Extratropical Cyclones: Their Mesoscale Structure, Precipitation and Role in the Transport of Water

Abstract

The focus of this article is the nature of extratropical cyclones and in particular their effects on the water cycle. These cloud systems produce much of the precipitation found in mid-latitudes. Embedded features within the overall storm, such as precipitation bands, account for the greatest precipitation and these features are often, but not always, linked with frontal surfaces. Depending on the background large scale forcing, stability and moisture availability, the degree to which these systems produce precipitation from the available vapour (the precipitation efficiency) varies widely. Other roles played by these systems are, for example, the transport of moisture to high regions of the troposphere and the moistening of low levels through the evaporation or sublimation of falling precipitation, but little quantitative work on such aspects has been conducted. Extratropical cyclones therefore directly affect the large scale water cycle through their impact on precipitation and the re-distribution of vapour throughout the troposphere. Remote sensing plays a critical role in advancing the study of extratropical cyclones and their impacts by providing quantitative observations of critical features that often cannot be measured by any other means.