Multiscale Analysis of Low-Level Vertical Fluxes on Day 261 of GATE

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  • 1 Department of Environmental Sciences, Unïversity of Virginia, Charlottesville 22903
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Abstract

Data from a wide variety of measurement platforms are integrated to analyze a GATE cloud cluster and its environment. Lower tropospheric mass and moisture fluxes are computed on several scales using rawinsonde, aircraft, radar and satellite data from 18 September 1974. Lower tropospheric mass and moisture budget analyses are combined with GATE tethered-balloon measurements of cloud properties at cloud base to diagnose active cloud and turbulent fluxes in three areas of different scale ranging from 2.3-34.8 × 1010 m 2 (1.8-28.2° latitude)2.

The significant convection was concentrated in the region of strongest and deepest low-level convergence and highest conditional instability. Observed layer clouds were well correlated with levels of synoptic-scale divergence. Despite large differences in low-level convergence and echo-area coverage, all three regions exhibited similar vertical eddy moisture fluxes at cloud base. Increased area coverage by precipitating clouds was found to be associated with increased subsidence and reduced turbulent moisture flux in the air outside of these clouds.

Abstract

Data from a wide variety of measurement platforms are integrated to analyze a GATE cloud cluster and its environment. Lower tropospheric mass and moisture fluxes are computed on several scales using rawinsonde, aircraft, radar and satellite data from 18 September 1974. Lower tropospheric mass and moisture budget analyses are combined with GATE tethered-balloon measurements of cloud properties at cloud base to diagnose active cloud and turbulent fluxes in three areas of different scale ranging from 2.3-34.8 × 1010 m 2 (1.8-28.2° latitude)2.

The significant convection was concentrated in the region of strongest and deepest low-level convergence and highest conditional instability. Observed layer clouds were well correlated with levels of synoptic-scale divergence. Despite large differences in low-level convergence and echo-area coverage, all three regions exhibited similar vertical eddy moisture fluxes at cloud base. Increased area coverage by precipitating clouds was found to be associated with increased subsidence and reduced turbulent moisture flux in the air outside of these clouds.

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