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Water Vapor and ice Mass Transported into the Anvils Of CCOPE Thunderstorms: Comparison with Storm Influx and Rainout

Andrew J. HeymsfieldNational Center for Atmospheric Research, Boulder, Colorado

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Karen M. MillerNational Center for Atmospheric Research, Boulder, Colorado

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Abstract

The transport of water substance (ice and vapor) into the anvils of midlatitude continental thunderstorms is examined. Doppler radar reflectivity fields and horizontal and vertical windfields, in situ anvil measurements, and environmental soundings were used to estimate the anvil water mass flux for approximately five-minute intervals over one hour periods in six moderate to severe storms.

Vapor and ice mass fluxes into the anvil time-averaged for the study periods are about equal. Ratios of the time-averaged sums of these fluxes (A¯) to aircraft-derived cloud base influx (from Fankhauser) range from 18% to greater than 100%. Estimated accuracies are ±30 to 40%. Anvil fluxes exceed rainout at cloud base level as derived from radar reflectivity data by Fankhauser for half the storms.

It is shown that influx values alone are not reliable predictors of total storm condensation rates. The water mass storage term is evaluated and is found to be unimportant in relation to influx for all but one storm studied. Both A¯/influx and A¯/ rainout are highly correlated with the vertical shear of the horizontal winds.

Changes in the ice mass flux in the anvil with respect to altitude and distance from the updraft imply the absence of mesoscale ascent in the anvil.

Abstract

The transport of water substance (ice and vapor) into the anvils of midlatitude continental thunderstorms is examined. Doppler radar reflectivity fields and horizontal and vertical windfields, in situ anvil measurements, and environmental soundings were used to estimate the anvil water mass flux for approximately five-minute intervals over one hour periods in six moderate to severe storms.

Vapor and ice mass fluxes into the anvil time-averaged for the study periods are about equal. Ratios of the time-averaged sums of these fluxes (A¯) to aircraft-derived cloud base influx (from Fankhauser) range from 18% to greater than 100%. Estimated accuracies are ±30 to 40%. Anvil fluxes exceed rainout at cloud base level as derived from radar reflectivity data by Fankhauser for half the storms.

It is shown that influx values alone are not reliable predictors of total storm condensation rates. The water mass storage term is evaluated and is found to be unimportant in relation to influx for all but one storm studied. Both A¯/influx and A¯/ rainout are highly correlated with the vertical shear of the horizontal winds.

Changes in the ice mass flux in the anvil with respect to altitude and distance from the updraft imply the absence of mesoscale ascent in the anvil.

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