STRATOSPHERIC HORIZONTAL WAVE-NUMBER SPECTRA OF WINDS, POTENTIAL TEMPERATURE, AND ATMOSPHERIC TRACERS OBSERVED BY HIGH-ALTITUDE AIRCRAFT

Horizontal wavenumber power spectra of vertical and horizontal wind ve locities, potential temperatures, and ozone and N2O mixing ratios, as measured in the mid-stratosphere during 73 ER-2 flights (altitude appr oximate to 20 km) are presented. The velocity and potential temperatur e spectra in the 100 to 1-km wavelength range deviate significantly fr om the uniform -5/3 power law expected for the inverse energy-cascade regime of two-dimensional turbulence and also for inertial-range, thre e-dimensional turbulence. Instead, steeper spectra approximately consi stent with a -3 power law are observed at horizontal scales smaller th an 3 km for all velocity components as well as potential temperature. Shallower spectra are observed at scales longer than 6 km. For horizon tal velocity and potential temperature the spectral indices at longer scales are between -1.5 and -2.0. For vertical velocity the spectrum a t longer scales becomes flat. It is argued that the observed velocity and potential temperature spectra are consistent with gravity waves. A t smaller scales, the shapes are also superficially consistent with a Lumley-Shur-Weinstock buoyant subrange of turbulence and/or nonlinear gravity waves. Contemporaneous spectra of ozone and N2O mixing ratio i n the 100 to 1-km wavelength range do conform to an approximately unif orm -5/3 power law. It is argued that this may reflect interactions be tween gravity wave air-parcel displacements and laminar or filamentary structures in the trace gas mixing ratio field produced by enstrophy- cascading two-dimensional turbulence.