The Balance Level in Convective Storms

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Abstract
Doppler radar observations of convective storms at vertical incidence show a height at which the mean reflectivity-weighted particle velocity relative to the ground is zero, i.e., the particles are just balanced by the updraft. This height is defined as the “balance level” or BL. While a transient BL may appear at any height in the storm, a steady or quasi-steady BL is found to exist only near maxima in the updraft profile. Such maxima provide a means of separating the particle size spectrum into rising and falling groups of comparable reflectivity at a discrete height. Two BL's have been identified, one at a primary updraft maximum near the storm top and the other at a secondary maximum lower down. The continued existence of the lower BL depends upon whether or not the group of rising particles, which grow further in the updraft above the secondary maximum, turn downward and fall back through the BL with fall speeds greatly in excess of the associated updraft speed there. Under conditions of str... Abstract Doppler radar observations of convective storms at vertical incidence show a height at which the mean reflectivity-weighted particle velocity relative to the ground is zero, i.e., the particles are just balanced by the updraft. This height is defined as the “balance level” or BL. While a transient BL may appear at any height in the storm, a steady or quasi-steady BL is found to exist only near maxima in the updraft profile. Such maxima provide a means of separating the particle size spectrum into rising and falling groups of comparable reflectivity at a discrete height. Two BL's have been identified, one at a primary updraft maximum near the storm top and the other at a secondary maximum lower down. The continued existence of the lower BL depends upon whether or not the group of rising particles, which grow further in the updraft above the secondary maximum, turn downward and fall back through the BL with fall speeds greatly in excess of the associated updraft speed there. Under conditions of str...

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