Mesoscale Variability of Jet Stream Winds Observed by the Sunset VHF Doppler Radar

Sensitive Doppler radars have recently been developed that can routinely observe wind in the free atmosphere up to stratospheric heights. One of these, the 40 MHz Sunset radar, was used to observe the three-dimensional wind field associated with a polar front jet stream near Boulder on 15–16 April 1976. The south wind, which was the strongest component (of the wind), was sampled about once a minute for over 14 h over altitudes ranging from 5 to 13 km MSL at 1 km intervals. The temporal variability of the south wind at each height is presented along with the average variability for all heights over the 14 h period. The average variability closely follows a 1/3 power law at least out to 4 h lag time. Since the 1/3 power law is consistent with inertial range turbulence theory, and since turbulence cannot possibly be three-dimensionally isotropic on these scales, it is suggested that the observations might be interpreted as evidence for a two-dimensional, −5/3 inertial range.