Early theoretical models suggested that waves generated by instability of a shear layer in a gravitationally stratified fluid should have wavelengths perhaps 7 times the shear layer thickness. More recent work, however, has discovered that the presence of a rigid lower boundary (such as the earth's surface) introduces new unstable modes at substantially larger wavelengths. In this brief note we show that observations of gravity waves generated by shear instability in the temperate-latitude troposphere support this more recent conclusion.