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M. Segal, M. Leuthold, R. W. Arritt, C. Anderson, and J. Shen

The diversity of small lakes' (size < 50 km) configurations, sizes, surrounding terrain, and land use combined with relative sparsity of observations complicates the observational evaluation of the lake breezes (LB) that are induced by these lakes. In the present article observational data obtained from available documents, data archives, and special projects were surveyed to suggest characterization of the LB features. The observational survey was complemented by conceptual evaluations. A preliminary generalization of the LB intensity and inland penetration in relation to the surrounding land use was inferred. The conceptual evaluation suggested that for a given lake width the prime factor affecting the LB intensity is the magnitude of the surface sensible heat flux over the surrounding land. Cooling related to the lake water temperature was indicated to have usually a secondary effect on the LB intensity for small lakes. Surface observations implied that the onshore penetration of the LB by the early afternoon hours is typically less than the characteristic width of the lake. Lower atmosphere observations indicated that the vertical extent of the LB may reach several hundred meters. Implications of the observed LB features in support of characterization of the real-world vegetation breeze are discussed.

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M. Segal, R. W. Arritt, J. Shen, C. Anderson, and M. Leuthold

Abstract

In this note the forcing of cumulus cloud clearing over and downwind from lakes during the warm season is evaluated conceptually by modeling and observational approaches. It is suggested that drying by dynamically induced subsidence and suppression of the CBL over the lake mutually contribute to the cloud clearing. The effect of background flow speed and the extent of potential clearing area is illustrated. Various implications of the cloud clearing are discussed.

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R. Damiani, J. Zehnder, B. Geerts, J. Demko, S. Haimov, J. Petti, G. S. Poulos, A. Razdan, J. Hu, M. Leuthold, and J. French

The finescale structure and dynamics of cumulus, evolving from shallow to deep convection, and the accompanying changes in the environment and boundary layer over mountainous terrain were the subjects of a field campaign in July–August 2006. Few measurements exist of the transport of boundary layer air into the deep troposphere by the orographic toroidal circulation and orographic convection. The campaign was conducted over the Santa Catalina Mountains in southern Arizona, a natural laboratory to study convection, given the spatially and temporally regular development of cumulus driven by elevated heating and convergent boundary layer flow. Cumuli and their environment were sampled via coordinated observations from the surface, radiosonde balloons, and aircraft, along with airborne radar data and stereophotogrammetry from two angles.

The collected dataset is expected to yield new insights in the boundary layer processes leading to orographic convection, in the cumulus-induced transport of boundary layer air into the troposphere, and in fundamental cumulus dynamics. This article summarizes the motivations, objectives, experimental strategies, preliminary findings, and the potential research paths stirred by the project.

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