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

Specular reflection is negligible for that frequency (961 MHz). Rayleigh scattering from waterdrop or particles is also negligible in the stratosphere.• The SFT temperature measurements provide informations for fluctuations larger thanabout 1 m.3 Data processing3.1 Radar dataThe PROUST radar is calibrated from the known cosmic noise: (e.g. VanZandt et al., 1978).(〈Cn〉 2 = 16π2k T N B rr2 S(1)0.38 P t λ 5/3r G B L N coh N code H(2l o /λ r ) ∆r)NSuch a radar equation is very usual except for the H and G B terms. The factor H(2l 0 /λ r )takes into account the departure of the temperature spectrum from the −5/3 power law forscales close to the dissipation scales. (Hill, 1978; VanZandt et al., 2000). As the range ofinterest (11−15 km) is still within the near field of the antenna, the two way gain, G B , has tobe numerically calculated and tabulated.3.2 SFT dataThe temperature fluctuations were partially denoised by using a wavelet decomposition. The“SFT Cn 2 ” is then evaluated from the temperature variance for the scale interval (2 − 5 m), assumedto lie within the inertial subrange. If the Kolmogorov hypotheses of an inertial subrangeapply, the temperature variance can be expressed as a function of Cn 2:The “SFT CT 2 ” estimate reads:var(l 1 , l 2 ) = 0.25C 2 T∫ k1k 2k −5/3 dk (2)CT 2 (l 1 , l 2 ) = 8 (2π)(2/3)var(l 1 , l 2 ) (3)3 l 2/32 − l 2/31For a dry atmosphere, as the lower stratosphere, C 2 T is simply related to C2 n :C 2 n = (0.7710 −6 P T) 2C 2 T (4)The temperature variance is smoothed with a 30 m width window (i.e. the radar range resolution)before to be converted into Cn 2. Of course, it should be noticed that C n 2 is evaluatedwhatever are the causes of temperature fluctuations (noise, buoyancy range - in which cases Cn2does not make any sense - or inertial turbulence).4 PROUST/SFT comparisonWhen comparing the processed data sets, we were not abbe to unambiguously identify anyturbulent layer simultaneously sampled by the radar and the SFT sondes. We therefore chooseto compare the statistical properties of the turbulence field as observed from both instruments.• There is a detectability threshold for radar estimates of Cn 2 , this threshold being altitudedependent. In order to compare the two Cn 2 estimates (radar and SFT), we first apply this radarthreshold to the SFT data.205