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Over the past twenty years, rainfall retrieval algorithms have been developed to retrieve rainfall and vertical hydrometeor structures from passive microwave observations by making use of the fact that weighting functions for various frequencies peak at different levels within a rainy atmosphere. GPROF is one of two TMI rainfall algorithms. It is physically based retrieval that finds the vertical hydrometeor profile that best fits the brightness temperatures in the available passive radiometer channels. Matching is achieved using a library of hydrometeor profiles generated by cloud-resolving models (CRMs). The hydrometeor profiles have a corresponding surface precipitation rate. The algorithm retrieves the hydrometeor profiles and associated surface rainfall using a Bayesian approach that gives the estimated expected values. The ability of CRMs to produce cloud structures that are reliable and representative of observed storms is crucial for the success of GPROF. The cloud mycrophysics are one of the keys to achieving this. In addition, CRMs have been a very useful tool for GPM-algorithm developers through Cloud-Radiation Simulations (CRS), one of the nine GPM disciplinary research themes. This paper will discuss how to generate consistent and comprehensive 4D cloud datasets from an improved (i.e., in regard to bulk and multi-moment microphysics) CRM for TRMM and GPM rainfall retrieval algorithm developers. These cloud datasets include CRM-simulated clouds and cloud systems from different geographic locations in the tropics and midlatitudes. By linking the CRM with a passive microwave radiative-transfer model and using satellite and airborne data, the performance of the "cloud physics" can be assessed and in turn modified and improved. This paper will also address how to assess and improve the performance of various latent and diabatic heating algorithms and develop an algorithm to retrieve the vertical structure of apparent moistening (Q2). Considering that the GPM will produce high (temporal and spatial) resolution heating and rainfall data, these algorithms will be used to obtain the temporal and spatial distributions of surface rainfall and the associated vertical heating and moistening profiles throughout the subtropical and midlatitudes.
    Keywords: Meteorology and Climatology
    Type: 3rd Global Precipation Mission Workshop; Jun 24, 2003 - Jun 26, 2003; Noordwijk; Netherlands
    Format: text
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  • 7
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    The Role of Aerosols on Precipitation Processes (2006)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Cloud physics is inevitably affected by the smoke particle (CCN, cloud condensation nuclei) size distribution below the clouds. Therefore, the size distributions parameterized as spectral bin microphysics are needed to explicitly study the effects of atmospheric aerosol concentration on cloud development, rainfall production, and rainfall rates for convective clouds. Recently, a detailed spectral--bin microphysical scheme was implemented into the Goddard Cumulus Ensemble (GCE) model. The formulation for the explicit spectral-bin microphysical processes is based on solving stochastic kinetic equations for the size distribution functions of water droplets (i.e., cloud droplets and raindrops), and several types of ice particles [i.e., pristine ice crystals (columnar and plate-like), snow (dendrites and aggregates), graupel and frozen drops/hail]. Each type is described by a special size distribution function containing many categories (i.e., 33 bins). Atmospheric aerosols are also described using number density size-distribution functions.
    Keywords: Meteorology and Climatology
    Type: 2006 Joint Assembly; May 23, 2006 - May 26, 2006; Baltimore, MD; United States
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  • 8
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    The Impact of Aerosols on Cloud and Precipitation Processes: Cloud-Resolving Model Simulations (2005)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Cloud microphysics are inevitable affected by the smoke particle (CCN, cloud condensation nuclei) size distributions below the clouds, Therefore, size distributions parameterized as spectral bin microphysics are needed to explicitly study the effect of atmospheric aerosol concentration on cloud development, rainfall production, and rainfall rates for convective clouds. Recently, a detailed spectral-bin microphysical scheme was implemented into the the Goddard Cumulus Ensemble (GCE) model. The formulation for the explicit spectral-bim microphysical processes is based on solving stochastic kinetic equations for the size distribution functions of water droplets (i.e., cloud droplets and raindrops), and several types of ice particles [i.e., pristine ice crystals (columnar and plate-like), snow (dendrites and aggregates), graupel and frozen drops/hail]. Each type is described by a special size distribution function containing many categories (i.e., 33 bins). Atmospheric aerosols are also described using number density size-distribution functions.
    Keywords: Meteorology and Climatology
    Type: IAMAS 2005; Aug 02, 2005 - Aug 12, 2005; Beijing; China
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  • 9
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    The Impact of Aerosols on Cloud and Precipitation Processes: Cloud-Resolving Model Simulations (2004)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Cloud microphysics is inevitably affected by the smoke particle (CCN, cloud condensation nuclei) size distributions below the clouds. Therefore, size distributions parameterized as spectral bin microphysics are needed to explicitly study the effects of atmospheric aerosol concentration on cloud development, rainfall production, and rainfall rates for convective clouds. Recently, two detailed spectral-bin microphysical schemes were implemented into the Goddard Cumulus Ensembel (GCE) model. The formulation for the explicit spectral-bin microphysical processes is based on solving stochastic kinetic equations for the size distribution functions of water droplets (i.e., cloud droplets and raindrops), and several types of ice particles [i.e. pristine ice crystals (columnar and plate-like), snow (dendrites and aggregates), graupel and frozen drops/hail]. Each type is described by a special size distribution function containing many categories (i.e. 33 bins). Atmospheric aerosols are also described using number density size distribution functions. A spectral-bin microphysical model is very expensive from a computational point of view and has only been implemented into the 2D version of the GCE at the present time. The model is tested by studying the evolution of deep tropical clouds in the west Pacific warm pool region and in the mid-latitude continent with different concentrations of CCN: a low "c1ean"concentration and a high "dirty" concentration. In addition, differences and similarities between bulk microphysics and spectral-bin microphysical schemes will be examined and discussed.
    Keywords: Meteorology and Climatology
    Type: 2nd International Workshop on NWP Model; May 17, 2004 - May 20, 2004; Seoul; Korea, Republic of
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  • 10
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    The Impact of Aerosols on Cloud and Precipitation Processes: Cloud-resolving Model Simulations (2004)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Cloud microphysics is inevitably affected by the smoke particle (CCN, cloud condensation nuclei) size distributions below the clouds. Therefore, size distributions parameterized as spectral bin microphysics are needed to explicitly study the effects of atmospheric aerosol concentration on cloud development, r d a U production, and rainfall rates for convective clouds. Recently, two detailed spectral-bin microphysical schemes were implemented into the Goddard Cumulus Ensembe1 (GCE) model. The formulation for the explicit spectral-bin microphysical processes is based on solving stochastic kinetic equations for the size distribution functions of water droplets (i.e., cloud droplets and raindrops), and several types of ice particles [i.e. pristine ice crystals (columnar and platelike), snow (dendrites and aggregates), graupel and frozen drops/hail]. Each type is described by a special size distribution function containing many categories (i.e. 33 bins). Atmospheric aerosols are also described using number density size-distribution functions. A spectral-bin microphysical model is very expensive from a computational point of view and has only been implemented into the 2D version of the GCE at the present time. The model is tested by studying the evolution of deep tropical clouds in the west Pacific warm pool region and in the mid-latitude continent with different concentrations of CCN: a low "c1ean"concentration and a high "dirty" concentration. In addition, differences and similarities between bulk microphysics and spectral-bin microphysical schemes will be examined and discussed.
    Keywords: Meteorology and Climatology
    Type: 14th International Conference on Clouds and Precipitation; Jul 18, 2004 - Jul 23, 2004; Bologna; Italy
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