The scientists disagree on the order of magnitude of the outer scale. The results are very dependent on the method used. The current estimates run from 10-100 m with the Mark III interferometer (Busher et Al., 1995), down to 50 m with COME-ON La Silla (Rigaut et Al. 1991), 5-8 m with a Hartmann-Shack at CFHT (Tallon, 1989) and 1-4 m with balloon borne microthermal sensors at Paranal during PARSCA92 (Fuchs, 1995).
Thanks to microthermal measurements, is is now demonstrated that thermal turbulence peaks inside very thin layers (Coulman et Al., 1995) but most wavefront calculations still use a formulation based on monotonic vertical distributions.