Midlatitude cyclonic cloud systems and their features affecting large scales and climate

Abstract

Abstract. Midlatitude cyclonic cloud systems are common occurrences that significantly impact our climate. In this review, attention is paid to those physical characteristics of these cloud systems with large-scale impacts that must be accounted for in climate simulations. Such attributes include atmospheric forcing, internal structure, surface influences, cloud layering, microphysics, precipitation, water cycling, and radiation. Because of their present limitations associated with, for example, grid sizes and simplified parameterizations, climate models cannot account for all the crucial impacts of these cloud systems. Future advances in the representation of these systems within climate models will need to rely in part on rigorous assessments of model capabilities in a variety of conditions. system. They contribute substantially to global and regional water and energy cycles because of organized vertical motions and latent heat exchanges occurring within the clouds, thereby redistributing and altering the vertical profiles of momentum and moisture. These clouds account for a major fraction of the precipitation (and therefore atmospheric heating) in midlatitudes, and they are associated with some of the main avenues for the latitudinal transport of moisture through the atmosphere [e.g., Lambert, 1988]. These cloud systems also account for a substantial portion of the large-scale cloud radiative forcing found in the midlatitudes. This is due in part to the production of high-level clouds [Wylie and Menzel, 1989;Wild et al., 1995] and to the enhanced cloud water path that occurs in association with these systems. In addition, the interaction of these layer cloud systems with orography often leads to enhanced clouds and precipitation. Because mountains are the source regions for many of the world's rivers, the role of orography in affecting the small-scale distributions (<20 km) of precipitation from these clouds is a critical problem IReinking, 1995]. Air-sea interaction is also important; deep water formation in the North Atlantic (and possibly other areas) may be enhanced through the associated cold air outbreaks linked with these cloud systems. The generation of the downward convection in these bodies of water represents a major aspect of the global oceanographic circulation [Webster, 1994].Global climate prediction models simulate some of the coarse characteristics of these cloud systems [e.g., Lambert, 1995], but they do not account for finer details [Bengtsson, 1995]. For example, McFarlane et al. [1992] showed that current models display a midlatitude peak in precipitation associated with these systems, though The purpose of this article is to summarize some of the current understanding of clouds associated with midlatitude cyclonic storms, with a focus on the processes and phenomena associated with them that can affect climate. The article brings together many recent developments in the study of these systems and relates these to their large-scale impact. It is intended that this article will draw the ...

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