A model dealing with interactions between the air and low stratiform clouds is presented based on the mixed-layer model Lilly (1968) pioneered and on Deardorffs three dimensional numerical model results. Its main new ...A model dealing with interactions between the air and low stratiform clouds is presented based on the mixed-layer model Lilly (1968) pioneered and on Deardorffs three dimensional numerical model results. Its main new aspects lie in 1) consideration of the natures of both the atmosphere and cloud; 2) a new entrainment velocity scheme with few arbitrary assumptions; 3) transition from one-mixed layer to two-mixed layer model; and 4) parameterization of radiation and precipitation calculations.The model results for radiation, moisture, and heat turbulent fluxes turn out to be in good agreement with those calculated or observed by Kawa (1988), Nicholls (1984), and Schmets et al. (1981) in California, the North Sea, and the North Atlantic, respectively.Basically, this paper furnishes the theoretical basis for a model to address questions concerning the time-evolution of thermodynamical profiles both in cloud and out of cloud. The applications of this model wil be in a separate paper.展开更多
This paper presents some results concerning applications of the coupled dynamical-radiational model of stratocumulus Ye developed (Ye, 1990, hereafter referred to as the DRS model). Basically, calculations involved he...This paper presents some results concerning applications of the coupled dynamical-radiational model of stratocumulus Ye developed (Ye, 1990, hereafter referred to as the DRS model). Basically, calculations involved here relate to the time-integration of the DRS model to estimate some time constants associated with the boundary layer and cloud developments. To obtain cloud lifetime (CLT), the time interval from its formation to its dissipation, different cloud instability criteria are compared, the mechanism for dissipating cloud are discussed, and thereby two new criteria for judging whether cloud can maintain are established. Following these criteria, the sensitivities of CLT to parameters such as the air-sea temperature difference, subsidence, and surface wind are estimated. The main interesting results about the sensitivities of the forming time (CFT) are a stable environment, such as cool sea, low wind, and strong subsidence, would prolong the existence of Sc, which has been predicted by the model calculations and strikingly tallies with statistical observations.Besides, with the DRS model and the CLT criteria, we follow a marine boundary layer, starting with clear sky, through the formation and development of clouds and rain, until their dissipation. On the whole, the model results fit the developing process of a typically stable marine boundary layer, and show some features Nicholls (1984) observed for daytime Sc.展开更多
基金This paper and its sequel are basically based on the author's doctoral thesis completed at NCAR.
文摘A model dealing with interactions between the air and low stratiform clouds is presented based on the mixed-layer model Lilly (1968) pioneered and on Deardorffs three dimensional numerical model results. Its main new aspects lie in 1) consideration of the natures of both the atmosphere and cloud; 2) a new entrainment velocity scheme with few arbitrary assumptions; 3) transition from one-mixed layer to two-mixed layer model; and 4) parameterization of radiation and precipitation calculations.The model results for radiation, moisture, and heat turbulent fluxes turn out to be in good agreement with those calculated or observed by Kawa (1988), Nicholls (1984), and Schmets et al. (1981) in California, the North Sea, and the North Atlantic, respectively.Basically, this paper furnishes the theoretical basis for a model to address questions concerning the time-evolution of thermodynamical profiles both in cloud and out of cloud. The applications of this model wil be in a separate paper.
文摘This paper presents some results concerning applications of the coupled dynamical-radiational model of stratocumulus Ye developed (Ye, 1990, hereafter referred to as the DRS model). Basically, calculations involved here relate to the time-integration of the DRS model to estimate some time constants associated with the boundary layer and cloud developments. To obtain cloud lifetime (CLT), the time interval from its formation to its dissipation, different cloud instability criteria are compared, the mechanism for dissipating cloud are discussed, and thereby two new criteria for judging whether cloud can maintain are established. Following these criteria, the sensitivities of CLT to parameters such as the air-sea temperature difference, subsidence, and surface wind are estimated. The main interesting results about the sensitivities of the forming time (CFT) are a stable environment, such as cool sea, low wind, and strong subsidence, would prolong the existence of Sc, which has been predicted by the model calculations and strikingly tallies with statistical observations.Besides, with the DRS model and the CLT criteria, we follow a marine boundary layer, starting with clear sky, through the formation and development of clouds and rain, until their dissipation. On the whole, the model results fit the developing process of a typically stable marine boundary layer, and show some features Nicholls (1984) observed for daytime Sc.
