Experimental Studies of the Thermal Radiation of a Cloudy Atmosphere

Feigelson, E. M.

doi:10.1007/978-94-009-6443-3_14

Cited by 7 publications

(9 citation statements)

References 5 publications

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“…The solar radiative flux divergence is positive through the whole layer: it reaches a maximum of O.l2"/hr 100-200 m beneath the upper boundary; above the cloud, it is O.O2"/hr; and in the sub-cloud layer it is O.Ol"/hr ( Figure 6~). The vertical profiles of fluxes and flux divergences agree with those determined by Monte-Carlo calculations (Feigelson, 1981).…”

Section: A Brief Description Of the Modelsupporting

confidence: 76%

Modelling of cloud formation due to air-sea interactions in an energy-active zone

Kondratyev¹,

Khvorostyanov²

1989

Boundary-Layer Meteorol

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A mesoscale 3D numerical model is described, with which detailed calculations have been made of turbulence and wind characteristics in the atmospheric boundary layer (ABL), as well as cloud particle size distribution, longwave and solar radiation fluxes and flux divergences, and atmosphere-ocean heat exchange. Based on numerical experiments simulating winter conditions of the Newfoundland energy-active zone of the ocean (EAZO), atmosphere-ocean energy exchange is investigated. It is shown that the basic mechanisms for the EAZO formation involve the following processes: (i) at the hydrological front between cold and warm ocean currents, the fluxes of sensible and latent heat grow significantly; (ii) at this front, in a particular synoptic situation, overcast low-level cloudiness forms, screening solar radiation so that in winter, the radiation budget at the front is reduced, and the radiative flux into the ocean is less than the energy release to the atmosphere; (iii) frequent occurrence of such synoptic situations with cloudiness decreases the oceanic enthalpy and creates negative SST anomalies. The transport of these anomalies by currents to the western coasts of the continents causes anomalies of weather and climate.

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Section: A Brief Description Of the Modelsupporting

confidence: 76%

Modelling of cloud formation due to air-sea interactions in an energy-active zone

Kondratyev¹,

Khvorostyanov²

1989

Boundary-Layer Meteorol

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“…[34] To complete the model, we also account for the light absorption of diffused light fluxes by gases present in a layer between a cloud and an ''effective'' underlying surface. To do so, we multiply t c (J 0 ) and t c (J) in equation (5) by the flux transmittance [Feigelson, 1984;Li, 2000]:…”

Section: Radiative Transfer Model: the Monochromatic Casementioning

confidence: 99%

“…Such an assumption is never valid. The concentration and size of droplets in clouds change with height [Feigelson, 1984]. Also, multilayered cloud systems are more common than a simple case of a single cloud layer [Grechko et al, 1973[Grechko et al, , 1975Platnick et al, 2003].…”

Section: Errors Of Retrievals As Applied To Vertically Inhomogeneous mentioning

confidence: 99%

Semianalytical cloud retrieval algorithm as applied to the cloud top altitude and the cloud geometrical thickness determination from top‐of‐atmosphere reflectance measurements in the oxygen A band

2004

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[1] The paper is devoted to the development of the asymptotic algorithm for the cloud top height h and the geometrical thickness l determination using measurements of the cloud reflection function. It is based on the asymptotic theory of the radiative transfer in the oxygen absorption bands and simple parameterization of the radiative transport in the atmosphere above and under a cloud. In particular, we have studied the influence of the error of the developed approximate theory on the accuracy of the retrieval of the pair (h, l ). It was assumed that there is only a single cloud layer having the same value of the liquid water content in all points inside the cloud. The values (h, l ) have been found, solving the inverse problem having as input the synthetic spectra of backscattered light. The synthetic spectra were found using the exact solution of the forward problem for given values of (h, l ). The retrieval technique was based on the asymptotic theory. We have found that the error of the cloud top height determination is smaller than 20 m, and the error of the cloud geometrical thickness determination is smaller than 500 m for solar angles 20-70 degrees, values of h in the range 1-12 km, values of geometrical thickness l in the range 0.5-2 km, and values of the cloud optical thickness changing in the range 10-50. The surface albedo has been assumed to be equal zero. We have also studied the influence of the cloud liquid water profile on the results of the retrieval of the pair (h, l ). It was found that the error of the cloud top height determination increases up to 600 m, if the assumed cloud has a changing with height liquid water content, and retrievals are made applying the inversion with assumed constant liquid water content profile. The error in the geometrical thickness increases up to 1 km in this case. Errors of the retrieval increase even further if the retrieval, on the basis of the homogeneous layer theory, is applied to the two-layered cloud system (e.g., the upper cloud consists of ice crystals and the lower cloud is in a liquid phase). This signifies the importance of the cloud vertical inhomogeneity on the retrieval results.

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“…However, it should be stressed that the optical thickness is highly correlated with the geometrical thickness of clouds. For instance, it was shown [Feigelson, 1981] that clouds having t < 5 are characterized by a geometrical thickness less than 200 m. It is difficult to expect that such thin clouds are horizontally homogeneous media. This requires taking the horizontal photon transport into account [Cahalan et al, 1994;Platnick, 2001], which is not considered in standard retrieval procedures [Arking and Childs, 1985;Nakajima and King, 1990].…”

Section: Introductionmentioning

confidence: 99%

A semianalytical cloud retrieval algorithm using backscattered radiation in 0.4–2.4 μm spectral region

et al. 2003

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[1] This study is devoted to the development of a semianalytical algorithm for the determination of the optical thickness, the liquid water path, and the effective size of droplets from spectral measurements of the intensity of light reflected from water clouds with large optical thickness. The probability of photon absorption by droplets in the visible and near-infrared spectral regions is low. This allows us to simplify and modify wellknown asymptotic equations of the radiative transfer theory, taking into account the fact that the single scattering albedo is close to one. Modified asymptotic equations are used to develop the inverse algorithm. We also avoid the use of the Mie theory, applying parametrizations and geometrical optics results with account for wave corrections. The main advantage of the method proposed lays in the fact that the equations derived not only provide a valuable alternative to the numerical radiative transfer solution but also are much more simple than equations of a conventional asymptotic theory. This simplicity allows both the simplification of the cloud retrieval algorithm and, even more important, the insight into various factors involved in a retrieval scheme.

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Experimental Studies of the Thermal Radiation of a Cloudy Atmosphere

Cited by 7 publications

References 5 publications

Modelling of cloud formation due to air-sea interactions in an energy-active zone

Modelling of cloud formation due to air-sea interactions in an energy-active zone

Semianalytical cloud retrieval algorithm as applied to the cloud top altitude and the cloud geometrical thickness determination from top‐of‐atmosphere reflectance measurements in the oxygen A band

A semianalytical cloud retrieval algorithm using backscattered radiation in 0.4–2.4 μm spectral region

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