The effect of wind shear on a puff

This paper corrects Hall's work in the light of more complete experiments which have established that a thermal is merely a special case of a buoyant puff. The general theory, presented here, applies to any isolated buoyant or non-buoyant puff in shearing surroundings of uniform potential density. This theory is then applied to the case of constant mass deficit and constant wind shear, and solutions are obtained in the form of algebraic equations and simple definite integrals. When these solutions are evaluated numerically, using experimentally determined constants, it is found that the ratio of the coefficients of vertical transport of momentum and heat attributable to the puff lies in the range 0.27 σ to 0.7 σ approximately, where σ is the (small) proportion of the area of the horizontal plane through any height which is occupied by puffs. Also, realistic variation of the angle of spread of puffs is found to produce a very considerable effect on the depth of the convective layer. Only narrow puffs rise far.