Studies by various investigators have shown that rising spherical balloons exhibit self-induced lateral motions which can introduce errors when the balloons are used for wind soundings. Balloons operating in the subcritical Reynolds number regime tend to move in a regular, spiral or zigzag path, and then even if the lateral motions are appreciable, the balloon path can rather accurately represent the horizontal wind averaged vertically over a thickness of 15 or more baboon diameters. Typical expandable neoprene balloons smaller than 1-m diameter at launch are within the subcritical regime at all altitudes and so would be expected to be good for soundings all the way from the ground up. Experimental data are presented for several sizes of 100 gm neoprene balloons, and the data are in agreement with this expectation.
Reynolds number effects, rise rates, and peak altitudes are considered for several balloon types. Neoprene balloons feature high peak altitudes and relatively fast ascent at the higher altitudes. A roughened 2-m diameter superpressure *Jimsphere” yields accurate soundings from ground to its peak of about 20 km, and initially rises fairly rapidly. Smooth superpressure balloons give accurate detailed soundings over a limited altitude range (about 12 to 20 km for 2-m diameter, for example).