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FEBRUARY 1989 SASSEN, GRIFFIN AND DODD 91Optical Scattering and Microphysical Properties of Subvisual Cirrus Clouds, and Climatic ImplicationsKENNETH SASSEN, MICHAEL K. GRIFFIN* AND GREGORY C. DODDMeteorology Department, University of Utah, Salt Lake City, Utah(Manuscript received 29 Februax~ 1988, in final form 18 May 1988) ABSTRACT The optical and microphysical
FEBRUARY 1989 SASSEN, GRIFFIN AND DODD 91Optical Scattering and Microphysical Properties of Subvisual Cirrus Clouds, and Climatic ImplicationsKENNETH SASSEN, MICHAEL K. GRIFFIN* AND GREGORY C. DODDMeteorology Department, University of Utah, Salt Lake City, Utah(Manuscript received 29 Februax~ 1988, in final form 18 May 1988) ABSTRACT The optical and microphysical
The case study presented here shows the following. The new parameterization allows ice crystal numbers and optical properties to be diagnosed in models that use a bulk microphysical parameterization. The ice particle numbers and the optical depth are two important properties that can be validated against observations. The new parameterization unifies the radiation and precipitation branches of the microphysical package. The ice crystal numbers and optical properties diagnosed are in reasonable
The case study presented here shows the following. The new parameterization allows ice crystal numbers and optical properties to be diagnosed in models that use a bulk microphysical parameterization. The ice particle numbers and the optical depth are two important properties that can be validated against observations. The new parameterization unifies the radiation and precipitation branches of the microphysical package. The ice crystal numbers and optical properties diagnosed are in reasonable
Experiment (PROBE) held in Kavieng, New Ireland, Papua New Guinea (PNG). This experiment in turn was part of the Tropical Ocean Global Atmosphere Coupled Ocean–Atmosphere Response Experiment. The aim of the experiment was to acquire a dataset on the optical and structural properties of cirrus clouds at an equatorial site at 2°S latitude. The cloud properties could then be compared with those obtained in midlatitude and tropical regions (e.g., Platt et al. 1987 , hereafter referred to as P6). The data
Experiment (PROBE) held in Kavieng, New Ireland, Papua New Guinea (PNG). This experiment in turn was part of the Tropical Ocean Global Atmosphere Coupled Ocean–Atmosphere Response Experiment. The aim of the experiment was to acquire a dataset on the optical and structural properties of cirrus clouds at an equatorial site at 2°S latitude. The cloud properties could then be compared with those obtained in midlatitude and tropical regions (e.g., Platt et al. 1987 , hereafter referred to as P6). The data
1. Introduction Atmospheric particles scatter and absorb solar radiation. Consequently, they influence the energy budget of the atmosphere–earth system. To be able to understand the interaction of radiation with particles their optical properties have to be determined. These properties depend on the compositions, structures, shapes, and sizes of the particles ( Levin and Lindberg 1979 ; Patterson 1981 ; Bohren and Huffman 1983 ; Hill et al. 1984 ; Schuerman et al. 1981 ; Zerull et al. 1980
1. Introduction Atmospheric particles scatter and absorb solar radiation. Consequently, they influence the energy budget of the atmosphere–earth system. To be able to understand the interaction of radiation with particles their optical properties have to be determined. These properties depend on the compositions, structures, shapes, and sizes of the particles ( Levin and Lindberg 1979 ; Patterson 1981 ; Bohren and Huffman 1983 ; Hill et al. 1984 ; Schuerman et al. 1981 ; Zerull et al. 1980
). Hansen et al. (1998) estimated the global-average direct forcing due to aerosols to be −0.4 (±0.3) W m –2 and the indirect forcing due to aerosols through changes in cloud to be −1.0 (+0.5/−1.0) W m –2 . These large uncertainties are due to inadequate knowledge of aerosol optical properties and to their large spatial and temporal variation. Despite the importance of aerosol effects, little reduction of the uncertainties associated with these effects has occurred over the last 10 yr. Regionally
). Hansen et al. (1998) estimated the global-average direct forcing due to aerosols to be −0.4 (±0.3) W m –2 and the indirect forcing due to aerosols through changes in cloud to be −1.0 (+0.5/−1.0) W m –2 . These large uncertainties are due to inadequate knowledge of aerosol optical properties and to their large spatial and temporal variation. Despite the importance of aerosol effects, little reduction of the uncertainties associated with these effects has occurred over the last 10 yr. Regionally
foresight is clearly a credit to the developers of ISCCP because, more than a quarter-century later, ISCCP remains a flagship description of the cloudy atmosphere. By analyzing visible and infrared radiances produced by geostationary and polar-orbiting meteorological satellites and applying assumptions regarding the layering of clouds in the atmosphere, their thermodynamic phases, and their properties, ISCCP describes a cloudy satellite pixel with the column visible optical depth ( Ï„ ) and cloud
foresight is clearly a credit to the developers of ISCCP because, more than a quarter-century later, ISCCP remains a flagship description of the cloudy atmosphere. By analyzing visible and infrared radiances produced by geostationary and polar-orbiting meteorological satellites and applying assumptions regarding the layering of clouds in the atmosphere, their thermodynamic phases, and their properties, ISCCP describes a cloudy satellite pixel with the column visible optical depth ( Ï„ ) and cloud
to what would happen to OFn/OAcfor temporal changes in cloud amount. He concludedthat global OF~/OAc was close to zero. However, thiswas not true for individual zones. Given a perturbation in cloud amount, various atmospheric mechanisms can feed back to either amplify or damp this perturbation. The origins of such feedback, let alone their sign, are not yet fully under stood. Much more and better data on the optical properties of clouds is needed. Because of the multi various nature of clouds
to what would happen to OFn/OAcfor temporal changes in cloud amount. He concludedthat global OF~/OAc was close to zero. However, thiswas not true for individual zones. Given a perturbation in cloud amount, various atmospheric mechanisms can feed back to either amplify or damp this perturbation. The origins of such feedback, let alone their sign, are not yet fully under stood. Much more and better data on the optical properties of clouds is needed. Because of the multi various nature of clouds
improved the physical understanding of cloud-top lightning optical emissions ( Suszcynsky et al. 2001 ; Light et al. 2001a ; Kirkland et al. 2001 ; Davis et al. 2002 ; Light and Jacobson 2002 ; Noble et al. 2004 ; Beasley and Edgar 2004 ). Credit is due to the study by Davis et al. (2002) for providing specific additional information on flash optical properties as a function of flash type, where the flash type is corroborated by the FORTE VHF data. Note that by discriminating flash type, one
improved the physical understanding of cloud-top lightning optical emissions ( Suszcynsky et al. 2001 ; Light et al. 2001a ; Kirkland et al. 2001 ; Davis et al. 2002 ; Light and Jacobson 2002 ; Noble et al. 2004 ; Beasley and Edgar 2004 ). Credit is due to the study by Davis et al. (2002) for providing specific additional information on flash optical properties as a function of flash type, where the flash type is corroborated by the FORTE VHF data. Note that by discriminating flash type, one
1. Introduction Atmospheric aerosols substantially affect the radiation budget of the earth–atmosphere system in both direct and indirect ways. The direct effect is directly related to scattering and absorption of solar radiation by aerosol particles (e.g., Charlson et al. 1992 ; Kiehl and Briegleb 1993 ). The indirect effect is seen in the way aerosols influence optical properties and the lifetime of clouds through cloud formation processes (e.g., Twomey 1977 ; Albrecht 1989 ). In the
1. Introduction Atmospheric aerosols substantially affect the radiation budget of the earth–atmosphere system in both direct and indirect ways. The direct effect is directly related to scattering and absorption of solar radiation by aerosol particles (e.g., Charlson et al. 1992 ; Kiehl and Briegleb 1993 ). The indirect effect is seen in the way aerosols influence optical properties and the lifetime of clouds through cloud formation processes (e.g., Twomey 1977 ; Albrecht 1989 ). In the
composed of optical groups, and each optical group is composed of optical events (see Mach et al. 2007 ). Note that x is not limited to flash-level properties; for example, one could use the area of the first group in a flash rather than flash area itself or both. In general, one is free to choose any optical information from the optical data (including concocting derived variables from the data); hence, the list of possible optical characteristics is virtually unlimited. However, a certain set of
composed of optical groups, and each optical group is composed of optical events (see Mach et al. 2007 ). Note that x is not limited to flash-level properties; for example, one could use the area of the first group in a flash rather than flash area itself or both. In general, one is free to choose any optical information from the optical data (including concocting derived variables from the data); hence, the list of possible optical characteristics is virtually unlimited. However, a certain set of
