Proceedings with Extended Abstracts (single PDF file) - Radio ...

Altitude (km)1514.51413.51312.51211.511−50 0 50Thorpe Displacement (m)1514.51413.51312.51211.5110 20 40 60L T(z)Figure 1: Left: Thorpe displacement for selected patches. Right: Modulus of the Thorpedisplacement.• As previously mentioned, whatever the nature of the fluctuations, a SFT Cn 2 might be evaluated,though not always meaningful. Prior to compare the two data set, one needs to determineif temperature fluctuations are turbulent or not.• We check for the slope of the spectrum (or the structure function) by comparing the ratio Rof two Cn 2 estimates from partially overlapping scale intervals.R = C2 n(l 1 , l 2 )C 2 n (l 3, l 4 )(5)If R < 0.5 or R > 2, the C 2 n estimates were considered as dubious (i.e. non-turbulent) andeliminated. This criterion was not very selective however (about 20 % of the data were discarded).• A new method for turbulent patch identification from high resolution temperature profile wasrecently proposed Piera et al. (2002):• The method is based an analysis of the Thorpe displacements d T .• The Thorpe displacements are compared to their potential error E dT , such an error beingevaluated from the temperature noise.• A data point is classified as signal if d T > E dT or if d T = 0, and is classified as uncertainotherwise.• A considered range (30 m depth) is retained if the number of signal points exceed thenumber of uncertain points.The Thorpe displacements of the selected turbulent layers are shown in figure (1). The comparisonof distributions of the radar and SFT estimates of Cn 2 are shown in figure (2). Afterpatches selection of the in-situ data, the two distributions compare surprisingly well.5 ConclusionsWe have compared very high-resolution radar (30 m) and in-situ (0.2 m) measurements:• We cannot identify any turbulent layer unambiguously sampled by both instruments.206